Persulfate enhanced pollutants oxidation efficiency and power generation in photocatalytic fuel cell with anodic BiOCl/BiOI and cathodic copper cobalt oxide

Electron transfer mediated photo-Fenton-like synergistic catalysis of Fe,Cu-doped MIL-101 coupled with Ag3PO4: Quantitative evaluation and DFT calculations

Widespread use of tetracycline (TC) results in its persistent residue and bioaccumulation in aquatic environments, posing a high toxicity to non-target organisms. In this study, a bimetal-doped composite material Ag3PO4/MIL-101(Fe,Cu) has been designed for the treatment of TC in aqueous solutions. As the molar ratio of Fe/Cu in composite is 1:1, the obtained material AP/MFe1Cu1 is placed in an aqueous environment under visible light irradiation in the presence of 3 mM peroxydisulfate (PDS), which forms a photo-Fenton-like catalytic system that can completely degrade TC (10 mg/L) within 60 min. Further, the degradation rate constant (0.0668 min-1) is 5.66 and 7.34 times higher than that of AP/MFe and AP/MCu, respectively, demonstrating a significant advantage over single metal-doped catalysts. DFT calculations confirm the strong adsorption capacity and activation advantage of PDS on the composite surface. Therefore, the continuous photogenerated electrons (e-) accelerate the activation of PDS and the production of SO4•-, resulting in the stripping of abundant photogenerated h + for TC oxidation. Meanwhile, the internal circulation of FeⅢ/FeⅡ and CuⅡ/CuⅢ in composite also greatly enhances the photo-Fenton-like catalytic stability. According to the competitive dynamic experiments, SO4•- have the greatest contribution to TC degradation (58.93%), followed by 1O2 (23.80%). The degradation intermediates (products) identified by high-performance liquid chromatography-mass spectrometry (HPLC/MS) technique indicate the involvement of various processes in TC degradation, such as dehydroxylation, deamination, N-demethylation, and ring opening. Furthermore, as the reaction proceeds, the toxicity of the intermediates produced during TC degradation gradually decreases, which can ensure the safety of the aquatic ecosystem. Overall, this work reveals the synergy mechanism of PDS catalysis and photocatalysis, as well as provides technical support for removal of TC-contaminated wastewater.

Sustainable degradation of pollutants, generation of electricity and hydrogen evolution via photocatalytic fuel cells: An Inclusive Review

Environmental pollution and energy crisis have recently become one of the major global concerns. Insincere discharge of massive amount of organic and inorganic wastes into the aqueous bodies causes serious impact on our environment. However, these organic substances are significant sources of carbon and energy that could be sustainably utilized rather than being discarded. Photocatalytic fuel cell (PFC) is a smart and novel energy conversion device that has the ability to achieve dual benefits: degrading the organic contaminants and simultaneously generating electricity, thereby helping in environmental remediation. This article presents a detailed study of the recent advancements in the development of PFC systems and focuses on the fundamental working principles of PFCs. The degradation of various common organic and inorganic contaminants including dyes and antibiotics with simultaneous power generation and hydrogen evolution has been outlined. The impact of various operational factors on the PFC activity has also been briefly discussed. Moreover, it provides an overview of the design guidelines of the different PFC systems that has been developed recently. It also includes a mention of the materials employed for the construction of the photo electrodes and highlights the major limitations and relevant research scopes that are anticipated to be of interest in the days to come. The review is intended to serve as a handy resource for researchers and budding scientists opting to work in this area of PFC devices.

Treatment of diluted palm oil mill effluent (POME) synchronous with electricity production in a persulfate oxidant-promoted photocatalytic fuel cell

Attributable to the prosperous production growth of palm oil in Malaysia, the generated palm oil mill effluent (POME) poses a high threat owing to its highly polluted characteristic. Urged by the escalating concern of environmental conservation, POME pollution abatement and potential energy recovery from the effluent are flagged up as a research topic of interest. In this study, a cutting-edge photocatalytic fuel cell (PFC) system with employment of ZnO/Zn nanorod array (NRA) photoanode, CuO/Cu cathode, and persulfate (PS) oxidant was successfully designed to improve the treatment of POME and simultaneous energy production. The photoelectrodes were fabricated and characterized by field emission scanning electron microscopy with energy (FESEM), X-ray diffraction (XRD), energy-dispersive X-ray (EDX), and Brunauer, Emmett, and Teller analysis (BET). Owing to the properties of strong oxidant of PS, the proposed PFC/PS system has exhibited exceptional performance, attaining chemical oxygen demand (COD) removal efficiency of 96.2%, open circuit voltage (Voc) of 740.0 mV, short circuit current density (Jsc) of 146.7 μA cm-2, and power density (Pmax) of 35.6 μW cm-2. The pre-eminent PFC/PS system performance was yielded under optimal conditions of 2.5 mM of persulfate oxidant, POME dilution factor of 1:20, and natural solution pH of 8.51. Subsequently, the postulated photoelectrocatalytic POME treatment mechanism was elucidated by the radical scavenging study and Mott-Schottky (M-S) analysis. The following recycling test affirmed the stability and durability of the photoanode after four continuous repetition usages while the assessed electrical energy efficiency revealed the economic viability of PFC system serving as a post-treatment for abatement of POME. These findings contributed toward enhancing the sustainability criteria and economic viability of palm oil by adopting sustainable and efficient POME post-treatment technology.

