ChemSusChem最新文献

CO₂ electroreduction (CO₂R) using Cu catalysts under acidic conditions currently receives substantial attention as it allows to limit detrimental (bi)carbonate salts formation and precipitation. However, it usually requires high concentrations of K-based electrolytes for suppressing hydrogen evolution (HER) and favoring C₂ products formation. Here we used crown-ethers in order to immobilize alkali cations at the surface of the catalyst and show that this strategy not only allows suppressing HER with much less concentrated electrolyte but also orientates the reaction towards CH₄ formation during acidic CO₂R. The utilization of 10 different crown-ethers allowed to study the effect of the structure of the ligand and the nature of the cation on CO₂R selectivity. The largest Faradic Efficiency for methane (FE_CH4 = 55%) was obtained under an applied current density of −150 mA.cm⁻², using the 4′-amino-benzo-15-crown-5-Na⁺ complex.

Aluminum–sulfur (Al–S) batteries are garnering significant interest as candidates for affordable energy storage systems due to their high theoretical capacity of 1672 mAh g^–1 and the cost-effectiveness of naturally abundant aluminum and sulfur. Nevertheless, challenges such as poor cyclic reversibility and limited practical capacity have resulted in only a few reversibly operating Al–S cells to date. In this study, we introduce an improved Al–S battery configuration by incorporating a novel VN@graphene catalyst into the sulfur cathode in Al–S battery applications. Comprehensive electrochemical tests and ex situ characterizations reveal that, during discharge, the catalyst effectively suppresses the polysulfide shuttle effect through strong adsorption, whereas during charging, it enhances sulfide redox kinetics. Consequently, the modified Al–S cell delivers an initial capacity of approximately 1354 mAh g^–1, maintaining around 507 mAh g^–1 after 200 cycles.

Green hydrogen adoption demands intensive research efforts focusing on improving the performance and durability of electrodes used in water electrolyzers, enabling cheaper hydrogen production on a commercial scale. For catalyzing the oxygen evolution (OER) and hydrogen evolution (HER) electrode reactions in a water electrolyzer, the state-of-the-art electrocatalysts used are expensive and scarce, thus preventing their successful commercialization. There is a dire-need to replace those expensive catalysts with cheaper, earth-abundant non-platinum group of transition metals. Heterointerface engineering could be employed as an effective strategy to synthesize such kind of electrocatalysts to tune the electronic and catalytic properties of these environmentally friendly transition metal electrocatalysts. In this report, we have studied the heterointerface formation between Ni₃S₂ and MnO₂ phases using two synthesis approaches: sequential as well as simultaneous growth methods. Our studies show that sequential growth exhibits a critical impact on the chemical and electrocatalytic behavior of the as-synthesized vertically aligned nanoflakes. When Ni₃S₂ was grown over the MnO₂ phase, it resulted in the most superior bifunctional electrocatalytic activity. Along with the electrical impedance measurement, X-ray photoelectron spectroscopy and Raman spectroscopy reveal that the interfacial charge transfer due to heterointerface formation via sequential growth is more effective than the simultaneous method of heterojunction preparation. The best catalyst exhibits a lowering of OER overpotentials of 300 mV and HER onset overpotentials of 230 mV, surpassing the standard catalysts. DFT study has been performed to correlate the experimental and theoretical reaction kinetics over Ni₃S₂@MnO₂@NF heterointerfaces, which suggests a lower overpotential of 1.391 V when Ni₃S₂ is grown over MnO₂ for OER as compared with the MnO₂ (1.719 V) grown over Ni₃S₂. Ni₃S₂@MnO₂@NF electrodes registered a low cell voltage of 1.68 V at 10 mA cm⁻² current density in an alkaline water electrolysis prototype, performing better than the standard catalyst in terms of cell voltage and operation stability at higher current densities of up to 50 mA cm⁻². This study shows how strategic design of interfaces in heterojunction can control the overall catalytic performance.

