High quantum efficiency of hydrogen production from methanol aqueous solution with PtCu-TiO2 photocatalysts

Abstract

Methanol with 12.5 wt% H₂ content is widely considered a liquid hydrogen medium. Taking into account water with 11.1 wt% H₂ content, H₂ synthesis from the mixture of water and methanol is a promising method for on-demand hydrogen production. We demonstrate an atomic-level catalyst design strategy using the synergy between single atoms and nanodots for H₂ production. The PtCu-TiO₂ sandwich photocatalyst achieves a remarkable H₂ formation rate (2,383.9 µmol h^-1) with a high apparent quantum efficiency (99.2%). Furthermore, the oxidation product is a high-value chemical formaldehyde with 98.6% selectivity instead of CO₂, leading to a nearly zero-carbon-emission process. Detailed investigations indicate a dual role of the copper atoms: an electron acceptor to facilitate photoelectron transfer to Pt, and a hole acceptor for the selective oxidation of methanol to formaldehyde, thus avoiding over-oxidation to CO₂. The synergy between Pt nanodots and Cu single atoms together reduces the activation energy of this process to 13.2 kJ mol^-1.