Good electronic transport capacity and low lattice thermal conductivity are beneficial for thermoelectric applications. In this study, the potential use as a thermoelectric material for the recently synthesized two-dimensional TiS3 monolayer is explored by applying first-principles method combined with Boltzmann transport theory. Our work demonstrates that carrier transport in the TiS3 sheet is orientation-dependent, caused by the difference in charge density distribution at band edges. Due to a variety of Ti–S bonds with longer lengths, we find that the TiS3 monolayer shows thermal conductivity much lower compared with that of transition-metal dichalcogenides such as MoS2. Combined with a high power factor along the y-direction, a considerable n-type ZT value (3.1) can be achieved at moderate carrier concentration, suggesting that the TiS3 monolayer is a good candidate for thermoelectric applications.Keywords: Boltzmann transport equation; carrier mobility; first-principles calculations; thermal conductivity; thermoelectric performance; TiS3 monolayer; transition-metal trichalcogenide (TMTC);

•Mesoscale simulation of dispersion and alignment of CNT composites.•Dispersion possibility and average angle are proposed to do statistical measurements.•Long CNTs in well dispersed composites are well aligned.Dispersion and alignment of carbon nanotubes (CNTs) in polymer composites in equilibrated and shear flow conditions are studied using dissipative particle dynamics (DPD). Dispersion possibility and average angle are proposed to quantitatively measure the degree of dispersion and alignment of CNTs. Higher degree of the CNT dispersion is obtained by decreasing DPD repulsion parameter. Notable improvement of the alignment is achieved by increasing the volume fraction and the length of CNTs. The increase of CNT volume fraction is particularly efficient in enhancing the alignment of well dispersed composites when CNTs are long and the alignment of poorly dispersed composites when CNT volume fraction is small (<9.4%).Figure optionsDownload full-size imageDownload as PowerPoint slide

A series of mullite SmMn2O5 oxides were prepared by citric acid (CA), hydrothermal (HT) and co-precipitation (CP) and combustion of ethylene glycol and methanol solutions (EG&M) methods, and tested for NOx-assisted soot combustion. The catalyst performance tests were conducted under “loose” contact conditions and the physical and chemical properties characterized by XRD, FTIR, BET, SEM, XPS, and O2-TPD and H2-TPR measurements. The SmMn2O5-EG&M catalyst possessed a distinct morphology with slabs separated by interconnected macropores, and exhibited the overall highest catalytic activity for soot combustion. The corresponding T10, T50, and T90 were 283 °C, 368 °C, and 420 °C, respectively, and the CO2 selectivity was 99.6%. The soot combustion activation energy for the SmMn2O5-EG&M catalyst is 65 kJ mol−1. O2-TPD and H2-TPR measurements demonstrated higher mobility and better reducibility of surface adsorbed oxygen for the EG&M sample. The soot combustion is greatly accelerated by the NO2-assisted mechanism under a NO + O2 atmosphere and further enhanced by the interconnected macropores of the catalyst, facilitating an intimate contact between the soot and the catalyst. Our study reveals that SmMn2O5 mullite is an effective catalyst for NOx-assisted soot combustion.

The effect of exposed facets and oxygen vacancies on the catalytic activity of PdxCe1−xO2−δ nanorods for low-temperature CO oxidation has been investigated based on both experimental and theoretical methods. PdxCe1−xO2−δ nanorods with exposed {100} and {110} facets are more active than those with the {111} facet, and such superior active facets can become selectively accessible by modulating the calcination temperature. Moreover, a post H2 reduction process further enhances the low temperature activity of PdxCe1−xO2−δ composites with a CO initial conversion temperature as low as 24 °C. It is suggested that the enhanced activity by the H2 reduction process is mostly attributed to the promotion of oxygen vacancy concentration on the exposed facets. This is in reasonable agreement with the theoretical prediction that the CO oxidation proceeds via an oxygen vacancy-mediated Eley–Rideal mechanism on PdxCe1−xO2−δ nanorods. Our work highlights the importance of both exposed facets and oxygen vacancies on low temperature CO oxidation for PdxCe1−xO2−δ nanorod catalysts.

