Boosting the Performance of Electrochemical CO2 Reduction to HCOOH through the Interaction of Pyridinic Nitrogen with Sn

Abstract

The development of efficient and stable catalysts for electrochemical CO₂ reduction (CO₂RR) to formic acid (HCOOH) is of great practical significance for balancing energy and environmental issues. SnO₂ shows potential application of the CO₂RR to HCOOH, while its low current carrier density and inappropriate adsorption energy for crucial intermediates limit its performance in terms of activity and selectivity. In this study, phthalocyanine (Pc) and tetraphenyl porphyrin (TPP) were loaded onto SnO₂ nanosheets forming composite materials with different types of N (SnO₂/Pc and SnO₂/TPP), respectively. In Pc, both pyridinic N and pyrrolic N are present, while only pyrrolic N is present for TPP. XPS analysis reveals that the obvious electronic interaction happened between the pyridinic N and Sn, regulating the electronic states of Sn sites. As a result, SnO₂/Pc composites can selectively convert CO₂ to HCOOH with a Faraday efficiency up to 90.25% and partial current density up to 16.15 mA cm^–2 at −1.3 V vs RHE, higher than SnO₂/TPP and SnO₂. Density functional theory (DFT) calculations further prove that the superior catalytic performance of SnO₂/Pc comes from its moderate adsorption energy for *OCHO and *HCOOH, which is beneficial for *HCOOH desorption.