Assessing the potential of biochar derived from sewage sludge for photoelectrode fabrication: methods, mechanisms, and conclusions

Abstract

Previous studies often utilized metal catalysts in the preparation of photoelectrodes. However, this research marks the first instance of utilizing biochar as a catalyst in such a preparation. The biochar catalytic layer was synthesized by loading sewage sludge-derived biochar onto nickel foam using the sol–gel method. The performance of the photoelectrode was evaluated using tetracycline (TC) as a probe. The photoelectrode BCPE-800, prepared using biochar derived at 800 °C, achieved 98.52% TC degradation within 60 min, with a reaction rate constant of 0.0635 min⁻¹. It also exhibited excellent stability and recyclability, maintaining 90% removal efficiency after six cycles. Quenching experiments and EPR spectroscopy showed that h⁺ acted as the primary active species, while ˙OH and ¹O₂ also contributed to the TC degradation. Based on the intermediates identified by LC-MS, the study proposed two degradation pathways. The research effectively recycled sewage sludge and offered cost-effective possibilities for photoelectrocatalytic technology, highlighting its practical applications.