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

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.