NO Oxidation Performance Research Articles

Catalytic oxidation of NO over SmMn2O5 nanostructures derived from different Mn precursors

In this work, SmMn2O5 nanostructures with different morphologies (particles, flower-like, mixed-structure) were effectively synthesized through a hydrothermal method. The differences of the counter anions (CH3COO−, NO3−, and Cl−) in Mn precursors make the periphery of crystal nucleus have different concentrations of ions during the formation of SmMn2O5 nanostructures, which have been used to explain the evolution of morphology. Compared with Pt/Al2O3, the catalytic performance of NO oxidation for three morphologies shows higher maximum efficiency. The 50% conversion temperature is lower (230 °C vs. 275 °C) and the maximum conversion efficiency is higher (81% at 282 °C vs. 68% at 314 °C) for SmMn2O5 with flower-like by comparison with SmMn2O5 with particles and mixture shapes. The specific surface area is in the order of flower-like > mixed-structures > particles, which is the same as the order of performance for NO oxidation of SmMn2O5 nanostructures. The results of XPS and H2-TPR indicate that the superior catalytic performance of SmMn2O5 with flower-like arises from the existence of more amount of Mn4+/ Mn3+, which can act as the surface active sites. This work offers a promising way for the morphological control of SmMn2O5 with Mn precursors to improve the catalytic performance of NO oxidation.

Understanding the impact of poison distribution on the performance of Diesel oxidation catalysts

Detailed understanding of the poisoning mechanism in Diesel oxidation catalysts (DOCs) is the key to prevent long term catalyst deterioration in vehicles. The present work studies artificial phosphorus (P) poisoning methods applied to a commercial DOC. Cores of the DOC monolith were exposed to increasing amounts of P precursor by impregnation and by spraying. While impregnation leads to a homogeneous poison distribution in the catalytic layers, elemental analysis revealed that the spraying results in radial and axial P gradients that mimic the distribution of this poison previously observed in vehicle aged DOCs. The activity tests under simulated Diesel exhaust evidenced that P deposition by spraying was more detrimental than by impregnation and caused a more severe decrease in NO oxidation performance. Sequential treatments comprising exposure to P, thermal treatment and exposure to sulphur (S) interleaved by activity tests were performed to gain deeper insight into the catalyst deactivation mechanism.

Investigation of performances of commercial diesel oxidation catalysts for CO, C3H6, and NO oxidation.

Four commercial monolithic diesel oxidation catalysts (DOCs) with two different platinum group metal (PGM) loadings and Pt:Pd ratios of 1:0, 2:1, 3:1 (w/w) were investigated systematically for CO, C3H6, and NO oxidation, CO-C3H6 co-oxidation, and CO-C3H6-NO oxidation reactions via transient activity measurements in a simulated diesel engine exhaust environment. As PGM loading increased, light-off curves shifted to lower temperatures for individual and co-oxidation reactions of CO and C3H6. CO and C3H6 were observed to inhibit theoxidation of themselves and each other. Addition of Pd to Pt was found to enhance CO and C3H6 oxidation performance of the catalysts while the presence and amount of Pd was found to increase the extent of self-inhibition of NO oxidation. NO inhibited CO and C3H6 oxidation reactions while NO oxidation performance was enhanced in the presence of CO and C3H6 probably due to the occurrence of reduced Pt and Pd sites during CO and C3H6 oxidations. The optimum Pt:Pd ratio for individual and co-oxidations of CO, C3H6, and NO was found to be Pt:Pd = 3:1 (w/w) in the range of experimental conditions investigated in this study.

Sr doping effect on the structure property and NO oxidation performance of dual-site doped perovskite La(Sr)Co(Fe)O3

In this work, the physico-chemical properties of the La1-xSrxCo0.8Fe0.2O3 (x = 0, 0.3，0.4，0.5，0.6) catalysts were systematically studied as well as their catalytic activity for NO oxidation. When Sr2+ substituted at La3+ site, [CoO6] octahedral distortion is amended and the crystal structure transited from rhombohedral to cubic. Co(III) electronic configuration turned from high/intermediate spin state to low spin sate with empty eg filling. Imbalanced positive charge induced by Sr2+ was compensated by tetravalent Co(IV) ions and oxygen deficiencies together. All these factors resulted in better reducibility of Co, increasing oxygen deficiencies and more mobile oxygen species. Thus, NO conversion of 67–69% was attained over the Sr-doped catalysts at 300 °C, much higher than the undoped catalysts (NO conversion of 24.3%). A significant decrease of the apparent activation energy (Ea), from 68 kJ/mol down to ~52 kJ/mol, was observed as well. Based on the kinetics results, NO oxidation over the perovskite catalysts is a typical superficial process determined by adsorbed NO and surface oxygen species.

