Ammonium-salt-assisted post-loading: a cost-effective route to high-performance Co–N–C with enriched active sites on the surface for nitroarene hydrogenation

Abstract

Co–N–C catalysts are promising alternatives to noble-metal systems for nitroarene hydrogenation. However, it remains challenging to develop cost-effective synthetic routes that afford high-performance Co–N–C catalysts capable of meeting the requirements of industrial applications. Herein, we present an ammonium salt-assisted post-loading strategy for constructing Co–N–C catalysts at extremely low cost, enabling efficient hydrogenation under mild conditions. Specifically, using a low-cost N-doped carbon support, Co sites are introduced by impregnation, followed by high-temperature carbonization in the presence of an ammonium salt, yielding Co/NC-AM with abundant single-atom Co (Co₁) and Co nanoparticles (Co_NPs). These sites work synergistically: Co_NPs promote homolytic activation of H₂, whereas substrates preferentially adsorb and activate on Co₁ sites. More importantly, such a synthetic strategy exposes the sites on the surface of the carbon matrices, without carbon encapsulation, thereby enhancing their utilization efficiency. Consequently, Co/NC-AM delivers superior performance for the hydrogenation of nitro compounds and offers excellent cost advantages, possessing the highest cost–performance ratio among all reported catalysts. This work presents a technically feasible and economically attractive route to synthesizing M–N–C catalysts, applicable not only to hydrogenation but also to other processes.