Hydrogen fuel is among the cleanest renewable resources and is the best alternative to fossil fuels for the future. Hydrogen can be best produced by means of electrolysis or photoelectrolysis of water among the various routes available for hydrogen production. So far, Pt has been recognized as the best electrode material for electrochemical hydrogen production. However, the cost of the catalyst, activity, and durability make Pt-catalyzed hydrogen production unsuitable on a commercial scale. It has hence become imperative to explore low-cost, highly active and durable HER catalysts to replace platinum as a catalyst. This perspective provides key concepts and the current status of the research on the properties of nanocatalysts that influence the hydrogen evolution reaction. Important structural features controlling the surface chemistry (i.e. facets, defects, dopants), nature of supports (graphene, CNTs, black phosphorus), role of heteroatoms, media and morphology are the key points of discussion in this perspective.

BiVO4 is a promising photoanode material for photoelectrochemical water splitting applications due to its narrow band gap i.e., ̴ 2.4 eV, suitable band-edge positions, non-toxicity and high stability. Here, we...

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CdS is a well-known semiconductor for photoelectrochemical (PEC) water splitting applications, but the efficiency of this semiconductor is limited due to the high recombination rate of electron–hole pairs. Here, we have adopted a strategy to modify the CdS photoanode by the incorporation of a hole scavenger, cobalt phosphate (CoPi), and an electron scavenger, multi-walled carbon nanotubes (CNTs), which would lead to the simultaneous extraction of electron–hole pairs generated in CdS. An improved suppression of the charge-carrier recombination and effective charge transfer has been attained in case of the CdS–CNT–CoPi composite and is demonstrated using the PEC studies. The CdS–CNT–CoPi composite shows a 90-fold enhancement in photocurrent when compared to CdS at 1.23 V versus the reversible hydrogen electrode. The ternary composite also showed much higher PEC activity compared to the binary composites of CdS–CNT and CdS–CoPi. The fundamental mechanism behind the enhanced PEC activity was understood by the ultrafast transient absorption spectroscopic studies, which provides insights into the kinetics of charge transfer. Such mechanistic studies would be helpful for the optimization of efficiency and design of such photoanodes.