EES catalysis最新文献

Correction for ‘High photocatalytic yield in the non-oxidative coupling of methane using a Pd–TiO₂ nanomembrane gas flow-through reactor’ by Victor Longo et al., EES. Catal., 2024, 2, 1164–1175, https://doi.org/10.1039/D4EY00112E.

Platinum dissolution is one of the primary factors affecting the stability of Pt-based catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). It is a significant challenge to prevent the dissolution of Pt and enhance the durability of Pt-based catalysts. In this study, we employed a one-step rapid Joule thermal shock method to fabricate a stable ORR catalyst with embedded Pt₅Ce alloy (E-Pt₅Ce). The strong catalyst-support interactions between the Pt–C layer suppress particle agglomeration and Ostwald ripening, and its steric hindrance effect reduces the electronic density at Pt sites, decreasing the adsorption energy of Pt with oxygen-containing intermediates and preventing Pt dissolution. The Pt–C layer also increases the accessibility of active sites, boosting the ORR activity. In acidic media, E-Pt₅Ce shows a mass activity (MA) and specific activity (SA) of 2.86 A mg_Pt⁻¹ and 2.03 mA cm⁻², outperforming the commercial Pt/C by factors of approximately 15 and 5, respectively. When used as a cathode catalyst for a PEMFC, the MA at 0.90 V is almost twice the DOE 2025 target. After stability testing, there is no prominent loss in catalytic activity. Density functional theory calculations confirm that the Pt–C coordination bonds also serve as reactive sites. This work uncovers the mechanism of action of the Pt–C coordination layer, which plays a crucial role in the preparation and performance of ORR catalysts.

The development of noble metal-free dye-sensitized photocatalytic systems (DSPs) for CO₂-to-CO conversion remains limited. Current literature primarily focuses on a single strategy: the simultaneous loading of both the photosensitizer (PS) and the catalyst (CAT) onto titanium dioxide nanoparticles (TiO₂ NPs) using anchoring groups. Here, we introduce an innovative method through immobilizing a positively-charged molecular CAT onto negatively-charged PS–TiO₂ NPs. Our approach yields promising results, including near-complete CO₂-to-CO conversion (∼100% CO) and exceptional stability, achieving 1658 turnover numbers versus the CAT and an apparent quantum yield efficiency (AQY) of 16.9%.

Methane is a critical energy resource but also a potent greenhouse gas, significantly contributing to global warming. To mitigate the negative effect of methane, it is meaningful to explore an effective methane conversion process motivated with green energy such as green electricity and sunlight. The selectivity and production rate are the key criteria in methane conversion. This review provides a comprehensive overview of recent efforts and understanding in methane conversion to valuable products, including oxygenates and hydrocarbons, by taking advantage of electrocatalysis and photocatalysis. The review begins with a general understanding of C–H bond activation mechanisms. It then focuses on electrocatalytic methane conversion (EMC) with an emphasis on catalyst design for oxygenate production, and photocatalytic methane conversion (PMC) with a particular focus on hydrocarbon production, especially ethylene (C₂H₄), due to the differences in oxygen sources between the two systems. An in-depth understanding of EMC and PMC mechanisms is also discussed to provide insights for improved catalyst design aimed at selective product generation. Finally, successful catalyst designs for EMC and PMC are summarized to identify challenges in achieving highly efficient and selective production of value-added chemicals and to offer clear guidance for future research efforts in green methane conversion.

Catalytic fast pyrolysis (CFP) of biomass is an efficient approach that can overcome the structural recalcitrance of solid biomass (e.g., crystalline cellulose) to produce sugar monomers and their derivatives within seconds. The composition of the product mixture, which is accumulated in a liquid called bio-oil, is highly tuneable through the use of in situ/ex situ catalysts for the downstream production of sustainable fuels and fine chemicals. This minireview summarises the recent advances in homogeneous and heterogeneous catalysts in the CFP production of versatile oxygenates as fuel precursors or bulk chemicals. First, a brief overview of primary CFP pathways, including cellulose-to-levoglucosan (LGA) conversion and the production of three important derivative anhydrosugars, is provided. Particular attention is paid to the roles of homogeneous and heterogeneous catalysts in promoting secondary reforming of LGA by dehydration and to alternative pathways via C3–C6 cyclisation or benzylic rearrangement over versatile catalysts (e.g., aqueous acids, zeolites, metal oxides) with Brønsted/Lewis acidity to produce a variety of oxygenates in bio-oil. This minireview may provoke more CFP technologies by clarifying the opportunities and challenges in the selective production of different reformed oxygenates, complementing CFP-based production of aromatics from biomass.

