H2O Coverage Research Articles

Theoretical insight into H2O impact on V2O5/TiO2 catalysts for selective catalytic reduction of NOx.

H2O in flue gas causes the deactivation of V2O5/TiO2 catalysts for selective catalytic reduction (SCR) of NOx with NH3 at low temperatures. Developing water resistance requires understanding the theoretical mechanism of H2O impact on the catalysts. The aim of this work was to clarify the adsorption process of H2O and the deactivation mechanism induced by H2O through density functional theory (DFT). The process of H2O adsorption was studied based on a modeled V2O5/TiO2 catalyst surface. It was found that H2O had a strong interaction with exposed titanium atoms. Water adsorption on the catalyst surface significantly alters the electronic structure of VOx sites, transforming Lewis acid sites into Brønsted acid sites. Exposed titanium sites contribute to the decrease of Lewis acidity via adsorbed water. Ab initio thermodynamic calculations show that H2O adsorption on V2O5/TiO2 is stable at low coverage but less favorable at high coverage. Adsorption of NH3 is the most critical step for the SCR of NOx, and the adsorption of H2O can hinder this process. The H2O coverage below 15% of adsorption sites could enhance the NH3 adsorption rate and have a limited effect on the acidity, while higher coverage impeded the adsorption ability of VOx sites. This work provided electron-scale insight into the adsorption impact of H2O on the surface of V2O5/TiO2 catalysts, presented thermodynamic analysis of the adsorption of H2O and NH3, paving the way for the exploration of V2O5/TiO2 catalysts with improved water resistance.

Low temperature ammonia synthesis from atomic N and water on rutile TiO2(110)

We have investigated the formation of ammonia (NH3) from atomic N and water (H2O) on a rutile(R)-TiO2(110) surface using the temperature-programed desorption method. The formation of NH3 can be detected after coadsorption of atomic N and H2O on the R-TiO2(110) surface, desorbing from the 5-fold coordinated Ti4+ (Ti5c) sites at about 400 K, demonstrating that the NH3 formation on R-TiO2(110) is feasible at low surface temperature. During the process, both hydroxyl groups at the bridging oxygen rows and H2O on the Ti5c sites contribute to the formation of NH3, which are affected by H2O coverage. At low H2O coverage, the direct hopping of hydrogen atoms may be the dominant process for hydrogen transfer; while H2O-assisted hydrogen atoms diffusion may be preferred at high H2O coverage. Our result will be of significant help to get a deeper insight into the fundamental understandings of hydrogenation processes during the NH3 synthesis.

Simulation of Pt80Au14Ti6 Work Function Change-Based Sensor of H2 Gas

Chemical reactions simulation in detecting hydrogen gas (H2) on Pt80Au14Ti6 sensor surface based on work function change (Δɸ) has been conducted. The simulation result is compared with laboratory results of detecting H2 gas. Three chemical reactions contained three coverages, H coverage (θH), O coverage (θO), and H2O coverage (θH2O). The simulation was run using MATLAB. This research can find the reaction parameter values such as the Arrhenius coefficient of H2O forming reaction on Pt (υf3Pt), H2O forming reaction on Au (υf3Au), i.e., H2O dissociation on Au (υf3Au ), O2 desorption on Ti (υd2Ti), H2O forming reaction on Ti (υf3Ti), and H2O dissociation on Ti (υf3Ti), i.e., 7.5×1014 s–1, 9.85×1015 s–1, 3.25×1015 s–1, 7.11×1015 s–1, 3.425×1015 s–1 and 2.725×1015 s–1, respectively. The simulation results also have the same trend as the laboratory results. However, the contact potential difference (CPD) simulation result, i.e., –240 mV, is not the same as the laboratory result, (–297± 9) mV. In addition, this simulation also obtained approximation coverage for atoms/molecules on PT80Au14Ti6 surface, i.e., θH = 0.665154 Mono Layer (ML); θO = 1.5621× 10–6 ML; and θH2O = 5.41676 ×10–5 ML.