Preparation of Pt/Al2O3 and PtPd/Al2O3 catalysts by supercritical deposition and their performance for oxidation of nitric oxide and propene

Pt/Al2O3 and bimetallic PtPd/Al2O3 catalysts were prepared via supercritical deposition method using supercritical carbon dioxide. The effects of Pt loading of Pt/Al2O3 and Pd addition to Pt/Al2O3 on particle size, particle size distribution (PSD) and activity for NO and C3H6 oxidation and C3H6-selective catalytic reduction (C3H6-SCR) were investigated. Pt/Al2O3 catalysts were prepared with Pt loadings of 0.6, 1.2 and 2.1 wt% and a bimetallic PtPd/Al2O3 catalyst was prepared with total metal loading of 1.4 wt% and Pt:Pd molar ratio of 1.3:1. A small fraction of the particles agglomerated after calcination at 550 °C. Around 98 % of the particles had an average particle size of ∼1 nm. The rest of the particles were larger and average size of these larger particles was ∼10 nm for monometallic catalysts and ∼6.5 nm for PtPd/Al2O3. All catalysts were found to be active for NO and C3H6 oxidation and C3H6-SCR reactions. NO oxidation performance of 1.2 wt% Pt/Al2O3 catalyst was the highest. C3H6 oxidation activity increased with increasing metal content. Light-off temperature for C3H6 oxidation shifted to higher temperature in the presence of NO, suggesting competitive oxidation of C3H6 and NO. Concentration profiles indicated that C3H6-SCR started when C3H6 conversion by oxidation reached 50 %; C3H6 was consumed both by oxidation and C3H6-SCR at higher conversions.

Recent advances in selective catalytic oxidation of nitric oxide (NO-SCO) in emissions with excess oxygen: a review on catalysts and mechanisms.

Nitric oxides (NOx, which mainly include more than 90% NO) are one of the major air pollutants leading to a series of environmental problems, such as acid rain, haze, photochemical smog, etc. The selective catalytic oxidation of NO to NO2 (NO-SCO) is regarded as a key process for the development of selective catalytic reduction of NOx by ammonia (via fast selective catalytic reduction reaction) and also the simultaneous removal of multipollutant (pre-oxidation and post-absorption). Until now, scholars have developed various types of NO-SCO catalysts, dividing the main groups into noble metals (Pt, Pd, Ru, etc.), metal oxides (Mn-, Co-, Cr-, Ce-based, etc.), perovskite-type oxides (LaMnO3, LaCoO3, LaCeCoO3, etc.), carbon materials (activated carbon, carbon fiber, carbon nanotube, graphene, etc.), and zeolites (ion-exchanged ZSM-5, CHA, SAPO, MCM-41, etc.) in this review. This paper summarizes the recent progress of the above typical catalysts and mostly analyzes the catalytic performance for NO oxidation in terms of the H2O and/or SO2 resistances and also the influencing factors, and their reaction mechanisms are described in detail. Finally, this review points out the key problems and possible solutions of the current researches and presents the application prospects and future development directions of NO-SCO technology using the above typical catalysts.

Enhancement effect of oxygen mobility over Ce0.5Zr0.5O2 catalysts doped by multivalent metal oxides for soot combustion

Ce0.5Zr0.5O2 catalysts promoted by multivalent transition metal (Mn, Fe, Co) oxides have been prepared for accelerating soot combustion. Compared with Ce0.5Zr0.5O2 catalyst, Mn- and Co-doped catalysts remarkably improved the catalytic activity of soot combustion, while the Fe-doped catalyst had a slightly effect on soot combustion. TEM, N2 adsorption-desorption isotherms and XRD were testified to find the correlation between catalytic activity and texture properties, the results revealed that texture properties of prepared catalysts were not sensitive to catalytic activity. However, the more active oxygen species and superior mobility of lattice oxygen species with more oxygen vacancies characterized by XPS, H2-TPR and O2-TPD were proved as significant roles on soot combustion after incorporation of various multivalent metals, especially for Mn and Co. Furthermore, Co-doped catalyst with the excellent NO-NO2 conversion capacity visibly reduced soot ignition temperature in 600 ppm NO + 10% O2 + N2 under tight contact and loose contact condition due to NO2 is a more effective oxidizing agent than O2. On the contrary, Fe-doped catalyst with slightly better redox performance and more oxygen vacancies reflected weaker NO oxidation performance than support that might be the reason of abundant adsorbed carbonates inhibiting further adsorption of NO and active oxygen species, which also led to the invisible promoting effect of soot combustion.

