Cu-based Oxygen Carrier Research Articles

Experimental assessment of reverse water gas shift integrated with chemical looping for low-carbon fuels

Chemical looping integrated with reverse water gas (CL-RWGS) shift is presented in this study using Cu-based oxygen carrier (OC) supported on Al2O3 has been used to convert the CO2 and H2 mixture stream into a syngas stream with a tailored H2 to CO ratio and relevant conditions. The results demonstrated consistent breakthrough curves during redox cycles, confirming the chemical stability of the material. In 10 consecutive cycles at 600 °C and 1 bar, bed temperatures increased by 184 °C and 132 °C across the bed during oxidation and reduction stages respectively. The cooling effects during RWGS showed a decline in solid temperatures demonstrating the effectiveness of the heat removal strategy while attaining a CO2-to-CO conversion close >48%. The outlet gas maintains a H2/CO ratio above 2, confirming the material's dual role as OC and catalyst. During complete CL-RWGS cycles, varying temperature from 500 °C to 600 °C at a constant H2/CO2 molar ratio (1.3) and pressure (1 bar) reduces the H2/CO molar ratio from 3.14 to 2.35, respectively with a remarkable continuous CO2-to-CO conversion > 40%. The decrease in H2/CO molar ratio with the increase in temperature is consistent with the expected results of equilibrium limited conditions. Additionally, in CL-RWGS cycles, pressure insignificantly affects product molar composition. The study showed the capability of Cu material in converting CO2 into syngas through the CL-RWGS technique.

Characterization of NOx Release during Combustion Synthesis and Cyclic Reaction Performance of Cu-Based Oxygen Carriers Prepared with Citric Acid

Characterization of NO_<i>x</i> Release during Combustion Synthesis and Cyclic Reaction Performance of Cu-Based Oxygen Carriers Prepared with Citric Acid

Identification of HCl corrosion mechanism on Cu-based oxygen carriers in chemical looping combustion

In chemical looping combustion (CLC) of coal, HCl has been demonstrated as the primary gaseous products of the chlorine in coal. Therefore, a comprehensive characterization of Cu-based oxygen carriers (OC) by HCl corrosion was meticulously conducted, including the activity retention, composition distribution and apparent morphology. The experiment consisted of three parts: (I) evaluating of the OC performance for 100 redox cycles with 7.8 vol% CH4; (II) investigating HCl-corrosion of OC by adding 50 ppmv HCl with 7.1 vol% CH4 for the subsequent 50 cycles; (III) regenerating of OC without HCl addition during the last 50 cycles. The reactivity of OC was attenuating via the HCl addition during the 101st–150th cycles (part II) due to the competition adsorption between HCl and CH4, especially for the partly reduced OC. While, in part III, the reactivity performance of OC was partially recovered because of the abundant cracks on the surface of OC particles which ensured the sufficient gas–solid contact. It should be noted that the single particle hardness index and service life were irreversibly decreased for the HCl-treated OC. Moreover, OC particles were fragmented and the inside Al2O3 balls were exposed on the surface of the HCl-treated OC in SEM image. This work will contribute to understanding the mechanism of Cl-corrosive OC and designing the Cl-resistant OC.

Chemical looping with oxygen uncoupling of biomass-derived hydrochar with Cu-based oxygen carriers modified by alkaline earth metals

In this paper, the effect of alkaline-earth metals (AEMs, Ca, Ba, and Sr) on the performance of CuO/ZrO2 oxygen carriers (OCs) and the hemical looping with oxygen uncoupling (CLOU) process of wheat-derived hydrochars with these Cu-based OCs were investigated. The results showed that after multiple cycles, the crystal phases of modified Cu-based OCs were the same as that of pure CuO/ZrO2 OC without any interaction between them. Due to the catalytic effects of AEMs, an increase in the decomposition of wheat and hydrochar-235 in modified Cu-based was observed at 500 °C. The combination of Ca and HTC promotes reoxidation, while Ba and Sr inhibit reoxidation. Notably, the Cu-based OCs exhibited moderate agglomeration after 20 redox cycles at 950 °C. The results of the kinetic analysis indicate that the chemical order models and diffusion models can suitably describe the first combustion stage for wheat and hydrochars with Cu-based OCs, respectively. The geometrical contraction model was also found to most suitably describe the second combustion stage of all samples. These results suggest that a combination of hydrothermal carbonization pretreatment with AEMs modification is an efficient approach for CLOU using CuO-based OCs.

