A perovskite/spinel structured LaFeO₃/Co₃O₄ heterojunction for photoelectrocatalytic applications in degradation of tetracycline and water splitting

Towards a dual-functioning photoelectrocatalyst for environmental remediation and green energy solutions, FTO-supported LaFeO₃/Co₃O₄ heterojunction photoanodes of different ratios were synthesized using sol-gel method for the photoelectrocatalytic (PEC) degradation of tetracycline in real wastewater and in overall water splitting. Structures and morphologies were investigated with XRD, XPS, FESEM, HRTEM. Photoluminescence and optical analysis showed that all the materials were visible light active and the heterojunction exhibited higher photocurrent density than LaFeO₃ and Co₃O₄ through a direct Z scheme heterojunction formation. LaFeO₃ 30 %/Co₃O₄ 70 % heterojunction demonstrated hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). It also showed improved OER with low onset potential and a photocurrent density above 10 mA/cm² in 1 M KOH at a lower over-potential. The heterojunction recorded a low Tafel slope of 102 mV dec⁻¹ indicating a faster reaction rate than the pristine semiconductors. The heterojunction exhibited a PEC degradation of 79 % in 10 ppm tetracycline. Real wastewater sample treatment showed a total organic carbon removal of 60 % and LCMS analysis informed the fragmentation patterns. The heterojunction showed improved stability (from chronopotentiometry and LSV data after 30 cycles) and h⁺ and ^° OH are the major species in the PEC degradation of tetracycline in real wastewater sample.