1D/3D hierarchical carbon skeleton confined NiFe nanoparticles with optimized three-phase interfaces as tri-functional electrocatalysts

Abstract

Rational design of transition metal-based durable multifunctional electrocatalysts for energy conversion still remains a major challenge. Herein, we report a novel 1D carbon nanotube-modified 3D hollow carbon sphere with a hierarchical structure and strong interfacial interactions. Good surface dispersion of the bimetal seeds on the carbon sphere can achieve uniform growth of curly CNT arrays. The porous 3D carbon skeleton can provide support structures to stabilize NiFe seeds for uniform growth of the CNTs and the carbon layer; thus abundant FeNi₃/(NiFe)₉S₈ heterostructures encapsulated inside the 1D/3D skeleton can act as spatially dispersed active sites to accelerate reaction kinetics. Moreover, the multilevel 1D/3D structure with high porosity and hydrophilicity can promote the infiltration of electrolyte into the internal structure, thus constructing an optimal gas–solid–liquid interface to enhance the electrocatalytic process. Therefore, N–HCS@NiFe can achieve an overpotential and potential of 228 mV and 1.348 V vs. RHE at 10 mA cm⁻² for the oxygen evolution reaction (OER) and the urea oxidation reaction (UOR), respectively, while the half wave potential and average electron transfer number of N–HCS@NiFe for the oxygen reduction reaction (ORR) are 0.80 V vs. RHE and 4.0, as well as excellent long-term stability at high current density for various reactions. This work provides a new strategy for the rational 1D/3D structural design and active metal spatial dispersion of multifunctional electrocatalysts for green and sustainable energy conversion applications.