@article{mishra_dudek_gaffney_ding_li_2023, title={Spinel oxides as coke-resistant supports for NiO-based oxygen carriers in chemical looping combustion of methane}, volume={424}, ISSN={["1873-4308"]}, url={https://doi.org/10.1016/j.cattod.2019.09.010}, DOI={10.1016/j.cattod.2019.09.010}, abstractNote={Due to their high activity for methane conversion under a cyclic redox scheme, supported nickel oxides are among the most extensively investigated oxygen carrier materials for chemical looping combustion (CLC) and reforming (CLR) of methane. However, coke formation remains as a key challenge for Ni-containing oxygen carriers. The current study investigates the effect of reducible, spinel-structured supports to enhance coke resistance of NiO-based oxygen carriers. It was hypothesized that reducible supports capable of continued yet slow lattice oxygen donation in the presence of methane can actively retard coke formation on the surface of the oxygen carriers. To evaluate such effects, NiFe2O4, MgFe2O4, and BaFe2O4 are investigated as coke-resistant, reducible supports for NiO using mass spectrometry (MS) and thermogravimetric analysis (TGA) during chemical looping cycles. All three reducible supports were capable of continuous oxygen donation over an extended period of time (>40 min) without signs of coke formation. When used as supports for NiO, the resulting oxygen carriers showed no sign of carbon deposition under typical methane CLC environments. In comparison, NiO supported on inert MgAl2O4 exhibited significant coke formation after only 2.5 min. Moreover, NiO supported on NiFe2O4 and BaFe2O4 exhibited faster redox activity and higher oxygen carrying capacity when compared to the inert MgAl2O4-supported NiO. Detailed investigation of the reduction behavior of NiFe2O4-supported NiO revealed extensive solid-state reactions and Ni/Fe exchanges among the support, NiO, and newly formed phases. Specifically, initial weight loss in NiFe2O4-supported NiO was associated with reduction of the oxygen carrier to metallic Ni and Fe3O4 phases. Subsequent coke inhibition was attributed to the slow reduction of Fe3O4 and FeO phases. Multi-cyclic redox studies indicated that NiFe2O4-supported NiO gradually lost its redox activity. In comparison, both MgFe2O4- and BaFe2O4-supported NiO exhibited satisfactory redox stability, activity, and coke resistance.}, journal={CATALYSIS TODAY}, publisher={Elsevier BV}, author={Mishra, Amit and Dudek, Ryan and Gaffney, Anne and Ding, Dong and Li, Fanxing}, year={2023}, month={Dec} }
 @article{mishra_shafiefarhood_dou_li_2020, title={Rh promoted perovskites for exceptional ?low temperature? methane conversion to syngas}, volume={350}, ISSN={["1873-4308"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85065818713&partnerID=MN8TOARS}, DOI={10.1016/j.cattod.2019.05.036}, abstractNote={By utilizing lattice oxygen of a reducible metal oxide (a.k.a. redox catalyst), chemical looping reforming (CLR) partially oxidizes methane to syngas without gaseous oxygen. Subsequent to methane partial oxidation (POx), the reduced metal oxide is re-oxidized with air to complete the two-step redox cycle. In essence, CLR accomplishes methane POx without the need for an air separation unit, offering a potentially more efficient route for syngas production. This study investigates Rh promoted and iron/strontium doped CaMnO3 as redox catalysts at relatively low temperatures (<700 °C). These redox catalysts takes advantage of Rh promoter for methane activation as well as the high redox activity of iron/strontium doped CaMnO3. It was determined that Sr and Fe doped CaMnO3 are highly active for methane conversion, showing lattice oxygen extraction of 2.2–4.5 wt.