Parametric investigation of electrodeposition of CuOx photoelectrodes for enhanced photoelectrochemical response

Copper oxide-based photoelectrodes are promising materials for photoelectrochemical applications due to their earth abundance and favorable optoelectronic properties. However, their photoelectrochemical performance is strongly influenced by phase composition, surface morphology, and processing conditions. In this study, CuO x -coated photoelectrodes were prepared via electrodeposition using citric acid and lactic acid as complexing agents, followed by thermal annealing at 400 °C. The effects of deposition chemistry, substrate configuration, deposition time, and annealing duration on the structural and photoelectrochemical properties of the electrodes were systematically evaluated. Structural and surface analyses confirmed that the preparation conditions significantly affected phase development and film morphology, while CuO was predominantly detected at the electrode-electrolyte interface. Photoelectrochemical measurements under 1-sun simulated solar illumination showed that electrode orientation, complexing-agent chemistry, deposition duration, and annealing time substantially influenced the photovoltage and photocurrent response. Lactic-acid-derived electrodes generated the highest photocurrent density, reaching 80 μA/cm 2 , exceeding the 60 μA/cm 2 obtained with citric acid, while citric-acid coatings produced a higher photovoltage of 75 mV compared to 20 mV. A deposition duration of 20 min and an annealing time of 1 h provided the most favorable photoelectrochemical response among the conditions investigated. These results demonstrate that controlled electrodeposition and thermal treatment provide an effective route for tuning the interfacial photoresponse of CuO x electrodes. The findings offer practical guidance for developing scalable copper oxide photoelectrodes for photoelectrochemical applications.