Biochars are increasingly used as soil amendment and for C sequestration in soils. The influence of feedstock differences and pyrolysis temperature on biochar characteristics has been widely studied. However, there is a lack of knowledge about the formation of potentially toxic compounds that remain in the biochars after pyrolysis. We investigated biochars from three feedstocks (wheat straw, poplar wood, and spruce wood) that were slowly pyrolyzed at 400, 460, and 525°C for 5 h (straw) and 10 h (woodchips), respectively. We characterized the biochars' pH, electrical conductivity, elemental composition (by dry combustion and X-ray fluorescence), surface area (by N adsorption), water-extractable major elements, and cation exchange capacity (CEC). We further conducted differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffractometry to obtain information on the biochars' molecular characteristics and mineralogical composition. We investigated trace metal content, total polycyclic aromatic hydrocarbon (PAH) content, and PAH composition in the biochars. The highest salt (4.92 mS cm) and ash (12.7%) contents were found in straw-derived biochars. The H/C ratios of biochars with highest treatment temperature (HTT) 525°C were 0.46 to 0.40. Surface areas were low but increased (1.8-56 m g) with increasing HTT, whereas CEC decreased (162-52 mmol kg) with increasing HTT. The results of DSC and FTIR suggested a loss of labile, aliphatic compounds during pyrolysis and the formation of more recalcitrant, aromatic constituents. X-ray diffractometry patterns indicated a mineralogical restructuring of biochars with increasing HTT. Water-extractable major and trace elements varied considerably with feedstock composition, with trace elements also affected by HTT. Total PAH contents (sum of EPA 16 PAHs) were highly variable with values up to 33.7 mg kg; irrespective of feedstock type, the composition of PAHs showed increasing dominance of naphthalene with increasing HTT. The results demonstrate that biochars are highly heterogeneous materials that, depending on feedstock and HTT, may be suitable for soil application by contributing to the nutrient status and adding recalcitrant C to the soil but also potentially pose ecotoxicological challenges.

In this paper, indium-doped zinc oxide (IZO) films were grown by spray pyrolysis, using zinc acetate and indium acetylacetonate precursors. The focus was on developing a solution recipe based on water as solvent, with only minor acetic acid content, as well as keeping the substrate temperature as low as possible-at 360°C. The process is therefore environment friendly and energy efficient. Despite the challenging conditions, the resulting IZO films were highly transparent and conductive. Their texture deviates strongly from the (002) texture of ZnO and depends on the indium content, which also influences the resistivity. The latter attains its minimum for an indium concentration of 4 at.% in the solution and decreases for increasing film thickness, reaching the value of (5.0 ± 0.1) 9 10 -3 X cm, mainly due to the increase in carrier mobility. The stability of the resistivity after high dose of UV irradiation was found to increase with the carrier density and the film thickness. Thick, highly doped films show minimal resistivity modification even after a total dose of 12.1 kJ/cm 2 UVA/ UVB irradiation. Finally, to demonstrate its applicability in devices, the IZO electrode was used for the fabrication of a lead-perovskite absorber solar cell, yielding an energy conversion efficiency of 6% and 910 mV open-circuit voltage.

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A comparative study is presented on chemical bath-deposited ZnO films, doped with the group-13 metals Al, Ga and In. The study reveals marked differences in dopant incorporation in the films, which increases in the order: In, Al and Ga. The presence of dopant in the solution induces significant modifications in the deposition rate, which varies between 110 and 40 nm min -1 . All films are (002)-textured, whereas the lattice stress evolution with the dopant type and concentration suggests that Ga has the highest degree of substitutional incorporation in Zn sites. The average visible transmittance is higher than 80%, while the infrared reflectivity depends on the free carrier density in the films, which is the lowest for undoped ZnO and increases in the order: In-, Al-and Ga-doped ZnO. Optical measurements also yield an inverse correlation between carrier density and mobility. Doping enlarges the bandgap, as well as the Urbach energy that is related to the films' disorder. The lowest electrical resistivity, measured by fourpoint probe, is 1.7 9 10 -2 X cm and is obtained for In-doped films after being exposed to ultraviolet light. Ga-doped films are found to exhibit the highest stability of the conductivity upon ultraviolet exposure.

Silicon is a promising candidate for anodes in lithium-ion batteries (LIB) due to its high theoretical capacity. However, Si has low electrical conductivity (theoretical: 6.7 x 10 -4 S cm -1 ). Proper conductive additive is needed in order to improve the electrical conductivity of Si-based anodes. Here we focus on applying two commercial conductive addictives: graphite and carbon black Super C65 for silicon-mesoporous carbon (Si/MC) composite anodes. The structure and morphology of the electrodes were characterized by nitrogen adsorption, scanning electron microscopy (SEM), and focus ion beam/transmission electron microscopy (FIB/TEM). Furthermore, the electrochemical performance of the electrodes was characterized by cyclic voltammetry, galvanostatic charge/discharge tests, and impedance spectroscopy. In principles, our work could be effective for the choice of conductive additives to improve the electrical performance of Si/MC anodes.