Performance of a kaolin-doped, magnetic Cu-based oxygen carrier in biomass combustion

Chemical looping combustion with oxygen uncoupling (CLOU) enables solid fuel combustion with CO2 capture at low cost due to the capacity of the oxygen carrier to release molecular oxygen. The present study is focused on testing the performance of a magnetic Cu-based oxygen carrier with reinforced mechanical properties owing to the addition of kaolin via the combustion of three types of biomass in a 1.5 kWth continuous CLOU unit. The effect of the main operating variables on process performance parameters was studied. Complete combustion of the different biomass types was achieved. Higher CO2 capture efficiencies were observed at 800–950 °C compared to the previous work done with this oxygen carrier without kaolin doping. The highest value of 97.5% CO2 capture efficiency was obtained at 950 °C during the combustion of pine sawdust. Moreover, the oxygen carrier retained its magnetic properties without any agglomeration problems after 80 h of hot circulation operation.

An innovative Cu-Al oxygen carrier for the biomass chemical looping gasification process

Biomass chemical looping gasification (BCLG) is a novel technology that enables the production of renewable syngas without the need for an external supply of energy or power while achieving negative carbon emissions. In this work, the behavior of a synthetic Cu-based (14 wt% CuO) oxygen carrier, Cu14Al_ICB, was tested for 45 h in a 1.5 kWth continuous unit using pine sawdust as fuel. The effect of the oxygen-to-fuel ratio (λ) and gasification temperature on syngas composition and gasification parameters, including fuel conversion, carbon capture, cold gas efficiency, and syngas yield, was studied. A decrease in the oxygen-to-fuel ratio increased molar flows of H2 and CO in the syngas, while an increase in gasification temperature mainly improved char gasification, also enhancing H2 and CO generation. High amounts of syngas with low CH4 molar flows (∼2.3 mol CH4/kg of dry biomass) were obtained under any conditions due to the catalytic effect of metallic copper on CH4 reforming reactions. Syngas yield values were achieved approximating those obtained with Ni-based solids. The oxygen carrier also had a very positive effect on tar removal, reaching tar concentration values similar to those obtained by operating under chemical looping combustion conditions. The attrition rate measured with this oxygen carrier was the lowest obtained to date for any oxygen carrier operating under BCLG conditions. In addition, the mechanical properties, reactivity, and oxygen transport capacity of the oxygen carrier were maintained throughout the campaign. Therefore, the Cu14Al_ICB oxygen carrier has proved to be an excellent material for the BCLG process.

Energy use of biogas through chemical looping technologies with low-cost oxygen carriers

Biogas is a renewable fuel generated in the anaerobic digestion of organic material. The expansion of biogas as a bioenergy source in the next decades leads to find new ways for its energy exploitation such as the Chemical Looping technologies. In this work, a low-cost Fe-based residue was used as oxygen carrier in two processes with biogas, namely Chemical Looping Combustion (CLC) and Chemical Looping Reforming (CLR). CLC process is focused on the energy production with CO2 capture. CLC experiments showed higher methane combustion efficiency (∼86%) than those referred in literature with other low-cost Fe-based materials. CLR process is dedicated to the production of syngas or hydrogen without CO2 emissions. Ni- or Cu-based oxygen carrier had been successfully used in order to catalyse the methane reforming. Here, the Fe-based material was also used for CLR. The biogas composition facilitated dry reforming of biogas to obtain syngas. In the dry-CLR of biogas, it was possible to reach about 55% methane conversion with a yield to syngas of 1.3 mol (CO + H2)/mol CH4. A suitable management of the effluent gas is proposed to maximize CH4 conversion and syngas yield, which includes CO2 separation, H2 purification and CH4 recirculation. Both results confirm the potential of the energy use of biogas under these technologies and the promising results with the new oxygen carrier developed.