•Defects and dopants in graphene are essential to prevent the metal clustering.•The interaction between H2 and metal@graphene is dipole–dipole interaction.•Charge transfer and dipole momentum are correlated to H2 adsorption energy.•Mg and Ca are the most promising candidates for multiple H2 adsorptions.Based on first-principles calculations, the H2 adsorptions onto six types of modified graphene substrates decorated with light metals (Li, Na, K, Be, Mg, Ca) are investigated to shed light on the factors affecting the H2 binding energies. It is demonstrated that the introduction of defects and dopants into graphene substrates is essential to prevent the metal clustering and achieve dispersed metal atoms desirable for H2 adsorption. The interaction between H2 and alkali/alkali-earth metal decorated graphene systems is attributed to the electrostatic effect induced by polarized dipole–-dipole interaction. Via introducing defects and hetero-atoms to modify the electronegativity of the local structure, the H2 adsorption energy can be tuned by choosing the combination of suitable metals and substrates. The calculated H2 binding strength is positively correlated to the charge transfer from the metal to the substrates and the dipole momentum of metal decorated substrates. Compared the cases with different metals decoration, Mg and Ca are expected to the most promising candidates for multiple H2 adsorptions.

Photoelectrochemical water splitting holds great potential for solar energy conversion and storage with zero greenhouse gas emission. Integration of a suitable co-catalyst with an absorber material enables the realization of highly efficient photocleavage of water. Herein, nanostructured hematite film was coated with an ultrathin and conformal CoOx overlayer through atomic layer deposition (ALD). The best performing hybrid hematite with a 2–3 nm ALD CoOx overlayer yielded a remarkable turn on potential of 0.6 VRHE for the water oxidation reaction. Moreover, material analyses revealed that the surface amorphous CoOx/Co(OH)2 component exhibited good optical transparency and hydrophilic properties, which were beneficial for the formation of an ideal hematite/electrolyte interface. In addition to the presence of the CoOx overlayer, a negative shift of flat band potential (VFB) as well as suppression of surface recombination helped to significantly promote the charge separation and collection properties, contributing to the overall solar conversion efficiency. As a result, the external quantum efficiency (IPCE) obtained on hematite increases by 66% at 1.23 VRHE.

A series of LaxSm1−xMn2Oδ (x = 0, 0.1, 0.3, 0.5) catalysts were synthesized through a co-precipitation method. The catalytic activity for NO oxidation was enhanced with La substitution, and the maximum activity was achieved at x = 0.3. XRD and HRTEM results revealed the formation of a multiphase oxide as well as the interface structure between the mullite (SmMn2O5) phase and Mn-rich perovskite (La0.96MnO3.05) phase. The main impact of different La/Sm molar ratios is the amount of surface adsorbed oxygen (Oads) and surface Mn4+ ions as revealed by XPS results. The NO oxidation performance was enhanced through La addition by promoting the decomposition of nitrate/nitrite species and desorption of NO2, improving the reducibility of surface adsorbed oxygen, as determined by H2-TPR, NO + O2-TPRD and in situ DRIFTS studies. Mono-, bi-dentate and bridged nitrates formed on the surface were determined to be the primary reaction intermediates.