Late-stage functionalization (LSF) enables the direct, site-selective modification of complex molecules and has become a key strategy in sustainable drug discovery and chemical biology. While homogeneous photocatalysis has traditionally dominated this field, recent advances in materials engineering and catalyst design have triggered a new interest in heterogeneous photocatalysis. Although classical heterogeneous photocatalysts such as metal oxides and carbon nitrides are long established, their nanoscale re-engineering and integration into LSF have only recently enabled enhanced reactivity, selectivity, and recyclability. This review surveys the recent evolution of heterogeneous photocatalytic systems, from traditional semiconductors to covalent organic frameworks and metal–organic frameworks, for selective LSF. By connecting developments in materials chemistry with photoredox catalysis, this contribution highlights the growing potential of heterogeneous photocatalysts as scalable and sustainable platforms for complex molecule synthesis.

Elemental first row transition metal electrocatalysts typically exhibit a tradeoff between Faradaic efficiency (FE) for the nitrate reduction reaction (NO₃RR) and selectivity toward NH₄⁺. Here, we find that NiFe alloys have high NO₃RR FE and substantially higher NH₄⁺ selectivity than Ni or Fe. We introduce “relative nitrate adsorption,” a simple descriptor of the difference in NO₃* and H* binding strength that rationalizes experimental trends in reaction rate order. This descriptor is consistent with competitive adsorption demonstrated in a microkinetic model that shows Fe inclusion promotes NO₃* adsorption and increased NO₃RR FE, but cannot describe the higher NH₄⁺ selectivity observed for NiFe alloys. In fact, calculated activation energies of subsequent reduction steps illustrate that no one active site motif can explain both improved FE and NH₄⁺ selectivity. Instead, our experimental and computational findings indicate NO₂* deoxygenation is promoted by Ni-rich active sites, whereas NO* dissociation is promoted by both surface Fe atoms and an underlying Fe lattice. These findings suggest that NiFe alloys leverage local site diversity via a spillover mechanism, explaining why the performance enhancements are similar regardless of the specific Ni/Fe ratio.

Organic carbonates play a central role as functional platform molecules for the manufacture of materials and chemicals. The atom-economical formation of cyclic carbonates from epoxides and CO₂ under mild catalytic conditions is a prime example of the concept of green chemistry. However, the sustainability of such strategies is often limited by the unfavorable parameters of the epoxide formation from olefin oxidation. Herein, a new, highly sustainable, triple-catalytic approach to the formation of biogenic cyclic carbonates from all-natural building blocks is documented. Three biogenic resources (fatty acid derivatives, O₂, CO₂) are combined with 100% atom-economy in the presence of easily accessible catalysts (porphyrin, VO(acac)₂, pyridine). Key step is a photo-oxygenation with full incorporation of O₂ into hydrocarbons. Use of the resultant cyclic carbonates in the synthesis of environmentally benign non-isocyanate polyurethanes is demonstrated.

Mechanochemical extrusion provides a sustainable and efficient approach for the preparation of mono- and bimetallic palladium and copper catalysts supported on nitrogen-doped carbons. In this study, palladium and copper mono- and bimetallic catalysts were synthesized via solvent-free extrusion and thoroughly characterized by XRD, HRTEM, N₂ physisorption, and XPS, revealing uniformly dispersed nanoparticles with strong metal–support and metal–metal interactions. The catalysts were evaluated in the model Sonogashira coupling of iodobenzene with phenylacetylene under continuous mechanochemical extrusion. The bimetallic Pd-Cu system exhibited superior activity and selectivity, effectively suppressing side reactions, such as phenylacetylene dimerization. A comprehensive parametric study, as well as analyses of substrate extent and catalyst recyclability, highlighted the crucial role of mechanical energy in enabling these transformations. Moreover, the dimerization of phenylacetylene was separately investigated, providing further insight into the formation of the corresponding dimer. Overall, these results demonstrate the ability of extrusion to finely control catalyst properties, optimize catalyst-substrate interactions, and offer a sustainable, solvent-free route to high-performance heterogeneous catalysts suitable for continuous-flow applications.

