Mimicking [FeFe]-Hydrogenase: PtNi Alloy on Halogen-Tuned Carbon Nanotubes for the Alkaline Hydrogen Evolution Reaction

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Abstract The kinetics of alkaline hydrogen evolution reactions (HERs) are fundamentally restricted by the high energy barrier for water (H2O) dissociation and the insufficient supply of protonic sources. Herein, inspired by the ingenious structure of [FeFe]-hydrogenases in nature, we present the design of a biomimetic electrocatalyst, namely, platinum−nickel (PtNi) alloy clusters on halogen-tuned carbon nanotubes (X-CNTs, X = F, Cl, or Br) to address these issues. In this design, the X-CNTs mimic the function of the organic ligands in [FeFe]-hydrogenases by enriching interfacial H2O molecules as the protonic source. The enriched interfacial H2O molecules then efficiently transfer to the halogen-modified PtNi clusters that mimic the active core of [FeFe]-hydrogenases for HER catalysis. Experimental and theoretical investigations show that the biomimetic PtNi@X-CNTs exhibit enhanced H2O adsorption, dissociation, and improved hydrogen adsorption free energy compared with PtNi@CNTs, therefore, achieving better alkaline HER performance. A small overpotential of 13 mV at 10 mA cm−2 and a turnover frequency of 31.6 s−1 at 50 mV for the HER were achieved with the optimum PtNi@F-CNTs, which are much better than those of the commercial Pt/C (5 wt %) catalyst.

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