Surface Oxidation Research Articles

Natural Surface Frustrated Lewis Pairs: The Concept and Beyond.

The reusable and separable surface frustrated Lewis pairs (SFLPs) open up a novel approach to efficient small-molecule activation and conversion in heterogeneous catalysis. However, SFLPs have only been reported on limited systems due to the difficulty in the design and synthesis process. The inherent Lewis pairs on various solid materials offer promising opportunities for finding natural SFLPs, providing a straightforward and efficient strategy to overcome the current limitations. In this concept, we retrospect the concept of natural SFLPs proposed on wurtzite crystal surfaces and identify other natural SFLPs that probably exist on solid materials, including reduced oxide surfaces, corrugated graphene, and perovskite quantum dots. Having focused on the reactivity of natural SFLPs in small-molecule activation, we discuss the current challenges, propose possible research directions, and highlight potential applications of natural SFLPs in heterogeneous catalysis.

Effect of carbon coating on improved electrical and electrochemical performance of Li3Co2SbO6

Abstract We reported a novel high voltage cathode having layered structure and manifold improvement (144%) in electrochemical performance on carbon coating Li3Co2SbO6. The carbon-coated Li3Co2SbO6 has been prepared using a high temperature solid-state method in an air medium with appropriate stoichiometry of the oxide and carbon source (sucrose). The x-ray diffraction and high-resolution transmission electron microscopy results have confirmed homogeneous carbon coating on oxide (Li3Co2SbO6) surface without disturbing phase, structure and morphology. The immediate effect of carbon coating resulted in electrical conductivity enhancement of the carbon coated Li3Co2SbO6 by four order of magnitudes ∼2.79 × 10−4 Scm−1 at room temperature vis-a-vis pristine Li3Co2SbO6. The electrochemical performance of the carbon coated Li3Co2SbO6 has shown sustainable improvement indicating redox activity by more than one Li+ transaction. The carbon coated Li3Co2SbO6 cathode exhibited an initial discharge capacity of 110 mAhg−1 compared to 45 mAhg−1 for its pristine counterpart. The improvement in electrochemical capacity on carbon coating, as reported in this work, is the highest ever compared to prior literature reports on Li3Co2SbO6.

Single-Particle Spectroelectrochemistry: Revealing the Electrochemical Tuning Mechanism of Chemical Interface Damping in 1,2-Benzenedithiol-Adsorbed Single Gold Nanorods.

Chemical interface damping (CID) is a newly proposed plasmon damping pathway based on interfacial hot-electron transfer from metal to adsorbate molecules. However, achieving in situ tunability of CID in single gold nanorods (AuNRs) remains a considerable challenge. Here, we present the CID effect induced by benzene 1,2-dithiol (BDT) molecule adsorption on single AuNRs and the effective electrochemical tunability of CID in BDT-adsorbed AuNRs immobilized on an indium tin oxide (ITO) surface. Manipulations of the electrochemical potential alter the electron density of AuNRs, thereby influencing and tuning the localized surface plasmon resonance (LSPR) spectrum, with cathodic potential blueshifting and anodic potential redshifting. The strong adsorption of BDT on Au induced CID in single AuNRs. The potential-induced LSPR scattering spectra of BDT-adsorbed AuNRs for linear potential sweep showed a stable LSPR spectral response, irrespective of the concentrations of BDT molecules. Due to the involvement of two Au-S bonds, BDT molecules have a higher free adsorption energy and a lower desorption rate on the Au surface. This resulted in a stable LSPR spectral response for a linear electrochemical potential sweep. Furthermore, a constant anodic and cathodic potential application showed the tunability of the CID at the BDT-Au interface.

Effects of nickel-deactivations on zeolites-Y of different SiO2/Al2O3 ratios in catalytic cracking of hydrocarbons

