Abstract: The principal aim of this work is to study the effect of the processes of sintering and Pd doping of SnO2 gas sensor materials on the conversion of CO to CO2. For this purpose, the gas phase above screen printed sensor material is investigated using FTIR spectroscopy, while surface area, porosity and particle size measurements are performed on the SnO2 powders. During sintering, larger agglomerates of primary particles are formed, which results in a larger conversion degree of CO. The effect of Pd doping of the tin dioxide film on the CO conversion is more pronounced. The transformation of CO starts at a lower temperature and the conversion degree increases remarkably.

Abstract: Hierarchical MoS2@TiO2 heterojunctions were synthesized through a one-step hydrothermal method by using protonic titanate nanosheets as the precursor. The TiO2 nanosheets prevent the aggregation of MoS2 and promote the carrier transfer efficiency, and thus enhance the photocatalytic and electrocatalytic activity of the nanostructured MoS2. The obtained MoS2@TiO2 has significantly enhanced photocatalytic activity in the degradation of rhodamineB (over 5.2times compared with pure MoS2) and acetone (over 2.8times compared with pure MoS2). MoS2@TiO2 is also beneficial for electrocatalytic hydrogen evolution (26times compared with pure MoS2, based on the cathodic current density). This work offers a promising way to prevent the self-aggregation of MoS2 and provides a new insight for the design of heterojunctions for materials with lattice mismatches.

Abstract: Air pollution, especially particulate matter (PM), is an increasingly urgent problem in urban environments, causing both short and long-term health problems, climate interference and aesthetical problems due to building fouling. Photocatalysis has been shown to be a possible solution to that end. In this work two complementary detection methods for photocatalytic soot oxidation are studied and their advantages and disadvantages are discussed. First, a colour-based digital image analysis method is drastically improved towards an accurate, detailed and straightforward detection tool, that enables simultaneous measurement of the degradation of different grades of soot fouling (for instance a shallow soot haze versus condensed soot deposits). In the next part, a second soot oxidation detection method is presented based on in situ FTIR spectroscopy. This method has the additional advantage of providing more insight into the photocatalytic soot degradation process by monitoring both gaseous and adsorbed intermediates as well as reaction products while the reactions are ongoing. As an illustration, the proposed detection strategies were applied on four different commercially available and synthesized photocatalytic materials. The digital image analysis showed that P25 (Evonik) is the fastest photocatalytic soot degrader of all studied materials for both a uniform soot haze as well as concentrated soot spots. Application of the in situ method showed that for all studied materials adsorbed formate-related surface species were formed and that commercially available ZnO nanopowder has the highest specificity towards complete mineralization into CO2. With this we aim to provide a set of complementary experimental tools for the convenient, reliable, realistic and standardised detection of photocatalytic soot degradation.

Abstract: BACKGROUND Laccase is an intensively researched enzyme for industrial use. Except for decolorisation measurements, HPLC analysis is the conventional method for monitoring the phenolic removal during laccase enzyme reaction. This paper reports an investigation of the continuous UV absorbance follow-up of the laccase reaction with steam pretreated poplar hydrolysate. RESULTS Vanillin was used as a model substrate and lignocellulose xylose rich fraction (XRF) as a biologically complex substrate for laccase detoxification. The reaction was followed by HPLC-UV as well as by UV spectrometric measurements. Results suggest that the reaction can be successfully monitored by measuring the change of UV absorbance at 280 nm, without previous compound separation. In case of XRF experiments the spectrophotometric follow-up is especially useful, as HPLC analysis takes a long time and provides less information than in case of single substrates. The method seems to be suitable for optimization and process control. CONCLUSION The obtained results can help to construct a fast, easy and straightforward monitoring system for laccase-phenolic substrate reactions.

