Optimized metal deficiency-induced operando phase transformation enhances charge polarization promoting hydrogen evolution reaction

Abstract

Electrochemical water reduction is one of the cleanest ways to produce hydrogen efficiently. Non-noble metal-based intermetallic compounds, particularly Ni-based ones, can be projected as potential water electrocatalysts because of N's low cost and high abundance. In this work, Ni’s crystal structure and electronic properties have been tuned by introducing Sn metal followed by operando structural transformation. The synthetically tuned deficiency of Ni in Ni_2-xSn (x = 0.35, 0.50, and 0.63) and operando-induced phase transformation of the room temperature orthorhombic Cmcm space group (Ni_2-xSn_RT) to the high-temperature hexagonal P6₃/mmc space group (Ni_2-xSn_HT) enhance the hydrogen evolution. Several controlled synthesis and electrochemical measurements indicate that Ni_1.5Sn_HT is the most active and stable HER catalyst because of its unique crystallographic structure and high charge transfer kinetics. The phase Ni_1.5Sn_RT was electrochemically transformed to the HT phase during the HER process and found to be extremely stable (150 h) in the chronoamperometric study.