Vicinal dihaloalkanes are extremely important structural units, and dihalogenation of alkenes provides a prospective way to access such moieties. Despite more than a century of development, it is still challenging and necessary to avoid the use of toxic and harmful halogenating reagents and develop more efficient, broader, functional group-tolerant, and skeleton-compatible strategies. We report herein the metal-free protocol for radical vicinal dichlorination and dibromination of olefins by a photocatalytic energy transfer strategy using N-halo-benzophenonimine (NXB) as the readily accessible halogenating reagent. This approach undergoes radical addition of a halogen atom derived from the N–X bond photolysis of NXB onto olefins, followed by a halogen-atom transfer process. This approach features facile operation, mild reaction conditions, and wide functional group tolerance and is compatible with a large number of complex scaffolds such as unsaturated fatty acids, terpene steroids, alkaloids, sugars, amino acids, and peptides.
{"title":"Metal-Free Radical Vicinal Dihalogenation of Olefins Enabled by Synergetic Photocatalytic Energy Transfer and Halogen-Atom Transfer","authors":"Hong-Chen Wang, Min-Hao Qi, Tu-Ming Liu, Peng-Fei Zhao, Chang-Yuan Xu, Dong-Tai Xie, Hao-Luo Jiang, Yi-Fan Li, Xiao-Heng Wang, Bing Han","doi":"10.1021/acscatal.5c06722","DOIUrl":"https://doi.org/10.1021/acscatal.5c06722","url":null,"abstract":"Vicinal dihaloalkanes are extremely important structural units, and dihalogenation of alkenes provides a prospective way to access such moieties. Despite more than a century of development, it is still challenging and necessary to avoid the use of toxic and harmful halogenating reagents and develop more efficient, broader, functional group-tolerant, and skeleton-compatible strategies. We report herein the metal-free protocol for radical vicinal dichlorination and dibromination of olefins by a photocatalytic energy transfer strategy using <i>N-</i>halo-benzophenonimine (NXB) as the readily accessible halogenating reagent. This approach undergoes radical addition of a halogen atom derived from the N–<i>X</i> bond photolysis of NXB onto olefins, followed by a halogen-atom transfer process. This approach features facile operation, mild reaction conditions, and wide functional group tolerance and is compatible with a large number of complex scaffolds such as unsaturated fatty acids, terpene steroids, alkaloids, sugars, amino acids, and peptides.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"111 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2025-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145645236","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-30DOI: 10.1021/acscatal.5c05048
Lebohang Macheli, Gerard M. Leteba, Boitumelo J. Matsoso, Bryan P. Doyle, Linda L. Jewell, Eric Van Steen
Fischer–Tropsch synthesis (FTS) is a cornerstone catalytic process for converting synthesis gas into liquid hydrocarbons, yet it suffers from limited selectivity and excessive methane formation. Here, we demonstrate that surface modification of cobalt oxide (Co3O4) nanoparticles with trimethylchlorosilane (TMCS), followed by calcination, yields pseudo single-atom SiOx species that form a distinct SiOx–Co interface. Unlike conventional silica coatings, these isolated SiOx moieties are ligand-like, electronically modifying surface cobalt atoms, without forming bulk SiO2 or siloxane domains. This interface enhances π-back-donation to carbon monoxide (CO), increases the heat of adsorption, and promotes CO bond cleavage, as confirmed by CO chemisorption and CO-temperature-programmed desorption (TPD). Catalysts modified in this way show over an order of magnitude increase in turnover frequency (TOF), alongside a marked decrease in methane selectivity and a shift toward C2–C5 hydrocarbons and oxygenates. These findings establish pseudo single-atom SiOx–Co interfaces as a powerful route to engineer activity and selectivity in FTS. Importantly, the approach avoids chlorine residues and is consistent with Cl removal during calcination. Beyond suppressing methane, the SiOx interface selectively promotes aldehydes, aligning with recent reports on oxide-modified Co catalysts. Pseudo single-atom oxide–metal interfaces emerge as a tunable strategy for enhancing both activity and selectivity in cobalt-based FTS catalysts.
