Characterization and electrochemical properties of stable Ni2+ and F- co-doped PbO2 coating on titanium substrate

A comprehensive review of PbO2 electrodes in electrocatalytic degradation of organic pollutants

This paper provides a systematic review of recent advancements in PbO2 electrodes for the electrocatalytic degradation of organic pollutants, emphasizing innovative breakthroughs and key technological optimizations in this domain. This work analyzes PbO2 electrode fabrication methods, assessing strengths/weaknesses, and summarizes recent advances in surface modification. Atomic-scale strategies such as elemental doping, composite oxides, and nanomaterial coupling, enhance its catalytic performance. Kinetic modeling and characterization confirm the improved efficiency and durability in organic contaminant mineralization. Kinetic and experimental analyses demonstrate the high efficiency and stability of modified PbO2 electrodes in degrading organic pollutants. Industrial feasibility analysis indicates that the PbO2 electrode demonstrates technical robustness, economic viability, and scalability for industrial implementation. This work elucidates direct/indirect oxidation mechanisms in electrocatalysis, revealing correlations between surface reactive sites and active oxidant generation, guiding electrode design optimization. Looking ahead, this paper proposes innovative trajectories for PbO2 electrode technology, such as exploring novel modified materials, intelligently designing hierarchical architectures, and integrating advanced systems with smart control. These directions aim to promote its widespread use in environmental protection for more efficient and eco-friendly organic pollutant treatment. This review enriches the theoretical framework for PbO2 electrode electrocatalytic degradation of organic contaminants and offers references and inspirations for future research.

Origin of the Activity of Electrochemical Ozone Production Over Rutile PbO2 Surfaces

Ozonation water treatment technology has attracted increasing attention due to its environmental benign and high efficiency. Rutile PbO2 is a promising anode material for electrochemical ozone production (EOP). However, the reaction mechanism underlying ozone production catalyzed by PbO2 was rarely studied and not well-understood, which was in part due to the overlook of the electrochemistry-driven formation of oxygen vacancy (OV) of PbO2. Herein, we unrevealed the origin of the EOP activity of PbO2 starting from the electrochemical surface state analysis using density functional theory (DFT) calculations, activity analysis, and catalytic volcano modeling. Interestingly, we found that under experimental EOP potential (i. e., a potential around 2.2 V vs. reversible hydrogen electrode), OV can still be generated easily on PbO2 surfaces. Our subsequent kinetic and thermodynamic analyses show that these OV sites on PbO2 surfaces are highly active for the EOP reaction through an interesting atomic oxygen (O*)-O2 coupled mechanism. In particular, rutile PbO2(101) with the "in-situ" generated OV exhibited superior EOP activities, outperforming the (111) and (110) surfaces. Finally, by catalytic volcano modeling, we found that PbO2 is close to the theoretical optimum of the reaction, suggesting a superior EOP performance of rutile PbO2. All these analyses are in good agreement with previous experimental observations in terms of EOP overpotentials. This study provides the first volcano model to explain why rutile PbO2 is among the best metal oxide materials for EOP and provides new design guidelines for this rarely studied but industrially promising reaction.

Enhancement of the peroxidase-like activity of hollow spherical FexNi1-xS2/SC nanozymes

Artificial nanozymes have been receiving considerable interest for their outstanding performance and wide application. However, their low activity results in a high concentration of substrates, costs, and environmental pollution. To enhance nanozymic activity, a composite, FexNi1-xS2/hollow carbon spheres (FexNi1-xS2/SC), was facilely synthesized by a solvothermal method. The response surface methodology (RSM) was used to optimize the Ni content in FexNi1-xS2/SC and the experimental conditions, where Fe0.75Ni0.25S2/SC exhibited the highest activity. The Km (Michaelis-Menten's constant) values of Fe0.75Ni0.25S2/SC are 0.025 and 0.021 mM with H2O2 and oxidized 3,3',5,5'-tetramethylbenzidine (TMB) as the substrates, respectively, which are 148 times and 20.5 times lower than those with HRP, 1.88 and 7.19 times lower than those of FeS2/SC, and 1.88 and 10.52 times lower than those of Fe0.8Ni0.2S2, meaning a strong affinity of Fe0.75Ni0.25S2/SC for the substrate. The catalytic efficiency (Kcat/Km) of Fe0.75Ni0.25S2/SC was 5.4 (H2O2) and 27.4 times (TMB), and 9.7 (H2O2) and 66.2 times (TMB) higher than those of FeS2/SC and Fe0.8Ni0.2S2, respectively. The effects of the synergistic interaction between Fe and Ni, the S-C bond formation, and the hollow carbon spheres on the activity were studied. A nanozymic mechanism was proposed. Fe0.75Ni0.25S2/SC could be used to detect cysteine (Cys) at room temperature in 1 min with a detection limit (LOD) of 0.049 μM.

Elaboration of Highly Modified Stainless Steel/Lead Dioxide Anodes for Enhanced Electrochemical Degradation of Ampicillin in Water

Lead dioxide-based electrodes have shown a great performance in the electrochemical treatment of organic wastewater. In the present study, modified PbO2 anodes supported on stainless steel (SS) with a titanium oxide interlayer such as SS/TiO2/PbO2 and SS/TiO2/PbO2-10% Boron (B) were prepared by the sol–gel spin-coating technique. The morphological and structural properties of the prepared electrodes were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). It was found that the SS/TiO2/PbO2-10% B anode led to a rougher active surface, larger specific surface area, and therefore stronger ability to generate powerful oxidizing agents. The electrochemical impedance spectroscopy (EIS) measurements showed that the modified PbO2 anodes displayed a lower charge transfer resistance Rct. The influence of the introduction of a TiO2 intermediate layer and the boron doping of a PbO2 active surface layer on the electrochemical degradation of ampicillin (AMP) antibiotic have been investigated by chemical oxygen demand measurements and HPLC analysis. Although HPLC analysis showed that the degradation process of AMP with SS/PbO2 was slightly faster than the modified PbO2 anodes, the results revealed that SS/TiO2/PbO2-10%B was the most efficient and economical anode toward the pollutant degradation due to its physico-chemical properties. At the end of the electrolysis, the chemical oxygen demand (COD), the average current efficiency (ACE) and the energy consumption (EC) reached, respectively, 69.23%, 60.30% and 0.056 kWh (g COD)−1, making SS/TiO2/PbO2-10%B a promising anode for the degradation of ampicillin antibiotic in aqueous solutions.