Precious metals are indispensable for applications ranging from catalysis to electronics; however, their limited availability and the environmental burden of conventional recovery methods raise urgent sustainability concerns. Herein, we propose a single-atom catalysis strategy that enables the efficient and selective recovery of Pd, Pt, Rh, and Au from industrial spent catalysts, ternary automotive catalysts, and electronic waste. Atomically dispersed Co sites activate peroxymonosulfate to generate multiple reactive O species, resulting in the rapid oxidative leaching of precious metals under mild conditions without the use of strong acids, toxic cyanide, or external irradiation. Mechanistic analyses reveal that both radical and nonradical pathways mediated by single-atom catalysts drive the oxidative leaching of precious metals. The experimental catalyst maintains atomic dispersion and activity over multiple recycling cycles, and its integration into a semi-continuous flow apparatus demonstrates its scalability and economic feasibility. By coupling atomic-level catalytic design with practical recovery performance, this study offers a green and sustainable platform for precious metal recycling and contributes to advancing circular economy strategies for resource efficiency.

With the increasing demand for sustainable plastic materials, the implementation of a circular plastics economy starting from designing environmentally friendly polymers and including effective recycling strategies is of the utmost importance. The biobased and biodegradable polyester polylactide (PLA) is a promising candidate for a sustainable, circular plastics economy. Polyesters can be chemically recycled to obtain monomers or value-added chemicals following either a closed- or open-loop recycling approach. However, the requirements for catalysts applicable in post-consumer waste recycling are high: Besides a high activity, robustness and scalability of the catalyst are important factors. We studied highly active, robust bisguanidine organocatalysts for the depolymerization of the polyesters polycaprolactone, polyethylene terephthalate, and PLA. Focusing on PLA, we investigated the structure–reactivity relationship of the length of the aliphatic linker between the guanidine functionalities to identify the most active catalyst: Bis(N,N,N′,N′-tetramethylguanidino)ethane (TMG₂e) depolymerizes PLA completely via alcoholysis within minutes under mild reaction conditions. The bisguanidine shows excellent activity for the alcoholysis of the investigated polymers, the ability to depolymerize binary and ternary plastic mixes, and robustness against additives, plasticizers, and other impurities in different post-consumer waste samples. Thus, TMG₂e has promising properties to be an asset for the implementation of a sustainable, circular plastics economy.

Catalytic copyrolysis of mixed plastic waste presents an attractive route for sustainable chemical recovery from difficult-to-recycle polymers. In this study, we investigated the aromatic product distribution from thermal and catalytic copyrolysis of polyethylene terephthalate (PET) and polypropylene (PP) using Py-GC-MS/FID. The synergistic interaction between PET and PP was minimal under noncatalytic copyrolysis. In contrast, HY and HZSM-5 zeolites significantly upgraded the pyrolysis vapors by enhancing aromatic formation during copyrolysis. Specifically, HZSM-5 exhibited a high selectivity toward benzenes and napthalenes, whereas HY favored the formation of value-added oxygen-containing aromatics such as benzaldehyde. Further, the intrinsic interaction was elucidated for the catalytic copyrolysis. The formation of alkylbenzenes and simple polycyclic aromatic hydrocarbons during catalytic copyrolysis over both catalysts showed a positive synergistic effect, which was ascribed to alkylation reaction and hydrocarbon pool mechanism. In the presence of HY, aromatization during PP cracking generated substantial hydrogen, which stabilized PET-derived aromatic radicals and reduced catalyst coking, and thereby increased the detectable volatiles. This resulted in a positive synergistic effect on all aromatics, with benzaldehyde showing a particularly notable increase. This work deepens the understanding of the catalytic copyrolysis mechanism and supports its potential in upcycling mixed plastic waste into high-value aromatics.