Utilization of Electrocoagulated Sewage as a Photoelectrocatalyst for Water Splitting

Electrocoagulation (EC) as a wastewater treatment process for the removal of pollutants has been demonstrated in numerous studies. However, proper management of solid waste generated after EC treatment is essential to minimize its environmental impact. Hence, more emphasis needs to be paid towards unused solid waste after EC treatment. The present study investigates the possibilities of utilizing waste released after the EC process as an electrocatalyst in the presence of sunlight. In this study, the sludge produced after domestic wastewater treatment by the EC process is collected and tested for water oxidation reaction under AM 1.5 illumination of simulated solar light. The sludge produced after EC treatment was characterized meticulously and confirmed to be the magnetite phase of iron oxide, which is used as a photoanode for photoelectrochemical (PEC) water splitting. The chemical composition of sludge is majorly dependent on the treatment time, which plays a crucial role in deciding the metal ions present in the sludge. After 30 min, which is the optimized time for EC treatment, sludge was studied as an efficient photoanode material. The band gap illumination of sludge (iron oxide) as working electrodes results in anodic current; the photocurrent appears at a bias of ca. 390 mV with respect to the flat-band potential. The PEC activity of waste is treatment-time dependent and decreases after reaching an optimal time of 30 min. A photocurrent density of 4.6 × 10^–6 A cm^–2 was found at the potential of 1.23 V (vs RHE) for sludge collected after 30 min of treatment time. It indicates that the sludge-derived photoanode has the potential to be an efficient component in PEC systems, contributing to the overall efficiency of water-splitting processes. Our experimental results show a new pathway of a “waste to energy” approach that aligns with the principles of circular economy and sustainable resource management.