NiCo2O4 spinel supported N-dopped porous Hollow carbon derived MOF functionalized SiO2 for efficient ORR electrocatalysis

The improvement of carbon-based metal-free electrocatalysts for the cathodic ORR that are environmentally benign, cost-effective, and highly durable is required for large-scale commercial applications of fuel cells. Herein, we developed the TiO2 nanoparticles supported by a nitrogen-doped carbon matrix with high surface defects derived by the pyrolysis of NH2-MIL-125 (MOF). The construction of controllable morphology, porosity, and particle size through the pyrolysis process can be obtained by introducing the SiO2 template during the NH2-MIL-125 synthesis. Moreover, the synergic covalent coupling between metal oxide spinel (AB2O4, especially NiCo2O4) and TiO2/N- doped nanocarbon effectively enhanced the ORR catalytic activity, particularly with high content of nickel atoms in the spinel due to the various valences of metals in spinel which accelerated the electron transfer during ORR. As a highly effective ORR electrocatalyst with an onset potential of −0.14 V vs Ag/AgCl, the as-prepared N3CO/Es-TiO2/NC exhibited not only high activity but also good stability in an alkaline environment compared to the Pt/C catalyst. The less current change after continuous 1000 cycles of cyclic voltammetry or the methanol addition may be due to the protective effect of the N-doped carbon carrier and the corrosion resistance of TiO2.