Comprehensive view on recent developments in hydrogen evolution using MoS2 on a Si photocathode: from electronic to electrochemical aspects

The generation of clean energy is necessary for future technological developments. The utilization of solar illumination to produce H2 from water electrolysis is an alternative route to address the issue. However, the reaction is a thermodynamically uphill task. Furthermore, designing a photocathode, which can use most of the incident radiation for the photoelectrochemical (PEC) reaction, plays an important role. Surface-modified p-Si can be an economically viable option. The sluggish electro-kinetics on the Si surface has been rectified with coatings of cocatalyst materials. In the current review, we have discussed the possible modifications performed on the p-Si surface to reduce the loss due to reflection and coating of the cocatalyst, e.g. MoS2 on p-Si to improve H2 evolution. The facile charge carrier kinetics at the electrode–electrolyte interface has also been discussed. The development of cocatalysts has been focused on our previous experience for two decades. From surface plasmon resonance to heteroatom doping, that is, intentional defect formation and heterostructure design, we have included a comprehensive discussion on cocatalysts. The energetics of single atom replacement and its implications for efficiency has been included. This review gives insights into the currently emerging cocatalyst design for PEC water splitting. In this regard, the review presents insights into the phase transformation in MoS2 during the PEC process using operando techniques. A discussion on the effect of single atom replacement in the inactive basal-MoS2 plane has been included.