Dual-functional CeO₂-Cu₂Se heterostructure nanocomposite for photocatalytic degradation and electrocatalytic water splitting

Electrochemical water electrolysis and photocatalysis are attractive strategies to address both sustainable energy production and wastewater treatment challenges. In this scenario, we report the dual-functional heterojunction catalyst CeO2-Cu2Se as a promising candidate prepared via a facile hydrothermal method. The optimised CeO2-Cu2Se catalyst exhibits outstanding electrochemical performance. The electrocatalytic, OER, and HER fabricated nanocomposite required a very low overpotential of 249 mV & 79 mV, slightly low Tafel slope of 48.2 mV dec-1 & 83.6 mV dec-1 at standard 10 mA cm-2 current density, low lying charge transfer resistance 0.08368 Omega, and exceptional everlasting stability of 72 & 95 h. The photocatalytic performance of the CeO2-Cu2Se catalyst was equally impressive, with a narrow band gap of 2.73 eV for effective sunlight utilization in the visible region. The catalyst achieved an exceptional 99.9% degradation efficiency for the degradation of pollutant dyes under 60 min of sunlight exposure, with high stability up to 6 cycles. The photocatalytic performance of the prepared catalyst was also investigated by varying the experimental conditions, showing optimal performance at a catalyst dosage of 6 mg, dye concentration of 30 ppm, and solution pH 8. The S-scheme is proposed to explore the charge transport mechanism of the targeted catalyst, thereby showing efficient charge carrier separation at the heterojunction interface. Moreover, the abundant chemical oxidation states and substantial electrochemical surface area 1600 cm2 of CeO2-Cu2Se explored from XPS and ECSA are also evident in their effective photocatalytic and electrochemical performance. Hence, this work demonstrates CeO2-Cu2Se nanocomposite as an ideal class of earth-abundant and economically exceptional bifunctional catalyst for renewable energy production and water pollution control. This dual functionality of CeO2-Cu2Se nanocomposite eliminates the need for commercial integrated water treatment and hydrogen production systems and provides a valuable design for developing next-generation multifunctional catalysis.