The development of low-cost non-precious-metal electrocatalysts with high activity and stability in the oxygen reduction reaction (ORR) remains a great challenge. Heteroatom-doped carbon materials are receiving increased attention in research as effective catalysts. However, the uncontrolled doping of heteroatoms into a carbon matrix tends to inhibit the activity of a catalyst. Here, the in situ activation of a uniquely structured nitrogen-doped carbon/Ni composite catalyst for the ORR is demonstrated. This well-designed catalyst is composed of a nitrogen-doped carbon shell and embedded metallic nickel. The embedded Ni nanoparticles, dispersed on stable alumina with a high specific surface area for protecting them from agglomeration and in an unambiguous composite structure, are electron-donating and are shielded by the nitrogen-doped carbon from oxidation/dissolution in harsh environments. The electronic structure of the nitrogen-doped carbon shell is modulated by the transfer of electrons at the interface of nitrogen-doped carbon-Ni heterojunctions owing to the Mott-Schottky effect. The electrochemically active surface area result implies that the active sites do not relate to Ni directly and the enhanced catalytic activity mainly arises from the modulation of nitrogen-doped carbon by nickel. XPS and theoretical calculations suggest that the donated electrons are transferred to pyridinic N primarily, which ought to enhance the catalytic activity intrinsically. Benefiting from these transferred electrons, the half-wave potential of the nitrogen-doped carbon/Ni composite catalyst is 94 mV positively shifted compared to the Ni-free sample.

CoB/Ni-foam was directly formed on a Ni-foam substrate using the electroless plating method. A membraneless DBFC with CoB/Ni-foam (7EP) as an anode showed a maximum power density of 230 mW cm−2.

We report here a supercatalyst for oxygen reduction of Pt/CN x /Ni in a unique ternary heterostructure, in which the Pt and the underlying Ni nanoparticles are separated by two to three layers of nitrogen-doped carbon (CN x), which mediates the transfer of electrons from the inner Ni to the outer Pt and protects the Ni against corrosion at the same time. The well-engineered low-Pt catalyst shows $780% enhanced specific mass activity or 490% enhanced specific surface activity compared with a commercial Pt/C catalyst toward oxygen reduction. More importantly, the exceptionally strong tune on the Pt by the unique structure makes the catalyst superbly stable, and its mass activity of 0.72 A/mg Pt at 0.90 V (well above the US Department of Energy's 2020 target of 0.44 A/mg Pt at 0.90 V) after 50,000 cyclic voltammetry cycles under acidic conditions is still better than that of the fresh commercial catalyst.

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