Improving Catalytic Behaviors of a Succulent-like Hierarchical Ni/NiCo Electrode for Direct Borohydride Oxidation by...

Direct borohydride fuel cells (DBFCs) are promising for high-energy-density power sources, but their practical application is limited by slow borohydride oxidation reaction (BOR) kinetics, competing hydrogen evolution reaction (HER), and insufficient catalyst durability. In this work, a succulent-like hierarchical Ni/NiCo catalytic electrode has been reported, which was prepared by a two-step constant-current deposition through combining electronic modulation strategy and structural engineering. In situ attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), COMSOL simulations, and electrochemistry testing demonstrate that Co incorporation induces tensile lattice strain and modulates the electronic structure of a Ni-based catalyst, while the hierarchical architecture with defect-rich features maximizes active site exposure, accelerates mass transport, and suppresses the oxidation of nickel and the competitive HER, thus enhancing the direct borohydride oxidation. Consequently, the Ni/NiCo electrode delivers outstanding catalytic activity, stability, and selectivity to BOR. Moreover, when used as the anode, DBFC can achieve an open-circuit voltage of 1.91 V and a peak power density of 413 mW cm^-2 and operate stably for 36 h under 50 mA·cm^-2 at room temperature. This work establishes a cost-effective route for the development of next-generation high-performance DBFC anode catalysts and also enriches preliminary understanding about the electronic regulation and hierarchical architecture of catalysts.