{"title":"Pseudo Single-Atom SiOx–Co Interfaces for Selectivity Control in Fischer–Tropsch Catalysis","authors":"Lebohang Macheli, Gerard M. Leteba, Boitumelo J. Matsoso, Bryan P. Doyle, Linda L. Jewell, Eric Van Steen","doi":"10.1021/acscatal.5c05048","DOIUrl":"https://doi.org/10.1021/acscatal.5c05048","url":null,"abstract":"Fischer–Tropsch synthesis (FTS) is a cornerstone catalytic process for converting synthesis gas into liquid hydrocarbons, yet it suffers from limited selectivity and excessive methane formation. Here, we demonstrate that surface modification of cobalt oxide (Co<sub>3</sub>O<sub>4</sub>) nanoparticles with trimethylchlorosilane (TMCS), followed by calcination, yields pseudo single-atom SiO<sub><i>x</i></sub> species that form a distinct SiO<sub><i>x</i></sub>–Co interface. Unlike conventional silica coatings, these isolated SiO<sub><i>x</i></sub> moieties are ligand-like, electronically modifying surface cobalt atoms, without forming bulk SiO<sub>2</sub> or siloxane domains. This interface enhances π-back-donation to carbon monoxide (CO), increases the heat of adsorption, and promotes CO bond cleavage, as confirmed by CO chemisorption and CO-temperature-programmed desorption (TPD). Catalysts modified in this way show over an order of magnitude increase in turnover frequency (TOF), alongside a marked decrease in methane selectivity and a shift toward C<sub>2</sub>–C<sub>5</sub> hydrocarbons and oxygenates. These findings establish pseudo single-atom SiO<sub><i>x</i></sub>–Co interfaces as a powerful route to engineer activity and selectivity in FTS. Importantly, the approach avoids chlorine residues and is consistent with Cl removal during calcination. Beyond suppressing methane, the SiO<sub><i>x</i></sub> interface selectively promotes aldehydes, aligning with recent reports on oxide-modified Co catalysts. Pseudo single-atom oxide–metal interfaces emerge as a tunable strategy for enhancing both activity and selectivity in cobalt-based FTS catalysts.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"10 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2025-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145645235","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-29DOI: 10.1021/acscatal.5c05769
Maximilian Seiß, Xiaoquan Chen, Bowei Yuan, Sebastian Dechert, Jana Roithová, Shengfa Ye, Franc Meyer
The catalytic oxidation of ammonia is relevant in the context of zero-carbon energy scenarios, for instance, in fuels cells or for hydrogen storage. Here, we report the diruthenium complex [LRu2(py)4(μ1,2-N2H4)](PF6)3 (1(PF6)3; HL = 3,5-bis(bipyridyl)pyrazole) and demonstrate its ability to catalyze the oxidation of ammonia at a low overpotential of 0.76 V. Notably, complex 1(PF6)3 is a molecular catalyst with a highly preorganized dinuclear substrate binding pocket to enforce the close proximity of two ammonia molecules and induce metal–metal cooperativity. The formation of N2 and H2 from ammonia during constant potential electrolysis was analyzed using gas chromatography as well as mass spectrometry in combination with 15N-labeling. Detailed electrochemical and spectroscopic studies, including voltammetry-coupled ESI-MS and gas phase photodissociation spectroscopy, provided mechanistic insights and identified [LRu2(py)4(N2H2)]3+ (33+) as a key intermediate, and DFT computations were used to evaluate possible reaction pathways as well as the electronic structures of relevant species. The combined experimental and computational findings allowed to propose a catalytic cycle where N–N coupling occurs at an early stage of the multi-PCET sequence in species [LRu2(py)4(NH2)2]3+, giving 13+ and then 33+ en route to N2. Furthermore, [LRu2(py)4(MeCN)2]3+ (23+) was identified as an off-cycle product leading to gradual catalyst deactivation.
{"title":"Electrocatalytic Ammonia Oxidation with a Highly Preorganized Metal–Metal Cooperative Diruthenium Complex","authors":"Maximilian Seiß, Xiaoquan Chen, Bowei Yuan, Sebastian Dechert, Jana Roithová, Shengfa Ye, Franc Meyer","doi":"10.1021/acscatal.5c05769","DOIUrl":"https://doi.org/10.1021/acscatal.5c05769","url":null,"abstract":"The catalytic oxidation of ammonia is relevant in the context of zero-carbon energy scenarios, for instance, in fuels cells or for hydrogen storage. Here, we report the diruthenium complex [LRu<sub>2</sub>(py)<sub>4</sub>(μ<sub>1,2</sub>-N<sub>2</sub>H<sub>4</sub>)](PF<sub>6</sub>)<sub>3</sub> (<b>1</b>(PF<sub>6</sub>)<sub>3</sub>; HL = 3,5-bis(bipyridyl)pyrazole) and demonstrate its ability to catalyze the oxidation of ammonia at a low overpotential of 0.76 V. Notably, complex <b>1</b>(PF<sub>6</sub>)<sub>3</sub> is a molecular