Effects of nickel deactivation on catalytic activities of three types of zeolites-Y (Y-5.1, USY-5.2, and VUSY-12) with varying SiO2/Al2O3 ratios were studied in cracking of hydrocarbons. Physicochemical characteristics such as crystalline phases, Ni oxidation states, morphology, acidity, surface area, and thermal stability of the samples were analysed. XRD revealed the absence of observable nickel compounds below 5 wt%, with NiO phase emerging at higher concentrations. Surface areas decreased from 826 to 615 m2/g (Y-5.1), 786–686 m2/g (USY-5.2), and 762–571 m2/g (VUSY-12) at 30 wt% Ni. The total acid sites also reduced from 17.247 to 9.826 µmol/g (Y-5.1), 15.464–8.854 µmol/g (USY-5.2), and 7.094–4.876 µmol/g (VUSY-12). XPS confirmed Ni2+ states. Catalytic cracking tests using n-Heptane demonstrated increases in C5-C6 alkanes, olefins, hydrogen, and methane yields as nickel concentration increased, with respective values of 64 %, 28 %, 79 % and 68 % for Y-5.1; 62 %, 28 %, 76 %, and 62 % for USY-5.2; and 58 %, 21 %, 75 %, and 60 % for VUSY-12. A corresponding decrease in heavier components were observed. The study demonstrates that nickel modification significantly impacts the physicochemical properties and catalytic performance of zeolite-Y and these depend strongly on the SiO2/Al2O3 ratios. The study gives further insights into the structural and catalytic modifications induced by nickel doping in zeolites, highlighting the potential of nickel-modified zeolites in promoting undesirable hydrogen and gas.

Glycerol surface pretreatment enabled Cu-Cu low-temperature direct bonding in ambient air

The broad application of Cu-Cu direct bonding is substantially constrained owing to the propensity of copper to oxidize, coupled with complex processes including elevated bonding temperatures and compulsory protective atmospheres. Glycerol is employed to diminish Cu oxide while concurrently preserving the reduced Cu surface in ambient air. Cu-Cu direct bonding was thus accomplished at a lower temperature range (150 °C–200 °C) in ambient air, leveraging glycerol pretreatment for the reduction and protection. The effectiveness of glycerol in curtailing the surface oxidation of Cu at 200 °C in ambient air was discovered. The bonding strength exhibited a steady increase from 19.5 MPa to 32.6 MPa as the bonding temperature escalated from 150 °C to 200 °C. Furthermore, in the case of bonding at 200 °C, the bonding interface presented a dense, continuous nature with minimal oxide and carbon residue. Concurrently, good electrical properties were observed at the bonding interface.

Influence of surface oxidation rate on the flotation of sphalerite and galena inhibited by gum arabic

Differences in the flotation behavior of galena and sphalerite using potassium permanganate (KMnO4) and gum arabic (GA) alone and using a mixture of KMnO4 and GA were investigated. The single mineral flotation tests revealed that when KMnO4 and GA were used individually, galena and sphalerite flotation were inhibited, but the reagent dosages required were large. Sphalerite was strongly inhibited by the addition of a tiny amount of GA after oxidation with KMnO4 while galena was not inhibited under the same conditions. Following oxidation by KMnO4, galena and sphalerite exhibited a significant 83 % difference in flotation recovery when 10 mg/L GA was used, which clearly showed the potential for the combined use of KMnO4 and GA to achieve flotation separation of galena from mixed lead-zinc ores. The inhibitory effect of GA on sphalerite was investigated through a combination of analytical techniques, including Microcalorimetry, Fourier Transform Infrared (FTIR) Spectroscopy, contact angle measurements, X-ray Photoelectron Spectroscopy (XPS), and Scanning Electron Microscopy (SEM) coupled with Energy Dispersive X-ray (EDS) analysis. The results displayed that sphalerite had a much higher oxidation rate than galena, resulting in more oxides and hydroxides. As a result, the sphalerite surface exhibits an increased availability of active sites favorable to GA adsorption, thereby impeding Butyl xanthate (PBX) adsorption. However, the galena surface was able to absorb PBX, resulting in mineral separation.

High-temperature time-dependent dielectric breakdown of 4H-SiC MOS capacitors

—With the rapid applications of silicon carbide metal–oxide–semiconductor field-effect transistor (SiC MOSFET) power devices, further improving the performance of SiC MOSFET device through enhancing its gate oxide reliability is one of the crucial directions. The density of interface states in a SiC MOSFET is a significant parameter that affects the reliability of the gate oxide layer. In this paper, the SiC MOS capacitors (MOSCAPs) were prepared by the 1250 °C dry oxidation and 1350 °C NO annealing process. Then, we analyzed the mechanisms of the breakdown by two group of ramped experiment. And we still evaluated the reliability of oxide layer via the high-temperature time-dependent dielectric breakdown (TDDB) tests on the prepared MOSCAPs, meanwhile, the temperature effect on the reliability was considered. Furthermore, the E, 1/E, and E models with Weibull plotting were used to calculate the tBD lifetimes and failure analysis was carried on the failed samples finally. The results indicate that: (1) the impact of the generation and accumulation of the traps in the oxide, which is the main mechanisms of device failure; (2) The prediction of lifetime was calculated with three models at different acceleration factors; (3) at high-temperature, although the lower the density of interface states is, the Si epitaxial growth and C cluster will manifest in the oxide surface and lead to the breakdown of SiC MOSCAPs.

