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Atomically dispersed M–N–C catalysts for the oxygen reduction reaction

In recent years, as one of the most promising candidates to replace platinum-based catalysts for the oxygen reduction reaction (ORR), atomically dispersed transition metal/nitrogen-doped carbon (M–N–C) materials have become a research hotspot in electrocatalysis. Compared with heterogeneous catalysts containing metal nanoparticles, the atomically dispersed M–N–C catalysts have better ORR performance due to their maximum atom utilization, effective active sites and satisfactory catalytic activity and stability. In this review, we will systematically summarize recent advances in advanced single atom M–N–C catalysts for the ORR. Firstly, the design principles, preparation methods and corresponding ORR electrocatalytic performance of atomically dispersed M–N–C catalysts are introduced in detail. In addition, in order to gain a deeper understanding of the synthesis–structure–property correlations, we will combine advanced characterization techniques and DFT calculations to discuss the coordination environment of active sites and mechanism of the ORR process. Finally, the opportunities and challenges for atomically dispersed M–N–C catalysts will be proposed to facilitate further development.