Pub Date : 2025-04-17DOI: 10.1021/acs.jpcc.4c08048
Nian Shi, Lili Hu, Shubin Chen, Jinjun Ren
Molybdate crystals tend to precipitate in nuclear waste glasses, significantly compromising their chemical and thermal stability, thereby rendering them unsuitable for long-term storage. However, the mechanisms by which glass composition influences the precipitation of molybdate crystals remain poorly understood. This study investigated this influence by preparing three series of molybdenum-doped sodium–calcium mixed aluminum borosilicate glasses using the melt-quenching technique. Solid-state nuclear magnetic resonance (SSNMR) spectroscopy, supplemented by Raman spectroscopy, was utilized to examine the glass structure at the atomic scale to reveal composition-dependent structural impacts on crystallization, while transmission electron microscopy (TEM) and X-ray diffraction (XRD) were employed to identify the precipitated crystals. The results demonstrate that increasing the Al2O3 content effectively suppresses molybdate crystal precipitation. It has been proven that high-valence cations differ in their ability to capture free oxygen, with the order of strength being Al3+ > Mo6+ > B3+ and Si4+. It is the strong ability of Al3+ to capture free oxygen and the formation of Al[4]–Ca2+–Mo[6] linkages that are responsible for inhibiting molybdate crystallization in the glass. An intriguing and important abnormal crystallization behavior was observed: a slight substitution of Na2O with CaO resulted in CaMO4 crystal precipitation, whereas larger substitutions paradoxically suppressed it. The findings reveal that in CaO–Na2O mixed aluminum borosilicate glasses, Al[4] preferentially attracts Na+ over Ca2+ to compensate for its negative charge. Meanwhile, Ca2+ ions are capable of forming an Al[4]–Ca2+–Mo[6] linkage, which Na+ ions cannot achieve. This fundamental difference results in the abnormal precipitation of CaMO4 crystals.
{"title":"Impact of Glass Compositions on Molybdate Crystallization in Borosilicate Glasses","authors":"Nian Shi, Lili Hu, Shubin Chen, Jinjun Ren","doi":"10.1021/acs.jpcc.4c08048","DOIUrl":"https://doi.org/10.1021/acs.jpcc.4c08048","url":null,"abstract":"Molybdate crystals tend to precipitate in nuclear waste glasses, significantly compromising their chemical and thermal stability, thereby rendering them unsuitable for long-term storage. However, the mechanisms by which glass composition influences the precipitation of molybdate crystals remain poorly understood. This study investigated this influence by preparing three series of molybdenum-doped sodium–calcium mixed aluminum borosilicate glasses using the melt-quenching technique. Solid-state nuclear magnetic resonance (SSNMR) spectroscopy, supplemented by Raman spectroscopy, was utilized to examine the glass structure at the atomic scale to reveal composition-dependent structural impacts on crystallization, while transmission electron microscopy (TEM) and X-ray diffraction (XRD) were employed to identify the precipitated crystals. The results demonstrate that increasing the Al<sub>2</sub>O<sub>3</sub> content effectively suppresses molybdate crystal precipitation. It has been proven that high-valence cations differ in their ability to capture free oxygen, with the order of strength being Al<sup>3+</sup> > Mo<sup>6+</sup> > B<sup>3+</sup> and Si<sup>4+</sup>. It is the strong ability of Al<sup>3+</sup> to capture free oxygen and the formation of Al<sup>[4]</sup>–Ca<sup>2+</sup>–Mo<sup>[6]</sup> linkages that are responsible for inhibiting molybdate crystallization in the glass. An intriguing and important abnormal crystallization behavior was observed: a slight substitution of Na<sub>2</sub>O with CaO resulted in CaMO<sub>4</sub> crystal precipitation, whereas larger substitutions paradoxically suppressed it. The findings reveal that in CaO–Na<sub>2</sub>O mixed aluminum borosilicate glasses, Al<sup>[4]</sup> preferentially attracts Na<sup>+</sup> over Ca<sup>2+</sup> to compensate for its negative charge. Meanwhile, Ca<sup>2+</sup> ions are capable of forming an Al<sup>[4]</sup>–Ca<sup>2+</sup>–Mo<sup>[6]</sup> linkage, which Na<sup>+</sup> ions cannot achieve. This fundamental difference results in the abnormal precipitation of CaMO<sub>4</sub> crystals.","PeriodicalId":61,"journal":{"name":"The Journal of Physical Chemistry C","volume":"8 1","pages":""},"PeriodicalIF":4.126,"publicationDate":"2025-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143842144","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-16DOI: 10.1021/acs.jpcc.5c00190
Oluwatosin Ohiro, Bryan R. Goldsmith