Tuning the surface structure of zinc oxide nanorods by oxide entities of Ni for enhanced degradation of chlorophenoxy herbicide and chlorinated phenols

The surface of hexagonal ZnO was subjected to preliminary treatment with Ni2+ ions that transformed into a homogeneously coated layer by air calcination process in the loading range of 0.3–5 % with respect to the weight of ZnO support. The enhanced absorption in the visible region evidenced the formation of a visible light-responsive oxide entities of Ni2+ and Ni3+ that was further authenticated by multiple edges of variable energy in bandgap analysis. The photoluminescence (PL) spectra revealed the potential role of surface oxides in prolonging the life span of photon-induced excitons. The majority formation of Ni2O3 among the oxide entities, as the surface layer was substantiated by XRD and XPS analysis. The homogeneity, texture, and microstructure of the coated layer were examined by FESEM and HRTEM analysis. The charge retention ability as a function of the thickness of the coated layer was estimated by chronopotentiometry whereas the SPIES measurements coupled with Mott-Schottky analysis facilitated the fetching of the flat band potential as well as the semiconducting electrical nature of the coated materials. The loading of the catalysts as well as the impregnation level for optimum degradation/removal was evaluated in sunlight exposure for the removal of 4-chlorophenol (4-CP). The catalyst with optimum activity i.e. 0.5 % Ni2+ impregnated ZnO, was tested for the removal of potential carcinogens that included 4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP) and 2,4-dichlorophenoxyacetic acid (2,4-D). The progress of the removal process was monitored by HPLC, and the extracted data was used for kinetic studies. The efficacy of the synthesized catalysts was further evaluated for the removal of a concoction of chlorophenol isomers i.e., 2-chlorophenol (2-CP), 3-chlorophenol (3-CP), 4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP), 2,5-dichlorophenol (2,5-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP), both in complete spectrum and visible region (400–800 nm) natural sunlight exposure and established the kinetics of the degradation process.

Onset Reaction Mechanism of Cr and S Poisoning on Perovskite Oxide Surfaces

Onset Reaction Mechanism of Cr and S Poisoning on Perovskite Oxide Surfaces

Organic-Inorganic Biocompatible Coatings for Temporary and Permanent Metal Implants.

The general trend of increasing life expectancy will consistently drive the demand for orthopedic prostheses. In addition to the elderly, the younger population is also in urgent need of orthopedic devices, as bone fractures are a relatively common injury type; it is important to treat the patient quickly, painlessly, and eliminate further health complications. In the field of traumatology and orthopedics, metals and their alloys are currently the most commonly used materials. In this context, numerous scientists are engaged in the search for new implant materials and coatings. Among the various coating techniques, plasma electrolytic oxidation (PEO) (or micro-arc oxidation-MAO) occupy a distinct position. This method offers a cost-effective and environmentally friendly approach to modification of metal surfaces. PEO can effectively form porous, corrosion-resistant, and bioactive coatings on light alloys. The porous oxide surface structure welcomes organic molecules that can significantly enhance the corrosion resistance of the implant and improve the biological response of the body. The review considers the most crucial aspects of new combined PEO-organic coatings on metal implants, in terms of their potential for implantation, corrosion resistance, and biological activity in vitro and in vivo.

Effects of oxidation‐induced aggregation structure transformation of aramid fiber on interfacial adhesion of epoxy resin

