Recent progress in noble metal nanocluster and single atom electrocatalysts for the hydrogen evolution reaction

Hydrogen, a renewable and clean energy carrier, is the best alternative to fossil fuels. Hydrogen evolution from water electrolysis using renewable electrical energy is quite attractive. Noble-metal-based materials are currently considered the best electrocatalysts for the hydrogen evolution reaction (HER) at the cathode of electrolysis cells. Noble metal nanocluster and single atom electrocatalysts as model materials with an ultra-small size and high atomic utilization have shown promising catalytic HER performance. In this paper, recent research efforts toward developing advanced noble metal nanocluster and single atom electrocatalysts supported on different support materials with high performance for water splitting catalysis are reviewed and analyzed in terms of their design, synthesis, characterization, catalytic mechanisms, and HER performance validation and optimization. The technical challenges in researching and developing such nanocluster and single atom HER electrocatalysts are discussed and future research directions are also proposed for overcoming the challenges toward their practical application.