A New Class of Molecular Electrocatalysts for Hydrogen Evolution: Catalytic Activity of M₃N@C_{2 n} (2 n = 68, 78, and 80) Fullerenes

The electrocatalytic properties of some endohedral fullerenes for hydrogen evolution reactions (HER) were recently predicted by DFT calculations. Nonetheless, the experimental catalytic performance under realistic electrochemical environments of these 0D-nanomaterials have not been explored. Here, for the first time, we disclose the HER electrocatalytic behavior of seven M₃N@2n (2n = 68, 78, and 80) fullerenes (Gd₃N@I_h(7)-C₈₀, Y₃N@I_h(7)-C₈₀, Lu₃N@I_h(7)-C₈₀, Sc₃N@I_h(7)-C₈₀, Sc₃N@D_5h(6)-C₈₀, Sc₃N@D_3h(5)-C₇₈, and Sc₃N@D₃(6140)-C₆₈) using a combination of experimental and theoretical techniques. The non-IPR Sc₃N@D₃(6140)-C₆₈ compound exhibited the best catalytic performance toward the generation of molecular hydrogen, exhibiting an onset potential of -38 mV vs RHE, a very high mass activity of 1.75 A·mg^-1 at -0.4 V vs RHE, and an excellent electrochemical stability, retaining 96% of the initial current after 24 h. The superior performance was explained on the basis of the fused pentagon rings, which represent a new and promising HER catalytic motif.