Precursor-Mediated Direct Growth of Defect-Rich Hierarchical Nanocarbons for Electrocatalytic Hydrogen Peroxide Production†

Abstract

Carbon-based nanomaterials show great potential in selective electrochemical oxygen reduction reaction (ORR) through two-electron (2e⁻) pathway for H₂O₂ production, which provides an eco-friendly alternative to industrial energy-intensive anthraquinone process. However, it still remains challenging to directly construct topological defects, which makes it difficult to study the working mechanism on 2e^– ORR. Herein, we propose a precursor-mediated chemical vapor deposition (CVD) approach for direct growth of topological defect-rich hierarchical nanocarbons. Boric acid (H₃BO₃) is introduced into the precursor for disturbing the nucleation and growth through decomposing B-containing species, which can in situ induce the formation of pentagon defects. The topological defect is found to be capable of introducing lattice strain, which can modify the electronic structure of nanocarbons and promote the key intermediate (*OOH) formation, thus greatly enhancing the 2e^– ORR performance. Experimentally, the 2e^– ORR selectivity shows a positive correlation to the topological defect density, where the average H₂O₂ selectivity reaches above 90% over a wide potential range with optimized concentration of H₃BO₃ as mediator. Moreover, in a flow cell, the hierarchical nanocarbons achieve a high H₂O₂ production rate of 998 mmol·g_catalyst⁻¹·h⁻¹ over 20 h of continuous electrocatalysis with stable current density (>100 mA·cm^–2) and Faradaic efficiency (> 90%). This work provides a straightforward method for the synthesis of active metal-free carbon-based catalyst for sustainable H₂O₂ production.