One-step construction of buried a-Si/c-Si junction photocathodes for boosting photoelectrochemical hydrogen production

The activity of Si-based photocathode for photoelectrochemical hydrogen production is mainly restricted by inadequate photovoltage and easy (photo)-corrosion, requiring complex doping or deposition techniques for improvement. Herein, a mild and feasible strategy is proposed to fabricate an amorphous Si/crystal Si (a-Si/c-Si) junction photocathode with co-deposited Pt cocatalyst. The a-Si layer acts as an electron transfer mediator to form an a-Si/c-Si buried junction with large energy band shift, thereby ensuring facile charge transfer. Meanwhile, the a-Si layer serves as a growth substrate to obtain controllable Pt nanoparticles. The Pt/a-Si/c-Si photocathode shows an onset potential of 0.42 V vs reversible hydrogen electrode (VRHE). A photocurrent up to - 35.0 mA cm-2 at 0 VRHE is obtained on Pt/a-Si/c-Si, which is much higher than that without a-Si layer. This study provides a practical manner for improving the photoresponse of planar Si-based photocathodes based on the construction of Si junction.