Oxygen Vacancy Formation Energy Research Articles

Accuracy of DFT computed oxygen-vacancy formation energies and high-throughput search of solar thermochemical water-splitting compounds

The computation of the oxygen vacancy formation energy using density functional theory is a critical factor in applications like solar thermochemical hydrogen production. However, when we calculate it using structures that are dynamically unstable, results in artificially reduced values and lack of convergence with cell size. By comparing the calculated values with experimental data, the authors can clearly see the importance of using dynamically stable structures for accurate calculations. This comparison also validates the reliability of density functional theory calculations. Furthermore, using a high-throughput approach, the authors perform such calculations to identify new candidates for solar thermochemical hydrogen production among ABO${}_{3}$ perovskite materials, demonstrating the striong influence of B-site cations on the oxygen vacancy formation energy.

Modification of BCZT piezoelectric ceramics by modulating oxygen vacancies in different sintering atmospheres

In this work, we regulated the oxygen vacancy concentration by sintering BCZT + 0.1 mol % Y + 0.1 mol % Nb [BCZT-0.1 mol % (Y + Nb)] ceramics under air, oxygen, argon, and vacuum atmospheres and examined the effect of oxygen vacancy concentration on phase composition, crystal structure, microstructure, and electrical properties. X-ray photoelectron spectrometry and X-ray diffraction Rietveld refinement showed that the air- and oxygen-sintered ceramic samples had lower oxygen vacancy concentrations, and the oxygen octahedral lattice distortion in the samples was stable when the R-O-T phases coexisted, forming a multiphase coexistence structure with more spontaneous polarization directions. The oxygen-sintering atmosphere is important in oxygen compensation, which promotes the formation of dense microstructure, thereby increasing the Curie temperature (TC). Oxygen vacancy formation energy was low in the argon and vacuum atmospheres, and some oxygen vacancies increased the mass transfer effect and grain growth. Nevertheless, excess oxygen vacancies increased the leakage current during polarization resulting in poor polarity, which prevents directional deflection of domains and degrades performance. The vacuum-sintered sample was calcined in 1000 °C air for oxygen supplementation sintering, and as the sintering time increased, the oxygen vacancy concentration decreased, the grains grew further, the density increased, and the piezoelectric properties improved. The oxygen-sintered BCZT-0.1 mol % (Y + Nb) samples had good comprehensive electrical properties (d33 = 547 pC/N, kp = 55%, εr = 5355, Pr = 10.63 µC/cm2, EC = 1.89 kV/cm, tan δ = 0.02, and TC = 102 °C).

Evolution hydrothermal aging resistance mechanism study of zirconium and manganese doped CeO2 catalysts in soot catalytic combustion based on low Miller indices crystal surface effect

The thermogravimetric analysis (TGA) experiments were carried out to reveal the mechanism of Zr and Mn doping on catalytic activity of CeO2 catalyst both fresh and after hydrothermal aging, and the lattice morphology and valence changes were characterized by means of Brunauer–Emmett–Teller (BET) method, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and H2-temperature programmed reduction (H2-TPR). Density functional theory (DFT) and molecular thermodynamics calculations were applied to investigate the change in catalytic activity, crystal surface energy and crystal morphology caused by hydrothermal aging. The maximum reaction rate temperature of fresh Mn/CeO2 (389 °C) is similar to that of CeO2 (371 °C) and lower than that of Zr/CeO2 (447 °C), but the catalytic performance of CeO2 decreases more severely after hydrothermal aging. The catalyst crystals show different degrees of crystal surface migration after hydrothermal aging, which leads to the reduction of Ce3+/Ce4+ ratio and the active sites shift. DFT calculations indicate that the doping of Zr and Mn reduces the surface energy of the low Miller indices surface and increases the oxygen vacancy formation energy, leading to better thermal stability and lower catalytic activity. The Zr and Mn doping also changes the adsorption energy and Gibbs free energy of H2O, which dominates the migration of (1 1 1) to (1 1 0) and (1 0 0) in the vapor environment. The crystal surface migration mechanism of CeO2 catalysts doped with Zr and Mn induced by H2O molecules at high temperature obtained in this study can provide a valuable addition to the regeneration of CeO2 catalysts in the after-treatment systems of diesel engines.

