A General Self‐Assembly Induced Strategy for Synthesizing 2D Ultrathin Cobalt‐Based Compounds Toward Optimizing Hydrogen Evolution Catalysis

Abstract Exploring a general method for synthesizing 2D compounds with high accessible surface area and nano‐thickness as advanced electrocatalysts is essential yet challenging. Herein, a self‐assembly induced reverse micelle templating method followed by topochemical transformation is developed to synthesize a series of cobalt‐based compounds with varied anions and similar ultrathin 2D structures. Electrocatalytic behaviors for the hydrogen evolution reaction (HER) are systematically investigated, which demonstrate enhanced performances of ultrathin 2D compounds than their agglomerated counterparts. Among them, 2D CoP is particularly prominent. The overpotential of 144 mV at 10 mA cm −2 , together with superb stability, place it among the best single‐phase phosphide HER catalysts reported thus far. Theoretical calculation and experimental results demonstrate the favorable valence electronic structure with moderate hydrogen adsorbability and good intracrystalline conductivity, as well as the homogeneous ultrathin 2D configuration with sufficiently exposed active sites and shortened intracrystalline electron transport route, are the dominant reasons that 2D CoP exhibits optimal electrocatalytic activity for HER. This study presents a novel and extendable strategy for synthesizing various 2D metal‐based compounds with valuable insights into the modulation essence of advanced electrocatalysts.