NO oxidation performance and kinetics analysis of BaMO3 (M=Mn, Co) perovskite catalysts.

Perovskite is an efficient and emerging catalyst for NO oxidation. In this study, BaMnO3 and BaCoO3 perovskite catalysts were synthesized by the sol-gel method, and their catalytic oxidation performances of NO were studied. The catalytic performances indicated that BaMnO3 and BaCoO3 perovskites had the highest NO oxidation activities with the NO conversions of 78.2% at 350°C and 84.3% at 310°C, respectively. The high activities of BaMnO3 and BaCoO3 perovskite catalysts were related to the abundant surface adsorption oxygen (OA = 76.21% and 78.57%, respectively) and the high concentration of Mn4+ (Mn4+/Mn = 66.95%) and Co3+ (Co3+/Co = 63.8%). Moreover, the results of FT-IR and kinetics revealed that NO and O2 adsorbed on the surface of samples and combined with the B-O band to form bidentate nitrate and bridging nitrate, which eventually was converted into NO2. The kinetics analysis revealed that the NO oxidation reaction followed the Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanisms. In addition, the activation energies were 36.453kJ/mol for BaMnO3 and 30.081kJ/mol for BaCoO3, implying that BaMnO3 and BaCoO3 provide low-cost and efficient catalysts, which can be comparable to Pt noble metal catalysts.

Carbon nanomaterial-SmMn2O5 nanocrystal composites with highly efficient catalytic oxidation of NO

SmMn2O5 has been reported as a promising substitute for noble metals to achieve highly efficient NO oxidation. In this work, the composites of carbon nanomaterials (carbon nanotubes and graphene oxide) and SmMn2O5 nanocrystals are successfully synthesized through a hydrothermal method, and their catalytic activities for NO oxidation are investigated as well. The performance evaluation indicates that the introduction of carbon nanotube and graphene oxide in the SmMn2O5 nanocrystal composites improve the activity for NO oxidation. Carbon nanotubes contribute to the improvement of the catalytic activity in the low-temperature region, while graphene oxide helps to increase activity in the high-temperature region. By the analysis of differential scanning calorimetry, the performance improvement of the NO oxidation is found to be dependent on the heat release of carbon nanomaterials in the different temperature regions. These results could provide a new way to improve the NO oxidation performance of SmMn2O5 nanocrystals.

Facile preparation of hollow MnOx-CeO2 composites with low Ce content and their catalytic performance in NO oxidation

The Mn-Ce mixed oxides are frequently used for catalytic oxidation of NO. However, to achieve better performance, a large amount of Ce element is usually engaged in the preparation, in spite of its low abundance and high cost. Herein, a facile sovothermal method was presented to prepare hollow MnOx-CeO2 composites. The structural and physiochemical properties of the products were carefully investigated and their catalytic performance was evaluated. The most active sample possesses a bulk Mn/(Mn + Ce) ratio of 74.5 %, which shows a maximum NO conversion of 90.6 % at 270 °C (GHSV = 120,000 h−1). It is believed that the superior catalytic activity is largely due to the enrichment of Ce element and the high content of Mn4+ species on the surface, while the porous structure is also beneficial.

