Nickel metal nanoparticles encapsulated by N-doped carbon nanotubes derived from g-C3N4 for efficient electrocatalytic oxygen reduction reaction

Abstract

The oxygen reduction reaction (ORR) electrocatalyst plays an important role in various renewable energy applications and energy conversion and storage fields. The design and synthesis of ORR catalysts with high activity, great stability, and low cost is a harsh challenge. Transition metal catalysts are deemed to be one of the promising alternatives to traditional Pt-based catalysts for oxygen reduction reactions. In this study, a nickel metal nanoparticle encapsulated by nitrogen-doped carbon tube composites (Ni/N-C-t) are fabricated by regulating the calcining temperature and using g-C₃N₄ as precursor in the presence of nickel nitrate. The Ni/N-C-800 catalyst which is calcined at 800 °C exhibits the largest specific surface area (152.1 m²·g⁻¹), abundant defects, mesoporous structures and more active reaction sites, demonstrating excellent ORR performance (half-wave potential of 0.80 V) and good stability (current retention rate of 64 % after 66 h longevity test). The attributes of high content of Ni-N_x, graphitic nitrogen, and pyridine nitrogen and largest specific surface area endow the catalyst of Ni/N-C-800 affluent reaction active sites and outstanding conductivity, thus boosting the ORR electrocatalytic performance. This study demonstrates a useful inspiration for the preparation of advanced oxygen reduction reaction electrocatalysts with g-C₃N₄ derivatives.