Integrating transition metal phosphide catalysts on WO3 photoanodes enabling robust photoelectrocatalytic water oxidation

Abstract

Photoelectrochemical (PEC) water splitting is a promising technology for clean hydrogen production and sustainable solar energy conversion. However, the low PEC performance of a pristine WO₃ photoanode is limited by the sluggish oxygen evolution kinetics and the severe photo corrosion. Herein, transition metal phosphides (MP_x = Ni₂P, Cu₃P, FeP and Co₂P) are employed as cocatalysts to optimize the surface reaction kinetics and long-time stability of the WO₃ photoanode, thereby improving the oxygen evolution reaction performance. Notably, MP_x cocatalysts, especially Ni₂P, play an important role in high PEC performance by promoting charge separation and transfer and hampering photocorrosion. As a result, the WO₃/Ni₂P photoanode achieves a photocurrent density of 1.67 mA cm⁻² at 1.23 V versus the reversible hydrogen electrode (vs. RHE) under AM 1.5 G illumination, which is about 2.78 times that of the pristine WO₃ photoanode, coupled with a negative onset potential shift. Moreover, the WO₃/Ni₂P photoanode presents long-term photostability of over 10 hours and a high Faraday efficiency of 93%. Linear sweep voltammetry (LSV) curves, intensity modulated photocurrent spectroscopy (IMPS), surface photovoltage spectroscopy (SPV) and time-resolved photoluminescence spectroscopy (TRPL) indicate that MP_x cocatalysts enhanced the efficiency of the photoelectrochemical (PEC) water splitting reaction by promoting charge separation and transfer and hampering photocorrosion. This work not only emphasizes the effective role of the Ni₂P cocatalyst in an integrated photoanode, but also offers a comprehensive understanding of the intrinsic roles of the cocatalyst in PEC water splitting application.