All kinds of industrial organic wastewater and organic pollutants produced by human activities will cause water pollution. These organic pollutants usually contain a variety of toxic chemical components, which can cause cancer, mutagenesis, poisoning and other hazards [1], [2], [3]. For example, Rhodamine B(RhB), methylene blue (MB) and antibiotics has been experimentally proved to be harmful [4], [5], [6]. Therefore, water pollution is considered to be one of the most important environmental problems [7], [8]. At present, membrane separation [9], adsorption [10], chemistry [11], electrochemistry [12], Fenton[13] and other technologies have been developed for the treatment of wastewater containing organic pollutants. Among these, the Fenton process is one of the most commonly used methods due to its cost-effectiveness and efficiency in removing organic pollutants from wastewater [14], [15]. This process employs hydrogen peroxide (H2O2) as an oxidant to generate a substantial amount of hydroxyl radicals (·OH) through Fenton reaction [16], [17], [18], [19]. The·OH radicals can decompose various organic compounds and ultimately degrade harmful organic pollutants into harmless CO2 and H2O[20], [21]. Currently, the most frequently studied Fenton processes for dye removal are Fenton catalysis, photo-Fenton, and electro-Fenton. However, the Fenton reagents studied thus far are typically catalysts synthesized with single metal or bimetallic bases, which generally exhibit low catalytic efficiency.
In recent years, multi-metal heterogeneous catalysts have become increasingly popular in research. Due to the geometric and electronic effects of alloys [22], [23], trimetallic materials have been found to possess superior properties such as high catalytic activity, high surface area, and faster electron transfer rates, when compared to single or bimetallic materials[24], [25]. Pd-based alloy nanomaterials, due to their polymetallic structure, can cause lattice shrinkage and improve electron transfer efficiency, resulting in excellent catalytic activity[26], [27]. As traditional thermal catalysis studies have shown that thermal effects can overcome the key obstacles of chemical reactions and accelerate reaction efficiency[28], [29], gold nanoparticles have good prospects in the field of photothermal applications due to their excellent light absorption and photothermal conversion ability[30], [31]. At the same time, early studies have also demonstrated that, with the assistance of H2O2, Au can catalyze the formation of hydroxyl radical and improve electron transfer rates[32]. However, since Pd and Au are expensive and prone to failure, the alloying of precious metals with non-precious metals is often used to prevent reagent failure and save costs. Therefore, designing polymetallic nanoalloys with regular morphology and superior performance remains a challenging problem to be solved.
In this study, we directly synthesized sea urchin-like PdCuAu nanomaterials using a simple one-step method in aqueous solution with the assistance of polyvinyl oxide (PEO). Through the photothermal reaction of PdCuAu NAs with the aid of H2O2, holes (h+) on metal nanoparticles were excited and hydroxyl radical (·OH) was generated. HCO3-, SO42- and NO3- produced in the catalytic system acted as electron donors to capture excited holes on metal nanoparticles, enabling electron cycling. Moreover, under near-infrared laser irradiation, PdCuAu NAs facilitated photothermal conversion and improved the temperature of the reaction system, which further enhanced the catalytic efficiency of Fenton. Compared to conventional iron-based Fenton reagents, the PdCuAu NAs exhibited higher efficiency in removing organic pollutants from wastewater, as demonstrated by the removal of methylene blue (MB), which was used as the model dye in our study. Scheme 1 details the degradation mechanism of the nanocatalyst. Our study represents the first application of PdCuAu NAS-mediated photothermal Fenton catalysis for dye removal and demonstrates its promising potential in wastewater treatment.