SmMn2O5 mullite has recently been reported to be a promising alternative to traditional Pt-based catalysts for environmental and energy applications. By performing density functional theory calculations, we have systematically investigated lattice oxygen reactivity and oxygen adsorption/dissociation/migration behaviors on low-index surfaces of SmMn2O5 mullite with different terminations. On the basis of the oxygen chemistry and thermodynamic stability of different facets, we conclude that (100)3+, (010)4+, and (001)4+ are reactive toward NO oxidation via either the Mars van Krevelen (MvK) or Eley–Rideal (ER) mechanism. Concrete NO → NO2 reaction paths on these candidate mechanisms have also been calculated. Both the (010)4+ and (001)4+ surfaces presented desirable activities. Bridge MnO sites on (010)4+ surface are identified to be the most active for NO oxidation through the ER mechanism with the lowest barrier of ∼0.38 eV. We have also identified that on all active sites considered in the current study, the rate-determining step in NO → NO2 oxidation reaction is the NO2 desorption. Our study gives an insight into the mechanisms of NO oxidation on SmMn2O5 mullite at the atomic level and can be used to guide further improvement of its catalytic performance.Keywords: density functional theory calculations; NO oxidation; oxygen chemistry; SmMn2O5 mullite

Composite Co3O4/TiO2 nanotube arrays (NTs) were fabricated via atomic layer deposition (ALD) of Co3O4 thin film onto well-aligned anodized TiO2 NTs. The microscopic morphology, composition, and interfacial plane of the composite structure were characterized by scanning electron microscopy, energy dispersion mapping, X-ray photoelectron spectra, and high-resolution transmission electron microscopy. It was shown that the ultrathin Co3O4 film uniformly coat onto the inner wall of the high aspect ratio (>100:1) TiO2 NTs with film thickness precisely controlled by the number of ALD deposition cycles. The composite structure with ∼4 nm Co3O4 coating revealed optimal photoelectrochemical (PEC) performance in the visible-light range (λ > 420 nm). The photocurrent density reaches as high as 90.4 μA/cm2, which is ∼14 times that of the pristine TiO2 NTs and 3 times that of the impregnation method. The enhanced PEC performance could be attributed to the finely controlled Co3O4 coating layer that enhances the visible-light absorption, maintains large specific surface area to the electrolyte interface, and facilitates the charge transfer.Keywords: atomic layer deposition; cobalt oxide; heterostructure; photoelectrochemical; titanium oxide; visible light

•The parameters of LI-MEAM are optimized for all the bcc transition metals.•Using the optimized parameters, most of physical properties are calculated.•The predicted results by LI-MEAM agree well with available experimental values.Lattice inversion modified embedded atom method (LI-MEAM), proposed as an alternative implementation of MEAM models by removing the many-body screening function and including the interactions from more nearest neighbors, was applied to the bcc transition metals, Fe, Cr, Mo, W, V, Nb, and Ta in the present work. The interatomic potential was parameterized by fitting to individual elastic constants, structural energy differences, vacancy formation energy, and surface energy using particle swarm optimization method. Various physical properties of individual elements, including structural properties, vacancy defect properties, surface properties, and thermal properties were presented along with experimental data and those calculated using the second nearest neighbor MEAM (2NN MEAM) in this article so as to evaluate the optimized parameters and verify the LI-MEAM model. It is shown that LI-MEAM potential could reasonably reproduce both the fitted and the predicted properties for all bcc transition metals.

Nanoporous carbon structures are promising candidates for hydrogen physisorption storage due to their high specific area and light weight. Using first-principles calculations, we predict a type of sp2–sp3 hybrid carbon network (HCN) with well-aligned and size-tunable nanopores that are suitable for hydrogen storage. The unique shape of the nanopores is beneficial for the selective Li atoms doping and induces an enhanced H2 binding energy that can be attributed to the improved interaction between polarized H2 and Li ion. A maximum weight percentage of hydrogen storage reaches 6.28 wt % with an average binding energy of −0.19 eV in Li-doped HCN. Together with the ultrahigh volumetric density of hydrogen (102 g/L), the HCN structure is a promising candidate for the hydrogen storage medium.

