Stabilization of CuO Nanostructures With Carbon on Rigid Substrates as a Photocathode for Photoelectrochemical Water Splitting

Photoelectrochemical (PEC) water splitting provides a promising approach for sustainable hydrogen production by directly converting solar energy into chemical fuel. However, it remains a great challenge to develop active, stable, and cost‐effective photoelectrodes to achieve efficient PEC performance. In this work, copper oxide nanostructured photoelectrodes were successfully grown on a seeded fluorine‐doped tin oxide substrate using a facile seed‐layer‐mediated hydrothermal method. Microstructural analysis and optimization of reaction conditions—precursor concentration, number of hydrothermal steps, and annealing temperature were done to obtain the best‐performing CuO/FTO NSs through a lengthy three‐step hydrothermal (HT‐3) process and initial poor photostability was resolved. Interestingly, incorporation of carbon not only enhanced the stability and PEC performance of the NSs but also reduced the number of hydrothermal steps required, saving time and energy consumption. Compared to unmodified CuO/FTO NSs, the photocurrent density of the carbon‐incorporated CuO/FTO NSs increased up to six times for a one‐step hydrothermal reaction (HT‐1). The enhanced PEC activity of carbon‐incorporated CuO/FTO NSs arises from the synergetic effect between carbon and CuO/FTO NSs, where carbon boosts light absorption and acts as an efficient charge collector and transporter, aiding the separation of photogenerated electron–hole pairs.