The Influence of Amino Anchoring Position on SnO2/Biochar for Electroreduction of CO2 to HCOOH

Abstract

Biochar derived from biomass resources as a carrier to load SnO₂ for electroreduction of CO₂ not only can benefit carbon emissions, but it also can achieve waste utilization. However, the weak CO₂ mass transfer and conductivity ability of SnO₂/biochar limits its applications to such eCO₂RR processes. This study focused on modifying SnO₂/biochar with amino groups and investigated the effects of positioning of amino groups on the catalyst’s physicochemical properties and electrocatalytic behaviors. Elemental analysis revealed that anchoring amino groups on biochar (SnO₂/C-NHx) is advantageous for increasing amounts of amino groups attached, thereby enhancing biochar adsorption energy and subsequently increasing the loading of Sn. The CO₂ adsorption curve indicated that amino groups anchored on biochar facilitate CO₂ adsorption due to high specific surface area of biochar. X-ray photoelectron spectroscopy showed that amino groups anchored on SnO₂ (NHx-SnO₂/C) resulted in highly electron-rich centers on Sn, which promoted electron transfer between the catalyst and CO₂. Electrochemical tests demonstrated the improved performance of amino-modified SnO₂/biochar. SnO₂/C-NHx exhibited enhanced Faraday efficiency, whereas NHx-SnO₂/C showed higher current density. The disparity in electrochemical performance can be mainly attributed to the different selectivity towards rate-controlling steps of electron transfer and mass transfer induced by the various positions of amino groups anchoring.