Synergetic analysis between polyvinyl chloride (PVC) and coal in chemical looping combustion (CLC)

This effort is to investigate three different Cu-based oxygen carriers (OCs) with polyvinyl chloride (PVC) and coal in chemical-looping combustion (CLC). The combustion process and synergetic analysis of PVC with coal were evaluated. There were four stages in the reaction of OCs with PVC, which HCl released from PVC could react with OCs at about 200–400 °C. CuO and CuO modified by limestone showed better immobilization of chlorine while CuO modified by iron ore and chrysolite inhibited the reaction of HCl with CuO. PVC char combustion temperature started at about 500 °C which were lower than that of coal char. The combustion efficiency of PVC CLC was all above 92%, except using Cu-Fe as OC which was about 88%. The presence of ZD in PVC showed positive effect on every stage. The addition of coal inhibited the reaction of HCl with CuO. The presence of PVC in ZD reduced the temperature of coal char and the addition of ZD in PVC increased the reaction rate. The synergistic effect was obvious between the PVC and coal blends which is beneficial for the complete combustion in solid fuel CLC

Developing magnetic, durable, agglomeration resistant and reactive copper-based oxygen carrier particles by promoting a kaolin-reinforced, manganese‑iron mixed oxide support

Chemical looping with oxygen uncoupling (CLOU) process, involves the use of two interconnected fluidized bed reactors, where oxygen carrier particles are able to release O2 at the fuel reactor operation conditions. Cu-based oxygen carriers containing a kaolin-reinforced MnFe mixed oxide as magnetic support, were prepared by granulation to improve their oxygen carrier properties by means of a simplified preparation method. A study was performed into the effect of kaolin concentration and calcination temperature on magnetic permeability, crushing strength, attrition, agglomeration resistance, and reactivity. Two oxygen carriers containing 28.5 wt% CuO-5 wt% kaolin and 30 wt% CuO-7.5 wt% kaolin, respectively, and both calcined at 1100 °C, were selected because they maintained their magnetic properties and reactivity after kaolin addition and showed improvement in their mechanical resistance. They were tested in a batch fluidized bed reactor (BFBR) to evaluate their fluidization behaviour. Low attrition rate without any agglomeration phenomena was observed for both of oxygen carriers up to temperature of 950 °C. The material prepared with 7.5 wt% kaolin demonstrated improved mechanical resistance, very low attrition rate and higher CuO utilization for the CLOU process after use in the BFBR, while maintaining reactivity during redox cycles and magnetic properties without agglomeration problems.

Outstanding performance of a Cu-based oxygen carrier impregnated on alumina in chemical looping combustion

Chemical looping combustion (CLC) allows the combustion of a fuel with inherent CO2 capture by using an oxygen carrier to transfer the oxygen from the air to the fuel. Previously to the CLC scale-up, tests should be done in lab-scale CLC units to determine the combustion performance of promising oxygen carriers and, at the same time, to evaluate the durability of these materials. For that, the effect of operating conditions on the oxygen carrier ageing should be considered, which is often disregarded. In this work, tests were done burning a simulated biogas stream in a continuous 500 Wth CLC unit with a promising Cu-based oxygen carrier (Cu14Al_ICB). Operating conditions were carefully selected to maximize the durability of this oxygen carrier while complete CH4 combustion was achieved. These operating conditions were based on limiting both the variation of solids conversion by choosing suitable solids circulation rates and the oxidation degree of the particles in the air reactor by minimizing the air excess. Thus, the Cu14Al_ICB material exhibited an excellent mechanical resistance, estimating a particle lifetime of 20,000 h at 900 °C. In addition, copper migration to the surface of the particles and loss of copper were not relevant. This is the first time that under certain operating conditions, a Cu-based oxygen carrier can exhibit outstanding mechanical properties during continuous CLC operation at 900 °C.

The intrinsic kinetic study on oxidation of a Cu-based oxygen carrier in chemical looping combustion

As the kinetic influencing factors were not considered properly in the previous studies, the obtained activation energies of copper oxidation were discrepantly ranging from 15.0 kJ/mol to 100.0 kJ/mol. The gas diffusion in the crucible and sample layer, the surface reaction and the defect diffusion of copper cations all have an impact on the conversion process of copper oxidation samples. Using the high diameter-height ratio crucible in our self-made TGA could effectively eliminate the gas diffusion in the crucible and reduce the error of the kinetic tests. Based on the previous four-step oxidation mechanism, the kinetic parameters of copper oxidation are identified using a grain-scale kinetic model, coupling with a defect transport model. The potential kinetic impact factors including the particle polydispersity, gas diffusion, defect diffusion, surface reaction and particle sintering are adequately considered in this work. First, it is found that the copper oxidation is not dominated by the defect diffusion in the solid product layer, but governed by the surface reaction in the gas–solid interface. The copper oxidation is likely to be adsorption-limited during the surface reaction in the gas–solid interface, and the intrinsic activation energy is identified as 48.0 kJ/mol. The particle-scale model is then performed to investigate the impact of physical properties of oxygen carrier particles. It can significantly accelerate the conversion rate of copper oxidation by means of decreasing the particle size and increasing the porosity. However, it is not advisable to decrease the grain size too much when preparing the oxygen carriers, for this will only increase diffusion resistance inside the particle for small grain. Finally, it can be found that in most conditions of the air reactor, Cu-based oxygen carrier with the grain size of 220–300 nm exhibits the best oxidation performance.

