Carbon doped cobalt nanoparticles stabilized by carbon shell for highly efficient and stable oxygen reduction reaction

The oxygen reduction reaction (ORR) is a key reaction in metal-air batteries and fuel cells. Herein, a novel carbon-doped Co nanoparticle coated with a carbon layer supported on the ordered macroporous titanium oxide (C-doped Co@C@TiO2) is designed as the highly efficient and stable ORR catalysts. The C-doped Co@C@TiO2 achieves the superior catalytic activity with an onset potential of 0.867 V and a limiting current density of-6.59 mA cm(-2), which is much lower than the commercial Pt/C (-5.93 mA cm(-2)). The turnover frequency (TOF) of the C-doped Co@C@TiO2 at the potential of 0.3 V (0.091 s(-1)) is nearly four times than the commercial Pt/C (0.025 s(-1)). This outstanding catalytical performance is attributed to the unique C-doped Co layer in Co nanoparticles, which can stable the OOH* and promote the desorption of OH*, and accelerate the catalyst surface regeneration in ORR. Meanwhile, the outer C layer with mesoporous channels can improve the stability and poisoning resistant of the C-doped Co nanoparticles, and the C-doped Co@C@TiO2 still retains 98% of the current density after the reaction for 60 h. It is worth noting that the assembled zinc-air battery with C-doped Co@C@TiO2 as the air cathode exhibits an ultra-high open circuit voltage of 1.51 V and an excellent durability of more than 41.6 days. This work provides one of the most promising non-noble metal-based catalysts for efficient and stable oxygen reduction reaction.