A p-n-p Configuration Based on the Cuprous Oxide/Silicon Tandem Photocathode for Accelerating Solar-Driven Hydrogen Evolution

Photoelectrochemical splitting of water into hydrogen is a potential route to motivate the application of solar-driven conversion to clean energy but is regularly limited by its low efficiency. The key to addressing this issue is to design a suitable photocathode configuration for high-efficiency photogenerated carrier separation and transmission to photocathode-surface reaction sites. In this work, we report a Si-Cu₂O tandem photocathode featuring a p-n-p configuration for solar-driven hydrogen evolution in an alkaline solution. Driven by this built-in field, the electrons induced from Si were transferred through FeOOH, which acted as electron tunnels, to combine with the holes from Cu₂O, triggering more electrons generated from Cu₂O to particiate in the surface reaction. Under simulated sunlight, the optimized photocathode achieved and maintained a photocurrent density of -11 mA/cm² at 0 V_RHE in alkaline conditions for 120 min, outperforming the reported tandem cell consisting of Si and Cu₂O photocathodes. Our results provide valuable insight into a feasible way to construct an optimized photocathode for efficient solar-driven H₂ evolution.