Lab-scale experimental demonstration of Ca[sbnd]Cu chemical looping for hydrogen production and in-situ CO2 capture from a steel-mill

In the present work, a lab-scale packed bed reactor has been used to decarbonize mixtures of inlet gases simulating the typical composition of blast furnace gases (BFG) and convert them to H2-rich streams by means of the CaCu chemical looping concept. The reactor was packed with 355 g of Cu-based oxygen carrier (OC) supported on Al2O3 and natural Ca-based sorbent. The three main reaction stages; namely (i) Calcium Assisted Steel-mill Off-gas Hydrogen (CASOH), (ii) Cu oxidation and (iii) Regeneration of carbonated Ca-based sorbent were examined. In CASOH stage, BFG is converted into H2-rich stream (17% by vol.) under the experimental conditions of 600 °C, 5.0 bar and S/CO molar ratio of 2.0. A controlled oxidation causes a mere 3.5% of CaCO3 to decompose during the Cu-oxidation stage. This resulted in a nearly pure N2 stream at 600 °C and 5.0 bar operating conditions. During the regeneration stage, BFG and mixture of BFG and CH4 is used as a reducing fuel. To ensure the amount of heat needed for the decomposition of CaCO3 during the reduction of CuO, a 1.4 CuO/CaCO3 molar ratio has been used. It resulted in 46% CO2 in N2 at the end of the reduction/calcination stage.

Hydrotalcite-Derived Copper-Based Oxygen Carrier Materials for Efficient Chemical-Looping Combustion of Solid Fuels with CO2 Capture.

Chemical-looping combustion (CLC) is a promising technology that utilizes metal oxides as oxygen carriers for the combustion of fossil fuels to CO2 and H2O, with CO2 readily sequestrated after the condensation of steam. Thermally stable and reactive metal oxides are desirable as oxygen carrier materials for the CLC processes. Here, we report the performance of Cu-based mixed oxides derived from hydrotalcite (also known as layered double hydroxides) precursors as oxygen carriers for the combustion of solid fuels. Two types of CLC processes were demonstrated, including chemical looping oxygen uncoupling (CLOU) and in situ gasification (iG-CLC) in the presence of steam. The Cu-based oxygen carriers showed high performance for the combustion of two solid fuels (a lignite and a bituminous coal), maintaining high thermal stability, fast reaction kinetics, and reversible oxygen release and storage over multiple redox cycles. Slight deactivation and sintering of the oxygen carrier occurred after redox cycles at an very high operation temperature of 985 °C. We expect that our material design strategy will inspire the development of better oxygen carrier materials for a variety of chemical looping processes for the clean conversion of fossil fuels with efficient CO2 capture.