Abstract: Diesel soot emissions deteriorate the appearance of architectural building materials by soot fouling. This soot deposition devalue the aesthetic value of the building. A solution to counteract this problem is applying titanium dioxide on building materials. TiO2 can provide air-purifying and self-cleaning properties due to its photocatalytic activity. In literature, photocatalytic soot oxidation is observed on glass or silicon substrates. However, degradation of soot by photocatalysis was not yet investigated on cementitious samples (mortar, concrete) although it is one of the most frequently used building materials. In this study, photocatalytic soot oxidation by means of TiO2 coated cementitious samples is addressed. The soot removal capacity of four types of TiO2 layers, coated on mortar samples, is evaluated by means of two detection methods. The first method is based on colorimetric measurements, while the second method uses digital image processing to calculate the area of soot coverage. The experimental data revealed that cementitious materials coated with commercially available TiO2 exhibited self-cleaning properties as it was found that all coated samples were able to remove soot. The P25 coating gave the best soot degradation performance, while the Eoxolit product showed the slowest soot degradation rate. In addition, gas chromatography measurements in a closed chamber experiment with P25 confirmed that complete mineralization of about 60% of the soot was obtained within 24 hours since CO2 was the sole observed oxidation product. Due to its realistic approach, this study proves that photocatalytic soot removal on TiO2 coated cementitious surfaces is possible in practice, which is an important step towards the practical application of self-cleaning building materials.

Abstract: A plasma-enhanced atomic layer deposition (ALD) process using the Ag(fod)(PEt3) precursor [(triethylphosphine)(6,6,7,7,8,8,8-heptafluoro-2,2-dimethy1-3,5-octanedionate)silver(I)] in combination with NH3-plasma is reported. The steady growth rate of the reported process (0.24 +/- 0.03 nm/cycle) was found to be 6 times larger than that of the previously reported Ag ALD process based on the same precursor in combination with H-2-plasma (0.04 +/- 0.02 nm/cycle). The ALD characteristics of the H-2-plasma and NH3-plasma processes were verified. The deposited Ag films were polycrystalline face-centered cubic Ag for both processes. The film morphology was investigated by ex situ scanning electron microscopy and grazing-incidence small-angle X-ray scattering, and it was found that films grown with the NH3-plasma process exhibit a much higher particle areal density and smaller particle sizes on oxide substrates compared to those deposited using the H-2-plasma process. This control over morphology of the deposited Ag is important for applications in catalysis and plasmonics. While films grown with the H-2-plasma process had oxygen impurities (similar to 9 atom %) in the bulk, the main impurity for the NH3-plasma process was nitrogen (similar to 7 atom %). In situ Fourier transform infrared spectroscopy experiments suggest that these nitrogen impurities are derived from NH surface groups generated during the NH3-plasma, which interact with the precursor molecules during the precursor pulse. We propose that the reaction of these surface groups with the precursor leads to additional deposition of Ag atoms during the precursor pulse compared to the H-2-plasma process, which explains the enhanced growth rate of the NH3-plasma process.

Abstract: Three upscaled multi-tube photocatalytic reactors designed for integration into HVAC (Heating, Ventilation and Air Conditioning) systems were proposed and evaluated using a CFD modelling approach, with emphasis on the flow, irradiation and concentration distribution in the reactor and hence, photocatalytic performance. Based on the obtained insights, the best reactor design was selected, further characterized and improved by an additional proof of concept study and eventually converted into practice. Subsequently, the scaled-up prototype was experimentally tested according to the CEN-EN-16846-1 standard (2017) for volatile organic compound (VOC) removal by an external scientific research center. The combined modelling and experimental approach used in this work, leads to essential insights into the design and assessment of photocatalytic reactors. Therefore, this study provides an essential step towards the optimization and commercialization of photocatalytic reactors for HVAC applications.

Abstract: TiO2-based photocatalysis has become a viable technology in various application fields such as (waste)water purification, photovoltaics/artificial photosynthesis, environmentally friendly organic synthesis and remediation of air pollution. Because of the increasing impact of bad air quality worldwide, this review focuses on the use and optimization of TiO2-based photocatalysts for gas phase applications. Over the past years various specific aspects of TiO2 photocatalysis have been reviewed individually. The intent of this review is to offer a broad tutorial on (recent) trends in TiO2 photocatalyst modification for the intensification of photocatalytic air treatment. After briefly introducing the fundamentals of photocatalysis, TiO2 photocatalyst modification is discussed both on a morphological and an electronic level from the perspective of gas phase applications. The main focus is laid on recent developments, but also possible opportunities to the field. This review is intended as a solid introduction for researchers new to the field, as well as a summarizing update for established investigators. (C) 2015 Elsevier B.V. All rights reserved.

