LAUSR

A facile microwave assisted strategy was employed to synthesize Ni3Bi2S2 nanocrystals. Variation in the synthesis conditions tuned the composition of monoclinic and orthorhombic phases of Ni3Bi2S2. The electrochemical HER activity of the catalyst with highest percentage of monoclinic phase, demonstrated a negligible onset potential of only 24 mV close to that of state-of-the-art Pt/C with an overpotential as low as 0.088V. DFT calculations predicted the monoclinic phase to exhibit the lowest adsorption free energy corresponding to hydrogen adsorption ( [[EQUATION]] ) and therefore, highest hydrogen evolution activity amongst the considered phases. Quasi-2D structure of monoclinic phase facilitates an increased charge-transfer between Ni and Bi favors the downward shift of the d-band centre to enhance the catalytic activity.