Facile Synthesis of Mo2C Nanocrystals Embedded in Nanoporous Carbon Network for Efficient Hydrogen Evolution.

Exploring facile and easily-scalable methods for synthesizing earth-abundant, cost-effective and efficient hydrogen evolution reaction ( HER) electrocatalysts is essential for the mass production of hydrogen as a clean and sustainable energy carrier. We report here a simple strategy to produce Mo2C nanocrystals embedded in carbon network ( Mo2C@C) by the direct pyrolysis of ammonium molybdate and polyvinylpyrrolidone ( PVP). It is found that PVP can be effectively used as a single source to form carbides and carbon network. The long polymer chain and coordinating capability with transition metal of PVP make it possible to form connected porous carbon network and well-dispersed Mo2C nanocrystals in several nanometers. The carbonization of PVP not only effectively in-situ prevents the aggregation of Mo2C nanocrystals during their formation, but also provides conductive porous matrix. As a result, the Mo2C@C composite exhibits the superior electrocatalytic performance for HER, which can be ascribed to the large number of active sites from plenty of small Mo2C nanocrystals and the efficient mass and electron transport network from carbon matrix. This strategy may inspire the exploration of cost-effective functional polymer as single source for both carbon precursor and nanostructure-directed reagent to mass-produce well-defined metal carbides nanostructures embedded in porous carbon network for energy applications. [ABSTRACT FROM AUTHOR]