Improved Charge Carrier Transport of Hydrogen-Treated Copper Tungstate: Photoelectrochemical and Computational Study

Thin films of copper tungstate (CuWO 4 ) have been prepared through electrodeposition and tested as the anode material for photoelectrochemical (PEC) water oxidation. We found that hydrogen-treatment over the synthesized CuWO 4 at high temperatures led to enhancement in the PEC performance for water oxidation. The origin of this activity enhancement is attributed to the enhanced kinetics of electron-hole pair separation due to the increased carrier concentration induced by oxygen vacancy formation upon hydrogen-treatment. The incorporation of oxygen vacancies also resulted in enhanced light absorbance in the visible light region because they introduce shallow donors as predicted by first-principles calculations. Nevertheless, incident photon to electron conversion efficiency (IPCE) measurements indicate that light absorbed at long wavelength region after hydrogen-treatment is not successfully utilized to oxidize water. This report provides insights on the effect of hydrogen-treatment on the structural, optical, and electronic properties of CuWO 4 .