Low-frequency noise characterization of gate oxide trap depth distribution of MOSFETs

To accurately obtain the depth distribution of the gate oxide traps that cause low-frequency noises, this study developed a discrete form of the low-frequency noise model in MOSFETs based on McWhorter's theory. The non-negative least squares (NNLS) method is employed to numerically solve the designed model. The low-frequency noises of planar Ge nMOSFETs with a gate stack match the prerequisite of the proposed form, which is dominated by carrier number fluctuations and is consistent with the McWhorter model. These transistors are used as the object of analysis in this study. By introducing a La2O3 cap layer to the gate stack, the gate oxide trap profiles calculated by the discrete model and the NNLS method showed obvious suppression of the traps in the HfO2 body and concentration of the traps in and near the SiO2/HfO2 interface. The research on both energy-dispersive x-ray spectroscopy and electron energy-loss spectroscopy has shown during annealing the diffusion of La into HfO2 and the appearance of La-rich layer at the SiO2/HfO2 interface in the Ge nMOSFET with a La2O3 cap. According to the existing first-principles calculations, the substitution of Hf in HfO2 by La increases the formation energy of oxygen vacancies, and the formation energy of oxygen vacancies in the HfnLamSixOy layer formed near the SiO2/HfO2 interface is lower than that of HfO2. The experimental and theoretical results support the physical connotation of the calculations and validate the solution proposed by this study.

Mn anchored zeolite molecular nest for enhanced catalytic ozonation of cephalexin

The molecular nest structured catalysts have demonstrated better performance than the traditional supported catalysts. However, they have not been tried in antibiotics or other organic pollutants removal from water by advanced oxidation processes (AOPs). Here we synthesized Mn anchored zeolite molecular nest (Mn@ZN) for the catalytic ozonation of cephalexin (CLX), which is the widely used antibiotic and also a refractory pollutant in water. The ozonation catalyzed by Mn@ZN achieves 97% of CLX degradation in only 2 min and a reaction rate constant of 0.2454 L·mg−1·s−1, which is 79.2 times higher than that of the non-catalytic ozonation. Even after ten cycles, the 0.46Mn@ZN/O3 still achieves a CLX degradation efficiency higher than 88% in 2 min, presenting an excellent stability. Mn ions stabilized by the molecular nests facilitate Lewis acid sites and oxygen vacancies, providing active sites for O3 sorption and decomposition into ·O2− and 1O2 through electrons transfer for the radical reaction with CLX. DFT calculation indicates that both the oxygen vacancy formation energy and the O3 adsorption energy of Mn@ZN are reduced by the Mn species introduction. This study finds a fascinating catalyst of Mn@ZN for the catalytic ozonation of antibiotics, and also a smart design strategy for zeolite confined metals catalysts for water treatment.

Neural network and experimental thermodynamics study of YCrO3-δ for efficient solar thermochemical hydrogen production

ABO3-type perovskites have been demonstrated as promising redox materials for solar thermochemical H2 production. In this work, a new energy material screening method based on the neural network system is designed as a feasible way to search for promising H2 production materials. The predicted oxygen vacancy formation energy of the selected YCrO3-δ is 4.199 eV, hinting excellent H2 production potential. Thermogravimetric analysis shows that the doping of Zr into YCrO3-δ improves oxygen formation capacity, leading to the maximum δ of 0.106. The molar enthalpy and entropy of YCr0.75Zr0.25O3-δ have the positive relationship with δ, and the maximum values of which are 273.7 kJ mol−1 and 164.9 J mol−1 K−1 respectively. Based on the equilibrium thermodynamic principle, the peak H2 yield is predicted to be 444.6 μmol g−1. Considering material kinetic limitation, gas-solid heat recovery and parameter sensitivity, the maximum H2 production efficiency of YCr0.75Zr0.25O3-δ is 17.3%. The combination of neural network and material thermodynamics provides a new pathway to design promising H2 production materials, and the screened YCrO3-δ presents excellent solar thermochemical H2 production capacity.

Evolution hydrothermal aging mechanism for Ag/CeO2 catalysts in regeneration of catalytic diesel particulate filter with DFT calculation.

