Cu Nanocluster-Loaded TiO₂ Nanosheets for Highly Efficient Generation of CO-Free Hydrogen by Selective Photocatalytic Dehydrogenation of Methanol to Formaldehyde

Safe storage and transportation of H₂ is a fundamental requirement for its wide applications in the future. Controllable release of high-purity H₂ from a stable storage medium such as CH₃OH before use offers an efficient way of achieving this purpose. In our case, Cu nanoclusters uniformly dispersed onto (001) surfaces of TiO₂ nanosheets (TiO₂/Cu) are selectively prepared by thermal treatment of HKUST-1 loaded TiO₂ nanosheets. One of the TiO₂/Cu composites, TiO₂/Cu_50, exhibits remarkably high activity toward the selective dehydrogenation of CH₃OH to HCHO with a H₂ evolution rate of 17.8 mmol h^–1 per gram of catalyst within a 16-h photocatalytic reaction (quantum efficiency at 365 nm: 16.4%). Theoretical calculations reveal that interactions of Cu nanoclusters with TiO₂ could affect their electronic structures, leading to higher adsorption energy of CH₃OH at Ti sites and a lower barrier for the dehydrogenation of CH₃OH by the synergistic effect of Cu nanoclusters and TiO₂, and lower Gibbs free energy for desorption HCHO and H₂ as well.