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Ultrathin N-Doped Mo<sub>2</sub>C Nanosheets with Exposed Active Sites as Efficient Electrocatalyst for Hydrogen Evolution Reactions

Jin JiaGuangzhou Key Laboratory for Surface Chemistry of Energy Materials, New Energy Research Institute, School of Environment and Energy, South China University of Technology, Guangzhou Higher Education Mega Center, Guangzhou, Guangdong 510006, People’s Republic of ChinaTanli XiongGuangzhou Key Laboratory for Surface Chemistry of Energy Materials, New Energy Research Institute, School of Environment and Energy, South China University of Technology, Guangzhou Higher Education Mega Center, Guangzhou, Guangdong 510006, People’s Republic of ChinaLili ZhaoState Key Laboratory of Crystal Materials, Center of Bio & Micro/Nano Functional Materials, Shandong University, 27 Shandanan Road, Jinan, Shandong 250100, People’s Republic of ChinaFulei WangState Key Laboratory of Crystal Materials, Center of Bio & Micro/Nano Functional Materials, Shandong University, 27 Shandanan Road, Jinan, Shandong 250100, People’s Republic of ChinaHong LiuState Key Laboratory of Crystal Materials, Center of Bio & Micro/Nano Functional Materials, Shandong University, 27 Shandanan Road, Jinan, Shandong 250100, People’s Republic of ChinaRenzong HuSchool of Materials Science and Engineering, South China University of Technology, Guangzhou, Guangdong 510640, People’s Republic of ChinaJian ZhouNational Laboratory of Solid State Microstructures and Department of Materials Science and Engineering, Nanjing University, 22 Hankou Road, Nanjing, Jiangsu 210093, People’s Republic of ChinaWeijia ZhouGuangzhou Key Laboratory for Surface Chemistry of Energy Materials, New Energy Research Institute, School of Environment and Energy, South China University of Technology, Guangzhou Higher Education Mega Center, Guangzhou, Guangdong 510006, People’s Republic of ChinaShaowei ChenDepartment of Chemistry and Biochemistry, University of California, 1156 High Street, Santa Cruz, California 95064, United States

2017en

ABI

Аннотация

Probing competent electrocatalysts for hydrogen evolution reaction (HER) of water splitting is one of the most hopeful approaches to confront the energy and environmental crisis. Herein, we highlight ultrathin N-doped Mo2C nanosheets (N-Mo2C NSs) in the role of greatly efficient platinum-free-based electrocatalysts for the HER. The transformation of crystal phase and structure between MoO2 nanosheets with a thickness of ∼1.1 nm and N-Mo2C NSs with a thickness of ∼1.0 nm is studied in detail. Structural analyses make clear that the surfaces of the N-Mo2C NSs are absolutely encompassed by apical Mo atoms, hence affording an ideal catalyst prototype to expose the role of Mo atoms for the duration of HER catalysis. Theoretical calculations demonstrate that the nanosheet structure, N doping, and particular crystalline phase of Mo2C produce more exposed Mo active sites, including Mo atoms on the C plane and doped N atoms. Through detailed electrochemical investigations, N-Mo2C NSs possess HER activity with an onset potential of −48.3 mV vs RHE, Tafel slope of 44.5 mV dec–1, and overpotential of 99 mV vs RHE at the cathodic current density of 10 mA cm–2 with excellent long-term stability. Lastly, the calcination temperature and dicyandiamide amount can obviously affect the phase transformation and surface structure of molybdenum carbide, resulting in an adjustable HER activity. This synthesis mechanism will facilitate the understanding and optimization of Mo-based electrocatalysts in the energy conversion field.

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DOI: 10.1021/acsnano.7b06607

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