Recent advances in carbon-based electrocatalysts for oxygen reduction reaction

Fuel cells are one of the most promising clean energy devices to substitute for fossil fuel in the future to alleviate energy crisis and environmental pollution. As the key reaction on the cathode in the fuel cells, oxygen reduction reaction (ORR) still requires efficient noble metal catalysts such as the commercial Pt/C to boost the reaction for its sluggish kinetics. Therefore, it is critical to design earth-abundant carbonbased catalysts with high efficiency and long-term stability to replace the noble metal-based catalysts. This review focuses on the recent progress about carbon-based ORR catalysts including non-metal doped carbon materials, transition metal-nitrogen-carbon species, transition metal carbides/carbon, single atom catalysts, and other carbon hybrids. And we further infer that the excellent ORR performances can be achieved by the balance of geometric and electronic structures of catalysts such as conductivity, surface area, hierarchical porous structure, defect and doping effect. Additionally, the perspective development trend is also proposed to guide the rational designation of carbon-based catalysts for ORR and even extend to other energy storage and conversion fields in the future.