A series of La0.8Sr0.2Mn1-xCuxO3 perovskite-type catalysts were prepared through a sol-gel method and evaluated for formaldehyde catalytic oxidation. Experimental and DFT studies were performed to reveal the role of the Cu dopant on formaldehyde oxidation over La0.8Sr0.2Mn1-xCuxO3 catalysts and determine the optimal doping amount of Cu. The perovskite with a Cu substitution content of 0.2 exhibited the highest catalytic activity and good thermal stability for formaldehyde oxidation. The degree of Cu substitution significantly influenced the textural properties of the catalysts. The La0.8Sr0.2Mn0.8Cu0.2O3 catalyst exhibited the highest specific area, pore volume, and crystalline degree, which enabled the availability of more active sites for formaldehyde adsorption. The introduction of bivalent Cu2+ resulted in a charge imbalance that was compensated by the increased Mn4+/Mn3+ ratio of the perovskite. Partial substitution of Mn by Cu cations enhanced the oxygen mobility of perovskites, which was ascribed to a synergy between surface Cu and Mn atoms. The La0.8Sr0.2Mn0.8Cu0.2O3 catalyst presented excellent oxygen mobility and thus promoted formaldehyde catalytic oxidation. DFT calculation results indicated that the absolute value of the formaldehyde adsorption energy on the surface Cu-O site was higher than that on the Mn-O site. The Cu dopant facilitated formaldehyde adsorption and promoted the transfer of more electrons from formaldehyde to the catalyst, which was beneficial for formaldehyde activation and subsequent oxidation. Finally, combining the in situ FTIR measurements with DFT calculations revealed the reaction mechanism of formaldehyde oxidation on the La0.8Sr0.2Mn1-xCuxO3 perovskite. Based on the experimental and theoretical methods, herein, the corresponding reaction cycle of formaldehyde oxidation is proposed. The reaction cycle contained seven elementary reaction steps, in which O2 dissociation was the rate-limiting step with the highest energy barrier of 1.47 eV.

Formaldehyde (HCHO) is a typical air pollutant that severely endangers human health. The Cu-Mn spinel-structure catalyst exhibits good catalytic oxidation activity for HCHO removal. Theoretical calculation study of density functional theory (DFT) was performed to provide an atomic-scale understanding for the oxidation mechanism of HCHO over CuMn2O4 surface. The results indicate that the (110) surface containing alternating three-coordinated Cu atom and three-coordinated Mn atom is more active for HCHO and O2 adsorption than the (100) surface. The Mars-van-Krevelen mechanism is dominant for HCHO catalytic oxidation. This reaction pathway of MvK mechanism includes HCHO adsorption and dehydrogenation dissociation, CO2 formation and desorption, O2 adsorption, H2O formation and surface restoration. In the complete catalytic cycle of HCHO oxidation, the second dehydrogenation (CHO* -> CO* + H*) shows the highest energy barrier and is recognized as the rate-limiting step. The relationship of temperature and reaction rate constant is found to be positive by the kinetic analysis. The minimum activation energy of the MvK mechanism via the direct dehydrogenation pathway is 1.29 eV. This theoretical work provides an insight into the catalytic mechanism of HCHO oxidation over CuMn2O4 spinel.

To address the issue of surface enrichment of A-site ions in perovskite and the resulting suppression of catalytic activity, the La0.8Sr0.2Mn0.8Cu0.2O3 was modified by treatment with dilute nitric acid (2 mol/L) and dilute acetic acid (2 mol/L). The results show that the effect of dilute nitric acid treatment on the morphology and catalytic activity of the catalyst is more significant. The specific surface area of the catalyst after dilute nitric acid treatment (268.78 m2/g) is seven times higher than before treatment (37.55 m2/g). The low-temperature catalytic oxidation activity of HCHO of the catalyst after dilute nitric acid treatment is significantly improved, achieving a 50

Cu–M bimetal catalysts show excellent catalytic activity towards the CO 2 reduction reaction.

