Multifunctional metal-phosphide-based electrocatalysts for highly efficient solar hydrogen production integrated devices

Abstract

Uninterrupted H₂ production from water electrolysis powered by sunlight is critical for the development of hydrogen economy. The key to realize this purpose is to construct integrated devices involving energy storage and water splitting and corresponding efficient electrocatalysts, which remains a significant challenge. Herein, we developed a new type of solar hydrogen production integrated device using rechargeable zinc–air battery as energy storage media and energy driven device and alkaline water electrolyzer as the H₂ production terminal, wherein highly active FeNi phosphide-carbon hybrid materials prepared from the organophosphonic acid modified polyaniline polymer were employed as advanced electrode catalysts for the trifunctional HER/OER/ORR to improve device efficiency. Density functional theory calculations demonstrate that the hetero-engineering between FeNi phosphide and carbon modulates the d-band center, thereby improving the adsorption of intermediates during reactions. Further, the fabricated zinc–air battery with metal phosphide-based catalyst as an air cathode displays large power density (117 mW cm⁻²), excellent charge–discharge capability (voltage gap of 0.74 V at 10 mA cm⁻²), and outstanding cycling stability (over 500 h). The assembled water splitting electrolyzer also delivers low overpotentials (1.67 V at 20 mA cm⁻²) and excellent stability. Furthermore, two zinc–air batteries in series powered the overall water-splitting cell achievingan average H₂ production rate of 0.24 mL min⁻¹, demonstrating significant prospects for H₂ production. Ultimately, this integrated water electrolysis device exhibited excellent stability in 15 day tests with the commercial silicon photovoltaic cell as the power source by day and the rechargeable zinc–air batteries provide electricity at night, without any decay in the performance. This work may provide new opportunities for low-cost and uninterruptible solar hydrogen production by constructing integrated devices.