Higher-valent nickel oxides with enhanced two-electron oxygen reduction in advanced electro-Fenton system for organic pollutants degradation
Wenjun Zhang, Thao Thi Le, Dongyup Shin, Subhajit Nandy, Jae Won Choi, Sae Yane Paek, Chang‐Kyu Hwang, Jin Hyeng Kim, Jin Hyueng Kim, Hoyoung Suh, Keun Hwa Chae, Seung Yong Lee, Sang Soo Han, Sang Hoon Kim, Jong Min Kim, Jong Min Kim
Abstract
A higher-valent NiO catalyst, enriched with trivalent Ni (Ni 3+ ) and exposed {111} crystal facets, was developed to enhance selective two-electron oxygen reduction (2e – ORR) for electrochemical hydrogen peroxide (H 2 O 2 ) production, leading to highly efficient organic pollutant removal. The catalyst was synthesized via a precipitation method, incorporating crystal facet and cation vacancy engineering to expose active sites. It demonstrated 96 % selectivity and 59 A g −1 mass activity, attributed to weakened *OOH binding, as shown by density functional theory. Integrated into an advanced electro-Fenton (EF) flow cell, the system achieved 100 % removal of 200 mL of 50 ppm bisphenol A (BPA) in 4 minutes, with 93 % total organic carbon removal within 2 hours. This study provides a scalable and efficient solution for decentralized environmental remediation and wastewater treatment. • A novel {111}-NiO catalyst with Ni vacancies shows 96% selectivity and 59 A g −1 mass activity for H 2 O 2 electrosynthesis. • The catalyst achieves over 85 % Faradaic efficiency for H 2 O 2 production across various pH conditions. • Combining a flow cell and electro-Fenton process enables fast and complete BPA removal, outperforming conventional methods.