catalyst with a highly preorganized dinuclear substrate binding pocket to enforce the close proximity of two ammonia molecules and induce metal–metal cooperativity. The formation of N<sub>2</sub> and H<sub>2</sub> from ammonia during constant potential electrolysis was analyzed using gas chromatography as well as mass spectrometry in combination with <sup>15</sup>N-labeling. Detailed electrochemical and spectroscopic studies, including voltammetry-coupled ESI-MS and gas phase photodissociation spectroscopy, provided mechanistic insights and identified [LRu<sub>2</sub>(py)<sub>4</sub>(N<sub>2</sub>H<sub>2</sub>)]<sup>3+</sup> (<b>3</b><sup><b>3+</b></sup>) as a key intermediate, and DFT computations were used to evaluate possible reaction pathways as well as the electronic structures of relevant species. The combined experimental and computational findings allowed to propose a catalytic cycle where N–N coupling occurs at an early stage of the multi-PCET sequence in species [LRu<sub>2</sub>(py)<sub>4</sub>(NH<sub>2</sub>)<sub>2</sub>]<sup>3+</sup>, giving <b>1</b><sup><b>3+</b></sup> and then <b>3</b><sup><b>3+</b></sup> en route to N<sub>2</sub>. Furthermore, [LRu<sub>2</sub>(py)<sub>4</sub>(MeCN)<sub>2</sub>]<sup>3+</sup> (<b>2</b><sup><b>3+</b></sup>) was identified as an off-cycle product leading to gradual catalyst deactivation.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"3 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2025-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145619418","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-29DOI: 10.1021/acscatal.5c05807
Samuel B. Portillo, Yuhan Mei, Mohammadreza Kosari, Elizabeth Nguyen, Abhijit Talpade, Fanxing Li
In this study, a set of iron-substituted strontium hexaaluminate materials (SrFexAl12–xO19) were synthesized and evaluated for catalytic methane decomposition (CDM) using a concentrated methane feed (PCH4 = 0.9 atm). Despite their lower surface areas, it is showcased that the SrFexAl12–xO19 materials can be quite active for CDM, reaching overall carbon yields up to 8.08 gC·gcat–1 or 15.68 gC·gFe–1 at GHSV = 5 L·g–1·h–1. In situ XRD under a reducing environment indicates that catalytic activity for high iron-containing samples (x ≥ 6) originates from the collapse of the parent SrFexAl12–xO19 structure to α-Fe supported on residual SrAl2O4 and FeAl2O4. Further in situ XRD studies on bulk Fe3C under the presence of CH4 show that iron carbide is metastable and will transform to BCC α-Fe in the range between 600 and 800 °C and subsequently to FCC γ-Fe and Fe3C ≥900 °C. Analogous in situ XRD experiments on SrFe9Al3O19 under CH4 show a clear sequential phase transformation of α-Fe → γ-Fe → Fe3C and the evolution of a small amount of graphite after testing, which suggests that Fe3C is catalytically active for CDM. Density functional theory (DFT) calculations further probed the energetics of surface carbon diffusion on Fe3C and methane dehydrogenation on low-index facets of BCC α-Fe, FCC γ-Fe, and Fe3C, respectively. These results, based on in situ measurements coupled with detailed ab initio calculations, give nuanced perspectives on the active phases for iron-based CDM catalysts and CNT growth.
{"title":"Strontium Iron Hexaaluminates for COx-Free Hydrogen and Carbon Nanotubes via Catalytic Decomposition of Methane","authors":"Samuel B. Portillo, Yuhan Mei, Mohammadreza Kosari, Elizabeth Nguyen, Abhijit Talpade, Fanxing Li","doi":"10.1021/acscatal.5c05807","DOIUrl":"https://doi.org/10.1021/acscatal.5c05807","url":null,"abstract":"In this study, a set of iron-substituted strontium hexaaluminate materials (SrFe<sub><i>x</i></sub>Al<sub>12–<i>x</i></sub>O<sub>19</sub>) were synthesized and evaluated for catalytic methane decomposition (CDM) using a concentrated methane feed (<i>P</i><sub>CH4</sub> = 0.9 atm). Despite their lower surface areas, it is showcased that the SrFe<sub><i>x</i></sub>Al<sub>12–<i>x</i></sub>O<sub>19</sub> materials can be quite active for CDM, reaching overall carbon yields up to 8.08 g<sub>C</sub>·g<sub>cat</sub><sup>–1</sup> or 15.68 g<sub>C</sub>·g<sub>Fe</sub><sup>–1</sup> at GHSV = 5 L·g<sup>–1</sup>·h<sup>–1</sup>. <i>In situ</i> XRD under a reducing environment indicates that catalytic activity for high iron-containing samples (<i>x</i> ≥ 6) originates from the collapse of the parent SrFe<sub><i>x</i></sub>Al<sub>12–<i>x</i></sub>O<sub>19</sub> structure to α-Fe supported on residual SrAl<sub>2</sub>O<sub>4</sub> and FeAl<sub>2</sub>O<sub>4</sub>. Further <i>in situ</i> XRD studies on bulk Fe<sub>3</sub>C under the presence of CH<sub>4</sub> show that iron carbide is metastable and will transform to BCC α-Fe in the