First-principles calculations based on density functional theory were carried out to explore the interfacial properties of the WO3/BiOCl heterojunction aiming at gaining insights into the roles the interface played in the overall photocatalytic performance. The interfacial effects of the WO3 combination with BiOCl on electronic properties, charge transfer and visible-light response were investigated in detail. The density of states analysis showed that the interfacial structures resulted in a suitable band alignment to separate the excited carriers into two sides of the interface and thus, the electrons–holes recombination could be effectively suppressed. Moreover, excited holes could be readily transferred across the interface from the valence band maximum (VBM) of BiOCl to the VBM of WO3 under visible-light irradiation without being trapped in interfacial mid-gap states.

LaCoO3 perovskite has recently received great attention as a potential alternative to precious metal based NO oxidation catalysts. We report here a comprehensive first-principles study of the NO oxidation kinetics on differently re-constructed hexagonal-phase LaCoO3 facets. Among the 42 low-index facets considered, the (102) LaO-, (104) O2- and (0001) LaO3-terminated facets were found to be thermodynamically stable and likely to be exposed in LaCoO3 oxide nanoparticles. Among these stable facets, the (0001) LaO3-terminated surface is catalytically most active towards NO oxidation, with the reaction proceeding through the mono-vacancy Mars–van Krevelen mechanism. Our study shed light on the atomistic scale NO oxidation mechanism on LaCoO3 facets and can aid further optimization of the catalyst.

Distinct from the common well faceted ZnO nanorods (R-ZnO), ZnO nanotetrapods (T-ZnO) exhibited a remarkable catalytic activity for the thermal decomposition of ammonium perchlorate (AP): the activation energy at high temperature decomposition (HTD) was significantly decreased to 111.9 kJ mol−1, much lower than 162.5 kJ mol−1 for pure AP and 156.9 kJ mol−1 for AP with R-ZnO. This was attributed to more abundant atomic steps on the surface of T-ZnO than that of R-ZnO, as evidenced by HRTEM and density function theory (DFT) calculations. It was shown that the initiation step of perchloric acid (PA) decomposition happened much faster on stepped T-ZnO edges, resulting in the formation of active oxygen atoms from HClO4. The formed oxygen atoms would subsequently react with NH3 to produce HNO, N2O and NO species, thus leading to an obvious decrease in the activation energy of AP decomposition. The proposed catalytic mechanism was further corroborated by the TG-IR spectroscopy results. Our work can provide atomic insights into the catalytic decomposition of AP on ZnO nanostructures.

•HSE was used to study the electronic and optical properties of new B10 ZnO phase.•Band gap is ranging from 6.08 to 7.06 eV under high pressure from 236 to 316 GPa.•The optical constants undergo a blue shift with the increasing pressure.To extend our knowledge on the tetragonal PbO-type (B10) phase of ZnO under high pressure, we used the hybrid functional theory to calculate its electronic and optical properties. Our calculations indicate that the B10 phase is a transparent insulator and has an indirect band gap ranging from 6.08 to 7.06 eV with pressure increasing from 236 to 316 GPa. The B10 phase under 236 GPa has excellent dielectric properties except metallic behaviors at around 25 and 37 eV photon excitation. We found a blue shift in optical properties of the B10 phase with the increase of pressure.

ZnO micro/nanocrystals with different percentages of the exposed (0001) facets were synthesized by a facile chemical bath deposition method. Various characterizations were carried out to understand the relationship between particle shape, exposed (0001) facets, and catalytic activity of ZnO nanocrystals for the thermal decomposition of ammonium perchlorate (AP). An enhancement in the catalytic activity was observed for the ZnO micro/nanocrystals with a higher percentage of the exposed (0001) facets, in which the activation energy Ea of AP decomposition was lowered from 154.0 ± 13.9 kJ/mol to 90.8 ± 11.4 kJ/mol, 83.7 ± 15.1 kJ/mol, and 63.3 ± 3.7 kJ/mol for ZnO micro/nanocrystals with ca. 18.6%, 20.3%, and 39.3% of the exposed (0001) facets. Theoretically evidenced by density functional theory calculations, such highly exposed (0001) facets can be favorable for the adsorption and diffusion of perchloric acid, and also facilitate the formation of active oxygen which can lead to the oxidation reaction of ammonia more completely in the catalytic decomposition of AP.

