Trimetallic oxyhydroxides as active sites for large-current-density alkaline oxygen evolution and overall water splitting

Abstract

• FeCoNi(S) exhibited a low overpotential of 252 and 293 mV to deliver current densities of 100 and 500 mA cm -2 in alkaline media, respectively. • When FeCoNi(S) was used as a bifunctional catalyst for overall water splitting, only a low cell voltage of 1.84 V was needed to acquire 500 mA cm -2 with stability over 2000 h. • As the active sites, the Ni(Fe,Co) trimetallic oxyhydroxides evolved from FeCoNi(S) during reconstruction displayed the lowest overpotential for OER with the trend of Ni(Fe,Co)OOH > Ni(Co)OOH > NiOOH, which was also applicable to oxides, selenides, etc. Earth-abundant electrocatalysts for large-current-density water splitting under alkaline condition are desirable. Oxygen evolution reaction, which is a bottleneck of the overall water splitting, faces the problems of complicated reconstruction and deficiency in rational design of active sites. Herein, we report a series of transition metal chalcogenides for alkaline OER. Among them, FeCoNi(S) displayed a low overpotential of 293 mV to deliver a current density of 500 mA cm −2 , which is in the top level of non-precious metal based OER electrocatalysts. A combination of (ex) in situ characterizations and DFT calculation shows that Ni(Fe,Co) trimetallic oxyhydroxides were the active sites for highly-efficient OER. Furthermore, for FeCoNi(S), when used as a bifunctional catalyst for water splitting, it only required a cell voltage of 1.84 V to deliver ∼500 mA cm −2 with extraordinary long-term stability over 2000 h. This work provides the comprehension of high-efficiency, robust catalysts for OER and overall water splitting at large current densities in alkaline media.