Development of a 3D Ni-Mn binary oxide anode for energy-efficient electro-oxidation of organic pollutants

Abstract

The depletion of clean water resources and the consequent accumulation of contaminants in aquatic systemsmust be urgently addressed by means of innovative solutions. Electro-oxidation (EO) is considered a promisingtechnology, prized for its versatility and eco-friendliness. However, the excessively high prices and the toxicityassociated with some of the materials currently employed for EO impede its broader application. This studyintroduces cost-effective Ni-Mn binary oxide anodes prepared on Ni foam (NF) substrate. A scalable synthesisroute that enables a 35-fold increase in the production of active material through a single optimization step hasbeen devised. The synthesized binary oxide material underwent electrochemical characterization, and itseffectiveness was assessed in an electrochemical flow-through cell, benchmarked against single Ni or Mn oxidesand more conventional alternatives like boron-doped diamond (BDD) and dimensionally-stable anode (DSA). Thenovel binary oxide anode demonstrated exceptional performance, achieving complete removal of phenol at verylow current density of 5 mA cm-², along with an 80% of chemical oxygen demand (COD) decay within only60 min. The NF/NiMnO₃ anode outperformed the BDD and DSA when using comparable projected surface areas,owing to its high porosity and ability to produce hydroxyl radicals, as confirmed from the degradation profiles inthe presence of radical scavengers. Furthermore, GC/MS analysis served to elucidate the degradation pathwaysof phenol.