Photocatalytic activity of MoS2 with water monolayers: Global optimization.

Atomically thin MoS2 has emerged to be promising for photocatalytic water splitting benefiting from its suitable geometrical and electronic structure for light harvesting. A better understanding of how water molecules affect the band edge levels of MoS2 is critical for promoting the interfacial reactivity. Here, we determine the structures of water monolayers on MoS2 using global optimizations achieved by molecular dynamics in combination with local minimization. It is shown that cyclic water clusters are formed on a surface through a hydrogen-bonding network. The absolute band edge positions are explored taking into account the derivative discontinuity of the exchange-correlation functional. Shifts in band edges are observed with the increase in H2O coverage, while bandgaps tend to be slightly decreased. In particular, the band alignment relative to water redox potentials has been investigated in detail. We find that the dimer configuration is likely to suppress the hydrogen evolution reaction (HER), while the polygon clusters lift the conduction band by 0.2-0.7eV, and thus, they would enhance HER. This effect is explained in terms of the linear dependence of the band edge offset on an interface electric dipole arising from water assemblies.

(Digital Presentation) H2o and CO2 Surface Contamination of the Lithium Garnet Li7La3Zr2O12 Solid Electrolyte

Garnet-type Li7La3Zr2O12 is a promising solid-state electrolyte for lithium (Li)-ion batteries, and it readily reacts with H2O and CO2 when exposed to ambient air. Such reactions form a contamination layer on Li7La3Zr2O12, which is detrimental to the battery operation. Here, using first-principles calculations, we investigate the adsorption and reactions of H2O and CO2 on a Li7La3Zr2O12 surface. We show that H2O reacts through the exchange of protons and Li+ and produces metal hydroxide species. At high H2O coverage, half of the H2O molecules dissociate, while the other half remain intact. CO2 reacts with the Li7La3Zr2O12 surface directly to produce carbonate species. We clarify that the individual reactions of H2O and CO2 with Li7La3Zr2O12 are thermodynamically more favorable than the co-adsorption of H2O and CO2. Finally, we demonstrate that low temperature and high partial pressure promote the reactions of H2O and CO2 with Li7La3Zr2O12. Our study provides guidance on processing conditions for the garnet Li7La3Zr2O12 solid electrolyte to minimize its surface contamination.

Customizing the microenvironment of CO2 electrocatalysis via three‐phase interface engineering

AbstractConverting CO2 into high‐value fuels and chemicals by renewable‐electricity‐powered electrochemical CO2 reduction reaction (CRR) is a viable approach toward carbon‐emissions‐neutral processes. Unlike the thermocatalytic hydrogenation of CO2 at the solid‐gas interface, the CRR takes place at the three‐phase gas/solid/liquid interface near the electrode surface in aqueous solution, which leads to major challenges including the limited mass diffusion of CO2 reactant, competitive hydrogen evolution reaction, and poor product selectivity. Here we critically examine the various methods of surface and interface engineering of the electrocatalysts to optimize the microenvironment for CRR, which can address the above issues. The effective modification strategies for the gas transport, electrolyte composition, controlling intermediate states, and catalyst engineering are discussed. The key emphasis is made on the diverse atomic‐precision modifications to increase the local CO2 concentration, lower the energy barriers for CO2 activation, decrease the H2O coverage, and stabilize intermediates to effectively control the catalytic activity and selectivity. The perspectives on the challenges and outlook for the future applications of three‐phase interface engineering for CRR and other gas‐involving electrocatalytic reactions conclude the article.