S-scheme Sb2WO6/g-C3N4 photocatalysts with enhanced visible-light-induced photocatalytic NO oxidation performance

Normal photocatalysts cannot effectively remove low-concentration NO because of the high recombination rate of the photogenerated carriers. To overcome this problem, S-scheme composites have been developed to fabricate photocatalysts. Herein, a novel S-scheme Sb2WO6/g-C3N4 nanocomposite was fabricated by an ultrasound-assisted method, which exhibited excellent performance for photocatalytic ppb-level NO removal. Compared with the pure constituents of the nanocomposite, the as-prepared 15%-Sb2WO6/g-C3N4 photocatalyst could remove more than 68% continuous-flowing NO (initial concentration: 400 ppb) under visible-light irradiation in 30 min. The findings of the trapping experiments confirmed that •O2− and h+ were the important active species in the NO oxidation reaction. Meanwhile, the transient photocurrent response and PL spectroscopy analyses proved that the unique S-scheme structure of the samples could enhance the charge separation efficiency. In situ DRIFTS revealed that the photocatalytic reaction pathway of NO removal over the Sb2WO6/g-C3N4 nanocomposite occurred via an oxygen-induced route. The present work proposes a new concept for fabricating efficient photocatalysts for photocatalytic ppb-level NO oxidation and provides deeper insights into the mechanism of photocatalytic NO oxidation.

Facile synthesis of F-doped g-C3N4/Bi2Fe4O9 heterostructure with Z-scheme for enhanced photocatalytic performance in NO oxidation

Graphitic carbon nitride (g-C3N4) with fluorine (F) doping was synthesized by a hydrothermal technique, and F-doped g-C3N4/Bi2Fe4O9 composites were synthesized by electrostatic self-assembly technique. The crystal structures were studied by X-ray diffraction, the morphology was determined by transmission electron microscope images, and the F doping was verified by energy dispersive X-ray analysis, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The N2 adsorption/desorption results showed that introducing Bi2Fe4O9 nanoparticles into F-doped g-C3N4 reduced the specific surface area and volume of the pores. This could be attributed to the Bi2Fe4O9 nanoparticles partially blocking the pores of F-doped g-C3N4. The photocatalytic performance of F-doped g-C3N4/Bi2Fe4O9 composites was studied by oxidizing NO under visible irradiation. The photocatalytic performance indicated that the presence of Bi2Fe4O9 increased the photocatalytic activity of F-doped g-C3N4 by up to ~100%. The increased photocatalytic performance could be ascribed to a decreased combination rate of the charge carriers. Moreover, scavenger testing study showed that the reactive species, including h+, O2, and ·O2−, played important roles in the photocatalytic reactions.

C3N4 with engineered three coordinated (N3C) nitrogen vacancy boosts the production of 1O2 for Efficient and stable NO photo-oxidation

The introduction of nitrogen vacancy to C3N4 holds promise in the photocatalytic behavior improvement. Yet, minimal literatures on reaction and stability mechanisms are presently available in the NO-oxidation reaction of C3N4. Here C3N4 with three coordinated (N3C) nitrogen vacancy was prepared by directly calcining the mixture of azodicarbonamide and melamine. Unlike previously reported C3N4 that exhibits an obvious deactivation beyond 30 min (>10% loss of reactivity after one cycle) and high in-situ formed NO2 concentration (>100 ppb), the C3N4 with three coordinated (N3C) nitrogen vacancy exerts increased NO-oxidation performance (40.3%, ~2.28 times higher than that of pristine C3N4 with a NO-removal rate of 17.7%) and suppressed in-situ produced NO2 (36.3 ppb, decreased by 76.6 ppb compared to pure C3N4) as well excellent stability (<2% loss of activity after a 5 h cycling test). DFT calculations reveal that, intermediates (NO2) and end-products (NO2– and NO3–) can weakly adsorp on the surface of C3N4 with three coordinated (N3C) nitrogen vacancy, thus rendering a well maintained activity. Based on the time-dependent ESR measurements, the 1O2 generation, which achieving from the O2 activation process, can compensate for the consumption of major reactive species and thus support the remarkable reusability. Therefore, this study provides a potential and sustainable route for the steady and efficient NO-oxidation.

Low-temperature performance controlled by hydroxyl value in polyethylene glycol enveloping Pt-based catalyst for CO/C3H6/NO oxidation

To decrease the diesel vehicle emission, polymer-assisted platinum-based catalysts having an improvement in the dispersion of platinum were developed. This work investigated the structure and redox properties of platinum nanoparticles assisted by polyethylene glycol (PEG) with different hydroxyl value and supported on SiO2-Al2O3 following carbonization and air roasting treatments. Ultraviolet-visible (UV–vis) spectra, in situ FTIR and structural characterization measurements reveal that PEG400-assisted catalyst presents a great interaction with platinum species, affecting the electronic intensity and dispersion of platinum. Reactivity tests show that PEG400-assisted Pt-based catalysts have a better low-temperature catalytic performance in CO, C3H6 and NO oxidation, decreased by around 10−30 °C. It is concluded that the differences in reactivity could be related to the formation and stabilization of platinum species during the preparation.

