Polyethylenimine modified nickel phosphide nanosheets: Interfacial proton boosts hydrogen evolution reaction
Hydrogen evolution reaction (HER) is an important half reaction in water electrolysis. According to Nernst equation, increasing the interfacial proton concentration may be an effective strategy for reducing the overpotential of HER. Based on interface engineering strategy, herein, we successfully synthesize the polyethyleneimine (PEI) modified nickel phosphide (NiP2) nanosheets on carbon cloth (CC) nanohybrids (denoted as PEI@NiP2-CC). The multiple physical characterization prove that PEI molecules are firmly anchored on NiP2 surface due to strong N-Ni bond interaction. In both acidic and neutral media, the solution protons are enriched at PEI@NiP2-CC/electrolyte interface due to the protonation -NH2 groups at PEI molecules. The effect of PEI molecular weight (MW) on HER activity is explored in detail. The MW optimized PEI@NiP2-CC nanohybrids show only 44 and 100 mV overpotential for HER in acidic and neutral media, which are much better than un-modified NiP2-CC nanohybrids. This work provides a solid basis for the correlativity between surface modification and catalytic activity.