Initial oxidation of 3C-SiC (111) in oxidizing atmosphere containing water vapor: H2O adsorption from first-principles calculations

First-principles calculation based on density-functional theory (DFT) were employed to investigate H2O adsorption on 3C-SiC (111) surface for understanding atomic initial oxidation mechanism of CVD-SiC in oxidizing atmosphere containing water vapor. Firstly, Si-terminated 3C-SiC (111) slabs with intense surface states were constructed. Then, adsorption energy calculations demonstrated that the optimized structure of total dissociation of H2O molecule (SO structure) is relatively stable. The charge density difference plots of the corresponding O and Si atoms also indicated that the O and Si atoms in SO structure are more stable than those in the other structures. Besides, all orbital energies of relevant atoms in three stable structure shifted to the lower energy levels. From energy barrier analysis, the complete dissociation of H2O molecule on the SiC (111) surface had to overcome higher energy barrier than the partial dissociation, meaning that H2O molecules preferred to partially dissociate into OH radicals and H atoms on Si-terminated 3C-SiC (111) surface. By the analyses of geometry, charge transfer and bond population, OH⋯O hydrogen bond network gradually was generated on the surface with increasing H2O coverage. Furthermore, the bond energy of the formed OH⋯O hydrogen bond between two *OH radicals is higher than that between *OH and *O2H group, owing to electronegativity difference of corresponding O atoms.

Formation of SO[formula omitted]H[formula omitted] on the Pt{110}([formula omitted]) surface. A DFT study

Density functional theory is used to calculate energy differences for two surface reactions on the Pt{110}(1×2) surface : SO2↔ SO + O and SO3↔ SO2 + O, first. Formation of SO3 is preferred energetically. Second, several pathways for the formation of SO4H2 are compared from co-adsorbed SO3 and H2O on the mentioned surface. Results reveal an energy difference (endothermic process) of ≈1.5 eV. However, this value decreases to 1.17 eV when the van der Waals interactions are included. Increasing the coverage of H2O to four molecules per SO3 molecule, increases the energy difference to 1.70 eV. However, the energy difference is decreased to 1.06 eV when van der Waals interactions are taken into account in the calculations.

Highly sensitive detection of [formula omitted] adsorbed on Si(111)7 [formula omitted] 7 and Si(100)2 [formula omitted] 1 surfaces by means of slow highly charged Xe ions

The proton yields from Si(111)7 × 7 and Si(100)2 × 1 reconstructed surfaces irradiated with slow (v<0.25vBohr) highly charged Xe ions are obtained. H2O molecules adsorbed over time on the surfaces at room temperature, under ultra-high vacuum can be detected as an increase of the proton yield. For the Si(100)2 × 1 surface, the proton yield with HCI-irradiation time is discussed based on temporal variation of the H2O coverage. The proton desorption efficiency with Xe50+ is more than about ten times and twice as compared with Xe29+ and Xe44+, respectively. For the Si(111)7 × 7 and Si(100)2 × 1 surfaces, the proton yield in each time increases with the charge states q to the power of 6 and 4, respectively, and is changed with time with the power laws held on.

Critical Water Coverage during Forsterite Carbonation in Thin Water Films: Activating Dissolution and Mass Transport.

In geologic carbon sequestration, CO2 is injected into geologic reservoirs as a supercritical fluid (scCO2). The carbonation of divalent silicates exposed to humidified scCO2 occurs in angstroms to nanometers thick adsorbed H2O films. A threshold H2O film thickness is required for carbonate precipitation, but a mechanistic understanding is lacking. In this study, we investigated carbonation of forsterite (Mg2SiO4) in humidified scCO2 (50 °C and 90 bar), which serves as a model system for understanding subsurface divalent silicate carbonation reactivity. Attenuated total reflection infrared spectroscopy pinpointed that magnesium carbonate precipitation begins at 1.5 monolayers of adsorbed H2O. At about this same H2O coverage, transmission infrared spectroscopy showed that forsterite dissolution begins and electrical impedance spectroscopy demonstrated that diffusive transport accelerates. Molecular dynamics simulations indicated that the onset of diffusion is due to an abrupt decrease in the free-energy barriers for lateral mobility of outer-spherically adsorbed Mg2+. The dissolution and mass transport controls on divalent silicate reactivity in wet scCO2 could be advantageous for maximizing permeability near the wellbore and minimize leakage through the caprock.