AbstractThe large‐scale pretreatment and efficient surface activation of aramid fibers (AFs) before composite fabrication remains a major challenge. In this study, we developed a heat treatment–induced surface modification method to change the reactive groups on AFs. Results indicated that the O/C ratio and the number of ester groups on the AFs as well as the surface morphology of the AFs could be flexibly controlled using the heat treatment–induced surface modification method. Furthermore, the surface oxidation mechanism of the AFs changed from point oxidation to surface oxidation during heat treatment. As the heat‐treatment time increased, the crystallinity and tensile strength of the AF monofilament considerably increased. An optimal heat‐treatment time of 30 min was provided considering that long‐time heating (>30 min) would destroy the surface molecular chains. Under this optimal heat‐treatment time, the number of ester groups reached the maximum, which enhanced the reactivity of the AFs in the epoxy resin matrix. The interfacial shear strength between the AFs treated for 30 min and epoxy resin microdroplet increased by 12.64%, reaching as high as 18.17 MPa. Moreover, the contact angle between the AF monofilament and epoxy resin droplet reached a minimum value of 54.7°. Furthermore, the thickness of the interfacial bond layer between the AFs and epoxy resin reached 50–60 nm. These results provide effective theoretical guidance for the large‐scale application of AFs in composite materials.

Operando Surface X‐Ray Diffraction Studies of Epitaxial Co3O4 and CoOOH Thin Films During Oxygen Evolution: pH Dependence

AbstractTransition metal oxides, especially cobalt oxides and hydroxides, are of great interest as precious metal free electrode materials for the oxygen evolution reaction (OER) in electrochemical and photoelectrochemical water splitting. Here, we present detailed studies of the potential‐ and pH‐dependent structure and structural stability of Co3O4 and CoOOH in neutral to alkaline electrolytes (pH 7 to 13), using operando surface X‐ray diffraction, atomic force microscopy, and electrochemical measurements. The experiments cover the pre‐OER and OER range and were performed on epitaxial Co3O4(111) and CoOOH(001) films electrodeposited on Au(111) single crystal electrodes. The CoOOH films were structurally perfectly stable under all experimental conditions, whereas Co3O4 films exhibit at all pH values reversible potential‐dependent structural transformations of a sub‐nanometer thick skin layer region at the oxide surface, as reported previously for pH 13 (F. Reikowski et al., ACS Catal. 2019, 9, 3811). The intrinsic OER activity at 1.65 V versus the reversible hydrogen electrode decreases strongly with decreasing pH, indicating a reaction order of 0.2 with respect to [OH−]. While the Co3O4 spinel is stable at pH 13, intermittent exposure to electrolytes with pH≤10 results in dissolution as well as gradual degradation of its OER activity in subsequent measurements at pH 13.

Ultra‐Thin Strain‐Relieving Si1−xGex Layers Enabling III‐V Epitaxy on Si

AbstractThe explosion of artificial intelligence, the possible end of Moore's law, dawn of quantum computing, and the continued exponential growth of data communications traffic have brought new urgency to the need for laser integration on the diversified Si platform. While diode lasers on group III‐V platforms have long‐powered internet data communications and other optoelectronic technologies, direct integration with Si remains problematic. A paradigm‐shifting solution requires exploring new and unconventional materials and integration approaches. In this work, it is shown that a sub‐10‐nm ultra‐thin Si1−xGex buffer layer fabricated by an oxidative solid‐phase epitaxy process can facilitate extraordinarily efficient strain relaxation. The Si1−xGex layer is formed by ion implanting Ge into Si(111) and selectively oxidizing Si atoms in the resulting ion‐damaged layer, precipitating a fully strain‐relaxed Ge‐rich layer between the Si substrate and surface oxide. The efficient strain relaxation results from the high oxidation temperature, producing a periodic network of dislocations at the substrate interface, coinciding with modulations of the Ge content in the Si1−xGex layer and indicating the presence of defect‐mediated diffusion of Si through the layer. The epitaxial growth of high‐quality GaAs is demonstrated on this ultra‐thin Si1−xGex layer, demonstrating a promising new pathway for integrating III‐V lasers directly on the Si platform.

Effect of Natural Inhibitors on the Corrosion Properties of Grade 2 Titanium Alloy.

This study investigates the effects of natural inhibitors (pomegranate, algae, and tomato extracts) on the corrosion resistance of titanium (grade 2). To deepen understanding the inhibition mechanism, Molecular Dynamic (MD) and Monte Carlo (MC) simulations were employed to analyze adsorption behaviors and identify optimal adsorption sites on titanium oxide (TiO2) surfaces for compounds within the inhibitors. Results indicate non-flat adsorption orientations, with pomegranate peel extract components showing superior inhibition capabilities, attributed to the formation of strong O-H chemical bonds with the TiO2 surface. In the experimental part of the study Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Polarization (PDP) were conducted. Two electrolytes were tested: a solution 3.5% NaCl and a solution 0.5 M NaOH. All the tests were performed with 5% of inhibitor and with the reference solution. Also, inhibition efficiency was calculated on the base of PDP tests. The study found that pomegranate extract can act as a good corrosion inhibitor for titanium alloy in aqueous solutions 0.5 M NaOH. This was demonstrated by the increase in the corrosion potential and impedance modulus and decrease in the corrosion current density after the addition of pomegranate extract to the solution. However, in a 3.5% NaCl solution, the efficacy of pomegranate extract was less pronounced, probably due to the high aggressivity of the electrolyte. Tomato and algae extract have instead shown very low inhibition effects in all the tested conditions.

