Novel cobalt/nickel-tungsten-sulfide catalysts for electrocatalytic hydrogen generation from water

The potential of water (photo) electrolysis technology to provide hydrogen as a fuel on a large scale depends on how viable electrocatalysts for the water oxidation reaction (WOR) and the hydrogen evolution reaction (HER) are and whether they can be constructed from elements which are abundant in the Earth's crust. Here we show that ternary sulfides of cobalt-tungsten and nickel-tungsten (MWSx where M is Co or Ni) are efficient and robust electrocatalysts for the HER in water over a wide pH range. These novel ternary sulfides were readily grown on a conducting electrode surface by employing a scalable electrodeposition process from aqueous solutions of [M(WS4)(2)](2-). In terms of HER activity, the MWSx catalysts represent attractive alternatives to platinum. Moreover, we show that the HER activity is governed by the nature of the metal M within M-S-W heterobimetallic sulfide centres, located in the WS2-like layered structure of MWSx. Our work provides structural andmechanistic keys to understand how HER activity is promoted in previously described nickel and cobalt-doped molybdenum and tungsten sulfide materials.