Hydrogen Evolution from Neutral Water Catalyzed by Cobalt Sulfide Nanoparticles

Solar-driven water splitting to produce hydrogen and oxygen is widely considered as a sustainable approach to meet the increasing global energy demand, in which hydrogen acts as a green energy carrier. The slow kinetics of hydrogen evolution reaction (HER) in water necessitates the development of novel HER catalysts. A great number of HER catalysts employing expensive metals, such as Pt, have been reported, but the associated scarce and cost prohibit their wide application. A few solid-state catalysts employing earth-abundant elements have also been reported, however most of them only function in organic or strong acidic media. To make water splitting economically viable and environmentally friendly, ideal HER catalysts must exhibit competent and robust performance in neutral water. Considering the cost, earth abundance, and working environment in practical applications, our group has been focusing on developing transition metal chalcogenides as HER catalysts in neutral water. Recently we have prepared cobalt sulfide nanoparticles via a hydrothermal method, which exhibit excellent hydrogen evolution catalysis in pH 7 buffer. More encouraging results have been obtained when the cobalt sulfide nanoparticles were prepared in the presence of mildly oxidized graphene sheets. The high specific surface area and excellent conductivity of graphene significantly enhanced the catalytic performance. The remarkable stability of the cobalt sulfide nanoparticles allowed us to carry out HER catalysis over a long period of time in neutral aqueous media as well as in natural water collected from the Great Salt Lake