Determining the Effect of Cation (Ti/Zr) Doping in Bismuth Oxide for Electrochemical CO2 Reduction to Formic Acid: A DFT Study

Abstract

First-principles-based density functional theory (DFT)calculationswere used to explore the electrochemical CO2 reduction(ECR) activity of cation-doped Bi2O3. We studiedthe ECR reaction over pure and doped Bi2O3 (100)surfaces and demonstrated Gibbs free energy diagrams of HCOOH formationvia COOH and HCOO pathways. Compared with pure bismuth oxide, dopingcan alter the rate-determining step and reduce the Gibbs free energyfrom 2.98 to 0.11 eV. The CO2 reduction activity was foundto be most productive on the TiZr-Bi2O3 surface with onset potentials of -0.23 and 0.55 V via theCOOH and HCOO pathways, respectively. The probability of CO formationthrough the ECR reaction was also investigated using Gibbs free energycalculations, and it was found that Bi2O3, Ti-Bi2O3, Zr-Bi2O3, andTiZr-Bi2O3 displayed insufficient ECRactivity to produce CO. We also compared the selectivity of the ECRreaction and the hydrogen evolution reaction (HER) to demonstratethe practicality of the electrocatalysts.