Behavior of coal-chlorine in chemical looping combustion

This work focuses on two aspects: (i) the behavior of coal-derived chlorine in chemical looping combustion (CLC); (ii) the potential adverse impacts of primary gaseous chlorine (i.e., HCl) on Cu-based oxygen carrier (OC). The inactivation mechanism of the sol-gel-derived CuO/Al2O3 OC is investigated. Systematic experiments are conducted in a batch fluidized reactor. First, in CLC of coal, chlorine distribution including HCl, Cl2, Cl adsorbed in the outlet tube and Cl in solid phase is studied under various bed inventories, temperatures and gas atmospheres. The main gaseous Cl from coal is HCl, which shows a high reactivity towards CuO and is partially physically adsorbed by Al2O3. Unconverted HCl is 15.63 ± 0.20%, which could result in corrosion of the CO2 transportation line and compression equipment. What's more, the coal ash exhibits a dechlorination function by forming KCl and CaCl2. The CO2 atmosphere and high temperature in fuel reactor show a promotion on the conversion of coal-Cl to HCl. Then, the corrosion of various OC components is evaluated by a mixture gas with 400 ppm HCl, i.e., Cu-Al (whole OC), CuO (active phase) and Al2O3 (inert support phase). It is found that a part of HCl is converted to Cl2 via the Deacon reaction (4HCl + O2 = 2H2O + 2Cl2) and oxidized by CuO (2CuO + 4HCl = 2CuCl + Cl2 + 2H2O). At the high concentration of HCl (400 ppm) atmosphere, CuO is partially lost from the OC, producing the gaseous copper chlorides, i.e., CuCl and (CuCl)3, which are found to be condensed in the outlet tube. Besides, the solid-phase copper chlorides also degrade the oxygen donation capacity of the OC. Finally, the migration path of coal-chlorine during CLC is summarized. This work will contribute to the development of Cl-resistance OCs and control approaches for Cl emission.

Redox Reaction Kinetics of a Fe–Cu-Based Oxygen Carrier Measured with Microfluidized Bed Thermogravimetric Analysis

Redox Reaction Kinetics of a Fe–Cu-Based Oxygen Carrier Measured with Microfluidized Bed Thermogravimetric Analysis

Techno-economic analysis of a chemical looping combustion process for biogas generated from livestock farming and agro-industrial waste

Biogas is a renewable fuel that is generated from the decomposition of organic matter through the process of anaerobic digestion. The compound that provides biogas with its energy value is CH4, which accounts for between 40% and 75% of the gas, with CO2 being the other main component of this fuel. Although the biogas valorization process is carbon neutral, the overall process can become carbon negative with the application of CO2 capture technologies, such as chemical looping combustion (CLC). This work presents a techno-economic analysis of a 5 MWth plant for the generation of biogas from livestock farming and agro-industrial waste to produce electricity + heat or heat only (base cases), or for further treatment in a CLC unit (CLC cases), where the captured CO2 is converted into a raw material, e.g. for the production of greenhouse crops. Results from the comparative study of five different oxygen carriers used in CLC are also presented.The profitability of the base cases was evaluated by means of the Levelized Cost of Electricity (LCOE) and Levelized Cost of Thermal Energy (LCOTE) metrics, whereas the economic performance of the CLC cases was measured by the Levelized Cost of CO2 (LCOCO2). LCOE gave a value of €139.90/MWh for the base case, and LCOTE was €56.50/MWh for the modified base case, where biogas was combusted in a boiler to produce only heat. With regard to the CLC cases, LCOCO2 values ranged between €148.60 per tonne for a highly reactive, synthetic Cu-based oxygen carrier and €177.10 per tonne for ilmenite.Finally, by comparing the economic results obtained in this work with those found in the literature for conventional biogas production plants and greenhouse crop production processes, it can be concluded that the implementation of CLC technology in biogas plants has the potential to become a profitable and environmentally sustainable option for the valorization of organic waste because the CO2 generated in the fuel reactor of the CLC unit can be considered a marketable, high value-added product for the niche market of the greenhouse farming of horticultural crops.

Influence of an Oxygen Carrier on the CH4 Reforming Reaction Linked to the Biomass Chemical Looping Gasification Process.

A major challenge in biomass chemical looping gasification (BCLG) is the conversion of CH4 and light hydrocarbons to syngas (CO + H2) when the goal is the use for bioliquid fuel production. In this work, tests were performed in a batch fluidized bed reactor to determine the catalytic effect on the CH4 reforming reaction of oxygen carriers used in the BCLG process. Three ores (ilmenite, MnGB, and Tierga), one waste (LD slag), and five synthetic materials (Fe10Al, Fe20Al, Fe25Al, Cu14Al, and Ni18Al) were analyzed. These results were compared to those obtained during ∼300 h of continuous biomass gasification operation in a 1.5 kWth BCLG unit. The low-cost materials (ores and waste) did not show any catalytic effect in the CH4 reforming reaction, and as a consequence, the CH4 concentration values measured in the syngas produced in the continuous prototype were high. The synthetic oxygen carriers showed a catalytic effect in the CH4 reforming reaction, increasing this effect with increasing temperature. With the exception of the Ni-based oxygen carrier (used as a reference), the Cu-based oxygen carrier, working at 940 °C, showed the best catalytic properties, in good agreement with the low CH4 concentration values measured in the syngas generated in the continuous unit. The tests performed in a batch fluidized bed reactor were demonstrated to be very useful in determining the catalytic capacity of oxygen carriers in the CH4 reforming reaction. This fact is highly relevant when a syngas with a low CH4 content is desired as a final product.