CuMn 2 O 4 spinel has been regarded as a highly efficient sorbent for Hg 0 capture from flue gas.The regenerability and recyclability of CuMn 2 O 4 sorbent are mainly associated with the mercury speciation adsorbed on its surface.However, the effect mechanism of HCl on Hg 0 transformation over CuMn 2 O 4 sorbent is still elusive.Experiments were conducted to understand the effect of HCl on Hg 0 transformation over CuMn 2 O 4 sorbent.The results indicate that CuMn 2 O 4 sorbent is a mesoporous material and possesses a good thermal stability.CuMn 2 O 4 shows >95% Hg 0 removal efficiency in a wide temperature window of 50-350 • C. The favorable electron-transfer environment caused by the mixed valence states of Cu and Mn cations is responsible for the excellent Hg 0 removal performance of CuMn 2 O 4 sorbent.CuMn 2 O 4 shows a higher Hg 0 adsorption capacity of 4774.57μg/g.Hg 0 adsorption process over CuMn 2 O 4 sorbent can be well described by the developed kinetic model.Hg 0 removal efficiency of CuMn 2 O 4 sorbent does not depend on the presence of HCl.Mercury species adsorbed on the CuMn 2 O 4 sorbent in the presence of HCl mainly exist in the forms of HgO and HgCl 2 O 8 • H 2 O. HCl shows a significant effect on mercury speciation over CuMn 2 O 4 sorbent.Most of HgO species will be transformed into HgCl 2 O 8 • H 2 O in the presence of HCl.

A combination study of density functional theory (DFT) calculation and microkinetic analysis was carried out to investigate A-site tuning effect on formaldehyde (HCHO) oxidation over La-Mn perovskite catalysts (A = Sr, Ag, and Sn). The oxygen mobility of A-doped LaMnO3 catalysts and reaction mechanism of HCHO oxidation on catalyst surfaces were investigated. The microkinetic simulation was performed to quantitatively determine the activity of catalysts toward the HCHO catalytic oxidation. The results indicated that A-site tuning weakens the binding energy of Mn-O bond of LaMnO3 surface and facilitates the formation of surface oxygen vacancy. The presence of dopants can significantly reduce the activation energy of O-2 dissociation, which ascribes to the facilitation of electron transfer between oxygen species and catalyst surfaces. The reaction cycle of HCHO oxidation contains seven steps: HCHO adsorption, HCHO* dehydrogenation, CHO* dehydrogenation, CO2 desorption, H2O desorption, O-2 adsorption and oxygen vacancy recovery. The dopants promote HCHO adsorption and reduce the activation energy of HCHO oxidation. Two elementary steps control the overall reaction rate of HCHO oxidation. CHO* dehydrogenation step has the largest degree of rate control value at low temperature and O-2 adsorption step controls the whole reaction at high temperature

The spinel-type CuMn2O4 catalyst exhibits good catalytic activity towards benzene oxidation, but the catalytic oxidation mechanism is not established. Theoretical calculations were implemented to unearth the reaction mechanism of benzene catalytic oxidation over CuMn2O4 catalyst through density functional theory (DFT). The results indicate that benzene adsorption on both Cu-terminated and Mn-terminated surfaces are controlled by the chemisorption mechanism. The Cu-terminated surface is more active for benzene adsorption than the Mn-terminated surface. Cu atom is regarded as the primary active site. During benzene catalytic oxidation, benzene firstly undergoes dehydrooxidation reaction to generate phenoxy group (C6H6* → C6H5* → C6H5O*). Two reaction channels are responsible for the ring-opening and oxidation reactions of phenoxy group, including benzoquinone- and cyclopentadienyl-dominated channels. In the benzoquinone-dominated channel, C6H4O2* is produced from phenoxy dehydrogenation and oxidation, and then decomposes into acetylene via the ring-opening reaction (C6H4O2* → C4H2O2* → C4H2O4* → C2H2*). Compared with the benzoquinone-dominated channel, the cyclopentadienyl-dominated channel is dominant for phenoxy group oxidation. Phenoxy group decomposes to generate cyclopentadienyl. C5H5* is dehydrogenated and oxidized to form cyclopentadienone. Finally, C5H4O* is oxidized to form carbon dioxide through a nine-step reaction pathway. The ring-opening reaction (C5H4O* → C3H2O*) has the highest energy barrier of 283.45 kJ/mol, and is identified as the rate-determining step of benzene catalytic oxidation.

