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Summary
Modulating the electronic asymmetricity of catalysts is an effective method for optimizating the elementary steps of water dissociation and hydrogen adsorption/desorption process for the alkaline hydrogen evolution reaction (HER). Herein, uniform Ru nanoclusters anchored on N doped ultrathin carbon nanosheets (Ru/NC) are synthesized to optimize the asymmetricity electronic properties of supported Ru for efficient HER. It is found that Ru and NC with a large work function difference (Delta phi) leading to the formation of stronger asymmetrical charge distributions of Ru that electron-deficient high-valence Ru (Run+) coupling with low-valence Ru (Ru0). Experimental and theoretical studies indicate the Run+ sites lowered the energy barrier for water dissociation and provided enough hydrogen proton to promote the hydrogen spillover from the Run+ to Ru0 sites, and Ru0 sites can enhance H desorption process, thus synergistically enhancing the hydrogen evolution activity. Notably, the Ru/NC catalyst exhibits a high alkaline HER activity (21.9 mV@10 mA cm-2, 29.03 mV dec-1). The role of electronic asymmetricity on supported Ru nanoclusters for the alkaline HER are demonstrated, which will provide guidelines for the rational design of high-efficiency alkaline HER catalysts. @@@ The large work function difference between Ru and NC leads to the formation asymmetrical charge distributions of supported Ru that electron-deficient high-valence Ru (Run+) coupling with low-valence Ru (Ru0). The Run+ sites lowered the energy barrier for water dissociation and Ru0 sites can enhance H desorption process, thus, synergistically enhancing the hydrogen evolution activity.image