Sillenite Bi12MO20 (M = Ti, Ge, Si) nanofibers have been fabricated through a facile electrospinning route for photocatalytic applications. Uniform Bi12MO20 (M = Ti, Ge, Si) nanofibers with diameters of 100–200 nm and lengths of up to several millimeters can be readily obtained by thermally treating the electrospun precursors. The photocatalytic activities of these nanofibers for degradation of rhodamine B (RhB) were explored under UV-visible light. The band structure and the degradation mechanisms were also discussed. The fibrous photocatalysts of Bi12TiO20, Bi12SiO20 and Bi12GeO20 exhibit different photocatalytic behaviours, which are attributed to the microstructure, band gap, and electronic structures.

A BiOCl–Bi2WO6 heterojunction with a chemically bonded interface was synthesized via a facile one-step solvothermal method. A series of characterization techniques (XRD, XPS, TEM, SEM, EDS etc.) confirmed the existence of a BiOCl–Bi2WO6 interface. The heterojunction yielded a higher photodegradation rate of Rhodamine B under visible light irradiation compared to its individual components. Theoretical studies based on density functional theory calculations indicated that the enhanced photosensitized degradation activity could be attributed to the favorable band offsets across the BiI–O–BiII bonded interface, leading to efficient interfacial charge carrier transfer. Our results reveal the photosensitized mechanism of BiOCl–Bi2WO6 heterojunctions and demonstrate their practical use as visible-light-driven photocatalytic materials.

We discover through first-principles calculations a new type of nanoporous carbon network structure formed out of small diameter nanotubes that features unique sp2-sp3 bonding hybridizations and highly ordered 1-D channels for Li-ion diffusion. Unlike other graphitic materials that are primarily bonded by intertube/interlayer van der Waals forces, the predicted sp2-sp3 hybridized carbon networks (HCNs) are held together by strong sp3 covalent bonding at the junctions, with sp2-hybridized interconnects providing conducting π-electrons near the Fermi level. With well-aligned and size-tunable 1-D nanopores, we show that besides desirable high Li capacity, stable Li-ion intercalation voltage profile, and low diffusion barriers, the volumetric change of HCN between fully lithiated/delithiated phases is <1%, making it a very promising Li-ion battery anode candidate.

Density functional theory calculations are performed to study the band offsets at the interface of two photocatalytic materials BiOCl:Bi2WO6. It is found that the W–O bonded interface shows the most stability. An intrinsic interface fails to enhance the charge-carrier separation due to the improper band alignment between these two materials. Sulfur (S) is proposed to replace the bulk oxygen (O) site and thus tune the band edges of BiOCl to enhance the photocatalytic performance of the heterojunction. Furthermore, the presence of S provides an extra charge to generate a clean interface with minimal gap states that also benefits carrier migration across the heterojunction.

Recent experiments showed beneficial influence of vanadium doping on the electrochemical performance of lithium iron phosphate (LiFePO4) cathode materials. First-principles calculations have been performed to investigate the stability, electronic structure and lithium diffusivity of vanadium-doped LiFePO4 and to elucidate the origin of such improvement. It is found that vanadium prefers occupying Fe sites and leads to additional density of states within the intrinsic bandgap. By the nudged elastic band method, we show that the barrier of Li ions diffusion along the one dimensional channel in both LiFePO4 and FePO4 phases can be effectively reduced by vanadium doping. Structural analysis shows the lower diffusion barrier ties closely to a volumetric expansion of the diffusion channel.Highlights► We model vanadium doped lithium ion phosphates using GGA+U method. ► We theoretically determine the most energetically favorable site for phosphor dopant. ► Vanadium doping on iron site induces density of states within the bandgap. ► Vanadium is shown to reduce the lithium ion migration barrier. ► Reason for the reduced migration barrier is due to a volumetric expansion of the diffusion channel.