In order to avoid the high cost of existing precious metal catalyst like Pt, Ag/CeO2 was the most promising catalysts for mobile source soot emission control technologies, but there was a clear trade-off between hydrothermal aging resistance and catalytic oxidation performance hindered the application of this catalyst. In order to reveal the hydrothermal aging mechanism of Ag/CeO2 catalysts, the TGA (thermogravimetric analysis) experiments were investigated to reveal the mechanism of Ag modification on catalytic activity of CeO2 catalyst between fresh and hydrothermal aging and were also characterized with the related characterization experiments to in-depth research the lattice morphology and valence changes. The degradation mechanism of Ag/CeO2 catalysts in vapor with high-temperature was also explained and demonstrated based on density functional and molecular thermodynamics theories. The experimental and simulation data showed that the catalytic activity of soot combustion within Ag/CeO2 decreased more significantly after hydrothermal aging than CeO2 due to the less agglomerated, which caused by the decreased in OII/OI and Ce3+/Ce4+ compared with CeO2. As shown in density function theory (DFT) calculation, the decreased surface energy and the increased oxygen vacancy formation energy of the low Mille index surface after Ag modification led to the instability structure and the high catalytic activity. Ag modification also increased the adsorption energy and Gibbs free energy of H2O on the low Miller index surface compared to CeO2, indicating that the desorption temperature of H2O molecules in (1 1 0) and (1 0 0) was higher than (1 1 1) in CeO2 and Ag/CeO2, which led to the migration of (1 1 1) crystal surfaces to (1 1 0) and (1 0 0) in the vapor environment. These conclusions can provide a valuable addition to the regenerative application of Ce-based catalysts in diesel exhaust aftertreatment system the aerial pollution.

A first-principles investigation of the effects of strain and Pd-doping on ion transfer in LSCF bulk of solid oxide cells

Applied strain can be employed to tune ion migration properties in oxygen electrode bulk. Here migration properties of oxygen vacancy in Pd doped La1−xSrxCo1−yFeyO3−δ (LSCF) bulk (LSCFPd) were investigated with density functional theory under 3 % tensile and compressive strains. Formation energies of oxygen vacancy are reduced under tensile strain while they exhibit a nontrivial dependence as a function of compressive strain near Pd-doping sites. Migration barriers of oxygen vacancy in LSCF and LSCFPd bulks are also significantly reduced with tensile strain compared to that with non-strain. However, barriers near Pd-doping site increase greatly under compressive strain. The variation of oxygen vacancy formation and migration properties can be ascribed to the redistribution of atomic charges and local structural distortion caused by Pd-doping and applied strain. Results indicate that Pd-doping and application of tensile strain can significantly improve oxygen vacancy formation and migration properties.

Creating water-resistant oxygen vacancies in δ-MnO2 by chlorine introduction for catalytic ozone decomposition at ambient temperature

To alleviate the negative impact of water vapor on ozone decomposition, we proposed a chlorine-doping strategy to create water-resistant oxygen vacancies in δ-MnO2. Comprehensive characterizations illustrated that abundant oxygen vacancies were generated by chlorine-doping, while fewer water and intermediates accumulated during ozone decomposition. Accordingly, chlorine-doped δ-MnO2 exhibited excellent activity for ozone decomposition, keeping 97.7% removal of 2000 ppm ozone after running for 40 h under the relative humidity of 65%. DFT calculations confirmed that chlorine introduction reduced the formation energy of oxygen vacancies and enhanced the strength of Mn-O bond. The compressed Mn-O bonds liberate oxygen vacancies from being occupied by water vapor and reaction intermediates. This work demonstrates the effectiveness of chlorine introduction in creating oxygen vacancies and enhancing its resistance to water vapor, which affords a new avenue to design high-performance catalysts for ozone elimination.

Electrospun Ce–Mn oxide as an efficient catalyst for soot combustion: Ce–Mn synergy, soot-catalyst contact, and catalytic oxidation mechanism

Increasing the contact efficiency and improving the intrinsic activity are two effective strategies to obtain efficient catalysts for soot combustion. Herein, the electrospinning method is used to synthesize fiber-like Ce–Mn oxide with a strong synergistic effect. The slow combustion of PVP in precursors and highly soluble manganese acetate in spinning solution facilitates the formation of fibrous Ce–Mn oxides. The fluid simulation clearly indicates that the slender and uniform fibers provide more interwoven macropores to capture soot particles than the cubes and spheres do. Accordingly, electrospun Ce–Mn oxide exhibits better catalytic activity than reference catalysts, including Ce–Mn oxides by co-precipitation and sol-gel methods. The characterizations suggest that Mn3+ substitution into fluorite-type CeO2 enhances the reducibility through the acceleration of Mn–Ce electron transfer, improves the lattice oxygen mobility by weakening the Ce–O bonds, and induces oxygen vacancies for the activation of O2. The theoretical calculation reveals that the release of lattice oxygen becomes easy because of a low formation energy of oxygen vacancy, while the high reduction potential is beneficial for the activation of O2 on Ce3+-Ov (oxygen vacancies). Due to above Ce–Mn synergy, the CeMnOx-ES shows more active oxygen species and higher oxygen storage capacity than CeO2-ES and MnOx-ES. The theoretical calculation and experimental results suggest that the adsorbed O2 is more active than lattice oxygen and the catalytic oxidation mainly follows the Langmuir-Hinshelwood mechanism. This study indicates that electrospinning is a novel method to obtain efficient Ce–Mn oxide.

