Ultrasmall CoSe₂ Nanoparticles Grown on MoS₂ Nanofilms: A New Catalyst for Hydrogen Evolution Reaction

Non‐noble‐metal‐based and earth‐abundant electrocatalysts have been extensively investigated for the hydrogen evolution reaction (HER). However, they still suffer from large Tafel slopes high overpotentials, resulting in inferior HER catalytic activity. Herein, a novel, cost‐effective, electrochemically stable catalyst is presented by growing ultrasmall CoSe 2 nanoparticles on MoS nanofilms using facile hydrothermal method. The /MoS hybrid shows superior activity to both or alone their physical mixture. With slope as small 37.8 mV dec −1 , excellent properties an acidic solution. promising performance can be attributed synergistic effect of nanofilms. In addition, almost unchanged after 1000 cyclic voltammetric sweeps, indicating its long‐term durability under conditions.