Promoting electrochemical conversion of CO2 to formate with rich oxygen vacancies in nanoporous tin oxides

Defect engineering, especially oxygen vacancies (O-vacancies) introduction into metal oxide materials has been proved to be an effective strategy to manipulate their surface electron exchange processes. However, quantitative investigation of O-vacancies on CO2 electroreduction still remains rather ambiguous. Herein, a series of nanoporous tin oxide (SnOx) materials have been prepared by thermal treatment at various temperatures and reaction conditions. The annealing temperature dependent O-vacancies property of the SnOx was revealed and attributed to the balance tunning of the desorption of oxygen species and the continous oxidation of SnOx. The as-prepared nanoporous SnOx with 300 degrees C treatment was found to be highest O-vacant material and showed an impressive CO2RR activity and selectivity towards the conversion of CO2 into formic acid (up to 88.6%), and superior HCOOH incomplete current density to other samples. The ideal performance of the O-vacancies rich SnOx-300 material can be ascribed to the high delocalized electron density inducing much enhanced adsorption of CO2 with O binding and benefiting the subsequent reduction with high selectively forming of formic acid. (C) 2019 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.