Construction of Er³⁺ :YAlO₃ /RGO/TiO₂ Hybrid Electrode with Enhanced Photoelectrocatalytic Performance in Methylene Blue Degradation Under Visible Light

Much attention has been paid on doping TiO₂ to narrow its band gap to promote the absorption of visible light and restrain the recombination of electron-hole pairs to improve its efficiency in photoelectrocatalysis (PEC) under visible-light irradiation. However, the oxidation potential energy of photo-induced holes for the modified catalysts by visible-light excitation is lower than that without modification by UV excitation. In this work, we synthesized a co-coupled TiO₂ electrode (denoted ERT) with the Er³⁺ :YAlO₃ and reduced graphene oxide (RGO), achieving the synergetic effect of visible-light-to-UV up-conversion and response and great electron transfer ability. The effects of external bias voltage, electrolyte concentration and pH on the PEC activity were studied with the methylene blue (MB) as the target pollutant. The results indicated that PEC by the ERT electrode showed the highest MB removal compared with those by the electrodes coupled with RGO or Er³⁺ :YAlO₃ alone. In addition, the kinetic rate constant of the PEC process using the ERT electrode was higher than the sum of those of the photocatalytic and electrocatalytic processes. The optimal conditions for PEC by the ERT electrode were an external bias voltage of 1.0 V, 0.1 mol L^-1 Na₂ SO₄ and pH = 10.