Ru-Induced Defect Engineering in Co3O4 Lattice for High Performance Electrochemical Reduction of Nitrate to Ammonium

Amidst these growing sustainability concerns, producing NH4 + via electrochemical NO3 - reduction reaction (NO3RR) emerges as a promising alternative to the conventional Haber-Bosch process. In a pioneering approach, this study introduces Ru incorporation into Co3O4 lattices at the nanoscale and further couples it with electroreduction conditioning (ERC) treatment as a strategy to enhance metal oxide reducibility and induce oxygen vacancies, advancing NH4 + production from NO3RR. Here, supported by a suite of ex situ and in situ characterization measurements, the findings reveal that Ru enrichment promotes Co species reduction and oxygen vacancy formation. Further, as evidenced by the theoretical calculations, Ru integration lowers the energy barrier for oxygen vacancy formation, thereby facilitating a more energy-efficient NO3RR-to-NH4 + pathway. Optimal catalytic activity is realized with a Ru loading of 10 at.% (named 10Ru/Co3O4), achieving a high NH4 + production rate (98 nmol s-1 cm-2), selectivity (97.5%) and current density (≈100 mA cm-2) at -1.0 V vs RHE. The findings not only provide insights into defect engineering via the incorporation of secondary sites but also lay the groundwork for innovative catalyst design aimed at improving NH4 + yield from NO3RR. This research contributes to the ongoing efforts to develop sustainable electrochemical processes for nitrogen cycle management.

One-step synthesis of Pt-Nd co-doped Ti/SnO2-Sb nanosphere electrodes used to degrade nitrobenzene

Ti/SnO2-Sb electrodes possess high catalytic activity and efficiently degrade nitrobenzene (NB); however, their low service life limits their wide application. In this study, we used one-step hydrothermal synthesis to successfully prepare Pt-Nd co-doped Ti/SnO2-Sb nanosphere electrodes. Scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were applied to characterize the surface morphology, microstructure, and chemical composition of the electrodes, respectively. The electrochemical activity and stability of the electrodes were characterized via linear sweep and cyclic voltammetry, electrochemical impedance spectroscopy, and an accelerated service life test; their performance for NB degradation was also studied. An appropriate amount of Pt-Nd co-doping refined the average grain size of SnO2 and formed a uniform and compact coating on the electrode surface. The oxygen evolution potential, total voltammetric charge, and electron transfer resistance of the Ti/SnO2-Sb-Nd-Pt electrodes were 1.88 V, 3.77 mC/cm2, and 11.50 Ω, respectively. Hydroxy radical was the main active radical species during the electrolytic degradation of nitrobenzene with Ti/SnO2-Sb-Nd-Pt. After Pt-Nd co-doping, the accelerated service life of the electrodes was extended from 8.0 min to 78.2 h (500 mA/cm2); although the NB degradation rate decreased from 94.1 to 80.6%, the total amount of theoretical catalytic degradation of NB in the effective working time increased from 17.4 to 8754.1 mg/cm2. These findings reveal good application potential for the electrodes and provide a reference for developing efficient and stable electrode materials.

Electrochemical degradation of methylene blue by Pb modified porous SnO2 anode

A significant number of pollutants in wastewater can be electrocatalytically oxidized by SnO₂-Sb, a relatively inactive electrode. However, the arduous process of environmental remediation due to poor electrochemical performance and short service life of the traditional Ti/SnO₂-Sb electrode. In this work the SnO₂ electrode with a micron-sized sphere structure was prepared by in-situ hydrothermal. The results of the study that the electrode (Pb-10%) synthesized from the precursor solution in which the Pb:Sn molar ratio is 10% exhibits excellent electrooxidation properties. Impressiveing, the Pb-10% electrode displayed the small charge transfer resistance (10.71 Ω) and the high oxygen evolution potential (2.26 V vs. SCE). Thus, the electrochemical degradation experiment demonstrates that 100 mg L^-1 MB was degraded by Pb-10% electrode under the condition of initial pH = 5, and the decolorization rate reached 94.6%. Moreover, the influence of different parameters such as Pb doping amount, initial pH value of solution, initial concentration of MB and inorganic ions on degradation efficiency were also explored, in turn the practical application of electrodes in the field of purifying water resources is optimized. It is worth noting that the service life of the optimized electrode (100 mA cm^-2, 0.5 M H₂SO₄, 90 h) is about 12 times longer than that of the bare electrode (Sn-Sb). Therefore, the high-performance Ti/SnO₂-Sb electrode prepared in this work possesses vast application prospects in the electrocatalytic oxidation.