Role of Oxide-Derived Cu on the Initial Elementary Reaction Intermediate During Catalytic CO2 Reduction.

The catalytic role of oxide-derived Cu (OD-Cu) in promoting CO2 reduction (CO2R) to C2+ products has been appreciated for decades. However, the dynamic evolution of the surface oxidation states, together with their real correlation to the binding of reaction intermediates, remains unclear due to technical challenges. Here, we show the time-resolved spectroscopic signatures of key OD-Cu-CO2•- intermediates during catalytic CO2 reduction through one electron transfer from nanoseconds to seconds time scale. We generated the initial intermediate CO2•- radicals in the bulk solution and monitored the interfacial reaction kinetics with well-defined OD-Cu (Cu(0), Cu(I), and Cu(II)) nanoparticles. Combined with molecular simulations, transient absorption profiles analysis reveals that Cu(I) induced a faster CO2•- radical coupling reaction than Cu(0), whereas Cu(II) is only reduced to Cu(I) by the CO2•- radical. Furthermore, the newly developed multistep cumulative pulse methodology uncovered the transition in chemical states of mixed OD-Cu during radical coupling reactions. This pulse radiolysis study provides compelling evidence for the beneficial role of subsurface oxides in early time catalytic CO2 transformation.

Fabrication of B-C-N nanosheets on Rh(111) from benzene – borazine mixtures

Atomic level studies of solid state surfaces performed in ultra-high vacuum (UHV) had already an energetic 15–20 years past when our research group in Szeged started working in this field in mid 1970s. Till then several very important methods had been developed, like UHV technology, commercially available electron and photoelectron spectroscopy techniques, etc. Characterization of metal and semiconductor (oxide) surfaces and their adsorption properties had already been widely studied. In any case, the last 40–50 years also witnessed great discoveries and exciting new techniques. Considering only the activity related to heterogeneous catalysis, the main focus of our research group, new breakthrough methods emerged like HREELS, RAIRS, SPM, NAPXPS, EXAFS, NEXAFS. Along this path, new experimental and theoretical approaches appeared like planar model catalysts and inverse catalysts, atomic level investigation and understanding of surface diffusion-controlled phenomena (particle growth and disruption, strong metal-support interaction (SMSI), decoration, spillover), atomic level identification of active sites, self-organized nano-systems, surface alloys and nanotemplates. It was great to participate in this magical activity for more than 50 years. Both internationally and locally in Szeged, in the last two decades, surface science has opened to the wide world of 2D materials like the semimetal graphene and the insulator hexagonal boron nitride. However, the formation of a mixed layer of C, B and N proved to be a difficult task due to the primary tendency for phase separation. In the present work, we report on a preparation method of honeycomb “BCN” materials on Rh(111) by using benzene/borazine mixtures as precursors. It was demonstrated that by a suitable choice of the growth parameters, the formation of large, separated graphene and h-BN islands can be avoided.

Atomistic oxidation mechanism of Bi0.5Sb1.5Te3 (0001) surface

Surface oxidation can potentially influence transport properties of thermoelectric materials and service performance of thermoelectric devices. Here, the oxidation mechanism of the (0001) surface of a widely used p-type TE material, Bi0.5Sb1.5Te3 (BST), was investigated using spherical aberration corrected scanning transmission electron microscopy (STEM). Combining atomic-resolution STEM and density function theory (DFT), it was revealed that oxidation occurs at room temperature in the dry air through O diffusion into the surface quintuple layer, facilitating formation of both cation and anion vacancies, weakening the Bi-Te and Sb-Te bonds, leading to oxidation product Sb2O3, amorphous Te, and Bi-rich BST. Formation of a thin O-rich cation-deficient quintuple layer on the surface and the Bi-rich BST region can significantly reduce the interfacial reaction between BST and Ni electrode, as the reaction layer thickness is reduced by 75% after the surface oxidation. This work provides essential structural information on surface oxidation mechanism and its influence on properties and performance of TE materials and devices.