Rational modification of traditional La0.5Sr0.5(Fe/Mn)O3 cathodes for proton-conducting solid oxide fuel cells: Inspiration from nature

By screening a series of La0.5Sr0.5MnO3-δ (LSM)-La0.5Sr0.5FeO3-δ (LSF) solid solutions using first-principles calculations, an optimal solid solution of LSM and LSF was chosen as the cathode for proton-conducting solid oxide fuel cells (H–SOFCs). In terms of oxygen vacancy formation energy, O2 adsorption energy, bond length of adsorbed O2, and O p-band center, La0.5Sr0.5Mn0.875Fe0.125O3 (LSMF125) and La0.5Sr0.5Mn25Fe0.75O3 (LSMF75) exhibited superior properties. Subsequent experimental investigations revealed that the H–SOFC with the LSMF75 cathode performed better than the cell with the LSMF125 cathode. The structure analysis revealed that LSMF75 has both Mn and Fe cations on its surface, similar to the designs of several naturally occurring enzymes, hence the increased cathode activity. By improving the LSMF75 cathode further, the cell utilizing the LSMF75 cathode attained a peak power density of 1238 mW cm-2 at 700 °C, which was much greater than that of the cells using the LSM or LSF cathodes, illustrating the benefits of using the LSM-LSF solid solution. Additionally, the good chemical stability of the LSMF75 cathode was maintained, allowing for 150 h of stable operation under operational conditions.

Facet Dependence and Vacancy-Controlled Reversibility of the Spinel-to-Rocksalt Phase Transformation at Co3O4 Surfaces

Transition-metal spinel oxides have attracted considerable interest as high-performance electrodes for electrochemical energy storage and conversion, where irreversible or reversible spinel–rocksalt (S–R) phase transformation at the oxide surface has been frequently observed, which sensitively controls their performance. Exploring key factors controlling the S–R transformation and its reversibility at the atomic scale is important for understanding the electrochemical performance of spinel oxides. Using Co3O4 nanoparticles as an example, which represent a promising electrocatalyst for the oxygen evolution reaction, we present in situ atomic-scale imaging of the S–R transformation by using aberration-corrected scanning transmission electron microscopy combined with the integrated differential phase contrast imaging technique to visualize oxygen anions and transition-metal cations simultaneously. We reveal that the S–R transformation is not only determined by the oxygen vacancy formation energy but also largely controlled by the surface polarity of the reconstructed rocksalt layer, leading to a faster S–R transformation at the (001) surface than the (111) surface. Moreover, cobalt and oxygen vacancies are directly identified at the spinel/rocksalt interface, leading to the formation of an intermediate defective rocksalt phase and a two-step S–R transformation process. The existence of the intermediate defective rocksalt phase or not decisively controls the reversibility of the two-step S–R transformation. The uncovered facet dependence and vacancy-controlled reversibility of the S–R transformation provide important insights into the shape-dependent reactivity and stability of spinel oxide electrodes for electrochemical energy applications.

Effects of impure ions in precursors on the formation of active oxygen in MnO2 for promoting VOCs oxidation

Impure ions in the precursor can cause the structural transition of prepared MnO2 catalysts and influence their activity in toluene catalytic oxidation. Here, the effects of K+ and SO42- on the catalytic activity of MnO2 are examined. Removing absorbed SO42- by repeating water washing facilitates the exposure of active sites on the surface of MnO2. The temperature for toluene conversion reaches 90% (T90) of catalysts decreases from 247 ºC to 238 ºC. While the loss of K+ during the water washing leads to the inferior performance of MnO2. Re-impregnating of K+ can stimulate the generation of active oxygen species on the surface of catalysts (K/MnO2), which showed elevated catalytic activity in toluene conversion (T90, 229 ºC). In addition, K/MnO2 performs good stability for toluene combustion in long-term operation. Density Function Theory calculations reveal that the formation energy of oxygen vacancy and the adsorption energy of toluene on the surface of catalyst decrease from 6.996 eV and − 0.079 to 5.482 eV and − 0.468 eV as the introduction of K+, respectively. Our results provide a complete understanding of the effects of impurity ions on the performance of manganese oxide for catalytic oxidation of toluene.