Iron oxide (Fe2O3) has been used as an effective sorbent to remove various heavy metals due to its large adsorption capacity and low cost. The cadmium capture capability of Fe2O3 sorbent was investigated in the simulated flue gas at the temperatures of 700-1100 degrees C. Fe2O3 sorbent exhibited much better Cd adsorption capability than SiO2 and Al2O3 sorbents. The largest Cd adsorption capacity of Fe2O3 sorbent was 86.7 mg/g at 700.C. The XPS analysis demonstrated that Fe3+ might partially participate in the cadmium adsorption process. A large quantity of CdO was generated and adsorbed on the Fe2O3 surface. The density functional theory (DFT) calculations were used to determine the active sites and the involved mechanism of different cadmium species adsorption over Fe2O3 sorbent. Cd, CdCl2, and CdO can be stably adsorbed on the Fe2O3 surface with the adsorption energies of -40.64 kJ/mol, -237.42 kJ/mol, and -375.03 kJ/mol, respectively. The results illustrate that the Fe atoms are the essential active sites for cadmium species adsorption on Fe2O3 surface. The orbital hybridization between cadmium atom and Fe site suggests that the strong interaction occurs during Cd adsorption process. Both physisorption and chemisorption mechanisms were responsible for the cadmium capture by Fe2O3 sorbent.

The reaction mechanism of dichloromethane (CH2Cl2) oxidation on LaMnO3 catalyst was investigated using density functional theory calculations. The results showed that CH2Cl2 dechlorination proceeds via CH2Cl2 → CH2ClO → HCHO. The adsorbed Cl∗ and formaldehyde (HCHO) are identified as the important intermediates of CH2Cl2 dechlorination process. The dissociated Cl atoms prefer to adsorb on the surface Mn sites. Surface hydroxyl groups are not directly involved in the CH2Cl2 dechlorination process, but react with the adsorbed Cl∗ to form HCl. The energy barrier of HCl formation is lower than that of Cl2 formation, indicating that hydroxyl groups facilitate the removal of adsorbed Cl∗ species. Three possible pathways of HCHO oxidation with the assist of lattice oxygen, active oxygen atom and hydroxyl groups were investigated. HCHO catalytic oxidation contains four steps: HCHO → CHO → CO → H2O desorption → CO/CO2 desorption. Compared with the HCHO oxidation by lattice oxygen and hydroxyl groups, HCHO oxidation assisted with activated oxygen atom is more thermodynamically favorable. A complete catalytic cycle was proposed to understand the preferable reaction pathway for CH2Cl2 oxidation on LaMnO3 catalyst. The catalytic cycle includes CH2Cl2 dechlorination, HCl formation and HCHO oxidation. The microkinetic analysis indicates that there are four steps controlling the reaction cycle: CH2Cl2∗ + ∗ → CH2Cl∗ + Cl∗, CH2OCl∗ + Cl∗ → CH2O∗ + Cl∗, O2∗ + ∗ → 2O∗, and CHO2∗ + OH∗ → CO2 + H2O∗.

Electrochemical CO2 reduction to energy-rich fuels and chemical feedstocks provides a sustainable route for the renewable energy storage and mitigation of CO2 emissions from human activity. However, the rational design of electrocatalysts with highly catalytic activity and product selectivity towards CO2 reduction remains a challenging task. Herein, the theoretical screening based on density functional theory (DFT) calculations was performed to design the two-dimensional single-atom catalysts (M@2D-FeS2) and to systematically investigate the catalytic activity of catalysts toward CO2 electroreduction. Co@2D-FeS2 shows superior catalytic activity and selectivity towards HCOOH production, and significantly suppresses the competing hydrogen evolution reaction (HER). The better HCOOH activity is associated with the lower d-band center and the localized charge distribution of transition metal atom. Ti@2D-FeS2 and V@2D-FeS2 exhibit good catalytic activity for CO production from CO2 electroreduction. Their overpotentials required for CO production are lower than that of the most active Au electrode. Ti@2D-FeS2 and V@2D-FeS2 serve as better catalysts to produce syngas. Cr@2D-FeS2 is a promising catalyst to produce CH4 from CO2 electroreduction. Cr@2D-FeS2 shows an exceptional performance for CH4 production, and outperforms the currently most active CO2RR-to-CH4 catalysts. Specifically, only a lower overpotential of 0.36 V is required to enable CO2 reduction to CH4. Cr@2D-FeS2 is also catalytically active towards C2H4 production due to the relatively lower overpotential of 0.64 V. The reduced overpotentials and excellent product selectivity could provide an encouraging motivation for experimental efforts to explore the advanced generations of highly-efficient CO2RR electrocatalysts.

