Rational construction of unique cobalt hydroxide fluoride microflower decorated with platinum-tin alloy onto nickel foam enabling efficient overall water splitting at ampere-level current densities

The development of efficient electrocatalysts capable of stable operation at ampere-level current densities is essential for industrial water electrolysis. Herein, based on the triple synergistic strategy of “hydrogen spillover-interfacial microenvironment regulation-wettability management”, platinum‑tin (PtSn) nano-alloy modified with dahlia-like cobalt hydroxide fluoride (Co(OH)F) grown on nickel foam (NF), denoted as PtSn/Co(OH)F/NF, was fabricated via hydrothermal and electrochemical deposition techniques. Toward hydrogen evolution reaction (HER), the hydrogen spillover effect is driven by a Gibbs free energy of hydrogen adsorption (ΔG_H) gradient between PtSn alloy and Co(OH)F carrier, leading to a significant increase in the active surface area at low platinum loadings. Additionally, tin (Sn) alloying accelerates water splitting kinetics by modulating the d-band center of platinum (Pt). For the oxygen evolution reaction (OER), the nanoneedle-induced tip effect enhances local electric fields, promoting hydroxide ion (OH⁻) enrichment and transport within the electrical double layer. Furthermore, the hierarchical “nanoneedle-nanoribbon-microflower” structure creates superhydrophilic and gas-repellent surface, facilitating rapid bubble release and mass transfer under high current densities. Thus, PtSn/Co(OH)F/NF delivered an overpotential of 15 ± 2 mV at 10 mA cm⁻², and merely 212 ± 1 mV and 378 ± 2 mV to achieve 1 A cm⁻² for HER and OER, respectively. Notably, cell voltages of only 1.47 and 1.68 V are required to achieve 10 and 500 mA cm⁻², with an operational stability of 240 h. The hydrogen spillover mechanism was confirmed via density functional theory (DFT) calculation. This rational design strategy yields low-Pt electrocatalysts with optimized morphology and high intrinsic activity, offering a promising route for green energy applications.