Heterogeneous Cu–Sn-PPy mediated synergistic photo-Fenton and photothermal catalysis for dye elimination

With the development of industry, large molecule organic pollutants such as petroleum compounds, aromatic and cyclic compounds, polycyclic aromatic hydrocarbons, and styrene that are highly stable and toxic have caused great harm to the air and water sources [1]. These Refinery organic contaminants (ROCs) have potential risks to human health and the ecological environment [2], making their harmless treatment a problem that researchers must solve. Traditional treatments for these types of pollutants mainly include physical adsorption [3], high-temperature incineration, and biological absorption [4,5]. In recent years, researchers have discovered that the Fenton catalytic system with the synergistic effect of photocatalysis and photothermal conversion can efficiently and cost-effectively remediate pollutants [[6], [7], [8]]. However, due to the nature of Fe-based catalysts, the catalytic activity of the Fenton catalyst is low at neutral pH, and the photostability [9,10] decreases during long-term application [11,12], causing significant changes in catalyst activity that make it difficult to exert its effectiveness in practical applications [13,14].

To address the above issues, a Copper-Stannum-Polyprolle-Heterogeneous (CSPHGs) catalytic system has been developed [[15], [16], [17]]. Herein, CSPHGs utilize Cu2O cubes as the core. Based on our previous research [18], Cu+ can be effective over a wider pH range. Effectively addressing the traditional Fe-based catalyst's weakness in catalytic performance under neutral conditions. In order to enhance the photocatalytic efficiency of Cu2O, we employed a non-uniform deposition method to deposit tin oxide (SnO2) onto the surface of Cu2O [[19], [20], [21]]. Tin oxide possesses similar atomic spacing and water splitting redox potentials to copper oxide, facilitating the formation of heterojunctions between Cu2O and SnO2 [22,23]. This heterojunction enables the occurrence of a Z-shaped charge transfer pathway, effectively enhancing the generation of electron-hole pairs [24]. In air, Cu2O is easily oxidized to CuO, resulting in poor photo-stability and hindering its reuse. This greatly increases the cost of catalysts [[25], [26], [27], [28]]. In order to address this issue and enhance the photothermal efficiency while improving the light absorption rate of the system, we forming a poly-pyrrole shell on the Cu–Sn oxide surface by oxidative polymerization [29,30]. Polyprolle is an extremely photothermal polymer with good photothermal conversion rate under NIR light irradiation [31] and good biocompatibility, which has been widely used in the preparation of medical materials, tissue engineering and drug release [32]. Therefore, Polyprolle can be used as a chelating agent to effectively reduce the direct contact of Cu+ with the environment, thus making CSPHGs almost harmless to the environment [33].

As shown in Scheme 1, the photo-thermal performance of the material under various conditions was evaluated. Then, the degradation performance of the CSPHGs was assessed using Rhodamine B (RhB) as a model dye. An exploration of the catalytic system's mechanism was conducted through the study of degradation products, and hypotheses for the RhB degradation process were proposed. Lastly, cell viability analysis demonstrated that CSPHGs is environmentally benign and reusable, highlighting its potential for natural applications.