% at 600 °C. However, the syngas selectivities are relatively low, with Sr doped CaMnO3 redox catalysts showing syngas selectivity ˜50% and Fe doped CaMnO3 doped redox catalysts showing syngas selectivity less than 5%. To further increase the syngas selectivity and yield, a reforming catalyst was placed downstream of the chemical looping bed. Under such a sequential bed scheme, 88–96% syngas selectivity was demonstrated for the redox catalysts. Optimization of the reaction conditions showed that a sequential bed composed of Rh promoted CaMn0.75Fe0.25O3 with a downstream reforming catalyst bed is capable of achieving syngas yields above 70% at 600 °C. The relatively low operating temperature and elimination of air separation unit make the redox catalysts and the sequential bed scheme a potentially attractive option for methane conversion.}, journal={CATALYSIS TODAY}, author={Mishra, Amit and Shafiefarhood, Arya and Dou, Jian and Li, Fanxing}, year={2020}, month={Jun}, pages={149–155} }
 @article{mishra_li_li_santiso_2019, title={Oxygen Vacancy Creation Energy in Mn-Containing Perovskites: An Effective Indicator for Chemical Looping with Oxygen Uncoupling}, volume={31}, ISSN={["1520-5002"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85061650487&partnerID=MN8TOARS}, DOI={10.1021/acs.chemmater.8b03187}, abstractNote={Chemical looping with oxygen uncoupling (CLOU) is a novel process for carbon dioxide capture from coal combustion. Designing a metal oxide oxygen carrier with suitable oxygen release and uptake (redox) properties represents one of the most critical aspects for CLOU. The current work aims to correlate oxygen vacancy creation energy of metal oxide oxygen carriers with their redox properties. Oxygen vacancy creation energies of CaMnO3−δ, Ca0.75Sr0.25MnO3−δ, CaMn0.75Fe0.25O3−δ, and BaMnO3−δ were determined through density functional theory (DFT) calculations. The effect of the Hubbard U correction on the ground state magnetic configurations and vacancy creation energies was investigated, along with the effect of lattice oxygen coordination environment. It was determined that Hubbard U only slightly changes the relative differences in vacancy creation energies between the Mn-containing perovskites investigated. Therefore, ranking of oxygen vacancy creation energies among the various oxides can be determined us...}, number={3}, journal={CHEMISTRY OF MATERIALS}, author={Mishra, Amit and Li, Tianyang and Li, Fanxing and Santiso, Erik E.}, year={2019}, month={Feb}, pages={689–698} }
 @misc{mishra_li_2018, title={Chemical looping at the nanoscale - challenges and opportunities}, volume={20}, ISSN={["2211-3398"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85047404801&partnerID=MN8TOARS}, DOI={10.1016/j.coche.2018.05.001}, abstractNote={The activity and long-term performance of oxygen carrier particles, which undergo cyclic reduction–oxidation (redox) reactions at elevated temperatures, are of critical importance to chemical looping processes. Although the significant thermal and redox stresses in chemical looping reaction make it challenging to stabilize metal oxide based oxygen carriers at the nanoscale, a number of promising approaches have been proposed and investigated over the past decade. This article summarizes recent advances in nanoscale oxygen carrier development. Mechanistic insights in the redox reactions of the oxygen carriers and their implications for the design and optimization of oxygen carriers for chemical looping combustion and partial oxidation reactions are also discussed.}, journal={CURRENT OPINION IN CHEMICAL ENGINEERING}, author={Mishra, Amit and Li, Fanxing}, year={2018}, month={Jun}, pages={143–150} }
 @article{dou_krzystowczyk_mishra_liu_li_2018, title={Perovskite Promoted Mixed Cobalt-Iron Oxides for Enhanced Chemical Looping Air Separation}, volume={6}, ISSN={["2168-0485"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85055169872&partnerID=MN8TOARS}, DOI={10.1021/acssuschemeng.8b03970}, abstractNote={Chemical looping air separation (CLAS) is a promising approach to produce high purity oxygen from air. Redox kinetics and oxygen carrying capacity of oxide-based oxygen carrier materials play a critical role in the overall performance of CLAS. In view of the fast lattice oxygen transport property of mixed-conductive perovskite materials, composites of La0.8Sr0.2CoxFe1–xO3 (LSCF) perovskite and mixed Co–Fe oxides (CF) were investigated for chemical looping air separation. The effects of Fe and perovskite addition were systematically examined by varying Co/Fe and LSCF/CF ratios. Increase of Fe in mixed Co–Fe oxides significantly increases oxidation kinetics of LSCF-CF composites while decreasing the rate of oxygen release. An optimized average redox rate was achieved by balancing the oxygen uptake (oxidation) and release (reduction) rates through tuning Co/Fe ratio, with the maximum occurring at a ratio of 9:1. Unpromoted Co–Fe mixed oxide exhibited a working oxygen capacity of 1.6 wt % at 850 °C. With the ...