Atomically dispersed WOx on amorphous silica (WOx/SiO2) is known to be an active catalyst for olefin metathesis. There has been longstanding interest in determining the structure of the WOx/SiO2 active sites, the mechanism of their activation from their precursor state, and characterizing their activity toward olefin metathesis. Atomistic knowledge is lacking about the formation mechanism and the identity of the kinetically active W-alkylidene site for ethene/trans-2-butene (C2/C4) metathesis to produce propene (C3). Herein, we analyze the active site formation mechanism and C2/C4 metathesis kinetics for WOx/SiO2 using density functional theory calculations and mean-field microkinetic modeling. We predict that the pseudo-Wittig reaction is the predominant mechanism for W-alkylidene active site formation from the most-abundant W6+ digrafted dioxo precursor (S0) using either C2 or C4 as the activating reagent. Although the W-ethylidene site could be formed by C2 or C4 reacting with S0, the W-methylidene and W-butylidene sites are formed only through S0 activation with C2 and C4, respectively. Microkinetic analysis predicts that the W-methylidene site exhibits an order of magnitude higher rate constant for metathesis reaction to C3 compared to the W-ethylidene site.
{"title":"Atomistic Modeling of the Active Site Formation Mechanism and Olefin Metathesis Kinetics for WOx/SiO2","authors":"Oluwatosin Ohiro, Bryan R. Goldsmith","doi":"10.1021/acs.jpcc.5c00190","DOIUrl":"https://doi.org/10.1021/acs.jpcc.5c00190","url":null,"abstract":"Atomically dispersed WO<sub><i>x</i></sub> on amorphous silica (WO<sub><i>x</i></sub>/SiO<sub>2</sub>) is known to be an active catalyst for olefin metathesis. There has been longstanding interest in determining the structure of the WO<sub><i>x</i></sub>/SiO<sub>2</sub> active sites, the mechanism of their activation from their precursor state, and characterizing their activity toward olefin metathesis. Atomistic knowledge is lacking about the formation mechanism and the identity of the kinetically active W-alkylidene site for ethene/trans-2-butene (C<sub>2</sub>/C<sub>4</sub>) metathesis to produce propene (C<sub>3</sub>). Herein, we analyze the active site formation mechanism and C<sub>2</sub>/C<sub>4</sub> metathesis kinetics for WO<sub><i>x</i></sub>/SiO<sub>2</sub> using density functional theory calculations and mean-field microkinetic modeling. We predict that the pseudo-Wittig reaction is the predominant mechanism for W-alkylidene active site formation from the most-abundant W<sup>6+</sup> digrafted dioxo precursor (S<sub>0</sub>) using either C<sub>2</sub> or C<sub>4</sub> as the activating reagent. Although the W-ethylidene site could be formed by C<sub>2</sub> or C<sub>4</sub> reacting with S<sub>0</sub>, the W-methylidene and W-butylidene sites are formed only through S<sub>0</sub> activation with C<sub>2</sub> and C<sub>4</sub>, respectively. Microkinetic analysis predicts that the W-methylidene site exhibits an order of magnitude higher rate constant for metathesis reaction to C<sub>3</sub> compared to the W-ethylidene site.","PeriodicalId":61,"journal":{"name":"The Journal of Physical Chemistry C","volume":"108 1","pages":""},"PeriodicalIF":4.126,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143837220","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-16DOI: 10.1021/acs.jpcc.5c01338
Ute N. Gries, Zixuan Guan, Joe Kler, William C. Chueh, Roger A. De Souza
The influence of surface steps on the rate of oxygen surface exchange was investigated for a perovskite-type oxide by means of 18O2/16O2 exchange. Seven vicinal (100)-oriented single-crystal samples of acceptor-doped SrTiO3 with TiO2-terminated surfaces and miscut angles between 0 and 3° were used, giving a variation in step density (ρst) of a factor of approximately 7. All samples were subjected together to a single high-temperature isotope exchange anneal (at T = 1023 K in pO2 = 0.1 bar, with pH2O < 10–7 bar) and were then analyzed by time-of-flight secondary ion mass spectrometry (ToF-SIMS). Numerical descriptions of the isotope diffusion profiles yielded the oxygen tracer diffusion coefficient for the bulk (D*), the oxygen isotope exchange coefficient for the surface (k*), and the space-charge potential at the surface (Φ0). Surprisingly, the k* data exhibited no increase with increasing ρst, suggesting that surface steps do not strongly promote oxygen surface exchange in this system under these conditions. The behavior of Φ0 as a function of ρst is consistent with preferential formation of oxygen vacancies both at under-coordinated oxide-ion sites of terraces and at under-coordinated oxide-ion sites of step edges and terraces.
