Hydrogen production through photoreforming processes over Cu2O/TiO2 composite materials: A mini-review

CuO is a promising low-cost semiconductor exhibiting a narrow band gap. The combination of p-type CuO with n-type TiO results in a p-n heterojunction highly beneficial to photocatalytic processes, due to the resulting capability of (i) absorbing visible light irradiation and (ii) promoting charge carrier separation. An intense scientific activity has been recorded in the field of H generation through water photosplitting and organic photoreforming over CuO/TiO-based composites. This literature survey aims at clarifying conflicting information on the preparation, characterization, and use of CuO/TiO composites for H evolution. Detailed information on analytical techniques devoted to uniquely identifying CuO has been provided. Preparation method, effect of pH, effect of sacrificial agent, chemical stability of CuO/TiO composites, and reaction mechanisms have been critically discussed. The highest efficiency values obtained over CuO/TiO photocatalysts have been reported. A solid groundwork on which developing new effective and low-cost materials for H generation has been provided.