Rational design of low-cost and efficient electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is imperative for renewable energy conversion. Herein, for the first time, a facile strategy to synthesize noble-free bimetallic sulfide heterostructure Ni3S2/Co3S4 nanocubes on nickel foam, is developed. The resulting sample would stimulate formation of high-valent Ni/Co sites, which can be verified by electronic coupling effect and XPS technique. The as-prepared bifunctional Ni3S2/Co3S4 electrode exhibits excellent electrocatalytic activity for HER and OER in 1 M KOH electrolyte. Moreover, when designed as cathode and anode simultaneously, it shows a considerably low cell voltage of 1.49 V at the current density of 10 mA cm-2, which is far surpassing most of the reported bifunctional metal sulfides. More importantly, the density functional theory (DFT) calculations evidence that bimetallic sulfide heterostructure boosts formation of lower barrier Gibbs free energies of H and O-containing intermediates (H* OH* OOH*), modulating the d-band center of Co sites, enhancing the charge transport performance of Ni and Co, increasing the valence of Co active site, thereby accelerating the intrinsic catalytic activity. Based on the results of XPS, Bader charge and electronic coupling effect, it is found that during the reaction, partially electrons prefer transfer from Ni2+ to Co3+ via the S2- bridging. This work suggests the importance of rational design and exploitation of bifunctional metal sulfides for promoting electrocatalytic activity of bimetallic sulfides.

Unveiling the high-valent bimetal cation enhanced electrocatalytic mechanism of bifunctional metal sulfides for overall water splitting

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.