Co-Adsorption of H2O, OH, and Cl on Aluminum and Intermetallic Surfaces and Its Effects on the Work Function Studied by DFT Calculations.

The energetics of adsorption of H2O layers and H2O layers partially replaced with OH or Cl on an Al(111) surface and on selected surfaces of intermetallic phases, Mg2Si and Al2Cu, was studied by first-principle calculations using the density function theory (DFT). The results show that H2O molecules tended to bind to all investigated surfaces with an adsorption energy in a relatively narrow range, between –0.8 eV and –0.5 eV, at increased water coverage. This can be explained by the dominant role of networks of hydrogen bonds at higher H2O coverage. On the basis of the work function, the calculated Volta potential data suggest that both intermetallic phases became less noble than Al(111); also, the Volta potential difference was larger than 1 V when the coverage of the Cl-containing ad-layer reached one monolayer. The energetics of H2O dissociation and substitution by Cl as well as the corresponding work function of each surface were also calculated. The increase in the work function of the Al(111) surface was attributed to the oxidation effect during H2O adsorption, whereas the decrease of the work function for the Mg2Si(111)–Si surface upon H2O adsorption was explained by atomic and electronic rearrangements in the presence of H2O and Cl.

Insight into the effect of Pd and Pd3Pb surface structure on activation of reactant O2 and product H2O in direct oxidative esterification

Density functional theory is performed to systematically study the effect of surface structure and facet of Pd and Pd3Pb catalysts on activity for O2, H2O activation, O diffusion and stability of resistance toward deactivation induced by H2O adsorption and aggregation. Our results show that flat (1 1 1) (Pd3Pb(1 1 1), Pd(1 1 1)) and (1 0 0) (Pd(1 0 0)) facets rather than stepped (2 1 1) facet (Pd(2 1 1), Pd3Pb(2 1 1)) are active surfaces, mathing well with our previous experimental result that Pd(1 1 1) and Pd3Pb(1 1 1) planes detected in Pd-Pb alloy, further confirm that main exposed Pd3Pb(1 1 1) surface of Pd3Pb promotes O2, H2O activation, O diffusion and inhibits H2O adsorption, aggregation. Moreover, preadsorbed O coverage and numbers of H2O on Pd3Pb have little effect on H2O adsorption and cluster forming. Therefore, Pd3Pb catalysts not only present better activity and stronger stability but also decrease cost than pure Pd. Firstly finding that surface average charge through Mulliken charge analysis serves as a indicator judging minimum active region. Higher activity and stability of Pd3Pb catalysts are attributed to exposed rhomboid active unit with Pb synergistic effect. Dependence of Pd and Pd3Pb catalyst’s activity and stability on surface structure and facet revealed may provide new way for designing better, stable Pd-Pb catalysts in direct oxidative esterification.

Water Adsorption on Ideal Anatase-TiO2(101) – An Embedded Cluster Model for Accurate Adsorption Energetics and Excited State Properties

Abstract A combined theoretical approach towards the accurate description of water on anatase-TiO2(101) was pursued in this study. Firstly, periodic slab calculations on the basis of density hybrid functionals (PBE0, HSE06) were performed in order to gain insight into the adsorption sites and geometric structure of the surface. For submonolayer coverage of H2O, the molecular adsorption of water is found to be the most stable one with quite similar energetics in PBE0 and HSE06. Moreover, the transition states towards the less preferred dissociative adsorption forms are predicted to be greater than 0.7 eV. Thus, water will not spontaneously dissociate and based on the Computational Hydrogen Electrode model an overpotential of about 1.71 V is needed to drive the overall oxidation. In addition, to validate our results for molecular adsorption of H2O, an embedded cluster model is carefully evaluated for the a-TiO2(101) surface based on the periodic slab calculations. Subsequent high-level DLPNO-CCSD(T) results are in close agreement with our periodic slab calculations since the interaction is found to mainly consist of electrostatic contributions which are captured by hybrid functionals. Finally, first results on optimized geometries in the excited state based on the photogenerated charge-transfer state are presented.

