Hierarchically Porous High-Entropy Metal Nitrides by a Solution Combustion-Ammonia Calcination Route for Efficient Electrosynthesis of Adipic Acid.

Abstract

Porous high-entropy metal nitrides (HENs) have great potential in catalysis and electrocatalysis, but remain unexplored due to severe challenge in precise synthesis and engineering of hierarchical structures. Herein, we report, for the first time, a facile yet general route, by taking advantage of solution combustion and ammonia calcination (SCAC), to prepare a series of HENs (HPHENs) with hierarchical pores and adjustable compositions. SCAC route not only produces in situ hierarchically porous structure by solvent evaporation and organic combustion but also drives the oxide-to-nitride conversion without destroying hierarchical pores. Compared with other electrocatalysts, HPHEN with multiple structural and compositional synergies remarkably decreases reaction energy barrier of the key intermediate and accelerates reactants transport for adipic acid electrosynthesis from cyclohexanone. The best (NiCuCoZnFe)₄N HPHEN holds recordable electrocatalytic performance, including 93.1% of Faradaic efficiency and 369.6 mmol h^-1 g^-1 of yield rate, all of which are superior than previously reported electrocatalysts. Meanwhile, high performance is also achieved in a flow reactor even with the long cycling time of 100 h, demonstrating its promise for practical applications. This work provides new insights into producing hierarchically porous high-entropy materials for selective electrosynthesis of high-value chemicals from various biomass sources.