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Bioinspired by the active sites of multicopper oxidases (MCOs), bi/multinuclear copper complexes have attracted great attention in promoting catalytic activity for the oxygen reduction reaction (ORR). Herein, we report the preparation of a Cu-N-C electrocatalyst Cu-BPOZ@CNB-400 for efficient ORR, which was obtained by low temperature pyrolysis of a dinuclear 2,5-bis(2-pyridyl)-1,3,4-oxadiazole (BPOZ) copper complex loaded on a N-doped carbon support at 400 °C. Cu-BPOZ@CNB-400 exhibited a half-wave potential ( E 1/2 ) of 0.86 V vs. RHE for the ORR in 0.1 M KOH solution, which was significantly higher than that of the Cu-BPOZ@CNB-800 ( E 1/2 = 0.83 V) catalyst treated under high temperature (at 800 °C) and the control catalyst Cu-Phen@CNB-400 ( E 1/2 = 0.82 V) derived from low-temperature-treatment (at 400 °C) of a mononuclear phenanthroline-coordinated-Cu complex loaded on a N-doped carbon support. When Cu-BPOZ@CNB-400 was applied as the cathode catalyst in zinc-air batteries a maximum power density ( P max ) of 127 mW cm -2 could be achieved, demonstrating comparable catalyst performance to the commercial 20 wt% Pt/C ( P max = 122 mW cm -2 ) and the control Cu-Phen@CNB-400 catalyst ( P max = 105 mW cm -2 ) under similar experimental conditions. Low-temperature pyrolysis of dinuclear copper complexes on a carbon support improved the charge transfer efficiency, inhibited metal aggregation, and could produce highly dispersed Cu-N-C catalysts with dinuclear copper sites for promoting the 4e - -reduction selectivity of the ORR. It thus provides a cost-effective approach for the controllable fabrication of efficient ORR catalysts to be applied for energy conversion devices.

Developing high performance noble-metal-free electrocatalysts as an alternative to Pt-based catalysts for the oxygen reduction reaction (ORR) in energy conversion devices is highly desirable. We report herein the preparation of a coordination-polymer (CP)-derived Fe/CP/C composite as an electrocatalyst for the ORR with excellent activity and stability both in solution and in Zn-air batteries. The Fe/CP/C catalyst was obtained from the pyrolysis of an iron porphyrin Fe(TPP)Cl (5,10,15,20-tetraphenyl-21 H ,23 H -porphyrin iron(III) chloride) grafted Zn-coordination polymer with dangling functional groups 4,4'-oxybisbenzoic acid and 4,4'-bipyridine ligands. The Fe/CP/C catalyst showed much higher ORR activity with a half-wave potential ( E 1/2 ) of 0.90 V ( vs. RHE) than the Fe/C catalyst ( E 1/2 = 0.85 V) derived from the carbon-black-supported Fe porphyrins in 0.1 M KOH solution. When Fe/CP/C was used as the cathode electrocatalyst in Zn-air batteries (ZABs), the ZABs achieved a significantly higher open circuit voltage (OCV = 1.43 V) and maximum power density ( P max = 142.8 mW cm -2 ) compared with Fe/C (OCV = 1.38 V, P max = 104.5 mW cm -2 ) and commercial 20 wt% Pt/C (OCV = 1.41 V, P max = 117.6 mW cm -2 ). Using dangling functional groups in CP to increase the loading efficiency of iron porphyrins offered a facile method to prepare high-performance noble-metal-free electrocatalysts for the ORR, which may provide promising applications to energy conversion devices.