Design of a novel fuel cell-Fenton system: a smart approach to zero energy depollution

Abstract

A model azo dye pollutant, Acid Orange 7 (AO7), was removed efficiently from an aqueous medium by a smart eco-friendly Fuel Cell-Fenton (FC-Fenton) system without any external power supply. In this approach, AO7 was degraded by an electro-Fenton process at a designed cathode (Carbon Felt (CF)/porous Carbon (pC)) supplied by direct clean electrical energy from abiotic glucose oxidation at a CF/gold anode (CF@Au). The highly active cathode was fabricated by an attractive route combining Atomic Layer Deposition (ALD) of ZnO on commercial carbon felts (CFs) followed by subsequent solvothermal conversion of the metal oxide to a metal organic framework (here ZIF-8). The as-prepared composite material was further calcined at high temperature under a controlled atmosphere. A pC-based support with high specific surface area and nitrogen as a dopant was thus obtained, enhancing both conductivity and electrocatalytic properties toward H₂O₂ production from oxygen reduction. Degradation kinetics of AO7 (0.1 mM initial concentration) at the CF@pC cathode was monitored by UV-vis spectrophotometry and High-Performance Liquid Chromatography (HPLC) to prove the efficiency of the composite material for the degradation of such a bio-refractory model molecule. Benefitting from the H₂O₂ production rate (9.2 mg L⁻¹ h⁻¹) by the pC layer, AO7 (35.0 mg L⁻¹) was degraded by the electro-Fenton process in acidic medium (pH = 3) with removal efficiency reaching 90% in 10 h. The durability of the system was extended for more than 2 months with an average power output of 170 mW m⁻², confirming this abiotic FC-Fenton system as a promising, green, future technology for both environmental and energy-related areas, including membrane-coupled reactor systems.