Peroxymonosulfate activated by photocatalytic fuel cell with g-C3N4/BiOI/Ti photoanode to enhance rhodamine B degradation and electricity generation

The development of traditional photocatalytic fuel cell (PFC) is severely hindered by poor visible-light response and limited reaction space. In this study, a visible-light responsive PFC with g-C₃N₄/BiOI/Ti photoanode was proposed and applied to activate peroxymonosulfate (PMS) to degrade rhodamine B. The degradation rate, maximum power density and maximum photocurrent density of the PMS/PFC system were respectively 95.39%, 103.87 μW cm^-2 and 0.62 mA cm^-2, which was respectively 1.28, 2.18, and 1.98 times that of PFC. The excellent performance is attributed to the production of more reactive oxygen species and the extension of the reaction space range after the activation of PMS. The activation pathway of PMS and charge transfer pathway of the photoanode were discussed in detail, and it was proposed that PMS was activated by Z-scheme heterojunction g-C₃N₄/BiOI/Ti photoanode.

0D boron carbon nitride quantum dots decorated 2D Bi4O5I2 as 0D/2D efficient visible-light-driven photocatalysts for tetracyclines photodegradation

A series of 0D boron carbon nitride quantum dots (BCNQDs) modified 2D Bi₄O₅I₂ (0D/2D Bi₄O₅I₂/BCNQDs) composites were synthesized and applied to photodegradation of tetracyclines (TCs), including tetracycline (TC) and oxytetracycline (OTC). The Bi₄O₅I₂/BCNQDs (1) (1 mL BCNQDs) composite exhibits the highest photocatalytic performance for TCs degradation. The degradation rate constants of TC and OTC by the optimal sample were 4.95 and 2.17 times that of Bi₄O₅I₂, respectively. This can be attributed to the fact that the narrow bandgap Bi₄O₅I₂ is the electron acceptor, and the oxygen-containing functional group with the negative charge on BCNQDs can promote the formation of photoexcited holes, which makes the effective separation of photoexcited carriers easier. Furthermore, the active substance (h⁺ and ·O₂^-) is the major active substance for TCs photodegradation. On this basis, the possible photocatalytic reaction mechanism of Bi₄O₅I₂/BCNQDs (1) composite is proposed. This study provides a new idea for 0D/2D interface engineering of BCNQDs heterojunction.

Enhanced bezafibrate degradation and power generation via the simultaneous PMS activation in visible light photocatalytic fuel cell

A collaborative system including peroxymonosulfate (PMS) activation in a photocatalytic fuel cell (PFC) with an BiOI/TiO₂ nanotube arrays p-n type heterojunction as photoanode under visible light (PFC(BiOI/TNA)/PMS/vis system) was established. Xenon lamp was used as the light source of visible light. A 4.6 times higher pseudo-first-order bezafibrate (BZF) degradation rate constant was achieved in this system compared with the single PFC(BiOI/TNA)/vis system. The radical quenching experiments revealed that the contribution of reactive oxidative species (ROS) followed the order of ¹O₂ ≈ h⁺ >> •OH > SO₄^•- >>O₂^•-. The EPR tests demonstrated that PMS addition enlarged the formation of ¹O₂, •OH and SO₄^•-, but suppressed O₂^•- yield. Interestingly, ¹O₂ was further proved to dominantly originated from the priority reaction between positive photoinduced holes (h⁺) and negatively charged PMS. Besides, N₂-purging tests and density functional theory calculation indicated that PMS probably reacted with residual photoinduced electron (e^-) on the more negative conduction band (CB) of BiOI to form •OH and SO₄^•-, but competed with dissolved oxygen. Other e^- transferred to the less negative CB of TNA through p-n junction will efficiently move to cathode through the external circuit. The greatly promoted power generation of PFC system was observed after PMS addition due to extra h⁺ consumption and efficient e^- separation and transfer. Besides, three possible pathways for BZF degradation were proposed including hydroxylation, fibrate chain substituent and amino bond fracture. This study can provide new insights into the mechanisms of PMS assisted photocatalysis and accompanying energy recovery.

Oxidation of gas phase ammonia via accelerated generation of radical species and synergy of photo electrochemical catalysis with persulfate activation by CuO-Co3O4 on cathode electrode

To enhance the efficiency of SO₄^- based advanced oxidation processes (AOPs) in synergy with photocatalysis in eliminating contaminants, heterogeneous CuO-Co₃O₄ catalysts were synthesized by a co-precipitation method and evaluated in oxidizing ammonia (NH₃). The removal of 96.1 % NH₃ at room temperature was achieved in persulfate/photo-electrochemical catalysis (PEC/PS). The factors influencing NH₃ removal include molar ratios of Cu/Co in CuO-Co₃O₄, external resistance and PS concentration. The activation of PS is affected by loading of metal oxides catalyst and its Cu/Co molar ratio (2 is optimal). On the catalyst surface, Co and Cu species were the primary reactive sites. The reaction mechanism involves the in-situ PS activation in synergy with PEC, accelerating the production of radical species, thereby enhancing ammonia oxidation and removal.