Designing the bimetallic catalysts by the adsorption strength of metal atoms for efficient oxygen reduction: A density functional theory study

Abstract

In this paper, a new design principle for bimetallic catalysts is proposed by combining strongly adsorbed atoms (SAA) with weakly adsorbed atoms (WAA) where the SAA and WAA are classified by the free adsorption energy of oxygen-containing intermediates on the metal atom. And the ORR performances of the bimetallic catalysts designed by the method are compared with the common single metal atom catalysts. The method is successfully confirmed as the overpotential of the Mn-based bimetallic catalysts decreases from 0.63 V in G-MnN4 to as low as 0.33 V, and that of the Fe-based bimetallic catalysts decreases from 0.76 V in G-FeN4 to 0.23 V. In addition, the correlation between adsorption free energy and adsorption bond length is revealed for the first time, and the optimal adsorption bond length is determined. Finally, the adsorption energy of O2 is plotted versus the free adsorption energy of three oxygen-containing intermediates for the first time, and a suitable adsorption energy of O2 is found to be -1.4∼-1.0 eV. These findings provide a new perspective for the design of high-performance bimetallic catalysts.