Interaction of carbon monoxide (CO) with transition metal surfaces is an essential part of CO oxidation catalysis. In this report, we investigate and compare CO adsorption behavior on Pt (1 1 1) and Pd (1 1 1) surfaces combining first-principles (FP) calculations and lattice gas Monte-Carlo (LG-MC) simulations. Our results indicate that despite stronger CO binding on Pd (1 1 1) at low coverage, more repulsive lateral interactions on Pd surface lead to a more rapid adsorption energy decrease with respect to coverage. This results in lower saturation coverage and weaker CO desorption energies on Pd (1 1 1), which could contribute to its excellent reactivity observed under high pressure reaction conditions.Graphical abstractHighlights►We model CO lateral interaction on Pt and Pd surfaces. ► Parameterized lattice gas model based on DFT calculations. ► CO adsorption is stronger on Pd (1 1 1) at low coverage. ► Lateral interactions drive a faster decrease of binding on Pd (1 1 1).

Sillenite Bi12MO20 (M = Ti, Ge, Si) nanofibers have been fabricated through a facile electrospinning route for photocatalytic applications. Uniform Bi12MO20 (M = Ti, Ge, Si) nanofibers with diameters of 100–200 nm and lengths of up to several millimeters can be readily obtained by thermally treating the electrospun precursors. The photocatalytic activities of these nanofibers for degradation of rhodamine B (RhB) were explored under UV-visible light. The band structure and the degradation mechanisms were also discussed. The fibrous photocatalysts of Bi12TiO20, Bi12SiO20 and Bi12GeO20 exhibit different photocatalytic behaviours, which are attributed to the microstructure, band gap, and electronic structures.

A BiOCl–Bi2WO6 heterojunction with a chemically bonded interface was synthesized via a facile one-step solvothermal method. A series of characterization techniques (XRD, XPS, TEM, SEM, EDS etc.) confirmed the existence of a BiOCl–Bi2WO6 interface. The heterojunction yielded a higher photodegradation rate of Rhodamine B under visible light irradiation compared to its individual components. Theoretical studies based on density functional theory calculations indicated that the enhanced photosensitized degradation activity could be attributed to the favorable band offsets across the BiI–O–BiII bonded interface, leading to efficient interfacial charge carrier transfer. Our results reveal the photosensitized mechanism of BiOCl–Bi2WO6 heterojunctions and demonstrate their practical use as visible-light-driven photocatalytic materials.

First-principles calculations based on density functional theory were carried out to explore the interfacial properties of the WO3/BiOCl heterojunction aiming at gaining insights into the roles the interface played in the overall photocatalytic performance. The interfacial effects of the WO3 combination with BiOCl on electronic properties, charge transfer and visible-light response were investigated in detail. The density of states analysis showed that the interfacial structures resulted in a suitable band alignment to separate the excited carriers into two sides of the interface and thus, the electrons–holes recombination could be effectively suppressed. Moreover, excited holes could be readily transferred across the interface from the valence band maximum (VBM) of BiOCl to the VBM of WO3 under visible-light irradiation without being trapped in interfacial mid-gap states.

LaCoO3 perovskite has recently received great attention as a potential alternative to precious metal based NO oxidation catalysts. We report here a comprehensive first-principles study of the NO oxidation kinetics on differently re-constructed hexagonal-phase LaCoO3 facets. Among the 42 low-index facets considered, the (102) LaO-, (104) O2- and (0001) LaO3-terminated facets were found to be thermodynamically stable and likely to be exposed in LaCoO3 oxide nanoparticles. Among these stable facets, the (0001) LaO3-terminated surface is catalytically most active towards NO oxidation, with the reaction proceeding through the mono-vacancy Mars–van Krevelen mechanism. Our study shed light on the atomistic scale NO oxidation mechanism on LaCoO3 facets and can aid further optimization of the catalyst.