Renewable electricity powered electrocatalytic CO₂ reduction (eCO₂R) is an emerging carbon-negative technology that upgrades CO₂ into valuable chemicals and simultaneously stores intermittent renewable energy. eCO₂R in anion exchange membrane (AEM)-based membrane electrode assemblies (MEAs) has witnessed high faradaic efficiency (FE). But severe CO₂ crossover in AEMs results in low CO₂ single-pass conversion (SPC_CO2) and burdens the energy-intensive CO₂ separation process. Utilizing cation exchange membranes (CEMs) and acidic anolytes, eCO₂R in acidic MEAs is capable of addressing the CO₂ crossover issue and overcoming the SPC_CO2 limits in their AEM counterparts. Alkali metal cations such as K⁺/Cs⁺ are always adopted in acidic MEAs to suppress the competing hydrogen evolution reaction (HER) and boost eCO₂R kinetics. However, K⁺/Cs⁺ accumulates and precipitates in the form of carbonate/bicarbonate salts in the cathode, which accelerates water flooding, deteriorates the gas-electrode–electrolyte interface, and limits the durability of acidic eCO₂R MEAs to a few hours. In this mini-review, we discuss the fundamentals of salt precipitation and water flooding and propose potential remedies including inhibiting K⁺/Cs⁺ accumulation, decreasing local CO₃²⁻/HCO₃⁻ concentration, and water management in gas diffusion electrodes (GDEs). We hope that this mini-review will spur more insightful solutions to address the salt precipitation and water flooding issues and push acidic eCO₂R MEAs toward industrial implementations.

Electrocatalytic conversion of liquid bicarbonate feedstock to formate is a promising reactive CO₂ capture technology. However, bicarbonate-fed electrolyzers have shown insufficient faradaic efficiencies (FEs) for formate production due to competing hydrogen evolution reactions. In this study, we developed a bicarbonate electrolyzer incorporating a porous membrane between a proton exchange membrane (PEM) and a hydrophilic bismuth cathode. By employing the intermediate membrane to enhance in situ CO₂ generation from 3.0 M KHCO₃, we achieved a formate FE of 84.6% even at a high current density of 300 mA cm⁻². This electrolyzer also achieved high CO₂ utilization efficiency (89%) and low full-cell voltage (3.1 V) at 100 mA cm⁻² owing to the rational designs of membrane electrode assemblies. Bicarbonate conversion to formate is accelerated through in situ CO₂ generation and selective CO₂ reduction reaction at a gas–liquid–catalyst triple-phase boundary. Additionally, the bicarbonate electrolyzer demonstrates high CO₂ utilization efficiency, long-term stability, and production of pure formate salt.

Oxygen-centered radicals are highly reactive and have played a key role in organic transformations since their discovery. Nowadays, the direct difunctionalization of alkenes involving oxygen-centered radicals is still underdeveloped due to the inherent properties of oxygen-centered radicals, especially the intermolecular radical addition of unactivated alkenes. Herein, we report an intermolecular oxygen-centered radical addition carbonylation reaction of unactivated alkenes under visible light irradiation. The transformation was initiated with the direct addition of alkoxycarbonyloxy radicals to alkenes, which then underwent aromatic migration under the intervention of carbon monoxide to achieve the targeted oxycarbonylation products.

The treatment of urea-containing wastewater is crucial for sustainable environmental development, given its low theoretical thermodynamic barrier (0.37 V), which can effectively replace the OER process in water electrolysis and enhance hydrogen production efficiency. Nevertheless, designing dual-functional catalysts capable of effectively performing catalytic tasks remains a challenge. Herein, in this work a cerium-doped nickel sulfide (Ce–NiS) catalyst is synthesized by an electrodeposition method, which is used as a bifunctional catalyst for electrolytic hydrogen production from urea-containing wastewater. Ce–NiS exhibits a higher Faradaic efficiency (FE, 91.39%) compared to NiS (67.52%) for hydrogen production from simulated urea-containing wastewater. In situ Raman spectroscopy reveals that Ce doping induces the reconstruction of NiS into high-valence nickel species (NiOOH), which is considered the actual active center for the electrochemical UOR process. Notably, the apparent electrochemical activation energy for the UOR decreased from 8.72 kJ mol⁻¹ (NiS) to 5.68 kJ mol⁻¹ (Ce–NiS), indicating that doping with Ce significantly reduces the energy barrier for the UOR and enhances the catalytic urea oxidation capability. This study employs a strategy of rare-earth metal (Ce) doping to enhance the efficiency of urea-coupled electrolytic hydrogen production, providing promising insights for energy recovery from urea-containing wastewater and the development of high-performance dual-functional catalysts.

Single-atom catalysts (SACs), possessing a uniform metal site structure, are a promising class of materials for selective oxidations of hydrocarbons. However, their design for targeted applications requires careful choice of metal–host combinations and suitable synthetic techniques. Here, we report iron atoms stabilised on defective hexagonal boron nitride (h-BN) via mechanochemical activation in a ball mill as an effective catalyst for propylene production via N₂O-mediated oxidative propane dehydrogenation (N₂O-ODHP), reaching 95% selectivity at 6% propane conversion and maintaining stable performance for 40 h on stream. This solvent-free synthesis allows simultaneous carrier exfoliation and surface defect generation, creating anchoring sites for catalytically-active iron atoms. The incorporation of a small metal quantity (0.5 wt%) predominantly generates a mix of atomically-dispersed Fe²⁺ and Fe³⁺ species, as confirmed by combining advanced microscopy and electron paramagnetic resonance, UV-vis and X-ray photoelectron spectroscopy analyses. Single-atom iron favours selective propylene formation, while metal oxide nanoparticles yield large quantities of CO_x and cracking by-products. The lack of acidic functionalities on h-BN, hindering coke formation, and firm stabilisation of Fe sites, preventing metal sintering, ensure stable operation. These findings showcase N₂O-ODHP as a promising propylene production technology and foster wider adoption of mechanochemical activation as a viable method for SACs synthesis.