CuFe2O4 is regarded as a promising candidate of catalyst for Hg0 oxidation in industrial flue gas. However, the microcosmic reaction mechanism governing mercury oxidation on CuFe2O4 remains elusive. Herein, experiments and quantum chemistry calculations were conducted for understanding the chemical reaction mechanism of oxygen-assisted mercury oxidation on CuFe2O4. CuFe2O4 shows the optimal catalytic activity towards mercury oxidation at 150 ºC. The reactivity difference of different lattice oxygen species is associated with its atomic coordination environment. The lattice oxygen coordinating with two octahedral Cu atoms and a tetrahedral Fe atom shows higher catalytic activity towards mercury oxidation than other lattice oxygen atoms. The inverse spinel structure of CuFe2O4 is favorable for O2 activation due to the Jahn-Teller effect, thereby promoting mercury oxidation. O2 molecule preferably adsorbs on iron active site and dissociates into active oxygen species. Hg0 oxidation is a three-step reaction process: Hg0 adsorption, Hg(ads) → HgO(ads), and HgO desorption. The energy barrier of mercury oxidation by chemisorbed oxygen is lower than that of mercury oxidation by lattice oxygen. The chemisorbed oxygen preserves higher reactivity towards mercury oxidation than lattice oxygen. Hg(ads) → HgO(ads) is the rate-determining step of mercury oxidation by chemisorbed oxygen because of the higher energy barrier of 116.94 kJ/mol. This work could provide the theoretical guidance for the diversified structure design of highly-efficient catalysts used for elemental mercury oxidation.

Oxygen vacancy (OV) has a close relationship with chlorinated volatile organic compounds catalytic oxidation. The role of OV for methylene chloride (DCM) decomposition over defective La-Mn perovskite catalyst was investigated using Density Functional Theoretical calculations. The adsorption characteristics and dissociation processes of reactants (DCM, O2 and H2O) on perfect and defective surfaces were comparatively studied. In DCM dechlorination process, the unoccupied orbitals of OV interact with binding orbitals of Cl atoms, and thus facilitate Cl abstraction. The dissociated Cl atoms are trapped by the OV on the defective surface. The activation energy of HCl formation (144.31 kJ/mol) with the assistant of hydroxyl groups is lower than that of Cl2 formation (250.86 kJ/mol) over defective LaMnO3 surface. OV (Lewis acid) and its proximal surface hydroxyls (Lewis base) tend to form the frustrated Lewis acid-base pairs, which can capture the dissociated Cl atoms with the assistance of protons into HCl. The surface hydroxyls can be regenerated readily from H2O dissociation at OV sites, thus achieving a sustainable Cl remove. Molecular O2 is easily activated and dissociated into O atoms by OV on defective surface. The atomic O adsorbed on surface Mn sites are the primary oxygen active species for DCM deep oxidation.

Mercury emitted from human activities has received increasing attention because of its extreme toxicity, persistence and bioaccumulation. The development of highly-efficient sorbent with abundant active sites that exhibit high affinity toward Hg0 is the key challenge for elemental mercury capture at low temperature. Herein, Cu-In spinel-type sulfides were synthesized through a hydrothermal synthesis. The Hg0 removal performance of CuxIn2-xS2 sorbents was evaluated in the temperature range of 75 °C to 175 °C. The synthesized CuxIn2-xS2 sorbents showed excellent performance for Hg0 removal at low temperatures, which perfectly matches the optimal temperature of flue gas at the downstream of desulfurization system. Hg0 removal efficiency of CuxIn2-xS2 sorbents significantly improved as the Cu proportion increased. CuInS2 sorbent showed superior mercury removal performance, the mercury removal efficiency reached 99.6% at 125 °C. O2 and NO showed a slight inhibition on Hg0 capture. The coexistence of SO2 and H2O showed no obvious negative effects on Hg0 removal. The CuInS2 sorbent displayed a superior tolerance to SO2 and H2O. TPD and XPS analyses demonstrated that the adsorbed mercury mainly existed in the form of mercuric sulfides (HgS). Hg0 adsorption over CuInS2 sorbent occurred via the Mars-Maessen mechanism. In this mechanism, Hg0 vapor was physically adsorbed on CuInS2 sorbent and then converted to HgS. This study provides future potential for applying CuxIn2-xS2 sorbents to capture gaseous mercury at low temperature.