Production of HO2 and OH radicals from near-UV irradiated airborne TiO2 nanoparticles.

The production of gas-phase hydroperoxyl radicals, HO2, is observed directly from sub-micron airborne TiO2 nanoparticles irradiated by 300-400 nm radiation. The rate of HO2 production as a function of O2 pressure follows Langmuir isotherm behaviour suggesting O2 is involved in the production of HO2 following its adsorption onto the surface of the TiO2 aerosol. Reduction of adsorbed O2 by photogenerated electrons is likely to be the initial step followed by reaction with a proton produced via oxidation of adsorbed water with a photogenerated hole. The rate of HO2 production decreased significantly over the range of relative humidities between 8.7 and 36.9%, suggesting competitive adsorption of water vapour inhibits HO2 production. From the data, the adsorption equilibrium constants were calculated to be: KO2 = 0.27 ± 0.02 Pa-1 and KH2O = 2.16 ± 0.12 Pa-1 for RH = 8.7%, decreasing to KO2 = 0.18 ± 0.01 Pa-1 and KH2O = 1.33 ± 0.04 Pa-1 at RH = 22.1%. The increased coverage of H2O onto the TiO2 aerosol surface may inhibit HO2 production by decreasing the effective surface area of the TiO2 particle and lowering the binding energy of O2 on the aerosol surface, hence shortening its desorption lifetime. The maximum yield (i.e. when [O2] is projected to atmospherically relevant levels) for production of gas-phase HO2, normalised for surface area and light intensity, was found to be at a RH of 8.7% for the 80% anatase and 20% rutile formulation of TiO2 used here. This yield decreased to as the RH was increased to 22.1%. Using this value, the rate of production of HO2 from TiO2 surfaces under atmospheric conditions was estimated to be in the range 5 × 104-1 × 106 molecule cm-3 s-1 using observed surface areas of mineral dust at Cape Verde, and assuming a TiO2 fraction of 4.5%. For the largest loadings of dust in the troposphere, the rate of this novel heterogeneous production mechanism begins to approach that of HO2 production from the gas-phase reaction of OH with CO in unpolluted regions. The production of gas-phase OH radicals could only be observed conclusively at high aerosol surface areas, and was attributed to the decomposition of H2O2 at the surface by photogenerated electrons.

The Double-Edged Sword Effect of Water in the Low-Temperature CO Oxidation on Pt(111) Surface

The positive and negative effects of water on low-temperature CO oxidation were comprehensively investigated on a Pt(111) surface by thermal desorption spectroscopy, X-ray photoelectron spectroscopy, and polarization-modulated infrared reflection absorption spectroscopy. At 110 K, the interaction between H2O and preadsorbed O2 forms the {O2(a)·(H2O)n} complex on the Pt(111) surface through hydrogen bonding. Upon heating the surface to 170 K, the O2 in the {O2(a)·(H2O)n} complex is subject to dissociation. On the O2-saturated Pt(111) surface (50 L O2/Pt(111)), part of the chemisorbed O2 on Pt(111) can be displaced by H2O and forms {O2(g)·(H2O)n} trapped by H2O molecules at high H2O coverage (>0.44 ML H2O). At this point, high H2O coverage also weakens the molecular oxygen dissociation. Regarding the CO oxidation, a new CO2 production channel by the interaction of CO with the {O2(a)·(H2O)n} complex at ∼153 K has been discovered by exposing H2O to the CO/O2/Pt(111) surface at 110 K, which dominates the low-t...