Insight into structure defects and catalytic mechanism for NO oxidation over Ce0.6Mn0.4Ox solid solutions catalysts: Effect of manganese precursors.

The effects of Mn precursors on structure defects and NO catalytic mechanism over Ce0·6Mn0.4Ox catalysts were fully investigated. The Ce0·6Mn0.4Ox-Ac catalyst, synthesized by using MnAc2 as a Mn precursor, showed the best catalytic activity for NO conversion (86.9%) at 250°C under high space velocity (40,000mLg-1 h-1). Detailed structure-activity relationship reveals that the abundant oxygen vacancies and the highly migratory oxygen species formed on Ce0·6Mn0.4Ox are the crucial factors that leading to the better NO oxidation activity than that of the other Ce0·6Mn0.4Ox-Y (YNO3, SO4, Cl) catalysts. In situ DRIFTS technique confirms that the differences in formation mode and desorption ability of N-based (nitrates, nitrites, and dimer nitroso) intermediate species are the vital factors for NO high-efficiency catalytic oxidation. The highly reactive surface intermediate species, like monodentate nitrates, were observed particularly on Ce0·6Mn0.4Ox-Ac catalyst, so that the NO oxidation performance on Ce0·6Mn0.4Ox-Ac catalyst was more active comparing with other Ce0·6Mn0.4Ox-Y catalysts. This study can broaden the horizons for understanding NO catalytic oxidation mechanism on serial Ce0·6Mn0.4Ox catalysts and serve as a reference guide in design of structure defects for functional materials by modulating precursor species.

Catalytic performance and reaction mechanism of NO oxidation over Co3O4 catalysts

Co3O4 nanorods and nanoparticles were prepared and differed in the overall particle sizes and shapes, while in both cases the catalytically active (110) lattice plane was mainly exposed. The forward rate of NO oxidation of Co3O4 nanorods, stated on catalyst weight, was higher than that of Co3O4 nanoparticles. However, the turnover frequency (TOF) numbers normalized by the surface Co3+ were almost the same, indicating that NO oxidation took place over the same active sites of surface Co3+ for both catalysts. Co3O4 nanorods had a larger number of exposed active sites than nanoparticles. The dissociation of surface O2*, formed by the quasi-equilibrated reaction of O2 molecules on vacant sites (*), assisted by gaseous NO to form NO2 and surface O*, was the rate-determining step in NO oxidation. In situ FTIR spectra confirmed that abundant bridged nitrates were formed on both Co3O4 nanorods and nanoparticles.

Carbon vacancy in C3N4 nanotube: Electronic structure, photocatalysis mechanism and highly enhanced activity

We demonstrated that carbon vacancy modified C3N4 nanotubes can be qualified for more efficient and selective oxidation of NO to NO3− under visible light illumination than the pristine counterpart. Tubular C3N4 with carbon vacancy was fabricated by facile pyrolysis of the hydrolyzed melamine-urea mixture under N2 gas. With the particular structural merits for tubular nanostructure and the introduction of suitable carbon vacancy density, richly available surface defect sites, and accelerated separation and transfer of photo-generated charge carriers, the as-prepared carbon vacancy modified C3N4 nanotubes exhibited an excellent photocatalytic NO oxidation performance. Based on ESR measurement and DFT calculation, the electronic structure of carbon vacancy was revealed. The surface carbon vacancy in C3N4 nanotubes can greatly facilitate the adsorption of NO and O2, therefore, leading to its superior photocatalytic selectivity in conversion of NO to NO3−. The present work provides new insights into the understanding of defective semiconductor photocatalysis.

