π–π Electron Conjugation-Assisted Synthesis of a Robust Heterostructured CoO-MoO2 Catalyst: Accelerated Ammonia Borane Hydrolysis for Hydrogen Evolution

Abstract

Heterostructured multicomponent catalysts can be developed to exploit their unique interfacial effects for enhancing their catalytic activities by optimizing their electronic structures. However, precisely fabricating heterostructures remains challenging owing to the complex interfacial properties and compatibility problems between the different materials. To address these challenges, the carbothermal shock (CTS) method was employed to produce robust heterostructured CoO-MoO2 catalysts supported on C (CoO-MoO2@C) with the aid of the extensive π–π electron conjugation of organic components. Co-based ZIF-67, which is a typical metal-organic framework, and molybdenum acetylacetonate were used as Co and Mo sources, respectively. The strong coupling between the π-electrons of the organic ligands and ultrafast Joule heating during CTS improved the interfacial compatibility between the Co and Mo oxides, leading to a significantly enhanced catalytic activity. The heterostructured CoO-MoO2@C catalyst exhibited a turnover frequency of 55.4 min⁻¹ in NH3BH3 hydrolysis for H2 production, displaying an improvement of 85.9% over that of the single-component CoO catalyst produced under equivalent conditions. Notably, the activation energy of CoO-MoO2@C was 29.3 kJ·mol–1. In addition, we proposed a novel descriptor, i.e., the “activity-activation energy quotient,” to comprehensively evaluate the energy efficiencies of catalysts in designing a low-energy-consumption catalyst. CoO-MoO2@C exhibited an activity-activation energy quotient of 1.89 min⁻¹·kJ⁻¹·mol, surpassing those of most reported Co-Mo-based catalysts. In summary, this study offers an advanced strategy for use in the structural design and precise fabrication of efficient non-noble-metal catalysts.