range between 600 and 800 °C and subsequently to FCC γ-Fe and Fe<sub>3</sub>C ≥900 °C. Analogous <i>in situ</i> XRD experiments on SrFe<sub>9</sub>Al<sub>3</sub>O<sub>19</sub> under CH<sub>4</sub> show a clear sequential phase transformation of α-Fe → γ-Fe → Fe<sub>3</sub>C and the evolution of a small amount of graphite after testing, which suggests that Fe<sub>3</sub>C is catalytically active for CDM. Density functional theory (DFT) calculations further probed the energetics of surface carbon diffusion on Fe<sub>3</sub>C and methane dehydrogenation on low-index facets of BCC α-Fe, FCC γ-Fe, and Fe<sub>3</sub>C, respectively. These results, based on <i>in situ</i> measurements coupled with detailed <i>ab initio</i> calculations, give nuanced perspectives on the active phases for iron-based CDM catalysts and CNT growth.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"32 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2025-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145619419","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-27DOI: 10.1021/acscatal.5c06689
Jiawang Li, Changqing Lin, Zhenyu Chen, Ji Huang, Bin Yang, Mingjie Lin, Pei Kang Shen, Zhi Qun Tian
Transition metal–nitrogen-carbon composites (M–N–C), which hold great promise as Pt-free oxygen reduction reaction (ORR) catalysts, still encounter issues such as low activity and insufficient durability in practical proton-exchange membrane fuel cells (PEMFCs). Herein, we present a specific design of Fe–N–C featuring rich submicropore vacancies (Fe–N–C-SMV). This was developed through a simple MgCl2·6H2O-assisted pyrolysis process of the complexing compound consisting of 1,10-phenanthroline and FeCl3. The submicropore vacancies (<1.0 nm) generated by MgCl2·6H2O break the molecular orbital symmetry of the FeN4 moiety, inducing an additional d-π interaction between Fe and the N dopant. This interaction not only significantly reduces the oxygen adsorption energy but also regulates the spin polarization of Fe, thereby effectively inhibiting the demetalation of Fe. As a result, the Fe–N–C-SMV delivered a half-wave potential of 0.84 V in 0.5 M H2SO4 and a minimal durability decay of 7.0 mV after 10,000 cycles. Moreover, it shows a high practical PEMFC performance, with a maximum power output of 822 mW cm–2 and a relatively low degradation rate of 0.665 mA cm–2 h–1. The crucial role of submicropore vacancies in simultaneously enhancing Fe–N–C discovered in this work provides an inspiration for developing nonprecious metal electrocatalysts for ORR in PEMFCs.
过渡金属-氮-碳复合材料（M-N-C）作为无pt氧还原反应（ORR）催化剂前景广阔，但在实际质子交换膜燃料电池（pemfc）中仍存在活性低、耐久性不足等问题。在此，我们提出了一种具有丰富亚微孔空位（Fe-N-C - smv）的Fe-N-C的特殊设计。这是通过简单的MgCl2·6h2o辅助热解过程，由1,10-菲罗啉和FeCl3组成的络合化合物。MgCl2·6H2O产生的亚微孔空位（<1.0 nm）打破了FeN4部分的分子轨道对称性，诱导了Fe与N掺杂剂之间额外的d-π相互作用。这种相互作用不仅显著降低了氧吸附能，而且调节了Fe的自旋极化，从而有效地抑制了Fe的脱金属。结果表明，Fe-N-C-SMV在0.5 M H2SO4中提供了0.84 V的半波电位，并且在10,000次循环后耐久性衰减最小，为7.0 mV。此外，它还显示出较高的实用PEMFC性能，最大功率输出为822 mW cm-2，降解率相对较低，为0.665 mA cm-2 h-1。本研究发现的亚微孔空位在同时增强Fe-N-C中的关键作用，为开发pemfc中用于ORR的非贵金属电催化剂提供了灵感。
{"title":"Fe–N–C Electrocatalyst with d-π Interaction Induced by Submicropore Vacancies for Durable Oxygen Reduction Reaction in Proton-Exchange Membrane Fuel Cells","authors":"Jiawang Li, Changqing Lin, Zhenyu Chen, Ji Huang, Bin Yang, Mingjie Lin, Pei Kang Shen, Zhi Qun Tian","doi":"10.1021/acscatal.5c06689","DOIUrl":"https://doi.org/10.1021/acscatal.5c06689","url":null,"abstract":"Transition metal–nitrogen-carbon composites (M–N–C), which hold great promise as Pt-free oxygen reduction reaction (ORR) catalysts, still encounter issues such as low activity and insufficient durability in practical proton-exchange membrane fuel cells (PEMFCs). Herein, we present a specific design of Fe–N–C featuring rich submicropore vacancies (Fe–N–C-SMV). This was developed through a simple MgCl<sub>2</sub>·6H<sub>2</sub>O-assisted pyrolysis process of the complexing compound consisting of 1,10-phenanthroline and FeCl<sub>3</sub>. The submicropore vacancies (<1.0 nm) generated by MgCl<sub>2</sub>·6H<sub>2</sub>O break the molecular orbital symmetry of the FeN<sub>4</sub> moiety, inducing an additional d-π interaction between Fe and the N dopant. This interaction not only significantly reduces the oxygen adsorption energy but also regulates the spin polarization of Fe, thereby effectively inhibiting the demetalation of Fe. As a result, the Fe–N–C-SMV delivered a half-wave potential of 0.84 V in 0.5 M H<sub>2</sub>SO<sub>4</sub> and a minimal durability decay of 7.0 mV after 10,000 cycles. Moreover, it shows a high practical PEMFC performance, with a maximum power output of 822 mW cm<sup>–2</sup> and a relatively low degradation rate of 0.665 mA cm<sup>–2</sup> h<sup>–1</sup>. The crucial role of submicropore vacancies in simultaneously enhancing Fe–N–C discovered in this work provides an inspiration for developing nonprecious metal electrocatalysts for ORR in PEMFCs.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"99 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2025-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145608707","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-26DOI: 10.1021/acscatal.5c06516