The electrochemical reduction of CO2 to syngas (H-2 + CO) offers a resultful solution for the ongoing carbon emission and energy crisis issues. However, there are still few efficient catalysts for CO2RR-to-syngas electrolysis. Herein, a density functional theory (DFT) study of the Cu-M (M = Cd, Zn, Ni, Ag, and Pd) bimetal catalysts (BMCs) for CO2RR and HER is reported. The results indicate that the reaction barrier is significantly changed in the electrochemical conversion of CO2 into CO and HER by changing the Cu/M ratio. d band center (epsilon(d)) has a good linear relationship with Delta G(H*), Delta G(COOH*) and Delta Ge-CO*, so epsilon(d) is a good descriptor for hydrogen reduction reaction (HER) and carbon dioxide reduction reaction (CO2 RR) activity. The Cu-Pd catalyst displays outstanding catalytic activity for HER and CO2RR. HER activity of the Cu-Pd catalyst is even comparable to that of the current most effective Pt catalysts. Compared with other catalysts with different Cu/M ratios (Cu/M = 0.5 and Cu/M = 2), the Cu-Cd catalyst at low Cu/Cd ratio (0.5) is the only catalyst which is more favorite to CO2RR than HER. This theoretical study may provide guidance to design the effective electrocatalysts for the CO2RR and HER, and shed light on the application of Cu-based bimetal materials in syngas production.

NOx is widely considered to be one of the most important components in the flue gas. A systematically theoretical study based on density functional theory was conducted to provide an atomic-level understanding of the effects of NOx on Pb adsorption over the Al2O3 surface. The results suggest that the adsorption energies of Pb over Al2O3 (110) surface are larger than those of Pb over Al2O3 (001) surface. Al2O3 (110) surface is more favorable for Pb adsorption than Al2O3 (001) surface. NO and NO2 are adsorbed at the same active adsorption site (surface Al atom). NOx competes with Pb for the active sites on the Al2O3 surface. The notable charge accumulation and depletion are accountable for the intense interaction of Pb and NOx-covered Al2O3 surface. At low concentration of NOx, the adsorption of NO and NO2 over Al2O3 surface increases the Pb adsorption capacity of Al2O3 sorbent through strengthening the activity of its neighbor Al and O sites. The formation of Pb-Al and Pb-N bonds can greatly strengthen Pb adsorption over Al2O3 (110) surface in the presence of NO/NO2. However, the high-concentration NO and NO2 inhibit Pb adsorption over Al2O3 surface due to the competitive adsorption between Pb and NO/NO2.

A series of Cu-Fe spinel-type catalysts were synthesized by sol-gel auto-combustion method for the catalytic combustion of HCHO. A combined experimental and theoretical investigation based on in situ FT-IR and density functional theory (DFT) was performed to uncover the reaction process of HCHO catalytic combustion on Cu-Fe spinel-type catalysts. The results show that CuxFe(3-x)O4 catalysts display the typical pattern of spinel structure. The chemical states of Cu and Fe cations on the catalyst surface include Cu-+,Cu- Cu2+, Fe2+ and Fe3+. Cu0.5Fe2.5O4 exhibits excellent HCHO oxidation efficiency and good water-resistance performance. The superior catalytic performance of Cu0.5Fe2.5O4 catalyst is closely associated with the high crystalline degree of spinel. The flexible valences of metal cations in spinel-type catalysts are beneficial for electron transfer, thus facilitates HCHO adsorption and oxidation. Formate species (HCO2) is the major reaction intermediate during HCHO combustion. The reaction pathway of HCHO catalytic combustion contains eight elementary steps: HCHO adsorption, H2CO2 dehydrogenation, HCO2 dehydrogenation, CO2 desorption, O-2 adsorption, OOH formation, H2O formation and desorption. HCO2 dehydrogenation is identified as the rate-determining step because of the highest energy barrier of 254.80 kJ/mol. (c) 2020 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Theoretical calculations based on density functional theory (DFT) were employed to uncover the molecular-level oxidation mechanism of HCHO over Pt/TiO2 surface. All the three possible reaction mechanisms including Eley-Rideal mechanism, Langmuir-Hinshelwood mechanism and Mars-Van Krevelen mechanism were deeply investigated to determine the primary channel of HCHO oxidation on Pt/TiO2 catalyst. The adsorption energies and geometries show that HCHO and O-2 are chemically adsorbed on Pt and Ti sites of the Pt/TiO2 catalyst surface, respectively. The adsorption energy of O-2 (-141.91 kJ/mol) is higher than that of HCHO (-122.03 kJ/mol). HCHO oxidation reaction mainly occurs through the Eley-Rideal mechanism: gaseous HCHO reacts with activated O produced from the dissociation reaction of molecular oxygen on Pt/TiO2 surface by comparing the three possible mechanisms. HCHO oxidation reaction prefers the pathway of HCHO -> H2CO2 -> HCO2 -> CO2. In the whole HCHO oxidation reaction, the elementary reaction of HCO2 dehydrogenation presents the highest activation energy barrier of 230.45 kJ/mol. Therefore, HCO2 dehydrogenation is recognized as the rate-determining step. The proposed skeletal reaction scheme can be used to well understand the microcosmic reaction process of HCHO oxidation on Pt/TiO2 catalyst. (C) 2020 Elsevier Ltd. All rights reserved.

