Modulating the degree of O vacancy defects to achieve selective control of electrochemical CO_(2) reduction products

Conversion of CO_(2) into high-value products using electrochemical CO_(2) reduction(ECR)technology is an effective way to alleviate global warming and reach carbon neutrality.The oxygen vacancies in heterogenous catalysis are generally considered as a powerful method to enhance the performance of ECR by promoting CO_(2) adsorption and activation.However,the extent of defects in oxygen vacancies-activity relation has rarely been studied.Herein,we prepared Cu-Cd bimetallic catalysts with adjustable oxygen defect degree by controlling the amount of cadmium addition.Fourier transform infrared spectroscopy characterization results reveal that the formation of oxygen vacancies is attributed to the asymmetric stretching of Cu-O by the addition of cadmium.Electrochemical results show that the oxygen defect degree can modulate the selectivity of ECR products.A low degree of oxygen defects(CuO)is generally associated with lower product Faraday efficiency(FE_(C2)/FE_(C1)≈114%),but overabundant oxygen vacancies(CuO_(2.625)-CdO_(0.375))are not entirely favorable to improving ECR activity(FE_(C2)/FE_(C1)≈125%)and single selectivity,while an appropriate degree of oxygen vacancies(CuO_(2.75)-CdO_(0.25))can facilitate the ECR process toward single product selective production(FE_(C2)/FE_(C1)≈296%).The theoretical calculation showed that the O vacancy formed on CuO and the interface between CdO and CuO were conducive to enhancing the formation of ^(*)COOH intermediate and promoting the generation of ethylene products.This study provides a new approach and insight into the selective production of single products for future industrial applications of ECR.

Screening promising TM-doped CeO_(2) monolayer for formaldehyde sensor with high sensitivity and selectivity

Developing convenient,fast-response and high-performance formaldehyde detection sensor is significant but challenging.Herein,two CeO_(2) phases(Fm■m and P4_(2)/mnm),three facets(CeO_(2)(100),CeO_(2)(110)and CeO_(2)(111))and three adsorption sites(top,bridge and hollow)are selected as substrate to interact with formaldehyde.Twenty-eight candidated transition metals(TM)are doped on CeO_(2) surfaces to investigate the performance of detecting formaldehyde by density functional theory.It shows that(i)CeO_(2) in a cubic fluorite structure with the space group Fm■m is suitable for formaldehyde adsorption compared with P4_(2)/mnm;(ii)TM-CeO_(2)(100)(TM=Au,Hf,Nb,Ta,Zr)are considered as candidated materials to absorb formaldehyde ascribed to lower adsorption energies.The d-band center,partial density of states,charge density difference and electron localization function are employed to clarify the mechanism of TM-doped CeO_(2) improving the performance of formaldehyde adsorption.It obviously displays that TM doped CeO_(2)(100)changes the d orbit and rearranges electrons resulting in the superior ability to the adsorbed formaldehyde.This work provides theoretical guidance and experimental motivation for the development of novel formaldehyde sensor based on metal oxide semiconductor materials.