Majed Alam Abir, Rachel E. Phillips, Jakob Klug, Gia Monte, Joseph Harrah, Kaden Schreiber, Madelyn R. Ball
The influence of gadolinium (Gd) on nickel (Ni)-based catalysts for CO2 methanation was studied. By varying the Gd content at a fixed Ni loading, we observed an enhancement in the CO2 methanation TOF from 0.009 to 0.03 s–1 with increasing Gd content, attributed to improved CO2 adsorption and increased metal reducibility, while the site density remained largely unchanged. From in situ FTIR studies, a possible reaction mechanism for CO2 methanation on Gd-modified Ni catalysts was proposed. The monometallic nickel catalyst exhibited strong CO adsorption, leading to catalyst deactivation over time, while in the presence of Gd, a CO + formate pathway was observed. This change in the likely mechanism due to the presence of Gd suppressed strong CO adsorption and improved catalyst stability over time.
{"title":"Gadolinium-Modified Nickel Catalysts for Enhanced CO2 Methanation","authors":"Majed Alam Abir, Rachel E. Phillips, Jakob Klug, Gia Monte, Joseph Harrah, Kaden Schreiber, Madelyn R. Ball","doi":"10.1021/acscatal.5c06516","DOIUrl":"https://doi.org/10.1021/acscatal.5c06516","url":null,"abstract":"The influence of gadolinium (Gd) on nickel (Ni)-based catalysts for CO<sub>2</sub> methanation was studied. By varying the Gd content at a fixed Ni loading, we observed an enhancement in the CO<sub>2</sub> methanation TOF from 0.009 to 0.03 s<sup>–1</sup> with increasing Gd content, attributed to improved CO<sub>2</sub> adsorption and increased metal reducibility, while the site density remained largely unchanged. From <i>in situ</i> FTIR studies, a possible reaction mechanism for CO<sub>2</sub> methanation on Gd-modified Ni catalysts was proposed. The monometallic nickel catalyst exhibited strong CO adsorption, leading to catalyst deactivation over time, while in the presence of Gd, a CO + formate pathway was observed. This change in the likely mechanism due to the presence of Gd suppressed strong CO adsorption and improved catalyst stability over time.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"55 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145600110","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-26DOI: 10.1021/acscatal.5c05829
Wen Li, Junjie Shi, Parinya Lewis Tangpakonsab, Bin Zhang, Thomas Haunold, Alexander Genest, Nevzat Yigit, Leonard Atzl, Esko Kokkonen, Yong Qin, Günther Rupprechter
The direct conversion of methane to methanol (DCMM) under continuous flow and atmospheric pressure offers notable environmental benefits and industrial promise, but remains a long-standing challenge due to the difficulty of activating CH4 while avoiding overoxidation of methanol. Here, we demonstrate that pure ceria (CeO2), without any metal promoters, enables gas-phase DCMM with up to 80% selectivity at 300–350 °C, upon optimization of the H2O/O2 ratio. At 550 °C, methanol and formaldehyde are formed at rates of 24 and 38 μmol g–1 h–1, respectively, both dropping below 1 μmol g–1 h–1 in the absence of O2. Ex situ transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy confirm that CeO2 maintains structural integrity and resists carbon deposition during reaction. Combining kinetic studies, steady-state in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS), and density functional theory (DFT) reveals that hydroxyl groups (OH), generated from water dissociation, play a multifaceted role: they facilitate C–H bond activation, promote methoxy formation, and enhance methanol desorption. In situ ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) directly reveals the evolution of surface intermediates and shows that cofeeding O2 and H2O suppresses CH3O and CHx accumulation while boosting methanol yield, indicating a rapid intermediate turnover as key to sustained activity. AP-XPS O 1s spectra further highlight that O2 promotes H2O dissociation, regenerating reactive OH groups and maintaining performance at elevated temperature. These findings offer molecular-level insights into how water and oxygen cooperatively tune reactivity, enabling efficient methane-to-methanol conversion on a metal-free oxide catalyst.
