Cu(ii)/Fe(ii) electron-deficient pairs as bifunctional catalysts for efficient PMS activation and solar-driven water evaporation

Abstract

Addressing the dual challenges of organic wastewater purification and freshwater regeneration requires innovative materials capable of multifunctional integration. This study presents a tactical design of metallic Cu-interfaced FeO composites (Fe/Cu-x) synthesized via a synergistic self-assembly and pyrolysis strategy. The interfacial Cu/FeO pairs, featuring electron-deficient Cu(II) and Fe(II) pairs along with promoted oxygen vacancies, afford abundant redox cycles to enable exceptional electron transfer and peroxymonosulfate (PMS) activation. The optimized Fe/Cu-800 catalyst achieved an excellent tetracycline (TC) degradation efficiency (k_obs = 0.235 min⁻¹) within 20 min, far outperforming the other controls including the Cu-free one and different temperature-derived, retained robust performance across wide pH ranges and in real water matrices, and exhibited rational recyclability. The dominant ·OH alongside other free radicals synergistically contribute to the TC degradation. Beyond catalysis, this study demonstrates the customizable integration of the powder catalyst into a monolithic form evaporator through a Ca²⁺-triggered hydrogel crosslinking strategy. This uniquely integrated system simultaneously accomplishes pollutant degradation and solar-driven clean water production. Under 1 sun irradiation, the evaporator achieved a TC degradation rate of 94.4% within 20 minutes and simultaneously realized a high-water evaporation rate of 1.313 kg m⁻² h⁻¹, demonstrating a significant dual-functional synergy effect. This research breaks the conventional single-function limitation by offering a novel “degrade-and-evaporate” platform, which emerges from precise interfacial engineering and modular device integration. It provides a sustainable and efficient technical pathway for integrated wastewater treatment and water resource regeneration.