Metal-Free B, N co-Doped Hierarchical Porous Carbon Electrocatalyst with an Excellent O2 Reduction Performance.

Fuel cells have attracted increasing attention due to their low cost, high energy density, low environmental pollution, and abundant raw materials. Oxygen reduction reaction (ORR) is a core technology of fuel cells, and the development of new electrocatalysts with high ORR performance is highly desirable. Herein, we synthesize a series of B, N co-doped hierarchical porous carbons using a soft template method with the integration of self-assembly, calcination and etching. The obtained materials exhibit hierarchical porous structures, controllable pore distribution, partial graphite structures, and B, N co-doping. They can function as the cost-effective and metal-free electrocatalysts, facilitating the diffusion of electrolyte ions and the improvement of ORR performance. Especially, the B, N co-doped porous carbon with the B-to-N molar ratio of 5 (BNC-5) displays a high ORR activity with a half-wave potential (E1/2 ) of 0.73 V, an onset potential (Eonset ) of 0.94 V, and a high limiting current density (JL ) of 5.98 mA cm-2 , superior to the N-doped C (NC) and BNC-1 (the B-to-N molar ratio=1), BNC-3 (the B-to-N molar ratio=3) and BNC-7 (the B-to-N molar ratio=7) under the identical conditions. Moreover, the BNC-5 exhibits good cycling stability after 5000 cyclic voltammetry (CV) cycles and excellent tolerance toward even 3 M methanol. This research provides a new approach for the facile synthesis of dual element-doped carbon electrocatalysts with high ORR performance.

Controllable synthesis of CoFe2Se4/NiCo2Se4 hybrid nanotubes with heterointerfaces and improved oxygen evolution reaction performance.

The rational construction of heterointerfaces in hollow nanohybrids is considered as a promising and challenging approach for enhancing their electrocatalytic performance. Herein, we demonstrate the synthesis of CoFe2Se4/NiCo2Se4 hybrid nanotubes (CFSe/NCSe HNTs) with open ends and abundant heterointerfaces. The CFSe/NCSe HNT hybrid nanotubes are obtained by using NiCo2-aspartic acid nanofibres (NiCo-Asp NFs) as the templates which can be converted to the CFSe/NCSe HNTs via proton etching, three metal coprecipitation, Kirkendall effect and anion-exchange reaction. The CFSe/NCSe HNTs may function as the oxygen evolution reaction (OER) electrocatalysts, and they exhibit a low overpotential of 224 mV at a current density of 10 mA cm-2 and outstanding stability with only 1.4% current density change even after 15 h, superior to those of the reported single-component counterparts. The obtained density of states and differential charge density confirm the existence of a heterointerface which can induce the accumulation of electrons at the interface of CFSe-NCSe and consequently increase the carrier density and electrical conductivity of the CFSe/NCSe HNTs. This research provides a new avenue for the fabrication of hollow nanohybrids with heterointerfaces.