Interfacial Electronic Modulation in Au–Tungstic Acid for Enhanced PEC Performance

Abstract

Harnessing cooperative effects at semiconductor–metal interfaces offers new opportunities for efficient solar-to-chemical conversion. Tungstic acid (H₂WO₄) is an attractive photoanode material due to its layered framework and proton-active lattice, yet its performance is limited by poor charge separation and sluggish interfacial kinetics. Here, we report the first systematic integration of proton-buffering H₂WO₄ with plasmonic Au nanoparticles to construct a dual-mode photoelectrochemical system. Structural, spectroscopic, and electrochemical characterizations reveal that Au decoration produces porous, crystalline films with intact lattice vibrations, extended visible absorption, and accelerated carrier dynamics. Compared to pristine H₂WO₄, the Au–H₂WO₄ electrodes exhibit a nearly 25-fold increase in photocurrent (~500 µA vs. 20 µA), a >60% reduction in charge-transfer resistance (~0.8 kΩ vs. 2.0 kΩ), and achieve ~92% dye removal within 90 min with a six-fold faster rate constant. Density functional theory (DFT) calculations show that Au lowers the effective work function from ~4.8 to 2.1 eV and establishes direct orbital pathways for electron extraction, fully consistent with the experimental data. Together, these results establish a unified mechanism in which plasmonic enhancement and protonic buffering act cooperatively to promote charge separation, stabilize hole accumulation, and accelerate interfacial charge transfer, offering a general design principle for advanced oxide-based photoelectrodes.