{"title":"Synergy of Oxygen and Water in Ceria-Catalyzed Direct Conversion of Methane to Methanol under Continuous Flow","authors":"Wen Li, Junjie Shi, Parinya Lewis Tangpakonsab, Bin Zhang, Thomas Haunold, Alexander Genest, Nevzat Yigit, Leonard Atzl, Esko Kokkonen, Yong Qin, Günther Rupprechter","doi":"10.1021/acscatal.5c05829","DOIUrl":"https://doi.org/10.1021/acscatal.5c05829","url":null,"abstract":"The direct conversion of methane to methanol (DCMM) under continuous flow and atmospheric pressure offers notable environmental benefits and industrial promise, but remains a long-standing challenge due to the difficulty of activating CH<sub>4</sub> while avoiding overoxidation of methanol. Here, we demonstrate that pure ceria (CeO<sub>2</sub>), without any metal promoters, enables gas-phase DCMM with up to 80% selectivity at 300–350 °C, upon optimization of the H<sub>2</sub>O/O<sub>2</sub> ratio. At 550 °C, methanol and formaldehyde are formed at rates of 24 and 38 μmol g<sup>–1</sup> h<sup>–1</sup>, respectively, both dropping below 1 μmol g<sup>–1</sup> h<sup>–1</sup> in the absence of O<sub>2</sub>. <i>Ex situ</i> transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy confirm that CeO<sub>2</sub> maintains structural integrity and resists carbon deposition during reaction. Combining kinetic studies, steady-state <i>in situ</i> diffuse reflectance infrared Fourier transform spectroscopy (<i>in situ</i> DRIFTS), and density functional theory (DFT) reveals that hydroxyl groups (OH), generated from water dissociation, play a multifaceted role: they facilitate C–H bond activation, promote methoxy formation, and enhance methanol desorption. <i>In situ</i> ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) directly reveals the evolution of surface intermediates and shows that cofeeding O<sub>2</sub> and H<sub>2</sub>O suppresses CH<sub>3</sub>O and CH<sub><i>x</i></sub> accumulation while boosting methanol yield, indicating a rapid intermediate turnover as key to sustained activity. AP-XPS O 1s spectra further highlight that O<sub>2</sub> promotes H<sub>2</sub>O dissociation, regenerating reactive OH groups and maintaining performance at elevated temperature. These findings offer molecular-level insights into how water and oxygen cooperatively tune reactivity, enabling efficient methane-to-methanol conversion on a metal-free oxide catalyst.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"55 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145609061","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-26DOI: 10.1021/acscatal.5c04079
Philipp Wichmann, Amelia Cox-Fermandois, Andreas M. Küffner, Uwe Linne, Tobias J. Erb, Maren Nattermann
The formate bioeconomy envisions production of formic acid from CO2 via (electro-)chemical conversion, followed by conversion to the product by engineered microbes or cell-free systems. One prominent way of expanding formate valorization is its reduction to formaldehyde, making highly efficient assimilation cascades accessible. This thermodynamically challenging reaction can be catalyzed by ATP-dependent activation followed by NAD(P)H-dependent reduction. Existing solutions rely on two-step cascades, or fusion enzymes thereof, and are limited by the fast hydrolysis of their formylated intermediates. Here, we show that carboxylic acid reductase can be engineered toward formate reduction, resulting in a single-enzyme solution that does not release intermediates. In addition, we discovered that this enzyme tolerates high formate concentrations when used inEscherichia coliwhole-cell conversion, conditions that strongly inhibit existing formate reduction cascades. We therefore provide a valuable addition to the toolbox of synthetic formate reduction, providing an enzyme compatible with applications amenable to high formate titers, such as whole-cell bioconversion or electrobiochemical cascades.
