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 because of its layered framework and proton-active lattice, yet its performance is limited by inefficient 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 characterization studies 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 (≈0.50 versus 0.02 mA cm⁻²) and a > 60% reduction in charge-transfer resistance (≈0.8 kΩ vs. 2.0 kΩ), and achieve ≈92% dye removal within 90 min with a rate constant approximately six times higher. Density functional theory (DFT) calculations show that Au incorporation induces a shift in the interfacial Fermi level and facilitates electron transfer through enhanced orbital coupling, consistent with the experimental observations. These results demonstrate a cohesive process wherein plasmonic enhancement and protonic buffering function synergistically to facilitate charge separation and stabilize hole accumulation.