Atomically Precise Ni Nanoclusters for Improving Hydrogen Evolution Reaction Performance

The generation of green hydrogen via electrocatalytic water splitting is an emerging strategy in the prospect of developing future energy devices. Herein, we designed watersoluble atomically precise Ni nanoclusters (NCs) on MoSe2 nanosheets (NSs) to enhance the hydrogen evolution reaction (HER) performance. The strong UV-vis absorption band and matrix-assisted laser deposition ionization (MALDI) time-of-flight mass spectra confirm the formation of Ni7 NCs. The energy dispersive X-ray spectroscopy mapping confirms the homogeneous distribution of Ni, Mo, and Se throughout the surface of the ultrathin NS. X-ray photoelectron spectroscopy study reveals the strong interfacial interaction between Ni NCs and MoSe2 in the nanocomposite by substantial electron density transferring from Ni NCs to the MoSe2 NSs. It is seen that the 5 wt % Ni/MoSe2 composite structure exhibits the most notable HER efficiency with an overpotential of 170 mV vs reversible hydrogen electrode @ 10 mA/cm2 which is significantly lower than that of bare MoSe2 NSs (350 mV). The significantly lower Tafel slope of the Ni/MoSe2 nanocomposite indicates that the HER kinetics of MoSe2 is accelerated in the presence of Ni NCs. The charge-transfer resistance of the nanocomposite is significantly low compared to pristine MoSe2, confirming the enhanced interfacial charge transfer. This work opens up further opportunities to design efficient and low-cost electrocatalysts for improving the HER performance by incorporating the advantages of both non-precious atomically precise metal NCs and transition-metal dichalcogenides in one system.