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

Cu2O is a promising low-cost semiconductor exhibiting a narrow band gap. The combination of p-type Cu2O with n-type TiO2 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 H2 generation through water photosplitting and organic photoreforming over Cu2O/TiO2-based composites. This literature survey aims at clarifying conflicting information on the preparation, characterization, and use of Cu2O/TiO2 composites for H2 evolution. Detailed information on analytical techniques devoted to uniquely identifying Cu2O has been provided. Preparation method, effect of pH, effect of sacrificial agent, chemical stability of Cu2O/TiO2 composites, and reaction mechanisms have been critically discussed. The highest efficiency values obtained over Cu2O/TiO2 photocatalysts have been reported. A solid groundwork on which developing new effective and low-cost materials for H2 generation has been provided.