N-doped carbon nanotube arrays Encapsuled with cobalt‑nickel alloy as superior free-standing electrodes for ultrahigh-rate hydrogen peroxide production

Abstract

Electrocatalytic oxygen reduction via the two-electron pathway (2e−-ORR) is an environmentally friendly and promising route for hydrogen peroxide (H2O2) production. Carbon-based catalysts with transition metal species have been widely investigated due to their high tunability. However, the H2O2 production performance of such catalysts is still far from the requirement of practical applications, owing to their contradiction between durability and ORR activity/selectivity. In this work, metal alloy is encapsulated within the free-standing N-doped carbon nanotube arrays, named NiCo-CNTs-x (x represents the duration of the cation substitution process in hours), to precisely regulate the activity and selectivity of nitrogen sites on the surface of the carbon layer, meanwhile hindering the dissolution of alloy inside the CNTs, thus realizing long-term stability and high-activity catalysis for 2e−-ORR. Therefore, the NiCo-CNTs-30 demonstrates high activity (onset potential around 0.7 V) and selectivity (greater than 85% within the range of 0–0.8 V), and delivers a high yield of 11.7 mg L−1 h−1 with no current decay or structural damage within 24 h, showcasing its exceptional long-term stability. The catalyst can also effectively degrade organic dyes, making it highly promising for industrial applications.