Low-temperature selective catalytic reduction (SCR) is an economical and feasible technology to effectively reduce NC% emissions from combustion sources. However, low-temperature SCR still suffers from low activity and SO2 H2O poisoning of catalysts. Here, a strategy to promote SCR activity and anti-poisoning ability was proposed through enhancing the metal-metal interaction. Ternary ferrite spinel material (CuMnFeO4) with a stronger metal-metal interaction was synthesized through incorporating Mn cations into the tetrahedral sites of CuFe2O4 spinel. CuMnFeO4 spinel mainly exists in an amorphous form and shows good SCR performance and SO2/H2O anti-poisoning ability in the temperature window of 200-350 degrees C. Density functional theory calculations were used to investigate the atomic-level reaction mechanism of NO reduction. Theoretical results indicate that NO and NH3 adsorptions over the CuMnFeO4 catalyst are controlled by the chemisorption mechanism. The interaction between reactants (NO and NH3) and the CuMnFeO4 surface is closely associated with the orbital hybridization of N and Fe atoms. The SCR reaction of NO with NH3 over the CuMnFeO4 catalyst is governed by a six-step process (NO -> NO* -> H2NNO* -> HNHNO* -> HNNOH*-> N-2* -> N-2), in which the first H-transfer reaction (H2NNO* HNHNO*) presents the highest activation energy barrier of 230.84 kJ/mol and is the rate-determining step of the NH3-SCR reaction. Finally, a SCR cycle reaction scheme was proposed to understand the reaction process of NO reduction over CuMnFeO4 spinel.

Ash slagging caused by pyrite (FeS2) transformation in coal-fired boilers is accompanied by sulfur evolution from pyrite oxidation during oxy-fuel coal combustion. Theoretical studies based on density functional theory (DFT) were performed to systematically understand the temperature-dependent sulfur evolution chemistry of CO2-assisted pyrite oxidation. The results show that there is a strong interaction between CO2 and FeS2 surface. The interaction intensity is promoted by the presence of surface O atom. The adsorbed CO2 molecule dissociates into CO molecule and active surface O atom, which can supply oxygen source for SO2 formation. CO molecule strips a lattice sulfur atom from FeS2 surface to generate COS species. CO2 decomposition on FeS2 surface at 1073 K is activated by 677.73 kJ/mol, and exothermic by 405.69 kJ/mol. SO2 evolution from CO2-assisted pyrite oxidation includes different elementary reaction steps: CO2 adsorption, CO2 decomposition, CO desorption, SO2 formation, SO2 desorption, and O replenishment. CO2 decomposition is regarded as the rate-limiting step of SO2 evolution. S vacancy produced from surface lattice sulfur consumption can be replenished by the active oxygen atoms from CO2 decomposition. Compared with COS formation pathway, sulfur evolution of CO2-assisted pyrite oxidation prefers SO2 formation pathway. The proposed reaction network can be used to better understand the CO2-mediated sulfur evolution chemistry of pyrite oxidation. (C) 2020 The Combustion Institute. Published by Elsevier Inc. All rights reserved.