Atomic-scale platinum deposition on photocathodes by multiple redox cycles under illumination for enhanced solar-to-hydrogen energy conversion

The fabrication of photoelectrochemical (PEC) cells using Cu₂O, a semiconductor light absorber that responds to infinite sunlight, requires techniques for loading and activating highly efficient cocatalysts to increase the hydrogen production selectivity. However, there has been relatively little interest in techniques for the deposition of efficient catalysts on PEC electrodes that can maximize the surface activation of the light absorption layer for water splitting, because precise control of the Pt loading at the atomic scale is difficult. We designed an intelligent multiple-redox illuminated deposition technique capable of depositing atomic-scale Pt catalysts with optimal performance on the photocathode surface. An Sb:Cu₂O/Cu₂O/Al:ZnO/TiO₂ photocathode with the proposed atomic-scale Pt catalyst has a high photocurrent density of 6.2 mA cm⁻² and a more positive onset potential of 0.71 V_RHE. In addition, the mass activity of this electrode is 3.35 times higher than that of Pt samples deposited by conventional methods, and the electrode also shows outstanding operational stability. The proposed approach enables a uniform catalyst distribution and position-selective deposition atomic-scale Pt by repeated redox reactions. Consequently, our proposal enables the simultaneous realization of enhanced conversion efficiency and low cost by the consumption of a relatively small quantity of Pt in controllable redox photodeposition.