Photoelectrochemical water splitting holds great potential for solar energy conversion and storage with zero greenhouse gas emission. Integration of a suitable co-catalyst with an absorber material enables the realization of highly efficient photocleavage of water. Herein, nanostructured hematite film was coated with an ultrathin and conformal CoOx overlayer through atomic layer deposition (ALD). The best performing hybrid hematite with a 2–3 nm ALD CoOx overlayer yielded a remarkable turn on potential of 0.6 VRHE for the water oxidation reaction. Moreover, material analyses revealed that the surface amorphous CoOx/Co(OH)2 component exhibited good optical transparency and hydrophilic properties, which were beneficial for the formation of an ideal hematite/electrolyte interface. In addition to the presence of the CoOx overlayer, a negative shift of flat band potential (VFB) as well as suppression of surface recombination helped to significantly promote the charge separation and collection properties, contributing to the overall solar conversion efficiency. As a result, the external quantum efficiency (IPCE) obtained on hematite increases by 66% at 1.23 VRHE.

A series of mullite SmMn2O5 oxides were prepared by citric acid (CA), hydrothermal (HT) and co-precipitation (CP) and combustion of ethylene glycol and methanol solutions (EG&M) methods, and tested for NOx-assisted soot combustion. The catalyst performance tests were conducted under “loose” contact conditions and the physical and chemical properties characterized by XRD, FTIR, BET, SEM, XPS, and O2-TPD and H2-TPR measurements. The SmMn2O5-EG&M catalyst possessed a distinct morphology with slabs separated by interconnected macropores, and exhibited the overall highest catalytic activity for soot combustion. The corresponding T10, T50, and T90 were 283 °C, 368 °C, and 420 °C, respectively, and the CO2 selectivity was 99.6%. The soot combustion activation energy for the SmMn2O5-EG&M catalyst is 65 kJ mol−1. O2-TPD and H2-TPR measurements demonstrated higher mobility and better reducibility of surface adsorbed oxygen for the EG&M sample. The soot combustion is greatly accelerated by the NO2-assisted mechanism under a NO + O2 atmosphere and further enhanced by the interconnected macropores of the catalyst, facilitating an intimate contact between the soot and the catalyst. Our study reveals that SmMn2O5 mullite is an effective catalyst for NOx-assisted soot combustion.

Density functional theory calculations are performed to study the band offsets at the interface of two photocatalytic materials BiOCl:Bi2WO6. It is found that the W–O bonded interface shows the most stability. An intrinsic interface fails to enhance the charge-carrier separation due to the improper band alignment between these two materials. Sulfur (S) is proposed to replace the bulk oxygen (O) site and thus tune the band edges of BiOCl to enhance the photocatalytic performance of the heterojunction. Furthermore, the presence of S provides an extra charge to generate a clean interface with minimal gap states that also benefits carrier migration across the heterojunction.

A series of LaxSm1−xMn2Oδ (x = 0, 0.1, 0.3, 0.5) catalysts were synthesized through a co-precipitation method. The catalytic activity for NO oxidation was enhanced with La substitution, and the maximum activity was achieved at x = 0.3. XRD and HRTEM results revealed the formation of a multiphase oxide as well as the interface structure between the mullite (SmMn2O5) phase and Mn-rich perovskite (La0.96MnO3.05) phase. The main impact of different La/Sm molar ratios is the amount of surface adsorbed oxygen (Oads) and surface Mn4+ ions as revealed by XPS results. The NO oxidation performance was enhanced through La addition by promoting the decomposition of nitrate/nitrite species and desorption of NO2, improving the reducibility of surface adsorbed oxygen, as determined by H2-TPR, NO + O2-TPRD and in situ DRIFTS studies. Mono-, bi-dentate and bridged nitrates formed on the surface were determined to be the primary reaction intermediates.