{"title":"Oxygen Surface Exchange on Stepped (100) Surfaces of Strontium Titanate","authors":"Ute N. Gries, Zixuan Guan, Joe Kler, William C. Chueh, Roger A. De Souza","doi":"10.1021/acs.jpcc.5c01338","DOIUrl":"https://doi.org/10.1021/acs.jpcc.5c01338","url":null,"abstract":"The influence of surface steps on the rate of oxygen surface exchange was investigated for a perovskite-type oxide by means of <sup>18</sup>O<sub>2</sub>/<sup>16</sup>O<sub>2</sub> exchange. Seven vicinal (100)-oriented single-crystal samples of acceptor-doped SrTiO<sub>3</sub> with TiO<sub>2</sub>-terminated surfaces and miscut angles between 0 and 3° were used, giving a variation in step density (ρ<sub>st</sub>) of a factor of approximately 7. All samples were subjected together to a single high-temperature isotope exchange anneal (at <i>T</i> = 1023 K in <i>p</i>O<sub>2</sub> = 0.1 bar, with <i>p</i>H<sub>2</sub>O < 10<sup>–7</sup> bar) and were then analyzed by time-of-flight secondary ion mass spectrometry (ToF-SIMS). Numerical descriptions of the isotope diffusion profiles yielded the oxygen tracer diffusion coefficient for the bulk (<i>D</i>*), the oxygen isotope exchange coefficient for the surface (<i>k</i>*), and the space-charge potential at the surface (Φ<sub>0</sub>). Surprisingly, the <i>k</i>* data exhibited no increase with increasing ρ<sub>st</sub>, suggesting that surface steps do not strongly promote oxygen surface exchange in this system under these conditions. The behavior of Φ<sub>0</sub> as a function of ρ<sub>st</sub> is consistent with preferential formation of oxygen vacancies both at under-coordinated oxide-ion sites of terraces and at under-coordinated oxide-ion sites of step edges and terraces.","PeriodicalId":61,"journal":{"name":"The Journal of Physical Chemistry C","volume":"38 1","pages":""},"PeriodicalIF":4.126,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143841872","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-16DOI: 10.1021/acs.jpcc.5c01081
Xiang Chen, Shaohua Chen, Pengxin Liu, Chaodan Pu
We report the efficient C–C coupling between benzyl alcohol and benzaldehyde to hydrobenzoin using CdSe/CdS quantum dots as visible-light photocatalysts and sodium oxide as a cocatalyst. The optimized conditions resulted in a reaction with a selectivity of hydrobenzoin >95%, an apparent quantum yield of 23.6% under the excitation by 520 nm LED, and a turnover frequency of 56.8 mmol g–1 h–1. Reactant concentration-dependent experiments demonstrated that benzaldehyde can process fast proton-coupled electron transfer, improving the utilization of photogenerated electrons. Photoluminescence quenching experiments and reactions with deuterated benzaldehyde confirmed that due to the in situ produced hydrogen ions, the hydroxymethyl radicals would process efficient reverse conversion from hydroxymethyl radicals to benzyl alcohol, resulting in noneffective charge transfer. Formation of sodium benzyloxide can eliminate the in situ produced hydrogen ions around the hydroxymethyl radical, suppressing this reverse conversion and improving the utilization efficiency of transferred holes and electrons.