Efficient degradation of polyacrylamide using a 3-dimensional ultra-thin SnO2-Sb coated electrode

Polyacrylamide (PAM) is widely used in polymer flooding processes to increase oil recovery while the byproduct of PAM-containing wastewater is a serious environmental issue. In this study, electrochemical oxidation process (EAOP) was applied for treating PAM wastewater using a new type of 3-dimensional ultra-thin SnO₂-Sb electrode. Nano-sized catalysts were evenly dispersed both on the surface and inside of a porous Ti filter forming nano-thickness catalytic layer that enhances the utilization and bonding of catalysts. This porous Ti electrode showed 20% improved OH· production and 16.3 times increased accelerated service life than the planar Ti electrode. Using this electrode to treat 100 mg L^-1 PAM, the TOC removal efficiency reached over 99% within 3 h under current density of 20 mA cm^-2. The EAOP could fastly break the long-chain PAM molecules into small molecular intermediates. With the porous electrode treating 5 g L^-1 PAM under current density of 30 mA cm^-2, EAOP reduced 94.2% of average molecular weight in 1 h and 92.0% of solution viscosity in 0.5 h. Moreover, the biodegradability of PAM solution was significantly improved as the solution BOD₅/COD ratio raised from 0.05 to 0.41 after 4 h treatment. The degradation pathway of PAM was also investigated.

Preparation of Ti/SnO2-Sb/Rare Earth Electrodes Containing Different Contents of Ni Intermediate Layer for Efficient Electrochemical Decolorization of Rhodamine B

Water contamination by dyes discharged from many industries is an environmental issue of great matter. Electrochemical oxidation is an advanced approach for wastewater treatment. In this study, the composite electrodes of Ti/SnO2-Sb-Ni/rare earth have been modified using rare earth elements (Re) Gd, Ce, Eu, and Er and various molar ratios of tin and nickel intermediate layer, and their electrochemical oxidation effects were scrutinized. To analyze the decolorization performance of the electrodes, Rhodamine B (RhB) dye was utilized as a target pollutant. Accelerated life testing indicated that the longer service life could be observed in Ni (3.5%)/Re and Ni (5%)/ Re electrodes compared with other modified Ni (0%, 1%, and 2%)/Re electrodes. Compared with the color removal efficiencies of the Ni (2%)/Re electrodes, the decolorization rate of 90% after treatment for 60 min and the low energy consumption of 3.621 kW h·m−3 can be achieved at the Ni (2%)/Gd electrode under the experimental condition of 100 mg·L−1 RhB. The best decolorization rate was observed at the Ni (2%)/Re electrodes among other Ni and no adding Ni-doped Re electrodes. The characterization of the electrodes was described, consisting of surface morphology, oxygen evolution potential, and a crystallographic and elemental combination of the coatings.

Electrochemical degradation of three phthalate esters in synthetic wastewater by using a Ce-doped Ti/PbO2 electrode

