EES catalysis最新文献

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.

Exploring cost-effective and efficient electrocatalysts for the hydrogen evolution reaction (HER) is essential for realizing green energy technologies such as water electrolyzers and fuel cells. To this end, identifying descriptors that determine the activity of the employed catalysts would render the process more efficient and help to design selective catalytic materials. Herein, cation distribution (δ) is presented as the activity descriptor for the HER on CoFe₂O₄ spinels. A one-step hydrothermal synthesis method is demonstrated for the fabrication of flower-shaped spinel CoFe₂O₄ nanosheets on Ni foam at various pH values with different cation distributions. XPS and Raman analyses revealed the cation distribution of Co and Fe as the main factor determining the catalytic activity of the material. This has been confirmed both experimentally and computationally. The catalyst with the largest δ (0.33) showed as low as 66 mV overpotential at −10 mA cm⁻² with exceptional stability for 44 hours of continuous electrolysis in 1 M KOH. Our study demonstrates cation distribution in spinels as a descriptor of their HER catalytic activity.

Direct liquid fuel cells have advantages over hydrogen-based fuel cells and lithium-ion batteries for portable and mobile applications due to their high volumetric energy density and the convenient storage or refueling of liquid fuels. Unfortunately, the electrochemical oxidation of liquid fuels (such as methanol, ethanol, and formic acid) currently corresponds to ∼50% of the energy losses of these devices at operating conditions. Moreover, state-of-the-art catalysts for such critical reactions are generally composed of precious metals such as Pt and Pd, hindering the cost-effective implementation of these technologies. The development of novel catalyst design principles for electrochemical liquid fuel oxidation has been constrained by its complex, structure-sensitive reaction energetics that can involve multiple parallel, competitive reaction intermediates and pathways. In this review, we aim to dissect and bridge the understanding of fundamental energetics and the materials engineering of novel catalysts for the electrochemical oxidation of various liquid fuels. By deconvoluting these reactions into the energetics of different critical elementary steps, we define essential descriptors that govern the activity and selectivity of electrochemical liquid fuel oxidation. Several universal and fundamental design principles are proposed to optimize the catalytic performance of state-to-the-art and emerging electrocatalysts by tuning the chemistry and electronic structure of active sites. This review aims to provide a unique perspective connecting the electro-oxidation energetics of different liquid fuels with mechanistic and materials-centric studies to provide a holistic picture connecting the fundamental surface science with materials engineering for the rational design of electrocatalysts for liquid fuel oxidation.

Alcohol-assisted water electrolysis offers an attractive path for on-demand hydrogen generation while concurrently producing value added carboxylates. However, the anodic alcohol oxidation reaction (AOR) often requires precious metal-based catalysts, yet is still plagued with high overpotential or limited mass activity. Herein we report a facile synthesis of medium entropy Au-doped PtAgRhCu alloy wavy nanowires for highly efficient AORs. The alloy design facilitates hydroxyl adsorption that promotes the conversion of the carbonaceous intermediates (e.g. CH₃CO*) to carboxylate products and weakens the adsorption of carboxylate products, resulting in greatly enhanced mass activity for four-electron AORs and highly selective upgrade of ethanol and ethylene glycol into value added acetate and glycolate. Furthermore, we constructed an alcohol assisted water electrolyser that delivers a current density of 100 mA cm⁻² at a cell voltage lower than 0.6 V and a current density of 1 A cm⁻² at a cell voltage of 1.2 V.

Computational approaches, such as density functional theory (DFT) in conjunction with descriptor-based analysis and computational hydrogen electrode, have enabled exploring the intricate interactions between catalyst surfaces and oxygen species allowing for the rational design of materials with optimized electronic structure and reactivity for oxygen reduction reaction (ORR). The identification of active sites and the tuning of catalyst compositions at the atomic scale have been facilitated by computational simulations, accelerating the discovery of promising ORR catalysts. In this contribution, the insights provided by the computational analysis to understand the fundamental reasons behind inherent ORR overpotentials in the experimental reported catalysts are discussed. Various strategies to overcome the limitations in ORR catalysis using computational design are discussed. Several alternative earth-abundant and cost-effective materials suggested by computational guidance to replace platinum-based catalysts are reviewed. The accuracy of DFT and the role of solvent and electrolyte pH are outlined based on the understanding provided by the computational insight. Finally, an overview of recent achievements in employing materials informatics to accelerate catalyst material discovery for ORR is provided. These computational advancements hold great promise for the development of efficient and cost-effective ORR catalysts, bringing us closer to realizing the full potential of fuel cells as efficient electrochemical energy conversion technologies.

Hybrid halide perovskites (HaPs) represent a class of material with excellent optoelectronic properties providing distinct avenues for disruptive photo(-electro) catalytic technologies. However, their photocatalytic activity, selectivity and stability remains a scientific and technological hurdle. In this perspective, we discuss fundamental aspects of perovskite based photocatalytic systems, specifically for CO₂ conversion and high value oxidation reactions, and highlight critical limiting factors and on-going challenges in the field. We critically assess the recent advances in designing halide perovskite hetero-interfaces and characterization methodologies which are often used to define the performance metrics. Furthermore, we outline important questions and identify emerging trends in relation to the remediation strategy towards improved photocatalytic performance and stability from halide perovskite semiconductors.