{"title":"Suppressing Reverse Radical Conversion via Diluting Local Hydrogen Ions for Efficient Photocatalyzed C–C Coupling between Benzyl Alcohol and Benzaldehyde","authors":"Xiang Chen, Shaohua Chen, Pengxin Liu, Chaodan Pu","doi":"10.1021/acs.jpcc.5c01081","DOIUrl":"https://doi.org/10.1021/acs.jpcc.5c01081","url":null,"abstract":"We report the efficient C–C coupling between benzyl alcohol and benzaldehyde to hydrobenzoin using CdSe/CdS quantum dots as visible-light photocatalysts and sodium oxide as a cocatalyst. The optimized conditions resulted in a reaction with a selectivity of hydrobenzoin >95%, an apparent quantum yield of 23.6% under the excitation by 520 nm LED, and a turnover frequency of 56.8 mmol g<sup>–1</sup> h<sup>–1</sup>. Reactant concentration-dependent experiments demonstrated that benzaldehyde can process fast proton-coupled electron transfer, improving the utilization of photogenerated electrons. Photoluminescence quenching experiments and reactions with deuterated benzaldehyde confirmed that due to the in situ produced hydrogen ions, the hydroxymethyl radicals would process efficient reverse conversion from hydroxymethyl radicals to benzyl alcohol, resulting in noneffective charge transfer. Formation of sodium benzyloxide can eliminate the in situ produced hydrogen ions around the hydroxymethyl radical, suppressing this reverse conversion and improving the utilization efficiency of transferred holes and electrons.","PeriodicalId":61,"journal":{"name":"The Journal of Physical Chemistry C","volume":"2 1","pages":""},"PeriodicalIF":4.126,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143837200","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-16DOI: 10.1021/acs.jpcc.4c08038
Anna Vidal-López, Joan Gassó-Capdevila, Miquel Solà, Albert Poater, Sergio Posada-Pérez
The conversion of carbon dioxide (CO2) into valuable products represents a promising strategy to mitigate CO2 emissions and enable sustainable energy storage. However, the development of efficient and selective catalysts for the electrocatalytic reduction of CO2 (CO2RR) remains a significant challenge. In this study, we explore the performance of first-row transition metal single atoms anchored on g-C3N4 monolayers as potential catalysts for the CO2RR. We employed density functional theory (DFT) calculations to investigate the hydrogen evolution reaction (HER) as a competing pathway to the CO2RR. Only the candidates that suppress the HER are promising candidates for the selective CO2RR. Our results indicate that Ni1/C3N4 emerges as the most promising catalyst due to its relatively moderate-to-high overpotential for the HER and a favorable reaction pathway that favors CO production through the HCOO* intermediate. Despite some challenges, such as the strong Ni–CO interaction hindering CO desorption, Ni1/C3N4 presents a viable route for CO2RR. Mn and Co single atoms exhibit slighly lower overpotential toward HER, overcoming one of the main limitations to be active and selective for CO2RR. Nevertheless, Co1/C3N4 shows large energy barriers for CO hydrogenation and HCOOH production, while Mn1/C3N4 opens the route for formic acid production. This work highlights the importance of evaluating the HER alongside the CO2RR to identify catalysts with optimal selectivity and efficiency.
{"title":"Hydrogen Evolution and Carbon Dioxide Reduction Pathways on Graphitic Carbon Nitride Decorated by Single Atoms of Transition Metals‡","authors":"Anna Vidal-López, Joan Gassó-Capdevila, Miquel Solà, Albert Poater, Sergio Posada-Pérez","doi":"10.1021/acs.jpcc.4c08038","DOIUrl":"https://doi.org/10.1021/acs.jpcc.4c08038","url":null,"abstract":"The conversion of carbon dioxide (CO<sub>2</sub>) into valuable products represents a promising strategy to mitigate CO<sub>2</sub> emissions and enable sustainable energy storage. However, the development of efficient and selective catalysts for the electrocatalytic reduction of CO<sub>2</sub> (CO<sub>2</sub>RR) remains a significant challenge. In this study, we explore the performance of first-row transition metal single atoms anchored on g-C<sub>3</sub>N<sub>4</sub> monolayers as potential catalysts for the CO<sub>2</sub>RR. We employed density functional theory (DFT) calculations to investigate the hydrogen evolution reaction (HER) as a competing pathway to the CO<sub>2</sub>RR. Only the candidates that suppress the HER are promising candidates for the selective CO<sub>2</sub>RR. Our results indicate that Ni<sub>1</sub>/C<sub>3</sub>N<sub>4</sub> emerges as the most promising catalyst due to its relatively moderate-to-high overpotential for the HER and a favorable reaction pathway that favors CO production through the HCOO* intermediate. Despite some challenges, such as the strong Ni–CO interaction hindering CO desorption, Ni<sub>1</sub>/C<sub>3</sub>N<sub>4</sub> presents a viable route for CO<sub>2</sub>RR. Mn and Co single atoms exhibit slighly lower overpotential toward HER, overcoming one of the main limitations to be active and selective for CO<sub>2</sub>RR. Nevertheless, Co<sub>1</sub>/C<sub>3</sub>N<sub>4</sub> shows large energy barriers for CO hydrogenation and HCOOH production, while Mn<sub>1</sub>/C<sub>3</sub>N<sub>4</sub> opens the route for formic acid production. This work highlights the importance of evaluating the HER alongside the CO<sub>2</sub>RR to identify catalysts with optimal selectivity and efficiency.","PeriodicalId":61,"journal":{"name":"The Journal of Physical Chemistry C","volume":"238 1","pages":""},"PeriodicalIF":4.126,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143837219","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-16DOI: 10.1021/acs.jpcc.5c00439