Production of hydrogen by chemical looping reforming of methane and biogas using a reactive and durable Cu-based oxygen carrier

The objective of this work was to assess the suitability of a synthetic Cu-based oxygen carrier in a continuous pilot plant for the production of blue and green hydrogen through the autothermal Chemical Looping Reforming (CLRa). In CLRa, methane is converted to a H2 + CO mixture through partial oxidation and reforming reactions in the fuel reactor. The degree of the partial oxidation of methane was defined by controlling the oxygen flow in the air reactor. Steam was used as reforming gas in natural gas to produce blue H2, but the existing CO2 in biogas was the reforming gas to produce green H2. Operating at 950 °C in the fuel and air reactors, CH4 conversion and H2 yield parameters were 96 % and 2.60 mol of H2 per mole of CH4, respectively. These experimental results were close to the theoretical values that could be achieved in the CLRa process. Furthermore, the physicochemical characterization of the samples extracted from the pilot plant throughout the experimental campaign revealed that the Cu-based oxygen carrier maintained its mechanical integrity and chemical stability under harsh operating conditions. Therefore, it can be concluded that Cu-based oxygen carriers can be considered a promising alternative to Ni-based materials for the production of blue and green hydrogen through the CLRa process.

Novel magnetic manganese-iron materials for separation of solids used in high-temperature processes: Application to oxygen carriers for chemical looping combustion

Different chemical looping processes allow burning or gasify solid fuels with inherent CO2 capture because the oxygen is transferred from air to the fuel through a metal oxide based material, which is named oxygen carrier. To improve process efficiency and CO2 capture, highly reactive synthetic materials could be used. One of the challenges of using solid fuels is the oxygen carrier separation from the ash, because loss of oxygen carrier particles is expected during ash drainage. So, their costs would have necessary the recovery of the synthetic oxygen carrier. Mn-Fe based materials show magnetic properties in the spinel phase, which could be used for a magnetic separation. When these Mn-Fe materials are used at high temperature under oxidizing or reducing atmospheres, stability of the spinel phase should be guaranteed in order to take advantage of the magnetic properties. The design of low reactive Mn-Fe based materials with magnetic properties, which can be used as a support material for other highly reactive and active phases, was the main objective of this work. In this sense, the support must have high crushing strength, low reactivity under oxidation and reduction atmospheres at high temperatures and permanent magnetism at low temperature for solids separation. Materials prepared with different Mn/(Mn + Fe) molar ratios and calcination conditions were evaluated regarding mechanical strength, inerticity and magnetic properties. A Cu-based oxygen carrier prepared on the optimal support was prepared and evaluated along 240 oxidation-reduction cycles in thermobalance (25 h experiment), exhibiting suitable mechanical and magnetic characteristics as well as high reactivity.

A Theoretical Study of the Oxygen Release Mechanisms of a Cu-Based Oxygen Carrier during Chemical Looping with Oxygen Uncoupling

The Cu-based oxygen carrier is a promising material in the chemical looping with oxygen uncoupling (CLOU) process, while its performance in the CLOU is significantly dependent on the oxygen release properties. However, the study of oxygen release mechanisms in CLOU is not comprehensive enough. In this work, the detailed oxygen release mechanisms of CuO(110) and CuO(111) are researched at an atomic level using the density functional theory (DFT) method, including the formation of O2, the desorption of O2 and the diffusion of O anion, as well as the analysis of the density of states. The results show that (1) the most favorable pathway for O2 formation and desorption occurs on the CuO(110) surface of O-terminated with energy barriers of 1.89 eV and 3.22 eV, respectively; (2) the most favorable pathway for O anion diffusion occurs in the CuO(110) slab with the lowest energy barrier of 0.24 eV; and (3) the total density of states for the O atoms in the CuO(110) slab shifts to a lower energy after an O vacancy formation. All of the above results clearly demonstrate that the CuO(110) surface plays a significantly important role in the oxygen release reaction, and the oxygen vacancy defect should be conducive to the reactivity of oxygen release in a Cu-based oxygen carrier.