Abstract: The use of fossil-based products induces a large environmental burden. To lighten this burden, green technologies are required that can replace their fossil-based counterparts. To enable the development of economically viable green technologies, an optimization towards both economic and environmental objectives is required. To perform this multi-objective optimization (MOO), the environmental techno-economic assessment (ETEA) methodology is extended towards a MOO-extended ETEA. The development of this MOO-extended ETEA is the main objective of this manuscript. As an example of a green technology, the concept of microalgae biorefineries is used as a case study to illustrate the MOO-extended ETEA. According to the results, all optimal value chains include open pond cultivation, a membrane for medium recycling and spray drying. The optimal economic value chain uses Nannochloropsis sp. in a one-stage cultivation to produce fish larvae feed, while the optimal environmental design uses Dunaliella salina or Haematococcus pluvialis to produce carotenoids and fertilizer or energy products, by means of anaerobic digestion or gasification. The crucial parameters for both environmental and economic feasibility are the content, price and reference impact of the main end product, the growth parameters and the biomass and carotenoid recovery efficiency alongside the different process steps. By identifying the economic and environmentally optimal algal-based value chain and the crucial drivers, the MOO-extended ETEA provides insights on how algae-based value chains can be developed in the most economic and environmentally-friendly way. For example, the inclusion of a medium recycling step to lower the water and salt consumption is required in all Pareto-optimal scenarios. Another major insight is the requirement of high-value products such as carotenoids or specialty food to obtain and economically and environmentally feasible algal-based value chain. Due to the modular nature of the MOO-extended ETEA, multiple processes can be included or excluded from the superstructure. Although this case study is limited to current microalgae biorefinery technologies, the MOO-extended ETEA can also be used to assess the economic and environmental effect of more innovative technologies. This way, the MOO-extended ETEA provides a methodology to assess the economic and environmental potential of innovative green technologies and shorten their time-to-market.

Abstract: In the commercialisation of photocatalytic air purifiers, the performance as well as the cost of the catalytic material plays an important role. Where most comparative studies only regard the photocatalytic activity as a decisive parameter, in this study both activity and cost are taken into account. Using a cost-effectiveness analysis, six different commercially available TiO2-based catalysts are evaluated in terms of their activities in photocatalytic degradation of acetaldehyde as a model reaction for indoor air purification.

Abstract: Bifunctionality is a key feature of many industrial catalysts, supported metal clusters and particles in particular, and the development of such catalysts for the CO2 reduction reaction (CO2RR) to hydrocarbons and alcohols is gaining traction in light of recent advancements in the field. Carbon-supported Cu nanoparticles are suitable candidates for integration in the state-of-the-art reaction interfaces, and here, we propose, synthesize, and evaluate a bifunctional Ni–N-doped-C-supported Cu electrocatalyst, in which the support possesses active sites for selective CO2 conversion to CO and Cu nanoparticles catalyze either the direct CO2 or CO reduction to hydrocarbons. In this work, we introduce the scientific rationale behind the concept, its applicability, and the challenges with regard to the catalyst. From the practical aspect, the deposition of Cu nanoparticles onto carbon black and Ni–N–C supports via an ammonia-driven deposition precipitation method is reported and explored in more detail using X-ray diffraction, thermogravimetric analysis, and hydrogen temperature-programmed reduction. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and energy-dispersive X-ray spectroscopy (EDXS) give further evidence of the presence of Cu-containing nanoparticles on the Ni–N–C supports while revealing an additional relationship between the nanoparticle’s composition and the electrode’s electrocatalytic performance. Compared to the benchmark carbon black-supported Cu catalysts, Ni–N–C-supported Cu delivers up to a 2-fold increase in the partial C2H4 current density at −1.05 VRHE (C1/C2 = 0.67) and a concomitant 10-fold increase of the CO partial current density. The enhanced ethylene production metrics, obtained by virtue of the higher intrinsic activity of the Ni–N–C support, point out toward a synergistic action between the two catalytic functionalities.