Yogesh Pokhrel, Meike Tack, Matteo Levantino, Sven Reichenberger, Anton Plech
The laser-induced fragmentation of colloidal nanoparticles represents a well-established method to obtain surfactant-free nanoclusters in liquids. While the typical fragmentation mechanisms for nanosecond and picosecond laser excitation have been linked to photothermal heating–melting evaporation and phase explosion processes (depending on the applied laser energy density), the subsequent growth processes on longer nano- to microsecond time scales and beyond remain mostly elusive. In the past, first insights into the role of electrostatic interactions between the formed nanoclusters mediated by inorganic salts have been highlighted. In this study, we intend to extend this concept toward the role of supporting particles with a high surface area such as graphene oxide to augment or quench growth processes. Compared with the laser fragmentation of gold nanoparticles in the absence of GO, larger final particle sizes of the formed clusters were observed when GO was present. Given the electrostatic repulsion between GO and Au clusters at a given pH value, the GO sheets take part in the fragmentation process by electrostatically confining the fragmented clusters that form during the laser-induced phase explosion of the initial gold nanoparticles. Consequently, larger final cluster sizes were observed in the presence of GO under electrostatically repulsive conditions.
{"title":"Caging Effect of Unbound Graphene Oxide Nanosheets during Gold Colloid Fragmentation under Electrostatic Repulsion","authors":"Yogesh Pokhrel, Meike Tack, Matteo Levantino, Sven Reichenberger, Anton Plech","doi":"10.1021/acs.jpcc.5c00439","DOIUrl":"https://doi.org/10.1021/acs.jpcc.5c00439","url":null,"abstract":"The laser-induced fragmentation of colloidal nanoparticles represents a well-established method to obtain surfactant-free nanoclusters in liquids. While the typical fragmentation mechanisms for nanosecond and picosecond laser excitation have been linked to photothermal heating–melting evaporation and phase explosion processes (depending on the applied laser energy density), the subsequent growth processes on longer nano- to microsecond time scales and beyond remain mostly elusive. In the past, first insights into the role of electrostatic interactions between the formed nanoclusters mediated by inorganic salts have been highlighted. In this study, we intend to extend this concept toward the role of supporting particles with a high surface area such as graphene oxide to augment or quench growth processes. Compared with the laser fragmentation of gold nanoparticles in the absence of GO, larger final particle sizes of the formed clusters were observed when GO was present. Given the electrostatic repulsion between GO and Au clusters at a given pH value, the GO sheets take part in the fragmentation process by electrostatically confining the fragmented clusters that form during the laser-induced phase explosion of the initial gold nanoparticles. Consequently, larger final cluster sizes were observed in the presence of GO under electrostatically repulsive conditions.","PeriodicalId":61,"journal":{"name":"The Journal of Physical Chemistry C","volume":"6 1","pages":""},"PeriodicalIF":4.126,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143841828","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-16DOI: 10.1021/acs.jpcc.5c0096810.1021/acs.jpcc.5c00968
Leah Ford, Ryan Burrows, Nicolas Raffaele and Nicholas A. Brunelli*,
Advancing the catalytic capabilities of zeolites like Sn-β requires a detailed understanding of the synthesis-structure–reactivity relationships. Sn-β is intriguingly complex, as it contains different types of catalytic sites that have been identified as the prominent active sites for different reactions. Previous work has indicated that the catalytic sites in Sn-β are affected by the composition and conditions during hydrothermal crystallization, forming a distribution of catalytic sites that are stable postsynthesis. However, our work reveals that postsynthetic transformations can occur at the catalytic sites, increasing activity in epoxide ring opening (ERO) of epichlorohydrin with methanol by a factor of 3. Specifically, when the calcination step is delayed, the catalytic sites transform. Standard characterization techniques demonstrate that bulk properties of the Sn-β are consistent for the batches calcined at different times, but 31P NMR measurements of materials dosed with trimethyl phosphine oxide reveal that the site distribution changes when calcination is delayed. After delaying calcination 14 or 21 days, Sn-β is determined to have 80% open-defect sites, a significant increase from the 50% observed for conventional materials. Sn-β with elevated quantities of open-defect sites then show an improvement in ERO activity over postcalcination time, suggesting a second transformation after calcination. Overall, the results demonstrate that Sn-β undergoes a dynamic process postsynthesis, and this work strengthens the connection between open-defect sites and ERO activity.
