Nanoengineered Advanced Materials for Enabling Hydrogen Economy: Functionalized Graphene–Incorporated Cupric Oxide Catalyst for Efficient Solar Hydrogen Production

Cupric oxide (CuO) is a promising candidate as a photocathode for visible‐light‐driven photo‐electrochemical (PEC) water splitting. However, the stability of the CuO photocathode against photo‐corrosion is crucial for developing CuO‐based PEC cells. This study demonstrates a stable and efficient photocathode through the introduction of graphene into CuO film (CuO:G). The CuO:G composite electrodes are prepared using graphene‐incorporated CuO sol–gel solution via spin‐coating techniques. The graphene is modified with two different types of functional groups, such as amine (—NH(2)) and carboxylic acid (—COOH). The —COOH‐functionalized graphene incorporation into CuO photocathode exhibits better stability and also improves the photocurrent generation compare to control CuO electrode. In addition, —COOH‐functionalized graphene reduces the conversion of CuO phase into cuprous oxide (Cu(2)O) during photo‐electrochemical reaction due to effective charge transfer and leads to a more stable photocathode. The reduction of CuO to Cu(2)O phase is significantly lesser in CuO:G‐COOH as compared to CuO and CuO:G‐NH(2) photocathodes. The photocatalytic degradation of methylene blue (MB) by CuO, CuO:G‐NH(2) and CuO:G‐COOH is also investigated. By integrating CuO:G‐COOH photocathode with a sol–gel‐deposited TiO(2) protecting layer and Au–Pd nanostructure, stable and efficient photocathode are developed for solar hydrogen generation.