Investigation of wettability and icing on the steel surface using laser surface treatment

Icing impairs normal functionality for a variety of industries and applications. Research on hydrophobic surfaces is being conducted to solve the icing problem. In this study, a hydrophobic surface was fabricated on SM490A using a nanosecond laser. The change in surface microstructure was observed. Hydrophilicity was immediately observed right after laser irradiation, and the contact angle increased over time, resulting in hydrophobicity. To explain the wettability conversion, X-Ray Photoelectron Spectroscopy (XPS) was used to observe changes in surface chemical composition and element bonding. It was observed that the level of Fe and O increased immediately after laser irradiation, resulting in surface oxidation. Since the presence of oxides has high surface energies, they contribute to super hydrophilic surfaces. Since the C−C(H) bond has low surface energy and the content of nonpolar C−C(H) bonds and C increased over time, the contact angle subsequently increases over time. When the ice shape was observed after dropping a droplet on the surface, the higher contact angle specimen reduced the attached area. Therefore, the surface treatment using a nanosecond laser can produce a hydrophobic surface on the SM490A specimens so that it may solve ice adhesion problems.

Developing adjustable micro- and mesopore structured carbon materials from wood via biotechnology for enhanced capacitive deionization

Capacitive deionization (CDI) has attracted significant investigation interest for its potential in low-cost, efficient, and non-selective ion removal. However, achieving high performance in adsorption capacity and efficiency remains challenging, particularly with conventional biomass-derived electrodes. In this study, we developed adjustable, intricately porous, and hydrophilic wood-derived nanocarbon electrodes for electrochemical deionization. Our approach utilized biological pretreatment white-rot fungi, followed by chemical activation, effectively disrupting the rigid crystalline-amorphous structure of wood to create open micro-mesoporous networks. The resulting CDI carbon electrodes featured a predominance of micropores (especially below 0.8 nm) and a pronounced mesoporous arrangement, with a specific surface area of 1788 m2/g and 48 % meso-porosity. Additionally, this process enhanced surface oxidation and nitridation, resulting in surfaces rich in oxygen- and nitrogen-containing functional groups. These characteristics enable the electrodes to achieve a maximum adsorption capacity of 28.78 mg/g within 30 min, outperforming the performance of common biomass-derived electrodes. Moreover, the electrodes demonstrated excellent adsorption capacities for other contaminants, including 29.76 mg/g for NaF, 30.12 mg/g for Cd(NO3)2, and 27.24 mg/g for Pb(NO3)2. This study offers a cost-effective and viable alternative to current CDI electrodes, advancing the field by providing a viable solution to the limitations of existing technologies.

An Electrochemical Study of the Effect of Sulfate on the Surface Oxidation of Pyrite.

Pyrite is one of the most abundant metal sulfide tailings and is susceptible to oxidation, yielding acidic mine drainage (AMD) that poses significant environmental risks. Consequently, the exploration of pyrite surface oxidation and the kinetic influencing factors remains a pivotal research area. Despite the oxidation of pyrite producing a significant amount of sulfate (SO42-), a comprehensive investigation into its influence on the oxidation process is lacking. Leveraging pyrite's semiconducting nature and the electrochemical intricacies of its surface oxidation, this study employs electrochemical techniques-cyclic voltammetry (CV), Tafel polarization, and electrochemical impedance spectroscopy (EIS)-to assess the effect of SO42⁻ on pyrite surface oxidation. The CV curve shows that SO42- does not change the fundamental surface oxidation mechanism of pyrite, but its redox peak current density decreases with the increase in SO42-, and the surface oxidation rate of pyrite decreases. The possible reason is attributed to SO42- adsorption onto pyrite surfaces, blocking active sites and impeding the oxidation process. Furthermore, Tafel polarization curves indicate an augmentation in polarization resistance with elevated SO42- concentrations, signifying heightened difficulty in pyrite surface reactions. EIS analysis underscores an increase in Weber diffusion resistance with increasing SO42⁻, indicating that the diffusion of Fe3+ to the pyrite surface and the diffusion of oxidized products to the solution becomes more difficult. These findings will improve our understanding of the influence of SO42- on pyrite oxidation and have important implications for deepening the understanding of surface oxidation of pyrite in the natural environment.