{"title":"Catalytic Site Dynamics in Sn-β Zeolites: A Time-Dependent Study of the Site Structure","authors":"Leah Ford, Ryan Burrows, Nicolas Raffaele and Nicholas A. Brunelli*, ","doi":"10.1021/acs.jpcc.5c0096810.1021/acs.jpcc.5c00968","DOIUrl":"https://doi.org/10.1021/acs.jpcc.5c00968https://doi.org/10.1021/acs.jpcc.5c00968","url":null,"abstract":"<p >Advancing the catalytic capabilities of zeolites like Sn-β requires a detailed understanding of the synthesis-structure–reactivity relationships. Sn-β is intriguingly complex, as it contains different types of catalytic sites that have been identified as the prominent active sites for different reactions. Previous work has indicated that the catalytic sites in Sn-β are affected by the composition and conditions during hydrothermal crystallization, forming a distribution of catalytic sites that are stable postsynthesis. However, our work reveals that postsynthetic transformations can occur at the catalytic sites, increasing activity in epoxide ring opening (ERO) of epichlorohydrin with methanol by a factor of 3. Specifically, when the calcination step is delayed, the catalytic sites transform. Standard characterization techniques demonstrate that bulk properties of the Sn-β are consistent for the batches calcined at different times, but <sup>31</sup>P NMR measurements of materials dosed with trimethyl phosphine oxide reveal that the site distribution changes when calcination is delayed. After delaying calcination 14 or 21 days, Sn-β is determined to have 80% open-defect sites, a significant increase from the 50% observed for conventional materials. Sn-β with elevated quantities of open-defect sites then show an improvement in ERO activity over postcalcination time, suggesting a second transformation after calcination. Overall, the results demonstrate that Sn-β undergoes a dynamic process postsynthesis, and this work strengthens the connection between open-defect sites and ERO activity.</p>","PeriodicalId":61,"journal":{"name":"The Journal of Physical Chemistry C","volume":"129 16","pages":"7787–7794 7787–7794"},"PeriodicalIF":3.3,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143863219","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-16DOI: 10.1021/acs.jpcc.5c01352
Yang Wang, Tongtong Luo, Yu Mu, Michael Goldstein, James Wilkes, Brooke Elander, Dunwei Wang, Udayan Mohanty, Junwei Lucas Bao
The inherent instability and low solubility of polysulfides in Mg-based electrolytes contribute to the poor performance of magnesium–sulfur (Mg–S) battery systems. To address these challenges, we utilize a combination of first-principle theory, spectroscopy, and electrochemical measurements to investigate the chemistry of Mg polysulfides. Our study reveals the critical role of polysulfide species present in the battery electrolyte in determining electrochemical stability and performance. Through detailed atomistic-level explorations of polysulfide conformations and their role in Mg–S chemistry, corroborated by experiments, we discover that the disproportionation of long-chain Mg polysulfides into shorter-chain compounds is thermodynamically favored at room temperature. In contrast, multiple polysulfide radical species can form under electrochemical conditions. Meanwhile, the dissociation of Mg2+ from the coordinating polysulfide anions is highly unfavorable regardless of the solvent used. Our theoretical predictions for UV–vis, Raman, and electron paramagnetic resonance (EPR) spectra, which account for the full ensemble of polysulfide conformers and species at thermodynamic equilibrium, align well with experimental data and facilitate reference peak assignments for future in situ studies of Mg–S systems. Furthermore, we separate the electrochemical contributions from the entire conformational ensemble by calculating the reduction potentials for the dominant Mg polysulfide species to clarify the principal redox pathways during the electrochemical cycling of Mg–S batteries. This theoretical electrochemical data is applied to explain key features in the discharge curve of an experimental Mg–S electrochemical cell. Our integrated approach provides important insights into the mechanistic behavior of Mg polysulfides in electrochemical systems. In particular, by dissecting the conformer-dependent thermal and electrochemical reactivities of Mg2+-polysulfide complexes, we enhance the fundamental understanding of their chemistry and establish new foundations for optimizing Mg–S battery design.
