Feng Liang-Liang, Li Guo-Dong, Liu Yipu, Wu Yuanyuan, Chen Hui, Wang Yun, Zou Yong-Cun, Wang Dejun, Zou Xiaoxin
State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University , 2699 Qianjin Street, Changchun, Jilin 130012, China.
ACS Appl Mater Interfaces. 2015 Jan 14;7(1):980-8. doi: 10.1021/am507811a. Epub 2015 Jan 5.
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.
分解水来制取氢气需要开发能够使该反应可行且高效节能的非贵金属催化剂。在此，我们表明硫钴矿（Co9S8）纳米颗粒可作为一种对析氢反应具有电化学活性的无贵金属材料，并且它们在中性溶液（pH 7）中能稳定工作，但在酸性（pH 0）和碱性（pH 14）介质中则不行。因此，我们进一步提出一种碳包覆策略，以在更宽的pH范围内提高Co9S8的耐久性和活性。具体而言，碳包覆的Co9S8纳米颗粒（Co9S8@C）是通过在氮气气氛中于700℃对硝酸钴和三硫氰尿酸的混合物进行直接热处理制备的。三硫氰尿酸在反应体系中既作为硫源又作为碳源。所得的Co9S8@C材料在从pH 0到14的宽pH范围内都具有高活性且运行良好，并且在酸性（pH 0）、中性（pH 7）和碱性（pH 14）介质中的析氢反应过程中法拉第产率接近100%。据我们所知，这是首次表明一种过渡金属硫族化物材料具有全pH范围高效且耐用的电催化活性。将Co9S8确定为催化活性相并开发碳包覆作为改进策略有望为高性能无贵金属析水催化剂的合理设计注入新的活力。
