C76 Nanospheres/Ni Foam as High-Performance Heterostructured Electrocatalysts for Hydrogen Evolution Reaction: Unveiling the Interfacial Interaction

Fullerenes have emerged as functional catalytic nanomaterials in a plethora of applications, mainly due to their distinctive electronic structures. Therefore, we investigated the electronic structures of different fullerenes (C60, C70, C76, C84, and C100) using density functional theory (DFT) calculations to identify the most suitable candidate as a hydrogen evolution reaction (HER) catalyst. The calculations showed that C76 exhibits the most convenient electronic structure suitable for HER. Consequently, the synergy between C76 nanospheres and nickel foam substrate as a highly efficient HER catalyst has been demonstrated and discussed. The results showed that C76 nanospheres???Ni foam exhibits a superior catalytic activity with an overpotential of 20 mV vs RHE at ???10 mA cm???2, which is almost the same as the benchmark Pt/C catalyst. The calculated free energy and band structure revealed a significant increase in the electron density at the C76/Ni foam interface, indicating the synergy between C76 nanospheres and Ni. Moreover, the exchange current density (J0), charge transfer coefficient (??), and mass activity (MA) were determined to elucidate the kinetics of the HER upon loading the Ni foam with different masses of C76. The electrodes containing 0.48 and 0.53 mg of C76 exhibited high ?? and J0, revealing very fast HER kinetics on their surfaces. This observed drastic increase in J0 is accompanied by a reduction in the activation barrier, which is in agreement with the DFT results.