Designing Highly Efficient Electrocatalyst for ORR and OER Based on Nb₂CO₂ MXene: The Role of Transition Metals and N-Doping Content

Abstract

Finding efficient and stable electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is imperative for advancing zinc-air batteries. Herein, the effect of transition metal anchored on Nb 2 CO 2 with different N content to form TM-N x -Nb 2 CO 2 on the catalytic activity of ORR and OER is investigated by density functional theory. Among all the designed TM-N x -Nb 2 CO 2 , Pt-N 12.50% -Nb 2 CO 2 , Pt-N 37.50% -Nb 2 CO 2 , Pt-N 50.00% -Nb 2 CO 2 , Pd-N 68.75% -Nb 2 CO 2 , and Pd-N 100% -Nb 2 CO 2 are excellent ORR electrocatalysts with η ORR values of 0.38, 0.36, 0.38, 0.38, and 0.34 V, respectively. Rh-Nb 2 CO 2 , Rh-N 12.50% -Nb 2 CO 2 , Rh-N 31.25% -Nb 2 CO 2 , Rh-N 37.50% -Nb 2 CO 2 , Rh-N 50.00% -Nb 2 CO 2 , Pt-N 50.00% -Nb 2 CO 2 , Rh-N 68.75% -Nb 2 CO 2 , and Rh-N 81.25% -Nb 2 CO 2 are excellent OER electrocatalysts with η OER values of 0.33, 0.37, 0.34, 0.36, 0.37, 0.34, 0.38, and 0.33 V, respectively. Notably, Rh-Nb 2 CO 2 and Pt-N 50.00% -Nb 2 CO 2 exhibit outstanding ORR and OER bifunctional catalytic activity with potential gap values of 0.80 and 0.72 V, respectively, which are higher than the activities of most reported bifunctional catalysts. Furthermore, electronic structure analysis indicates that the moderate adsorption strength of oxygen-containing intermediates on active centers is crucial for achieving highly active bifunctional catalysts for ORR and OER. This study provides a strategy for the design of novel ORR and OER catalysts using 2D MXene materials.