Design And Performance Of Cathode And Anode Catalysts For Electrochemical CO₂ Reduction

Electrochemical CO₂ reduction powered by renewable energy sources offers a sustainable route to produce valuable chemicals and fuels to realize carbon recycling,which is considered as an effective way to solve energy crises and environmental issues.However,the electrochemical CO₂ reduction is hampered by high overpotential and low product selectivity.What’s more,oxygen evolution reaction suffers from kinetically sluggish and significant overpotential loss.So it’s essential to design and fabricate efficient electrocatalysts.Revealing the relation between the atructure and performance is funfamentally important for the development of electrocatalysts.Cobalt based catalysts are considered as promising alternatives of noble metal catalysts.The surface and interface structure of cobalt oxide are modulated to enhance the oxygen evolution performance.Cobalt and iron oxide with hollow structure has been fabricated using ZIF-67 as template.The simultaneous structural and electronic modulation are achieved due to the homogenous Fe incorporation,delivering an ultralow overpotential of 274 mV at 10 mA cm^-2 and a very small Tafel slope of 31 mV dec^-1 in alkaline media.CoO-CeO₂ heterostructures with abundant nano-sized interfaces are prepared using similar method.The introduction of CeO₂ leads to high electron density around Co sites and enhanced adsorption of*OOH intermediates.The perfomance of the hybrids is further promoted during OER process,which can be ascribed to the armouphous phase formed due to surface Ce leaching.To improve the selectivity of hydrocarbon products from electrochemical CO₂reduction,the reaction mechanisms of the CO production and the subsequent C-C coupling are explored.Au nanoparticles are loaded on the 2D ultrathin Ti₃C₂-MXene nanosheets,which exhibits enhanced CO production.Au NPs/Ti₃C₂-MXene catalyst shows high CO specific activity(92.5μA cm^-2_surf)at-0.4 V vs RHE,which is 7.4 times that of Au NPs/C control catalyst.Notably,a shift of d-band center close to Fermi level is observed with Ti₃C₂-MXene as support,which increases the binding strength of*COOH intermediates and thus reduces the free energy of rate-limiting step.Moreover,to enhance the generation of CO intermediate for futher C-C coupling,Au is introduced into Cu-based catalyst.Phase-seperated Au/Cu O catalyst exhibits high C₂H₄ selectivity with faradaic efficiency of 34.8%,partial current density of 54.0 mA cm^-2 and production rate of 168.1μmol h^-1 cm^-2 at-0.9 V vs RHE.The*CO intermediate is easier produced at Au sites,and then transfer to Cu sites for subsequent C-C coupling to generate C₂H₄product.The effect of metal defects on the product distribution of CO₂ electrochemical reduction is further explored.A novel stepped cuprous oxide catalyst with abundant Cu vacancies is developed using NH₄Cl as etching agent,and the Cu_v-Cu₂O catalyst exhibits high C₂H₄ faradaic efficiency of 51.0%,partial current density of 15.7 mA cm^-2 and production rate of 48.7μmol h^-1 cm^-2 at-0.76 V vs RHE.Density functional theory calculations demonstrate that the Cu vacancy-enriched Cu₂O surface ensures strong adsorption to*COH but weak affinities to*CO and*CH₂ intermediates,which promotes CO₂ electroreduction to C₂H₄ products.