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

The kinetics of alkaline hydrogen evolution reactions (HERs) are fundamentally restricted by the high energy barrier for water (H 2 O) 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 H 2 O molecules as the protonic source. The enriched interfacial H 2 O 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 H 2 O 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.