Water as key to activity and selectivity in Co Fischer-Tropsch synthesis: γ-alumina based structure-performance relationships

Thirteen γ-alumina supports with different pore sizes and pore size distributions have been impregnated with cobalt and rhenium. The catalysts were tested for Fischer-Tropsch synthesis (FTS) under dry and enhanced water vapor pressure conditions. It is shown that there is a positive correlation between pore size and cobalt crystallite size of the reduced catalyst after incipient wetness impregnation as long as the pore size distribution is sufficiently narrow. There is a concurrent increase in C5+ with pore diameter due to higher chain propagation probabilities α3+. Higher α values are ascribed to larger cobalt crystallites that promote CO activation resulting in higher surface coverage of CHx monomers. Adding water vapor to the syngas feed has a strong positive effect on selectivity to higher hydrocarbons and activity. Water imposes a significant enhancement of α1 that is attributed to higher relative cobalt surface coverage of H2O(OH−) and CHx relative to hydrogen. Small pores are susceptible to condensation of water during FTS.

Methane steam reforming at low steam to carbon ratios over alumina and yttria-stabilized-zirconia supported nickel-spinel catalyst: Experimental study and optimization of microkinetic model

An experimental work to acquire reaction kinetic data of methane steam reforming (MSR) to produce syngas was carried out over alumina and yttria-stabilized-zirconia (YSZ) supported nickel-spinel catalyst (Ni-spinel). With the aim of making MSR more energy efficient, the catalyst was tested at 1.25 and 1.50 steam to carbon (SC) ratios, slightly higher than the stoichiometric ratio of 1.0 but far less than normally considered 3.0. The experiments were conducted at isothermal plug-flow conditions and at near atmospheric pressure in a laboratory scale quartz reactor for five different space times (STP) between 55ms and 277ms at three different temperatures of 973K, 1073K, and 1123K. Reaction kinetic data of MSR over Ni-spinel catalyst are presented in terms of methane conversion and products yield or selectivity. To simulate measured kinetic data in a 1D plug-flow reactor model, a surface microkinetic model of MSR over nickel based catalyst was adopted from the literature and validated by optimizing the kinetic parameters of the most influential elementary reaction steps. A stepwise approach based on a partial equilibrium analysis and a local sensitivity analysis was implemented to scrutinize the most influential elementary reaction steps. With the adjustment of only 12 parameters out of 78, the optimized microkinetic model predicted the exit flow rates of chemical species accurately for the entire operating space. Adsorption of H2O, desorption of H2(s), and reaction pairs of surface dehydrogenation of CH4(s) and CH2(s) or formation of CH(s) were found to be the most influential reaction steps for the studied operating conditions. Surface coverages of H(s), CO(s) and H2O(s) were increased in the case of optimized microkinetic model of Ni-spinel catalyst compared to the original microkinetic model. Increased surface coverage of H2O(s) in the case of optimized microkinetic model supports the experimental finding in the literature that the introduction of yttria to zirconia increases the activity of the oxygen pumping component.

The location of excess electrons on H2O/TiO2(110) surface and its role in the surface reactions

ABSTRACTExcess electrons play a key role in many of the properties of Titanium dioxide (TiO2). Understanding their behaviour is important for improving the performance of TiO2 in energy-related applications. Here, we describe a DFT + U study of the locations of the unpaired electron (UPE) on rutile TiO2(110) (R-TiO2(110)) surface and H2O/R-TiO2(110) surface. Our results show that the subsurface are preferred with R-TiO2(110) surface. In contrast to previous studies, we find that the UPE tends to migrate to the surface H2O-Ti5c (the five-coordinated titanium (Ti5c) at surface with H2O adsorption) with the increasing of H2O coverage and UPE concentration. In addition, we have shown that the UPE plays an important role in the O-H bond dissociation and other important elementary reactions in photo-catalytic H2O dissociation on R-TiO2(110) such as H, OH and H2 desorption. Specifically, it enhances the O-H bond dissociation, as well as H and H2 desorption from bridging hydroxyl and Ti5c-OH (the Ti5c with OH adsorption), but hinders the OH and H desorption from Ti5c. We believe our results afford a further understanding of the adsorbent dependent UPE migration, and the role of UPE in the surface reactions.

