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Ma R.,CAS Shanghai Institute of Ceramics | Ma R.,Shanghai Materials Genome Institute | Zhou Y.,CAS Shanghai Institute of Ceramics | Zhou Y.,Shanghai Materials Genome Institute | And 7 more authors.
Angewandte Chemie - International Edition | Year: 2015

The replacement of platinum with non-precious-metal electrocatalysts with high efficiency and superior stability for the hydrogen-evolution reaction (HER) remains a great challenge. Herein, we report the one-step synthesis of uniform, ultrafine molybdenum carbide (Mo2C) nanoparticles (NPs) within a carbon matrix from inexpensive starting materials (dicyanamide and ammonium molybdate). The optimized catalyst consisting of Mo2C NPs with sizes lower than 3 nm encapsulated by ultrathin graphene shells (ca. 1-3 layers) showed superior HER activity in acidic media, with a very low onset potential of -6 mV, a small Tafel slope of 41 mV dec-1, and a large exchange current density of 0.179 mA cm-2, as well as good stability during operation for 12 h. These excellent properties are similar to those of state-of-the-art 20 % Pt/C and make the catalyst one of the most active acid-stable electrocatalysts ever reported for HER. A step is all it takes: A nanocomposite of uniform, ultrafine Mo2C nanoparticles (NPs) encapsulated by ultrathin graphene shells was synthesized simply by the one-step annealing of a mixture of low-cost dicyanamide and ammonium molybdate (see picture). The resulting material served as a hydrogen-evolving electrocatalyst with excellent activity and long-term stability. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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