Switching CO_(2) Electroreduction Selectivity Between C_(1) and C_(2) Hydrocarbons on Cu Gas-Diffusion Electrodes

Regulating the selectivity toward a target hydrocarbon product is still the focus of CO_(2)electroreduction.Here,we discover that the original surface Cu species in Cu gas-diffusion electrodes plays a more important role than the surface roughness,local pH,and facet in governing the selectivity toward C_(1)or C_(2)hydrocarbons.The selectivity toward C_(2)H_(4) progressively increases,while CH_(4) decreases steadily upon lowering the Cu oxidation species fraction.At a relatively low electrodeposition voltage of 1.5 V,the Cu gas-diffusion electrode with the highest Cu^(δ+)/Cu^(0)ratio favors the pathways of∗CO hydrogenation to form CH_(4) with maximum Faradaic efficiency of 65.4%and partial current density of 228 mA cm^(−2)at−0.83 V vs RHE.At 2.0 V,the Cu gas-diffusion electrode with the lowest Cu^(δ+)/Cu^(0)ratio prefers C-C coupling to form C_(2)+products with Faradaic efficiency topping 80.1%at−0.75 V vs RHE,where the Faradaic efficiency of C_(2)H_(4) accounts for 46.4%and the partial current density of C_(2)H_(4) achieves 279 mA cm^(−2).This work demonstrates that the selectivity from CH_(4) to C_(2)H_(4) is switchable by tuning surface Cu species composition of Cu gas-diffusion electrodes.

Activation of Transition Metal(Fe,Co and Ni)-Oxide Nanoclusters by Nitrogen Defects in Carbon Nanotube for Selective CO_(2) Reduction Reaction

The electrochemical carbon dioxide reduction reaction(CO_(2)RR),which can produce value-added chemical feedstocks,is a proton-coupled-electron process with sluggish kinetics.Thus,highly efficient,cheap catalysts are urgently required.Transition metal oxides such as CoO_(x),FeO_(x),and NiO_(x)are low-cost,low toxicity,and abundant materials for a wide range of electrochemical reactions,but are almost inert for CO_(2)RR.Here,we report for the first time that nitrogen doped carbon nanotubes(N-CNT)have a surprising activation effect on the activity and selectivity of transition metal-oxide(MO_(x)where M=Fe,Ni,and Co)nanoclusters for CO_(2)RR.MO_(x)supported on N-CNT,MO_(x)/N-CNT,achieves a CO yield of 2.6–2.8 mmol cm−2 min−1 at an overpotential of−0.55 V,which is two orders of magnitude higher than MO_(x)supported on acid treated CNTs(MO_(x)/O-CNT)and four times higher than pristine N-CNT.The faraday efficiency for electrochemical CO_(2)-to-CO conversion is as high as 90.3%at overpotential of 0.44 V.Both in-situ XAS measurements and DFT calculations disclose that MO_(x)nanoclusters can be hydrated in CO_(2)saturated KHCO_(3),and the N defects of N-CNT effectively stabilize these metal hydroxyl species under carbon dioxide reduction reaction conditions,which can split the water molecules and provide local protons to inhibit the poisoning of active sites under carbon dioxide reduction reaction conditions.

A trace of Pt can significantly boost RuO_(2) for acidic water splitting

The development of highly potential electrocatalysts for acidic water electrolysis is particularly desirable for many energy‐related processes.Herein,we demonstrated a versatile strategy to activate and stabilize RuO_(2)‐based electrocatalyst for acidic water splitting by a trace of Pt,where Pt plays an essential role in promoting oxygen evolution reaction(OER),and can simultaneously act as the active site for hydrogen evolution reaction(HER).Compared with pure Ru oxide nanosheet assemblies(Ru ONAs),the“5%Pt‐containing”Ru ONAs(5%Pt‐Ru ONAs)achieve much enhanced OER activity in 0.5 and 0.05 mol/L H_(2)SO_(4),with much lower overpotentials of 227 and 234 mV at 10 mA cm^(‒2),respectively.Experimental and theoretical analyses reveal that the atomically dispersed Pt incorporating into RuO_(2)lattice is conducive to increasing the concentration of O vacancies,which effectively enhances the interaction with reaction intermediate and thus lowers the energy barrier for the formation of OOH*.Moreover,benefited from the presence of Pt,the formation of RuO_(2)is more achievable when proper annealing is applied.In addition to OER,due to the presence of active Pt,the HER performance of 5%Pt‐Ru ONAs can also be ensured,thereby realizing efficient acidic overall water splitting.Finally,the excellent activity can also be achieved without sacrificing stability.This work highlights an attractive strategy for designing active and stable RuO_(2)‐based electrocatalysts for acidic overall water splitting.

Ultrasound-driven fabrication of high-entropy alloy nanocatalysts promoted by alcoholic ionic liquids

High-entropy alloy nanoparticles(HEA-NPs)are highly underutilized in heterogeneous catalysis due to the absence of a reliable,sustainable,and facile synthetic method.Herein,we report a facile synthesis of HEA nanocatalysts realized via an ultrasounddriven wet chemistry method promoted by alcoholic ionic liquids(AILs).Owing to the intrinsic reducing ability of the hydroxyl group,AILs were synthesized and utilized as environmentally friendly alternatives to conventional reducing agents and volatile organic solvents in the synthetic process.Under high-intensity ultrasound irradiation,Au^(3+),Pd^(2+),Pt^(2+),Rh^(3+),and Ru^(3+)ions were coreduced and transformed into single-phase HEA(AuPdPtRhRu)nanocrystals without calcination.Characterization results reveal that the as-synthesized nanocrystals are composed of elements of Au,Pd,Pt,Rh,and Ru as expected.Compared to the monometallic counterparts such as Pd-NPs,the carbon-supported HEA nanocatalysts show superior catalytic performance for selective hydrogenation of phenol to cyclohexanone in terms of yield and selectivity.Our synthetic strategy provides an improved and facile methodology for the sustainable synthesis of multicomponent alloys for catalysis and other applications.