Defect-rich walnut-like copper-doped Ni(PO3)2 catalyst towards ammonia borane electrooxidation reaction with high performance

Abstract

Ammonia borane (NH₃BH₃, AB), a carbon-free-energy material, has attracted enormous attention not only as the hydrogen storage source but also as the anodic fuel for direct AB fuel cells (DABFCs). The rational design of electrocatalysts for AB oxidation reaction (ABOR) is the key to improve the electrochemical performance of DABFCs. Herein, copper-doped nickel metaphosphates (Cu–Ni(PO₃)₂) with modulated electronic structure and abundant lattice defects through tuning dopant ratios are synthesized and applied towards ABOR for the first time. The optimal Cu–Ni(PO₃)₂ catalyst shows excellent electrocatalytic performance with an onset potential of −0.282 V versus the reversible hydrogen electrode (vs. RHE) which is superior to the published noble-metal and other transition metal electrocatalysts. And the density functional theory (DFT) computations verified that the active sites in the Cu–Ni(PO₃)₂ towards ABOR are the dopant Cu ions, the optimized Ni ions, and the induced lattice distortions, which indicates that the doping of Cu ions can indeed improve the electrocatalytic activity of the host catalyst Ni(PO₃)₂. This work provides a new candidate for the electrocatalyst of ABOR.