Accelerated bubble departure and reduced overpotential with nanoengineered porous bifunctional Ni₅P₄ electrocatalyst for PV-driven water splitting

Solar-driven green hydrogen production is a promising sustainable technology though large-scale solar water splitting remains challenging due to expensive electrocatalyst. Herein, we propose a facile and low-cost approach to fabricate nanoengineered hierarchically porous Ni₅P₄ electrocatalyst (p-Ni₅P₄), which provides high surface area and enables fast gas diffusion. By coating p-Ni₅P₄ on Ni foam (NF), p-Ni₅P₄@NF has pores ranging from 50-500 nm to 200–600 μm and enlarges the electrochemically-active surface area by 5 times. p-Ni₅P₄@NF offers abundant cavities for gas nucleation and fast growth of H₂ bubble, and small bubbles (10–50 μm) depart quickly owing to the reduced contact line. By enhancing gas transfer and reducing bubble overpotential over 29%, p-Ni₅P₄@NF achieves excellent electrocatalytic performance with a low HER (145 mV), OER (197 mV) and overall water splitting potential (1.54 V) at 10 mA cm⁻². Powered by multijunction PV cell, the full electrolytic cell records a high solar-to-hydrogen efficiency of 14.5%.