Polyoxometalate-Surfactant Hybrids Directed Assembly of Ni3S2 into Hollow Microsphere as Pt-Comparable Electrocatalyst for Hydrogen Evolution Reaction in Alkaline Medium.

Abstract

A large surface area of catalytic sites and low electric resistance are desirable properties for electrocatalysts that lower the overpotential required for electrochemical reactions, such as the hydrogen evolution reaction (HER), in this study. In the presence of polyoxometalate (POM) and triblock copolymer pluronic (P123) as a hybrid soft template, the hydrothermal sulfurization of nickel foam leads to the formation of a hollow microsphere, assembled from the Ni3S2 motif. Sonication for preparing POM+P123 hybrids, while adjusting the POM content, is an effective strategy for synthesizing a Pt-like electrocatalyst with excellent hydrogen evolution efficiency. The reason is that both sonication and optimal POM content can simultaneously enhance the electroactive surface area and electron transfer of the Ni3S2 electrocatalyst. Adopting the optimal conditions, the three-dimensional porous network, composed of Ni3S2 hollow microspheres on the nickel foam, shows that the HER in an alkaline medium requires only 77 mV overpotential for a current density of 10 mA cm-2, with a robust long-term stability during a 25 h test. The performance at a large current density outperforms the current benchmark electrocatalyst (Pt) for HER.