title: Carbon-armored Co9S8 nanoparticles as all-pH efficient and durable H2-evolving electrocatalysts.
abstract: Splitting water to produce hydrogen requires the development of non-noble-metal catalysts that are able to make this reaction feasible and energy efficient. Herein, we show that cobalt pentlandite (Co9S8) nanoparticles can serve as an electrochemically active, noble-metal-free material toward hydrogen evolution reaction, and they work stably in neutral solution (pH 7) but not in acidic (pH 0) and basic (pH 14) media. We, therefore, further present a carbon-armoring strategy to increase the durability and activity of Co9S8 over a wider pH range. In particular, carbon-armored Co9S8 nanoparticles (Co9S8@C) are prepared by direct thermal treatment of a mixture of cobalt nitrate and trithiocyanuric acid at 700 °C in N2 atmosphere. Trithiocyanuric acid functions as both sulfur and carbon sources in the reaction system. The resulting Co9S8@C material operates well with high activity over a broad pH range, from pH 0 to 14, and gives nearly 100% Faradaic yield during hydrogen evolution reaction under acidic (pH 0), neutral (pH 7), and basic (pH 14) media. To the best of our knowledge, this is the first time that a transition-metal chalcogenide material is shown to have all-pH efficient and durable electrocatalytic activity. Identifying Co9S8 as the catalytically active phase and developing carbon-armoring as the improvement strategy are anticipated to give a fresh impetus to rational design of high-performance noble-metal-free water splitting catalysts.
authors.affiliation: State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University , 2699 Qianjin Street, Changchun, Jilin 130012, China.
authors.forename: Liang-Liang
authors.initials: LL
authors.lastname: Feng
authors.forename: Guo-Dong
authors.initials: GD
authors.lastname: Li
authors.forename: Yipu
authors.initials: Y
authors.lastname: Liu
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Wu
authors.forename: Hui
authors.initials: H
authors.lastname: Chen
authors.forename: Yun
authors.initials: Y
authors.lastname: Wang
authors.forename: Yong-Cun
authors.initials: YC
authors.lastname: Zou
authors.forename: Dejun
authors.initials: D
authors.lastname: Wang
authors.forename: Xiaoxin
authors.initials: X
authors.lastname: Zou
keywords: carbon; cobalt; hydrogen evolution; sulfide; water splitting