Alloying non-precious metals into Ni-based electrocatalysts for enhanced hydrogen oxidation reaction in alkaline media: A computational study

摘要

Alkaline anion exchange membrane fuel cells (AAEMFCs) are promising energy conversion devices because they can circumvent the use of precious metal catalysts. Hydrogen oxidation reaction (HOR) is the limiting reaction of the AAEMFC. Alloying metals with Ni is one method to enhance the HOR activity. However, the alloying effects are not fully identified. In this work, we investigated the HOR activity of non-precious Ni binary and ternary alloys using density functional theory (DFT) calculations. Together with the descriptor, H adsorption free energy (Delta G(H*)), free energy profiles based on the bifunctional mechanism suggest the Cu-doped Ni3Ti as the best catalyst. This result is further confirmed by the microkinetic model, where Cu-doped Ni3Ti exhibits Delta G(H*) and OH adsorption free energy (Delta G(OH*)) closest to the optimum values (0 and 0.8 eV, respectively). The adsorption trend is understood via the d-band center and magnetic moment of the surface atoms. Our investigation revealed the alloying effects on the HOR activity and provided theoretical guidance for improving the performance of Ni alloy based AAEMFCs.