Bifunctional nanocatalysts for water splitting and its challenges

Realization of large-scale hydrogen and oxygen production from splitting of water through competent and sustainable electrolysis is the most promising technique to resolve future energy crisis and offers energy resource with zero carbon footprints in the environment. Considerable efforts have devoted to uncovering materials that can catalyze the hydrogen evolution reaction (HER) effectively; however, the sluggish kinetics of the oxygen evolution reaction (OER) has been the bottleneck in the process, which lowers the overall energy conversion efficiency of water splitting. The ultimate research goal in water splitting is to produce affordable bifunctional electrocatalysts that can operate for both HER and OER, with high efficiency and durability. In this chapter, we summarize the recent progress in the development of nanocatalysts for each half-reaction HER and OER, as well as bifunctional electrocatalysts for overall water splitting. Different cost-effective earth-abundant metal-based catalysts, their performance, limitations, and potentials along with representative results are presented. In the end, the key challenges, opportunities, and possible strategies from the viewpoint of catalyst design and performance are outlined.