Optimized Copper-Modified Zinc Oxide Photoanodes for Solar-to-Hydrogen Evolution

This work presents a single-step method for producing cost-efficient copper-modified zinc oxide photoanodes through scalable chemical vapor deposition. The role of Cu incorporation is thoroughly investigated, with the identification of an optimized loading of the metal in these films. The optimally Cu-modified ZnO sample (CZO-5.6) achieved a stable photocurrent of approximately 1.22 mA cm^-2 at 1.23 V_RHE, along with a Faradaic efficiency of 89%. This enhanced performance was attributed to surface plasmon resonance (SPR) effects induced by copper nanoparticles, as evidenced by photoluminescence spectroscopy results. To promote stability under the experimental conditions of the PEC cell, the best-performing photoanode was further protected using amorphous TiO₂ deposited by atomic layer deposition. Amorphous TiO₂ coatings have been found to be exceptionally stable in alkaline solutions and highly conductive for photogenerated holes, offering a promising solution for PEC electrode protection. This work not only describes a method for fabricating photoanodes with high photocatalytic activity but also suggests a low-cost route toward the development of photocatalysts for hydrogen production.