ZIF-67-Derived Co-Based DSA Electrodes with Oxygen Vacancies for Degradation of 4-Nitrophenol in a 3D Electrocatalytic System

Abstract

p-Nitrophenol (4-NP) is a highly toxic and poorly biodegradable phenolic pollutant. In this study, a novel dimensionally stable anode (DSA), ZIF-67 derivative/Ti–x, was synthesized via a coating–calcination method using ZIF-67 as the precursor, and combined with steel slag particles to construct a 3D electrocatalytic system. Among the prepared electrodes, ZIF-67 derivative/Ti–450 exhibited the best performance, featuring uniform cobalt distribution, high Co(II) content, abundant oxygen vacancies, and chemisorbed oxygen. Electrochemical characterization revealed that Ti–450 had the highest oxygen evolution potential (1.71 V vs. SCE), the lowest charge transfer resistance (29.08 Ω), and the smallest Tafel slope (521 mV·dec⁻¹), indicating excellent catalytic activity. Under optimized operating conditions, the degradation efficiency of 4-NP reached 94.72% within 60 min. Mechanistic analysis showed that indirect oxidation was the dominant pathway, contributing 49.80% to the total degradation, followed by direct oxidation (33.35%) and adsorption on steel slag (11.57%). These results demonstrate the great potential of ZIF-67-derived electrodes coupled with steel slag in efficient 3D electrocatalytic systems for the removal of refractory organic pollutants from wastewater.