Fabrication of a Three-Dimensional Bionic Si/TiO₂/MoS₂ Photoelectrode for Efficient Solar Water Splitting

Solar water splitting for hydrogen production using semiconductors is widely accepted as one of the most promising routes to relieve the energy crisis and environmental issues caused by the excessive use of fossil fuels. However, the solar to hydrogen conversion efficiency of a Si photoelectrode is suppressed by overpotential, high reflectance, and/or instability in liquid electrolytes. Here, the Si/TiO2/MoS2 photoelectrode with three-dimensional (3D) bionic structure has been fabricated, which can protect Si from corrosion and reduce the reflection of the electrode surface. The TiO2 nanorods not only reduce the sudden change in refractive index from the electrolyte to the Si surface but also improve the problem of weak interface coupling between MoS2 and Si, improving the stability of the photoelectrode. The optimized photoelectrode in this work exhibits a photocurrent density of −0.24 mA/cm2 at 0 V vs RHE (reversible hydrogen electrode), an onset potential of 0.42 V vs RHE, and stability for more than 8 h under 1 sun of simulated solar illumination. The ternary heterojunction structure of Si/TiO2/MoS2 not only reduces its reflection but also improves its carrier separation and transport, thereby improving the photoelectrochemical performance of the photoelectrode.