Mesoporous and Skeletal Molybdenum Carbide for Hydrogen Evolution Reaction: Diatomite-Type Structure and Formation Mechanism

Molybdenum carbide (MoCx) has generated mounting attentions as noble-metal-free electrocatalysts for hydrogen evolution reaction (HER). Herein, triggered by the strategy of organic-inorganic hybrid oriented transformation in nature, we attempt to prepare a diatomite-type mesostructured MoCx electrocatalyst via the solid-state reaction between MoOx/DMF hybrid precursor and beta-cyclodextrin. Benefiting from the occurrence of the designed individual "mesoskeleton-forming" and "MoCx-generating" processes during pyrolysis, we successfully harvest the targeted electrocatalyst with mesostructural skeleton composed of inter-connected MoCx nanoparticles (similar to 20 nm) and nanorod-like morphology inheriting from its hybrid precursor. This crosslinked mesostructure can not only greatly decrease the diffusion resistance of reactants/products and promote the exposure of active sites, but also efficiently decrease the contact electrical resistance between neighboring MoCx nanoparticles. Importantly, the heterostructure of Mo2C and MoC on the nanorod is tunable in the synthesis process, which is proved to be favorable for the promoted HER performance in both acid and alkaline media. The strategy for synthesizing such nano-structures may open up new avenues for developing mesoskeletal materials.