A Ce-doped Ti/PbO₂ electrode was prepared in a deposition solution containing Ce³⁺ and Pb²⁺ ions by electrodeposition, and the surface morphology, crystal structure and elemental states were characterized by SEM, XRD and XPS. The electrode was used to investigate the simultaneous degradation of three phthalate esters (PAEs), i.e., dimethyl phthalate (DMP), diethyl phthalate (DEP) and dibutyl phthalate (DBP) in synthetic wastewaters. The results showed that the electrode exhibited excellent electrocatalytic activity and good reusability and stability, and the removal efficiencies of 5 mg L^-1 DBP, DMP and DEP in 0.05 M Na₂SO₄ (pH 7) reached 98.2%, 95.8% and 81.1% at current density of 25 mA cm^-2 after 10 h degradation, respectively. The degradation processes followed pseudo first-order kinetic model very well, and the observed rate constants of DBP, DEP and DMP were 0.42, 0.40 and 0.29 h^-1, respectively. The energy consumption in three PAEs degradation was also assessed. The main degradation products of the three PAEs were identified by using liquid chromatography-tandem mass spectrometry, and the possible degradation pathways mainly included dealkylation, hydroxyl addition, decarboxylation and benzene ring cleavage. This work is a promising candidate for efficient treatment of multiple PAEs in wastewater and protection of the aquatic ecological environment.

Facile sealing treatment with stannous citrate complex to enhance performance of electrodeposited Ti/SnO2-Sb electrode

Ti/SnO₂-Sb is a promising anode for electrochemical advanced oxidation process with advantages of low cost and no secondary pollution, while suffers from low work economy due to the short service life. In this study, a facile strategy was proposed to fabricate Ti/SnO₂-Sb electrode with high oxidation ability and long service life based on novelly sealing electrodeposited Sn-Sb coating with stannous citrate complex. The treated Ti/SnO₂-Sb electrode exhibited an accelerated service life of 41.5 h (100 mA cm^-2; 0.5 M H₂SO₄) and a degradation rate constant for methylene blue dye of 1.02 h^-1 which were respectively 11.9 and 2.5 times as that of the untreated electrode. It was found out that the complex could well repair the coating defects inside or outside and form a covering film to tighten the coating, and was then mineralized during the following calcination process to achieve a uniform, rough and highly active SnO₂-Sb catalytic layer. The distinctive structure was confirmed by XRD, SEM, XPS and FT-IR. The sealing treatment could be achieved by in situ electrodepositing Sn-Sb coating from or ex situ dipping Sn-Sb coating in solution containing stannous citrate complex followed by drying in air. This study provided a novel, facile and effective strategy to enhance performance of Ti/SnO₂-Sb electrode that could be easily achieved in both laboratory and industrial scales and combined with other strategies.

Electrochemical degradation of ciprofloxacin with a Sb-doped SnO2 electrode: performance, influencing factors and degradation pathways

Sb-doped SnO₂ electrodes were prepared with the practical sol–gel method and were used for the electrocatalytic degradation of ciprofloxacin (CIP) in aqueous solution. Results from the electrochemical characterization (including cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy) showed that the electrode with 16 coating times (SSO-16) had the highest oxygen evolution potential of 2.2 V (vs. SCE) and the highest electrochemically active area of 3.74 cm². The results of scanning electron microscopy and X-ray diffraction showed that the coating times could affect the surface morphology and crystal structure of the electrodes, and the SSO-16 electrode had a denser surface, higher crystallinity, and smaller grain size (28.6 nm). Moreover, the experimental parameters for CIP degradation with SSO-16 were optimized, and the removal ratio of CIP reached to almost 100% within 60 min. In addition, the possible degradation pathways of CIP were proposed. And the stability and reusability of the SSO-16 electrode were also studied. These results are valuable for the preparation of high electrocatalytic performance electrodes by a sol–gel coating method for electrochemical degradation of antibiotics.

Sb-doped SnO₂ electrodes with different coating times were prepared by an optimum sol–gel method and the application on the electrocatalytic degradation of ciprofloxacin in aqueous solution were investigated.