Abstract: Dislocations are always observed during crystal growth, and it is usually desirable to reduce the dislocation density in high-quality crystals. Here, the annihilation process of the 30 degrees Shockley partial dislocation pairs in CdTe is studied by first-principles calculations. We found that the dislocations can glide relatively easily due to the weak local bonding. Our systematic study of the slipping mechanism of the dislocations suggests that the energy barrier for the annihilation process is low. Band structure calculations reveal that the band bending caused by the charge transfer between the two dislocation cores depends on the core-core distance. A simple linear model is proposed to describe the mechanism of formation of the dislocation pair. More importantly, we demonstrate that hole injection can affect the core structure, increase the mobility, and eventually trigger a spontaneous mutual annihilation, which could be employed as a possible facile way to reduce the dislocation density.

Abstract: Rapid development of experimental techniques has enabled real time studies of solid gas reactions at the level reaching the atomic scale. In the present paper, we focus on a combination of atomic resolution STEM/EDX, which visualizes the reaction zone, and near ambient pressure (NAP) XPS, which collects information for a surface layer of variable thickness under reaction conditions. We compare the behavior of two affined topological insulators, Bi2Te3 and Sb2Te3. We used a simple reaction with molecular oxygen occurring at 298 K, which is of practical importance to avoid material degradation. Despite certain limitations, a combination of in situ XPS and ex situ cross-sectional STEM/EDX allowed us to obtain a self-consistent picture of the solid gas reaction mechanism for oxidation of Sb2Te3 and Bi2Te3 crystals, which includes component redistribution between the oxide and the subsurface layer and Te segregation with formation of a thin ordered layer at the interface. The process is multistep in case of both compounds. At the very beginning of the oxidation process the reactivity is determined by the energy benefit of the corresponding element oxygen bond formation. Further in the oxidation process, the behavior of these two compounds becomes similar and features component redistribution between the oxide and the subsurface layer.

Abstract: Plasma-treated liquids have great potential for biomedical applications. However, insight into the underlying mechanisms and the exact chemistry is still scarce. In this study, we present the combination of a 0D chemical kinetics and a 2D fluid dynamics model to investigate the plasma treatment of a buffered water solution with the kINPen (R) plasma jet. Using this model, we calculated the gas and liquid flow profiles and the transport and chemistry of all species in the gas and the liquid phase. Moreover, we evaluated the stability of the reactive oxygen and nitrogen species after plasma treatment. We found that of all species, only H2O2, HNO2/NO2-, and HNO3/NO3- are stable in the buffered solution after plasma treatment. This is because both their production and loss processes in the liquid phase are dependent on short-lived radicals (e.g. OH, NO, and NO2). Apart from some discrepancy in the absolute values of the concentrations, which can be explained by the model, all general trends and observations in our model are in qualitative agreement with experimental data and literature.

Abstract: Layered Li-rich/Mn-rich NMC (LMR-NMC) is characterized by high initial specific capacities of more than 250 mA h g(-1), lower cost due to a lower Co content and higher thermal stability than LiCoO2. However, its commercialisation is currently still hampered by significant voltage fade, which is caused by irreversible transition metal ion migration to emptied Li positionsviatetrahedral interstices upon electrochemical cycling. This structural change is strongly correlated with anionic redox chemistry of the oxygen sublattice and has a detrimental effect on electrochemical performance. In a fully charged state, up to 4.8 Vvs.Li/Li+, Mn4+ is prone to migrate to the Li layer. The replacement of Mn4+ for an isovalent cation such as Sn4+ which does not tend to adopt tetrahedral coordination and shows a higher metal-oxygen bond strength is considered to be a viable strategy to stabilize the layered structure upon extended electrochemical cycling, hereby decreasing voltage fade. The influence of Sn4+ on the voltage fade in partially charged LMR-NMC is not yet reported in the literature, and therefore, we have investigated the structure and the corresponding electrochemical properties of LMR-NMC with different Sn concentrations. We determined the substitution limit of Sn4+ in Li1.2Ni0.13Co0.13Mn0.54-xSnxO2 by powder X-ray diffraction and transmission electron microscopy to be x approximate to 0.045. The limited solubility of Sn is subsequently confirmed by density functional theory calculations. Voltage fade for x= 0 andx= 0.027 has been comparatively assessed within the 3.00 V-4.55 V (vs.Li/Li+) potential window, from which it is concluded that replacing Mn4+ by Sn4+ cannot be considered as a viable strategy to inhibit voltage fade within this window, at least with the given restricted doping level.