110th Anniversary: A Total Water Splitting Electrocatalyst Based on Borate/Fe Co-Doping of Nickel Sulfide

The design of tunable low-cost electrocatalysts efficient in both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) is central to the clean production of hydrogen without the reliance on platinum group metals (PGMs), which are the best known electrocatalysts for these reactions today. In this study, a catalyst-integrated electrode with a tunable composition (borate/Fe dual-doped Ni3S2 hollow microspheres on nickel foam) was fabricated by a self-templating method where the dopant contents can be easily varied by the precursor compounds. The catalyst-integrated electrode showed impressive OER and HER activities and good catalyst stability in an alkaline electrolyte. The performance of this electrode for total electrochemical water splitting was quite exceptional, requiring only a small overpotential of 364 mV to yield 50 mA cm(-2) of current density. The strong total water splitting performance can be attributed to the use of complementary anionic (borate) and cationic (Fe) doping of the nickel sulfide structure to improve various elementary processes in the OER and HER mechanisms.