Preparation of a SnO2–Sb electrode on a novel TiO2 network structure with long service lifetime for degradation of dye wastewater

Developing effective electrodes with long service lifetime for electrochemical degradation of dyes is of paramount importance for their practical industrial applications. We constructed a novel SnO₂–Sb electrode (Ti/TiO₂-NW/SnO₂–Sb electrode) based on a uniform TiO₂ network structure decorated Ti plate (Ti/TiO₂-NW) for a long-term electrocatalytic performance. The SnO₂–Sb coating layer on this electrode was grown on the Ti/TiO₂-NW by pulse electrodeposition. The introduction of the three-dimensional TiO₂-NW enhances the bonding strength between the Ti substrate and the SnO₂–Sb surface coating. An accelerated life test shows that the service life of Ti/TiO₂-NW/SnO₂–Sb electrode is 11.15 times longer than that of the traditional Ti/SnO₂–Sb electrode. The physicochemical properties of the electrodes were characterized through SEM, EDS, XRD and HRTEM. In addition, through LSV, EIS, CV and voltammetric charge analysis, it is found that compared with the traditional electrode, the Ti/TiO₂-NW/SnO₂–Sb electrode possesses a higher oxygen evolution potential, a lower charge transfer resistance and a larger electrochemical active surface area. Besides, this novel electrode also exhibits an outstanding electrocatalytic oxidation ability for degradation of acid red 73 in simulated sewage. After a 5 hours' test, the removal efficiency of acid red 73 and the COD reached 98.6% and 71.8%, respectively, which were superior to those of Ti/SnO₂–Sb electrode (89.1% and 58.8%). This study highlights the excellent stability of the Ti/TiO₂-NW/SnO₂–Sb electrode and provides an energy-efficient strategy for dye degradation.

A novel TiO₂ network structure modified SnO₂–Sb electrode has been prepared by electrodeposition with long service lifetime and low energy consumption.

Magnetic Assembled Anode Combining PbO2 and Sb-SnO2 Organically as An Effective and Sustainable Electrocatalyst for Wastewater Treatment with Adjustable Attribution and Construction

A new electrode consisting of a Ti/PbO₂ shell as main electrode (ME) and numerous Fe₃O₄/Sb-SnO₂ granules as auxiliary electrodes (AEs) was developed for flexible electrochemical oxidation (EO) treatment of wastewater. Material and electrochemical characterizations were carried out to study the impacts of the loading amount of the AEs on the attribution and construction of the electrode. Lignin, a complex group of polymeric macromolecules, was selected as the representative actual contaminant to test the real EO capability of the assembled electrodes with different AE loading amounts. The stability and recyclability of the electrodes were also investigated. Results showed that the roughness and the surface area of the electrode were increased with the increased loading amount of AEs, while improvement of the electrode properties was achieved only with the appropriate amounts of AEs. The optimum AE loading (such as 0.25 and 0.5 g on 6 cm² ME) boosted the EO performance of the anode toward lignin by ∼20%, making the electrode more capable in benzene ring opening. Excessive AEs were found to be unavailing, which only increased the percentage of the less accessible catalytic active sites. Moreover, a preliminary operating mechanism of this 2.5D electrode was proposed to evaluate the effect of AEs and further reveal the relationships of structure and activity of the 2.5D electrode. Finally, the electrode's lifetime was lengthened and further boosted via loading AEs and the subsequent recycling of AEs.

Preparation, characterization, and application of Ti/TiO2-NTs/Sb-SnO2 electrode in photo-electrochemical treatment of industrial effluents under mild conditions

Ti/TiO₂-NTs/Sb-SnO₂ electrode was prepared by gradient pulsed electrodeposition, and its electrochemical properties were evaluated. The catalytic activity and reusability of the electrode were tested by electrochemical oxidation (EO) and photoelectrochemical oxidation (PEO) of organics present in textile industry wastewater (TWW) and coffee bean processing industry wastewater (CWW). COD removal of ~ 41% was achieved after 5-h electrolysis under a constant applied current density of 30 mA cm^-2 for TWW and 50 mA cm^-2 for CWW. Nearly 14 and 18% increment in COD removal was observed under PEO for TWW and CWW, respectively. The turbidity of TWW reduced from 15 to ~ 3 NTU and the turbidity of CWW reduced from 27 to ~ 3 NTU by both EO and PEO. The % COD removal observed after 5-h electrolysis remained consistent for 7 repeated cycles; however, the catalytic activity of the electrode reduced gradually. These results suggested that the Ti/TiO₂-NTs/Sb-SnO₂ can be a potential electrode for the treatment of industrial wastewater.