}, number={11}, journal={ACS SUSTAINABLE CHEMISTRY & ENGINEERING}, author={Dou, Jian and Krzystowczyk, Emily and Mishra, Amit and Liu, Xingbo and Li, Fanxing}, year={2018}, month={Nov}, pages={15528–15540} }
 @article{haribal_he_mishra_li_2017, title={Iron-Doped BaMnO3 for Hybrid Water Splitting and Syngas Generation}, volume={10}, ISSN={["1864-564X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85029158363&partnerID=MN8TOARS}, DOI={10.1002/cssc.201700699}, abstractNote={Abstract}, number={17}, journal={CHEMSUSCHEM}, publisher={Wiley}, author={Haribal, Vasudev Pralhad and He, Feng and Mishra, Amit and Li, Fanxing}, year={2017}, month={Sep}, pages={3402–3408} }
 @article{mishra_galinsky_he_santiso_li_2016, title={Perovskite-structured AMn(x)B(1-x)O(3) (A = Ca or Ba; B = Fe or Ni) redox catalysts for partial oxidation of methane}, volume={6}, ISSN={["2044-4761"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84975156629&partnerID=MN8TOARS}, DOI={10.1039/c5cy02186c}, abstractNote={High oxygen carrying capacity, lack of loosely bound lattice oxygen, and preferential surface segregation of Ba make BaMnxB1−xO3 (B = Ni or Fe) based redox catalysts suitable for chemical looping reforming of methane with high syngas yield and coke resistance.}, number={12}, journal={CATALYSIS SCIENCE & TECHNOLOGY}, author={Mishra, Amit and Galinsky, Nathan and He, Feng and Santiso, Erik E. and Li, Fanxing}, year={2016}, pages={4535–4544} }
 @article{galinsky_mishra_zhang_li_2015, title={Ca(1-x)A(x)MnO(3) (A = Sr and Ba) perovskite based oxygen carriers for chemical looping with oxygen uncoupling (CLOU)}, volume={157}, ISSN={["1872-9118"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85007035468&partnerID=MN8TOARS}, DOI={10.1016/j.apenergy.2015.04.020}, abstractNote={Operated under a cyclic redox mode with an oxygen carrier, the chemical looping with oxygen uncoupling (CLOU) process offers the potential to effectively combust solid fuels while capturing CO2. Development of oxygen carriers capable of reversibly exchanging their active lattice oxygen (O2−) with gaseous oxygen (O2) under varying external oxygen partial pressure (PO2) is of key importance to CLOU process performance. This article investigates the effect of A-site dopants on CaMnO3 based oxygen carriers for CLOU. Both Sr and Ba are explored as potential dopants at various concentrations. Phase segregations are observed with the addition of Ba dopant even at relatively low concentrations (5% A-site doping). In contrast, stable solid solutions are formed with Sr dopant at a wide range of doping level. While CaMnO3 perovskite suffers from irreversible change into Ruddlesden–Popper (Ca2MnO4) and spinel (CaMn2O4) phases under cyclic redox conditions, Sr doping is found to effectively stabilize the perovskite structure. In-situ XRD studies indicate that the Sr doped CaMnO3 maintains a stable orthorhombic perovskite structure under an inert environment (tested up to 1200 °C). The same oxygen carrier sample exhibited high recyclability over 100 redox cycles at 850 °C. Besides being highly recyclable, Sr doped CaMnO3 is found to be capable of releasing its lattice oxygen at a temperature significantly lower than that for CaMnO3, rendering it a potentially effective oxygen carrier for solid fuel combustion and carbon dioxide capture.}, journal={APPLIED ENERGY}, author={Galinsky, Nathan and Mishra, Amit and Zhang, Jia and Li, Fanxing}, year={2015}, month={Nov}, pages={358–367} }