Bifunctional nickel and copper electrocatalysts for CO2 reduction and the oxygen evolution reaction

Abstract

In this study, a bifunctional electrocatalyst for CO₂ reduction and the O₂ evolution reaction (OER) was constructed from the electrodeposition of cuprous oxide (Cu₂O) and Ni on a carbon substrate. Different Ni thicknesses on Cu₂O were achieved by varying the time of chronopotentiometric deposition of Ni. Electrochemical CO₂ reduction was carried out at −0.89 V and −1.89 V vs. RHE, and it was found that formate and CO were the two major products. Cu₂O modified with a Ni overlayer with a thickness of ∼700 nm resulted in the highest formate faradaic efficiency of 18%, and Cu₂O resulted in highest CO faradaic efficiency of 7.9%. The enhanced faradaic efficiency for formate is attributed to the synergistic effect between Ni and Cu₂O due to maximized amounts of exposed bimetallic sites that facilitate CO₂ reduction. The electrocatalyst also produces ∼9 times more current density than previous studies using Ni–Cu₂O electrocatalysts for the OER. The ability of the Ni–Cu₂O thin films to catalyze both the OER and CO₂ reduction allows them to be incorporated in the first demonstration of a two-electrode CO₂ conversion device with a bifunctional catalyst. In this architecture, the device produces formate and CO with faradaic efficiencies of 16.0% and 19.7%, respectively.