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%.