{"title":"Engineering a Formic Acid Reductase","authors":"Philipp Wichmann, Amelia Cox-Fermandois, Andreas M. Küffner, Uwe Linne, Tobias J. Erb, Maren Nattermann","doi":"10.1021/acscatal.5c04079","DOIUrl":"https://doi.org/10.1021/acscatal.5c04079","url":null,"abstract":"The formate bioeconomy envisions production of formic acid from CO<sub>2</sub> via (electro-)chemical conversion, followed by conversion to the product by engineered microbes or cell-free systems. One prominent way of expanding formate valorization is its reduction to formaldehyde, making highly efficient assimilation cascades accessible. This thermodynamically challenging reaction can be catalyzed by ATP-dependent activation followed by NAD(P)H-dependent reduction. Existing solutions rely on two-step cascades, or fusion enzymes thereof, and are limited by the fast hydrolysis of their formylated intermediates. Here, we show that carboxylic acid reductase can be engineered toward formate reduction, resulting in a single-enzyme solution that does not release intermediates. In addition, we discovered that this enzyme tolerates high formate concentrations when used in<i><i>Escherichia coli</i></i>whole-cell conversion, conditions that strongly inhibit existing formate reduction cascades. We therefore provide a valuable addition to the toolbox of synthetic formate reduction, providing an enzyme compatible with applications amenable to high formate titers, such as whole-cell bioconversion or electrobiochemical cascades.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"37 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145600107","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-26DOI: 10.1021/acscatal.5c06417
Swarbhanu Ghosh, Parisa A. Ariya
The increase in atmospheric carbon dioxide (CO2), a significant greenhouse gas, must be addressed urgently due to its severe impact on the Earth’s climate system. Human activities and the excessive exploitation of natural resources are driving CO2 emissions to alarming levels. In response, utilizing atmospheric CO2 as a C1 feedstock has emerged as a vital strategy. Effectively converting CO2 into fuels and chemicals could provide a viable option for producing various industrial products. Consequently, researchers worldwide are focusing on the chemical utilization of CO2 to generate valuable chemicals, such as organic feedstocks and fuels, which could help reduce atmospheric CO2 levels. To combat the concerning rise in atmospheric CO2 concentrations, scalable strategies for the catalytic transformation of CO2 into high-value products like methanol and methane are being developed. Among these strategies, metal-free catalytic processes operate under ambient reaction conditions. These processes leverage advancements in catalysis by utilizing earth-abundant natural chemicals that are cost-effective, have a low carbon footprint, and are nonhazardous. Additionally, the heterogenization of homogeneous metal-free catalytic systems enhances their recyclability. This review aims to highlight the progress made in the chemical utilization of CO2 over the past decade, with a specific focus on metal-free catalytic systems.
{"title":"Designing the Future of Advancing Catalysis: Structural Trends in Metal-Free Systems for CO2 Conversion","authors":"Swarbhanu Ghosh, Parisa A. Ariya","doi":"10.1021/acscatal.5c06417","DOIUrl":"https://doi.org/10.1021/acscatal.5c06417","url":null,"abstract":"The increase in atmospheric carbon dioxide (CO<sub>2</sub>), a significant greenhouse gas, must be addressed urgently due to its severe impact on the Earth’s climate system. Human activities and the excessive exploitation of natural resources are driving CO<sub>2</sub> emissions to alarming levels. In response, utilizing atmospheric CO<sub>2</sub> as a C1 feedstock has emerged as a vital strategy. Effectively converting CO<sub>2</sub> into fuels and chemicals could provide a viable option for producing various industrial products. Consequently, researchers worldwide are focusing on the chemical utilization of CO<sub>2</sub> to generate valuable chemicals, such as organic feedstocks and fuels, which could help reduce atmospheric CO<sub>2</sub> levels. To combat the concerning rise in atmospheric CO<sub>2</sub> concentrations, scalable strategies for the catalytic transformation of CO<sub>2</sub> into high-value products like methanol and methane are being developed. Among these strategies, metal-free catalytic processes operate under ambient reaction conditions. These processes leverage advancements in catalysis by utilizing earth-abundant natural chemicals that are cost-effective, have a low carbon footprint, and are nonhazardous. Additionally, the heterogenization of homogeneous metal-free catalytic systems enhances their recyclability. This review aims to highlight the progress made in the chemical utilization of CO<sub>2</sub> over the past decade, with a specific focus on metal-free catalytic systems.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"29 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145600108","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-25DOI: 10.1021/acscatal.5c05030
Guangming Cai, Ya-Huei (Cathy) Chin
