Confined Synthesis: From Layered Titanate to Highly Efficient and Durable Mesoporous Cu/TiO2 Hydrogen Evolution Photocatalysts

Highly efficient, durable, and earth-abundant photocatalysts are of great interest toward practical photocatalytic conversion reactions, such as hydrogen generation and CO2 reduction. In this work, the intercalation and confinement of "copper ions" within layered titanate nanosheets enabled preparation of copper-modified TiO2 mesoporous spheres (Cu/TiO2), which contain well-dispersed small copper nanoparticles with a diameter of approximately 3-5 nm over the TiO2 mesoporous spheres. Without a cocatalyst (e.g., Pt), the obtained samples exhibited superior photocatalytic hydrogen evolution reaction (HER) activity (13.45 mmol/g/h) and excellent durability during a cyclic HER testing for 120 h, compared against 2.41 mmol/g/h of Cu-modified P25 TiO2. Computational simulations suggest that the Fermi level of small copper nanoparticles is located between the conduction band of TiO2 and the H+/H-2 reduction potential, and if extrapolated to nanoparticles, then this holds for particles up to approximately 9 nm. This would efficiently facilitate electron trapping and then transfer from TiO2 to copper followed by the reduction reaction, leading to excellent photocatalytic H-2 evolution reaction.