Investigation of a method for measurement of water vapor coverage on technical surfaces

Gas coverage on a surface can be determined by a desorption method, where the amount of gas is calculated by integrating the released flux. This measurement is straightforward in cases where desorbed gases do not re-adsorb on the surface of the measurement chamber. In that case, mass conservation laws are applicable, and the desorbed flux can be determined by the measurement of a pressure drop across an orifice of known conductance. In the case that gases re-absorbed on the surface, such as H2O on a metal surface, the flux through the orifice is not equal to the flux coming from the sample. To determine the surface coverage of H2O on the technical surface of different materials, we have developed a method where adsorption and desorption on the surface of the measurement chamber can be compensated during measurement.The sample is exposed to pure water vapor in a sample chamber at pressures between 6 mbar and 25 mbar. Measurements start with an isothermal expansion of water vapor from the sample chamber into the continuously pumped measurement chamber which has more than 100 times larger volume than the sample chamber. The pressure of the gas pulse during expansion and subsequent pump down is precisely measured with a capacitance diaphragm gauge, initially, and, at later times, with spinning rotor gauge. To detect water vapor which is adsorbed during expansion on the surfaces of the measurement chamber, the measurement and integration of pressure pulse is extended over several hours, until the pressure in measurement chamber drops to 1 × 10−7 mbar, which is the same pressure as before expansion. The product of effective pumping speed and the time integral of the measured pressure pulse is equal to the initial gas quantity in the sample chamber. This gas quantity is a sum of the fraction of the water vapor in the sample chamber volume and water adsorbed on the surfaces within the sample chamber. The latter is determined in a background measurement without the sample.We tested the method with samples of Ni foil having surface areas of 860 cm2 and 1720 cm2. The measured amount of adsorbed H2O was proportional to the area. Measured surface coverage was from 1.8 ML ± 0.2 ML at exposure to 20% of saturation pressure to 4.5 ML ± 0.4 ML at exposure to 95% of saturation pressure of H2O at temperature 23 °C.

Early Oxidation Processes on the Greigite Fe3S4(001) Surface by Water: A Density Functional Theory Study

Greigite (Fe₃S₄), the sulfide counterpart of the spinel-structured oxide material magnetite (Fe₃O₄), is a mineral widely identified in anoxic aquatic environments and certain soils, which can be oxidised, thereby producing extremely acid solutions of sulfur-rich wastewaters, so-called acid mine drainage (AMD) or acid rock drainage (ARD). Here we report a computational study of the partial replacement of sulfur (forming H₂S) by oxygen (from H₂O) in the Fe₃S₄(001) surface, derived from density functional theory calculations with on-site Coulomb approach and long-range dispersion corrections (DFT+U–D2). We have proposed three pathways for the oxidation of the surface as a function of H₂O coverage and pH. Different pathways give different intermediates, some of which are followed by a solid-state diffusion of the O atom towards its most stable position. Low levels of H₂O coverage, and especially basic conditions, seem to be essential, leading to the most favourable energetic landscape for the oxidation of the Fe₃S₄(001) surface. We have derived the thermodynamic and kinetic profile for each mechanism and plotted the concentration of H₂S and protons in aqueous solution and thermodynamic equilibrium with the stoichiometric and partially oxidized Fe₃S₄(001) surface as a function of the temperature. Changes in the calculated vibrational frequencies of the adsorbed intermediates are used as a means to characterise their transformation. We have taken into account statistical entropies for H₂S and H₂O and other experimental parameters, showing that this mineral may well be among those responsible for the generation of AMD.