Non‐thermal plasma‐assisted catalytic oxidation of NO in a dielectric barrier discharge reactor packed with MOx/Al2O3 (M = Mn or Co) as catalysts

AbstractBACKGROUNDPlasma catalysis has emerged as a powerful tool in converting a gas or gas mixture into other value‐added or environment‐friendly chemicals. However, a substantial research effort is needed to further understand the physical and chemical interactions between plasma and catalysts, and their contribution to the chemical reactions.RESULTSFor a given energy density (ED) of 535 ± 25 J L−1, a dielectric barrier discharge (DBD) reactor packed with Al2O3 achieved higher NO2 selectivity and N2O concentration than the DBD reactor alone. Two kinds of supported catalysts (MnOx/Al2O3 and CoOx/Al2O3) with different loading amounts were prepared to investigate the NO oxidation performance of the plasma‐catalytic process. The results indicated that 5 wt% MnOx/Al2O3 presented higher NO2 selectivity and N2O concentration than other catalysts. Packing the DBD reactor with catalysts also changed its discharge behavior. The discharge behavior of the packed‐bed DBD reactor also changed with variation in the loading amount of active metal oxide from 0 to 15 wt%, resulting in changes in NO oxidation performance. Fourier transform infrared (FTIR) and temperature‐programmed desorption (TPD) analysis results indicated that nitrates were formed during the non‐thermal plasma (NTP)‐assisted catalytic process.CONCLUSIONPacking catalysts into the NTP area can not only change the discharge behavior but also improve the oxidation performance of NTP. Both NO oxidation performance and N2O formation for the NTP‐assisted catalytic process have presented significant enhancement. Reducing N2O formation will still be a big challenge for NTP systems used in environmental applications. © 2019 Society of Chemical Industry

Mechanisms for enhanced catalytic performance for NO oxidation over La2CoMnO6 double perovskite by A-site or B-site doping: Effects of the B-site ionic magnetic moments

Diesel engine exhaust has been identified to be highly carcinogenic. In order to improve the control of diesel engine exhaust emissions, the diesel engine oxidation catalyst (DOC) + catalytic diesel particulate filter (CDPF) + selective catalytic reduction catalyst (SCR) + NH3 oxidation catalyst (ASC) united technology has become the mainstream technology for catalytic aftertreatment. Perovskite oxides have emerged as a promising catalyst for NO oxidation and can be used as the DOC. Undoped La2MMnO6 (M = Co, Fe, Ni, Cu) double perovskites, A-site Ba-doping (La2-xBax)CoMnO6 (%Ba = 0, 25%, 50%, 75%, 100%) perovskites and B-site Cu-doping La2Co1-yCuyMnO6 (y = 0, 0.25, 0.50, 0.75, 1) double perovskites were prepared by a facile molten-salt synthesis method and examined by XRD, SEM, BET, in situ DRIFTS, and XPS. In addition, we calculated the B-site ionic magnetic moments of the double perovskites μ which were contributed by the effective Bohr magneton number np of the B-site 3d transition metal ions, such as Mn3+, Mn4+, Co3+, Fe3+, Ni2+, and Cu2+. The correlations between the B-site ionic magnetic moments and the maximum NO conversion over all those double perovskites were also calculated. The B-site ionic magnetic moments has a strong positive correlation with the highest conversion rate of NO catalytic oxidation over all those double perovskites. That is, the higher the B-site ionic magnetic moments, the better the catalytic oxidation performance of NO over the double perovskites. So enhancing the B-site ionic magnetic moments by A-site doping is a method to improve the catalytic activity of NO oxidation over the perovskites. Increasing the B-site ionic magnetic moments is the key index to improve the catalytic activity of NO oxidation of the double perovskites by B-site doping.

Critical Role of Mullite-type Oxides’ Surface Chemistry on Catalytic NO Oxidation Performance

By combining low energy ion scattering spectroscopy and density functional theory calculation, we study the surface composition and surface formation energy of AMn2O5 (A = Sm, Bi) mullite-type oxides synthesized by different methods and their effects on NO catalytic performance. It is well-known that hydrothermal (HT) synthesis at low temperatures produces materials with higher specific surface areas (SSAs) compared with those synthesized by coprecipitation (CP) and high-temperature calcination; however, it is less clear how synthesis methods affect surface chemistry. We find that the NO oxidation performance of SmMn2O5–HT does not match the SSA increase when compared to the lower SSA SmMn2O5–CP. Combined experimental and theoretical investigation reveals that SmMn2O5–HT includes a higher fraction of inactive Sm-terminated surfaces, which explains its lower than expected activity. However, the surface chemistry change depends strongly on the A-site element. The exposed surfaces of BiMn2O5–CP are predomina...