Effect of different valence metals doping on methane activation over La2O3(001) surface

La2O3 as a catalyst is used for oxidative coupling of methane (OCM) reactions due to its excellent stability and high C2 selectivity, but poor activity on methane dissociation limits its wide application. Different valence metals are doped on the La2O3(001) surface to improve the methane conversion activity, and the activation of methane on metal-doped La2O3(001) surfaces has been investigated via the density functional theory (DFT) calculations. The relationship between the valence states of doped metals and the methane conversion activities shows that doping low valence metals (Li, Na, K, Mg, Ca, Sr and Ba) and equivalent metals (Al, Ga, In) can significantly improve the conversion activity of methane. Among them, the activation energy of methane on the Li-La2O3(001) surface is the lowest, which is only 13.0 kJ/mol. However, doping of high valence metals (Zr, Nb, Re and W) cannot improve the CH4 dissociation activity. Furthermore, the relationships between surface oxygen vacancy formation energies, acid-base properties and the activation energies of CH4 have also been investigated. The results show that with the increase of metal valence state, the oxygen vacancy formation energy increases, while the dissociation activity of CH4 decreases. The introduction of alkali and alkaline earth metals increases the alkalinity of La2O3(001) surface, and the alkalinity of La2O3(001) doped with the alkali metal is stronger than that with the alkaline earth metal, exhibiting higher dissociation activity of CH4. Our research may provide a guide for improving methane conversion activity on La2O3 catalysts.

Original self-assembled S-scheme BiOBr-(0 0 1)/Bi2SiO5/Bi heterojunction photocatalyst with rich oxygen vacancy for boosting CO2 reduction performance

Photocatalysis CO2 reduction into high-value-added chemical feedstocks is desirable for simultaneously addressing the solar energy storage, CO2 excess and energy shortage issues. In this work, a kind of original S-scheme BiOBr-(001)/Bi2SiO5/Bi (OSB) heterostructure photocatalyst with rich oxygen vacancies is in-situ synthesized, which significantly promotes the photocatalytic CO2 reduction performance. Interestingly, the lower formation energy of oxygen vacancy exhibits the easy feasibility on the BiOBr-(001) surface via the assistant of ultrasound. There exists the highest photocatalytic CO2 reduction activity to CO of 234.05 μmol g-1h−1 for OSB-20 sample (ultrasound time: 20 min), higher 3.3 times than OSB-0 sample (without ultrasound). Combined with experimental and calculated results, the significative formation mechanism, widened light-response range, highly-efficient separation/transfer paths and improved redox-reduction abilities of photogenerated electron-hole pairs for S-scheme OSB-20 heterostructure are investigated and proposed. Our findings provide new insights for the construction and synthesis of the S-scheme Bi-based heterojunction photocatalyst system.

Cobalt-free perovskite Ba0.95La0.05FeO3-δ as efficient and durable oxygen electrode for solid oxide electrolysis cells

Solid oxide electrolysis cells (SOECs) have been demonstrated as an efficient technique to improve energy utilization and alleviate the greenhouse effect. The commercialization of SOECs is limited by the oxygen electrodes, whose problems include high costs and unexpected degradation of cobalt/strontium. In this work, we systematically evaluated the oxygen evolution reaction (OER) performance of a cobalt-free and strontium-free material Ba0.95La–FeO3-δ (BLF) and the application of BLF as an oxygen electrode of SOECs by combining DFT calculation and experimental. We found that the BLF has excellent OER performance due to its low oxygen vacancy formation energies and oxygen adsorption energies on the surfaces. Under an applied electrolysis voltage of 1.5 V, the current density reaches 3.17 and 1.53 A cm−2 at 850 °C with 50%H2–50%H2O and 50%H2–50%CO2, respectively. The superb stability of the electrolysis cell was shown in the 200 h testing, which further demonstrated that BLF is a promising material for oxygen electrodes of SOECs.

