Ligand-assisted assembly of FeCo–phytate catalytic interfaces on WO3 photoanodes for dual enhancement of charge separation and oxygen evolution kinetics

Abstract

Inefficient separation of surface charges and slow kinetics of the oxygen evolution reaction (OER) persist as critical hurdles limiting the photoelectrochemical (PEC) water splitting efficiency. Herein, these challenges are addressed via a coordination self-assembly strategy by deploying ultrathin (∼2.5 nm) amorphous phytic acid (PA)-coordinated Fe and Co layers on WO₃ nanosheet arrays (WO₃@PA–FeCo). Under an applied potential of 1.23 V_RHE, the modified photoanode delivers a photocurrent density of 1.93 mA cm⁻², representing a 3.62-fold enhancement compared with pristine WO₃, with a 150 mV cathodic shift in the onset potential. Density functional theory, in situ attenuated total reflection-Fourier transform infrared spectroscopy, and surface photovoltage spectroscopy reveal dual enhancements: accelerated OER kinetics via lowered energy barriers for the O → OOH rate-determining step and improved surface charge separation efficiency. PA-coordinated metal complexes display universal applicability, elevating BiVO₄, TiO₂ and Fe₂O₃ photoanode performances. This study provides a versatile pathway for designing eco-friendly cocatalysts to synergistically optimize interfacial charge dynamics and catalytic processes in solar energy conversion systems.