Iron Catalyzed Cascade Construction of Molybdenum Carbide Heterointerfaces for Understanding Hydrogen Evolution.

The intercrystalline interfaces have been proven vital in heterostructure catalysts. However, it is still challenging to generate specified heterointerfaces and to make clear the mechanism of a reaction on the interface. Herein, this work proposes a strategy of Fe-catalyzed cascade formation of heterointerfaces for comprehending the hydrogen evolution reaction (HER). In the pure solid-phase reaction system, Fe catalyzes the in situ conversion of MoO2 to MoC and then Mo2 C, and the consecutive formation leaves lavish intercrystalline interfaces of MoO2 -MoC (in Fe-MoO2 /MoC@NC) or MoC-Mo2 C (in Fe-MoC/ß-Mo2 C@NC), which contribute to HER activity. The improved HER activity on the interface leads to further checking of the mechanism with density functional theory calculation. The computation results reveal that the electroreduction (Volmer step) produced H* prefers to be adsorbed on Mo2 C; then two pathways are proposed for the HER on the interface of MoC-Mo2 C, including the single-molecular adsorption pathway (Rideal mechanism) and the bimolecular adsorption pathway (Langmuir-Hinshelwood mechanism). The calculation results further show that the former is favorable, and the reaction on the MoC-Mo2 C heterointerface significantly lowers the energy barriers of the rate-determining steps.

A semi-encapsulated PdRh alloy heterojunction for the selective catalytic hydrogenation of nitrophenylacetylene to nitrostyrene.

Semi-hydrogenation usually requires an effective catalyst to ensure selectivity, especially when reducible groups coexist in a molecule. Pd is widely used in the semi-hydrogenation of alkynes to synthesize alkenes, but the selectivity control is still challenging. Herein, we design a catalyst with a semi-encapsulated PdRh alloy heterojunction in a carbon layer for the selective semi-hydrogenation of 3-nitrophenylacetylene (3-NPA). Benefiting from the presence of a PdRh alloy heterojunction and a semi-encapsulated structure, the catalyst delivers good selectivity and maintains high activity. In addition, the carbon shell can ensure the stability of the catalyst and prolong the service life. This study provides ideas for the rational design of a catalyst to achieve a selective hydrogenation reaction for practical applications.