Precise Interstitial Built-In Electric Field Tuning for Hydrogen Evolution Electrocatalysis.

The built-in electric field (BEF) has become an effective means of adjusting the electronic structure and hydrogen spillover to influence the adsorption of intermediates. However, the previously reported BEF cannot be tuned continuously and precisely. Herein, a series of nanocatalysts with interstitial BEF were successfully synthesized, and the effect of precisely tuned interstitial BEF on the intermediate's adsorption and hydrogen spillover was systematically investigated using changing the insertion of interstitial B. Three catalysts with different BEF strengths were obtained by changing the interstitial content (B 0.22 -Cu/NC, B 0.30 -Cu/NC, B 0.41 -Cu/NC), and it was demonstrated that B 0.30 -Cu/NC gave the best catalytic performance for hydrogen evolution reactions (HERs). The turnover frequency (TOF) value is shown to reach 0.36 s -1 at just -0.1 V vs. RHE, which is about 3 times that of Cu (0.12 s -1 ). For the HER, it is one of the best Cu-based catalysts reported to date (Table S3). Besides, when the catalyst was applied to the cathode of the PEM water electrolyzer, B 0.30 -Cu/NC exhibited long-time stability at a water-splitting current density of 500 mA cm -2 . Density functional theory and in situ Raman spectroscopy suggest that a suitable interstitial BEF can not only optimize the intermediate's adsorption but also promote hydrogen spillover.