Insights into methane to syngas on stoichiometric and defect Ce2(SO4)3 crystal surface

We present a first principles study using periodic density functional theory on the reaction between Ce2(SO4)3 oxygen carrier and CH4 during chemical looping partial oxidation. The (001) surface has an appropriate bond strength and oxygen vacancy (Ov) formation energy (Evac). Further analysis shows that CH4 has a weak adsorption performance on (001) surface, while CHx (x = 0–3) radicals have a strong electron density overlap. The lattice oxygen atoms tend to leave the crystal surface during adsorption process, which is conducive to the syngas formation. Compared with (102) surface, (001) surface has a lower dehydrogenation and syngas formation energy barrier. CH3 → CH2 + H serves as the rate-determining step on (102) surface, while on (001) surface is CH2 → CH + H (TS3). Ov effects are emphasized through the comparison of (102), (001) and Ov (001) surface. The corresponding energetic results show that the Ov facilitates the adsorption and dehydrogenation process. But when the Ov concentration is larger than 1.96%, increasing the Ov concentration does not continue to reduce the energy barrier of TS3. In summary, (001) surface has a better reaction performance, and Ov play a critical role in both adsorption and dehydrogenation process.

Unveiling surface stability and oxygen vacancy segregation of Yb2SiO5 and Lu2SiO5 by first‐principles calculations

AbstractRE2SiO5 (RE = Yb and Lu) are significant environmental barrier coating (EBC) materials, in which surface and oxygen vacancy play crucial roles in their structural stability and functionality. In this work, the structural configuration and thermodynamics of (1 0 0), (0 1 0), and (0 0 1) surfaces of RE2SiO5 are investigated by first‐principles calculations. The (0 0 1) surface is preferred energetically, which is attributed to the weak bond broken environment and large rare‐earth polyhedron distortion on this surface. Moreover, the formation energies of various oxygen vacancies on the stable (0 0 1) surface are estimated and the optimal location for oxygen vacancies is held by the [SiO4] tetrahedron. The oxygen vacancies are more likely to segregate on the surface because of the lower formation energies on the surfaces compared with those in the bulk. These findings are expected to enable the development of RE2SiO5‐based EBCs by tuning grain size and/or thin film growth orientation.

Promotion of MgO sorbents with eutectic carbonate doping for high-temperature and pressure CO2 capture

MgO-based sorbents are promising candidates for CO2 capture as they are widely available and feasible in thermodynamics, but the development of MgO-based sorbents operating at elevated temperature and pressure is still a challenging task due to sintering. Herein, we selected eutectic carbonates with high melting point as promoters for the application under elevated conditions. Among various eutectic carbonates, MgO with eutectic ternary LiNaK carbonate (ETC) doping exhibited the highest MgO conversion thanks to crystal defects based on the XRD analysis. The highest CO2 capture capacity of 0.73 gCO2/gsorbent was obtained with 20 wt% ETC at 400 °C and 2 MPa. With further elevation of operating parameters to 540 °C and 5 MPa, the sample still shows a stable MgO conversion of 0.69 after 30 cycles, where the material exhibits a porous structure that inhibits the sintering. The density function theory calculations reveal that the LiNaK doping lowers the formation energy of surface oxygen vacancy, providing possibility for the subsequent oxygen ion migration. The deep K incorporation is most effective to promote the oxygen ion diffusion with decreased oxygen ion migration energy barrier from 3.68 to 2.04 eV. This study can guide the design of high-performance CO2 sorbents at wider application conditions.

Oxygen Vacancy Promoted Generation of Monatomic Oxygen Anion over Ni2+ -Doped MgO for Efficient Glycolysis of Waste PET.

Developing efficient and eco-friendly catalysts for selective degradation of waste polyethylene terephthalate (PET) is critical to the circular economy of plastics. Herein, we report the first monatomic oxygen anion (O- )-rich MgO-Ni catalyst based on a combined theoretical and experimental approach, which achieves a bis(hydroxyethyl) terephthalate yield of 93.7 % with no heavy metal residues detected. DFT calculations and electron paramagnetic resonance characterization indicate that Ni2+ doping not only reduces the formation energy of oxygen vacancies, but also enhances local electron density to facilitate the conversion of adsorbed oxygen into O- . O- plays a crucial role in the deprotonation of ethylene glycol (EG) to EG- (exothermic by -0.6 eV with an activation barrier of 0.4 eV), which is proved effective to break the PET chain via nucleophilic attack on carbonyl carbon. This work reveals the potential of alkaline earth metal-based catalysts in efficient PET glycolysis.