First-principles design of hetero CoM (M = 3d, 4d, 5d block metals) double-atom catalysts for oxygen evolution reaction under alkaline conditions

As an extension of single-atom catalysts, the development of double-atom catalysts with high electrocatalytic activity for the oxygen evolution reaction (OER) is vital to facilitate hydrogen production and industrial applications. The CoM (M = 3d, 4d, 5d block metals) homo and double-atom catalysts supported on nitrogen-doped graphene (CoM/N(4)G) were prepared for electrochemical water oxidation under alkaline conditions, and the electrocatalytic activity was studied through density functional theory (DFT) calculations. The hetero CoCu/N(4)G double-atom catalyst indicated the highest OER activity with an onset potential of 0.83 V, while the homo Co(2)/N(4)G catalyst showed a higher onset potential of 1.69 V. The decoupled strain, dopant, and configurational effects based on the notable differences between the homo Co(2)/N(4)G and CoCu/N(4)G explained the enhanced OER activity, implying that the Cu dopant has a crucial impact on boosting the reactivity by reducing the affinity of reaction intermediates. The enhancement could also be understood from the perspective of the electron structure characteristic through d-orbital resolved density of states (ORDOS) (d(z(2)), d(xz), d(yz), d(xy), and d(x(2)−y(2))) analysis. From the ORDOS analysis, we found an apparent alteration of the key orbitals between Co(2)/N(4)G (d(z(2)), d(xz), and d(yz)) and CoCu/N(4)G (d(z2), d(xz), d(yz), and d(xy)) with a substantial change in the overlap ratio (X(d)). This theoretical study offers beneficial insights into developing a strategy for efficient OER catalysts utilizing a double-atom structure.