Catalysts for the oxygen reduction reaction (ORR) are highly important in fuel cells and metal-air batteries. Cheap ORR catalysts with ultrahigh electrochemical activity, selectivity, and stability are extremely desirable but still remain challenging. Herein, mesoporous NiCoO nanoplate (NP) arrays on three-dimensional (3D) graphene foam are shown to be a highly economical ORR catalyst. This mesoporous mixed-valence oxide can provide more electrocatalytic active sites with increased accessible surface area. In addition, graphene-foam-supported NiCoO NP arrays have a 3D hierarchical porous structure, which is of great benefit to ion diffusion and electron transfer. As a result, the mesoporous NiCoO NP arrays/graphene foam catalyst exhibits outstanding ORR performance with the four-electron reduction of O to HO in alkaline media. Furthermore, the mesoporous catalyst shows enhanced electrocatalytic activity with a half-wave potential of 0.86 V vs RHE and better stability compared with a commercial Pt/C catalyst.

Catalyst for oxygen reduction reaction (ORR) is of highly industrial importance for fuel cells and metal-air battery. ORR catalysts with high electrochemical activity, selectivity, stability and low cost are extremely desirable but still remain challenging. Herein, mesoporous Ni-doped Co 3 O 4 nanowire (NW) arrays are reported as a highly efficient and low-cost ORR catalyst. The Ni doping affords more electroactive sites and enhanced conductivity, and the mesoporous structure provides increased surface exposure, which may improve ion/electron transport and reduce charge transfer resistance. The NW arrays exhibit a high ORR activity with four-electron transfer reaction in alkaline media, a half-wave potential of 0.86 V vs. RHE and a superior stability to the commercial Pt (20 wt. %)/C catalyst. Our results suggest that the mesoporous Ni-doped Co 3 O 4 NW arrays could be a promising ORR catalyst for fuel cells and metal-air batteries.

Pyrite (FeS2) nanoparticles, a kind of Earth-abundant mineral, can efficiently activate molecular hydrogen under mild conditions.

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