The water–gas shift catalytic cycle (CO + H2O ⇄ CO2 + H2), in both the forward (WGS) and reverse (RWGS) directions, is a classical reaction central to fuel and chemical synthesis that interconverts reductant-and-oxidant pairs (red + ox → ox′ + red′), i.e., in WGS, CO (red) to CO2 (ox′) and H2O (ox) to H2 (red′), and in RWGS, H2 (red) to H2O (ox′) and CO2 (ox) to CO (red′). Within this cycle, the energy landscape and kinetic relevance of the steps have not yet been fully established and reconciled, especially on oxide surfaces, simply due to their structural complexities and changing oxygen contents. Here, we establish the mechanistic framework and associated barriers for each step of the cycle, in both directions, on modeled ceria (CeO2) through kinetic interrogations under induction, steady-state, and transient regimes, each providing distinct thermodynamic and kinetic insights into the barriers of individual steps and intraparticle O-atom diffusion between surface and bulk, as the oxygen content in CeO2–x varies (x = 0–0.2) and redistributes. In RWGS, surface O atom abstraction by H2 is the sole kinetically relevant step on partially reduced CeO2–x oxides (x = 0.024–0.038) with a barrier of 180 ± 3 kJ mol–1, determined from steady-state kinetics, whereas surface reoxidation by CO2 at O-vacancies is rapid with an apparent activation energy of 51 ± 1 kJ mol–1 that decreases with increasing O-vacancy formation energy, revealed by transient kinetic studies that decouple this step from the preceding kinetic bottleneck. In WGS, the reverse reaction, both surface O atom abstraction by CO (92 ± 21 kJ mol–1) and surface reoxidation by H2O (89 ± 6 kJ mol–1) are kinetically relevant, derived from steady-state rate measurements. Integrating findings from both reactions, we delineate a unified mechanistic paradigm underpinned by an experimentally determined, thermodynamically consistent energy landscape wherein the observed kinetic constraints for RWGS and WGS depend solely on the direction through which this landscape is traversed. These insights elucidate surface reactions, structural dynamics, and O atom transport underlying water–gas shift reactions on ceria under working conditions, providing a robust foundation for understanding how variations in chemical potential drive changes in oxygen content to enable efficient CO and CO2 conversions.
{"title":"Structural Dynamics and Energy Landscape of the Forward and Reverse Water–Gas Shift Catalytic Cycle on Ceria","authors":"Guangming Cai, Ya-Huei (Cathy) Chin","doi":"10.1021/acscatal.5c05030","DOIUrl":"https://doi.org/10.1021/acscatal.5c05030","url":null,"abstract":"The water–gas shift catalytic cycle (CO + H<sub>2</sub>O ⇄ CO<sub>2</sub> + H<sub>2</sub>), in both the forward (WGS) and reverse (RWGS) directions, is a classical reaction central to fuel and chemical synthesis that interconverts reductant-and-oxidant pairs (red + ox → ox′ + red′), i.e., in WGS, CO (red) to CO<sub>2</sub> (ox′) and H<sub>2</sub>O (ox) to H<sub>2</sub> (red′), and in RWGS, H<sub>2</sub> (red) to H<sub>2</sub>O (ox′) and CO<sub>2</sub> (ox) to CO (red′). Within this cycle, the energy landscape and kinetic relevance of the steps have not yet been fully established and reconciled, especially on oxide surfaces, simply due to their structural complexities and changing oxygen contents. Here, we establish the mechanistic framework and associated barriers for each step of the cycle, in both directions, on modeled ceria (CeO<sub>2</sub>) through kinetic interrogations under induction, steady-state, and transient regimes, each providing distinct thermodynamic and kinetic insights into the barriers of individual steps and intraparticle O-atom diffusion between surface and bulk, as the oxygen content in CeO<sub>2–<i>x</i></sub> varies (<i>x</i> = 0–0.2) and redistributes. In RWGS, surface O atom abstraction by H<sub>2</sub> is the sole kinetically relevant step on partially reduced CeO<sub>2–<i>x</i></sub> oxides (<i>x</i> = 0.024–0.038) with a barrier of 180 ± 3 kJ mol<sup>–1</sup>, determined from steady-state kinetics, whereas surface reoxidation by CO<sub>2</sub> at O-vacancies is rapid with an apparent activation energy of 51 ± 1 kJ mol<sup>–1</sup> that decreases with increasing O-vacancy formation energy, revealed by transient kinetic studies that decouple this step from the preceding kinetic bottleneck. In WGS, the reverse reaction, both surface O atom abstraction by CO (92 ± 21 kJ mol<sup>–1</sup>) and surface reoxidation by H<sub>2</sub>O (89 ± 6 kJ mol<sup>–1</sup>) are kinetically relevant, derived from steady-state rate measurements. Integrating findings from both reactions, we delineate a unified mechanistic paradigm underpinned by an experimentally determined, thermodynamically consistent energy landscape wherein the observed kinetic constraints for RWGS and WGS depend solely on the direction through which this landscape is traversed. These insights elucidate surface reactions, structural dynamics, and O atom transport underlying water–gas shift reactions on ceria under working conditions, providing a robust foundation for understanding how variations in chemical potential drive changes in oxygen content to enable efficient CO and CO<sub>2</sub> conversions.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"14 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2025-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145594165","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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