Heterostructured nanocatalysts to boost the hydrogen evolution reaction in neutral electrolyte

Water electrolysis under neutral conditions is key to the practical production of H₂ as a renewable energy source because of the minimized corrosion of the water electrolyzer and the direct use of seawater. However, the intrinsically slow kinetics of electrocatalytic water splitting in neutral conditions remains a formidable hurdle to the wide adoption of neutral water splitting technology. Ingenious and revolutionary design concepts for catalysts are thus in great demand to address this issue. Here, we systematically review the current development of HER catalysts in neutral media by categorizing them into three subgroups to address the issues associated with the elementary steps, respectively, of the HER mechanism. We also present the recent efforts to use nanocatalysts in practical water electrolyzers with neutral electrolytes or seawater. Finally, we discuss the present limitations and provide future research directions to guide the development of highly active and stable HER catalysts in neutral media.