{"title":"Conformational Flexibility Dictates Thermal and Electrochemical Reactivities of Magnesium Polysulfides for Magnesium–Sulfur Battery Applications","authors":"Yang Wang, Tongtong Luo, Yu Mu, Michael Goldstein, James Wilkes, Brooke Elander, Dunwei Wang, Udayan Mohanty, Junwei Lucas Bao","doi":"10.1021/acs.jpcc.5c01352","DOIUrl":"https://doi.org/10.1021/acs.jpcc.5c01352","url":null,"abstract":"The inherent instability and low solubility of polysulfides in Mg-based electrolytes contribute to the poor performance of magnesium–sulfur (Mg–S) battery systems. To address these challenges, we utilize a combination of first-principle theory, spectroscopy, and electrochemical measurements to investigate the chemistry of Mg polysulfides. Our study reveals the critical role of polysulfide species present in the battery electrolyte in determining electrochemical stability and performance. Through detailed atomistic-level explorations of polysulfide conformations and their role in Mg–S chemistry, corroborated by experiments, we discover that the disproportionation of long-chain Mg polysulfides into shorter-chain compounds is thermodynamically favored at room temperature. In contrast, multiple polysulfide radical species can form under electrochemical conditions. Meanwhile, the dissociation of Mg<sup>2+</sup> from the coordinating polysulfide anions is highly unfavorable regardless of the solvent used. Our theoretical predictions for UV–vis, Raman, and electron paramagnetic resonance (EPR) spectra, which account for the full ensemble of polysulfide conformers and species at thermodynamic equilibrium, align well with experimental data and facilitate reference peak assignments for future in situ studies of Mg–S systems. Furthermore, we separate the electrochemical contributions from the entire conformational ensemble by calculating the reduction potentials for the dominant Mg polysulfide species to clarify the principal redox pathways during the electrochemical cycling of Mg–S batteries. This theoretical electrochemical data is applied to explain key features in the discharge curve of an experimental Mg–S electrochemical cell. Our integrated approach provides important insights into the mechanistic behavior of Mg polysulfides in electrochemical systems. In particular, by dissecting the conformer-dependent thermal and electrochemical reactivities of Mg<sup>2+</sup>-polysulfide complexes, we enhance the fundamental understanding of their chemistry and establish new foundations for optimizing Mg–S battery design.","PeriodicalId":61,"journal":{"name":"The Journal of Physical Chemistry C","volume":"3 1","pages":""},"PeriodicalIF":4.126,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143841829","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
As gamma irradiation is helpful to control the morphology and structure of metal nanoparticles anchored on carbon materials, it is expected to be one of the alternatives for the preparation of shaped Pt-based catalysts for its oxygen reduction reaction (ORR) performance free of shape inducer. In this work, to study the morphological evolution mechanism of platinum nanoparticles (PtNPs) and its influence on the catalytic behavior of the catalyst, different doses of γ rays were employed to prepare the polygonal angle PtNP composites assisted with in situ hydrolysis of urea. γ Rays can induce the generation of reducing free radicals in solution to reduce metal ions and have a fragmentation effect on metal particles, which is beneficial for the formation of polygonal PtNPs. The samples with polygonal angle PtNPs demonstrated an excellent ORR performance with enhanced onset potential (908 mV), half-wave potential (821 mV), and superior limit current density (6.65 mA·cm–2) compared with the spherical PtNP catalysts. The enhanced ORR performance is attributed to the synergistic effect of pyridine N in reduced graphene oxide and the change in the structural morphology of PtNPs, which provides more catalytic active sites. The results indicate that the structural morphology of PtNPs under different doses of gamma irradiation is of great significance for the final performance of the obtained catalyst.
{"title":"Morphology Control of Pt Nanoparticles Loaded with Nitrogen-Doped Reduced Graphene Oxide Induced by γ Rays for Oxygen Reduction Reaction","authors":"Wei Wang, Zhishen Wang, Xiaomeng Zhao, Ming Zeng, Shengkai Liu, Zhiwei Xu","doi":"10.1021/acs.jpcc.5c01686","DOIUrl":"https://doi.org/10.1021/acs.jpcc.5c01686","url":null,"abstract":"As gamma irradiation is helpful to control the morphology and structure of metal nanoparticles anchored on carbon materials, it is expected to be one of the alternatives for the preparation of shaped Pt-based catalysts for its oxygen reduction reaction (ORR) performance free of shape inducer. In this work, to study the morphological evolution mechanism of platinum nanoparticles (PtNPs) and its influence on the catalytic behavior of the catalyst, different doses of γ rays were employed to prepare the polygonal angle PtNP composites assisted with in situ hydrolysis of urea. γ Rays can induce the generation of reducing free radicals in solution to reduce metal ions and have a fragmentation effect on metal particles, which is beneficial for the formation of polygonal PtNPs. The samples with polygonal angle PtNPs demonstrated an excellent ORR performance with enhanced onset potential (908 mV), half-wave potential (821 mV), and superior limit current density (6.65 mA·cm<sup>–2</sup>) compared with the spherical PtNP catalysts. The enhanced ORR performance is attributed to the synergistic effect of pyridine N in reduced graphene oxide and the change in the structural morphology of PtNPs, which provides more catalytic active sites. The results indicate that the structural morphology of PtNPs under different doses of gamma irradiation is of great significance for the final performance of the obtained catalyst.","PeriodicalId":61,"journal":{"name":"The Journal of Physical Chemistry C","volume":"7 1","pages":""},"PeriodicalIF":4.126,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143841875","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-16DOI: 10.1021/acs.jpcc.5c01670
Anastasiya A. Yazikova, Aleksandr S. Tomilov, Nikita A. Afimchenko, Igor L. Zilberberg, Anatoly R. Melnikov, Kristina A. Smirnova, Artem S. Poryvaev, Matvey V. Fedin
Development of viable quantum bits (qubits) is currently among the main challenges in quantum technologies. One approach to this problem that utilizes the potential of synthetic chemistry is the creation of molecular spin qubits (MSQs). Metal–organic frameworks (MOFs) are promising materials for scaling up MSQ systems while also exhibiting useful sorption properties. We report the adsorption of paramagnetic nitric oxide (NO) in MOF-808 and its modifications and for the first time propose an adsorbed “gas@MOF” concept to design MSQs. Continuous-wave electron paramagnetic resonance (CW EPR) allowed monitoring of the NO adsorption process that occurs at temperatures below 150 K and leads to immobilization of NO molecules within the MOF-808 matrix. Electron decoherence times Tm acquired by pulse EPR were found sufficiently long to perform simple spin manipulations (∼1.5 μs), which was demonstrated by a Rabi-oscillation experiment. Thus, gas molecules adsorbed in MOFs, “gas@MOF”, can act as potential spin qubits, as was exemplified by NO@MOF-808 as a proof of principle, and can be further extended to other paramagnetic gases and various MOFs.
{"title":"Paramagnetic Gas Adsorbed in Metal–Organic Framework: A Promising Platform for Spin Qubits Design","authors":"Anastasiya A. Yazikova, Aleksandr S. Tomilov, Nikita A. Afimchenko, Igor L. Zilberberg, Anatoly R. Melnikov, Kristina A. Smirnova, Artem S. Poryvaev, Matvey V. Fedin","doi":"10.1021/acs.jpcc.5c01670","DOIUrl":"https://doi.org/10.1021/acs.jpcc.5c01670","url":null,"abstract":"Development of viable quantum bits (qubits) is currently among the main challenges in quantum technologies. One approach to this problem that utilizes the potential of synthetic chemistry is the creation of molecular spin qubits (MSQs). Metal–organic frameworks (MOFs) are promising materials for scaling up MSQ systems while also exhibiting useful sorption properties. We report the adsorption of paramagnetic nitric oxide (NO) in MOF-808 and its modifications and for the first time propose an adsorbed “gas@MOF” concept to design MSQs. Continuous-wave electron paramagnetic resonance (CW EPR) allowed monitoring of the NO adsorption process that occurs at temperatures below 150 K and leads to immobilization of NO molecules within the MOF-808 matrix. Electron decoherence times <i>T</i><sub>m</sub> acquired by pulse EPR were found sufficiently long to perform simple spin manipulations (∼1.5 μs), which was demonstrated by a Rabi-oscillation experiment. Thus, gas molecules adsorbed in MOFs, “gas@MOF”, can act as potential spin qubits, as was exemplified by NO@MOF-808 as a proof of principle, and can be further extended to other paramagnetic gases and various MOFs.","PeriodicalId":61,"journal":{"name":"The Journal of Physical Chemistry C","volume":"58 1","pages":""},"PeriodicalIF":4.126,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143841873","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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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