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Recent reports post conflicting results on the atmospheric stability of Cs2TiBr6, a nontoxic, Earth-abundant solar energy conversion material. Here, a high-temperature melt of CsBr and TiBr4 yielde...

Covalently attached perylene monolayers serve as back contacts for Sb2S3 photoelectrochemical cells with a thianthrene+/0 front, rectifying contact. Covalent attachment of perylenetetracarboxylic dianhydride, PTCDA, to Si(111) utilizes an anhydride-to-imide conversion at surface-attached amines. For Sb2S3 solar absorbers, we hypothesized that a terminal thioperylene anhydride, i.e., S=C-O-C=S, formed from thionation of the terminal perylene anhydride would serve as a soft, electron-selective and hole-blocking back contact. We explored several routes to convert carbonyls to thiocarbonyls on surface-attached perylene anhydrides including Lawesson's reagent, P4S10, and a P4S10-pyridine complex. Here, P4S10 in toluene yielded the highest conversion as quantified by thioperylene-anhydride-S-to-imide-N ratios in X-ray photoelectron spectroscopy (XPS). Spectra demonstrated minimal residual reagent as determined by the absence of quantifiable phosphorus following sonication and rinsing. Photoelectrochemistry yielded an average |V oc| = 840 ± 90 mV with the highest value of 952 mV under ELH-simulated AM1.5G illumination for chemical-bath-deposited Sb2S3 in the strongly oxidizing thianthrene+/0 redox couple when thioperylene-anhydride-tethered surfaces formed the back contact. Sb2S3 absorbers in which perylene anhydride, esters, thionoesters, and thiols form the back contact yielded significantly decreased |V oc| magnitudes vs Sb2S3 on perylene-thioanhydride-terminated surfaces. We attribute the large V oc to the combination of favorable sulfur-functionalized surfaces for deposition, charge transfer properties of the perylene layer, and use of the thianthrene+/0 redox couple.

Hydrochar, as an energy-lean solid waste, is generated from an advanced biofuel conversion technique hydrothermal liquefaction (HTL) and always leads to environmental pollution without appropriate disposal. In this study, HTL-derived hydrochar is recycled and prepared as adsorbent used for Pb(Ⅱ) removal from wastewater. As the original porous structure of hydrochar is masked by oily volatiles remained after HTL, two types of oil-removal pretreatment (Soxhlet extraction and CO2 activation) are explored. The result shows that CO2 activation significantly enhances the adsorption capacity of Pb(Ⅱ), and the maximum adsorption capacity is 12.88 mg g−1, as evaluated using Langmuir adsorption model. Further, apart from oily volatiles, most inorganic compounds derived from wastewater-grown algae is enriched in hydrochar, causing a smaller surface area of hydrochar. An ash-removal alkali treatment following CO2 activation is introduced to dramatically increase the adsorption capacity to 25.00 mg g−1 with an extremely low Pb(II) equilibrium concentration of 5.1×10-4 mg L−1, which is much lower than the maximum level of Pb concentration in drinking water (set by World Health Organization). This work introduces an approach to reuse HTL-hydrochar as an inexpensive adsorbent in Pb-contaminated water treatment, which not only provides another possible renewable adsorbent candidate applied in the field of lead adsorption, but also finds an alternative route to reduce solid waste effluent from HTL process., Graphical abstract Image, graphical abstract

To bridge the gap between the cleanliness of a freshly cleaved surface of 2D BiOI and that available from a purely chemical-etching means, we subjected single-crystal BiOI to a series of surface treatments and quantified the resulting chemical states and electronic properties. Vapor transport syntheses included both physical vapor transport from single-source BiOI, as well as chemical vapor transport from Bi2O3 + BiI3 and from Bi + I2 + Bi2O3. Surface treatments included tape cleaving, rinsing in water, sonication in acetone, an aqueous HF etch, and a sequential HF etch with subsequent sonication in acetone. X-ray diffraction, XRD, and X-ray photoelectron spectroscopy, XPS, probed the resulting bulk crystalline species and interfacial chemical states, respectively. In comparison with overlayer models of idealized oxide-terminated or iodide-terminated BiOI, angle-resolved XPS elucidated surface terminations as a function of each treatment. Ultraviolet photoelectron spectroscopy, UPS, established work-function, and Fermi-level energies for each treatment. Data reveal that HF etching yields interfacial BiI3 at BiOI steps that is subsequently removed with acetone sonication. UPS establishes n-type behavior for the vapor-transport-synthesized BiOI, and surface work function and Fermi level shifts for each chemical treatment under study. We discuss the implications for processing BiOI nanofilms for energy-conversion applications.

The interfacial robustness of perovskite solar cells (PSCs) is important due to the potential for failure resulting from applied loads or deformation in devices that are fabricated on rigid or flexible substrates, and/or residual stresses due to thermal expansion mismatch between layers. Since these can occur across any of the interfaces within typical hybrid organic–inorganic perovskite solar cells, we explore the mechanisms of interfacial fracture between the layered structures of model hybrid organic–inorganic perovskite solar cells. Brazil disk interfacial fracture specimens enable studies of the mode-mixity dependence of interfacial fracture toughness for each interface. The robustness of interfaces is studied across a range of mode mixities between pure mode I and pure mode II. A combination of optical and scanning electron microscopy further elucidates the underlying crack/microstructure interactions and fracture modes. These reveal crack-tip shielding due to crack bridging and microcracking, which were modeled using a zone shielding model to predict the mode-mixity dependence of the interfacial fracture toughness values. We discuss the implications for the development of hybrid organic–inorganic perovskite solar cells with robust interfaces for scalable deployment of photovoltaics.

Incorporation of cesium (Cs) into the perovskite layer has become a good strategy to boost the stability and power conversion efficiency (PCE) of perovskite solar cells (PSCs). However, a suitable and scalable method of Cs incorporation in a perovskite film that does not cause a significant increase in the optical bandgap is needed. In this paper, we introduce a thin layer of CsBr into a formamidinium (FA)-rich mixed halide perovskite film using the thermal evaporation technique. The effects of the thickness of the CsBr layer on the microstructural, structural, and optoelectronic properties and surface chemical states of the perovskite film are then studied. The results indicate that the CsBr layer thickness is able to tune the microstructural and optoelectronic properties of the perovskite film. Planar PSCs fabricated with different thicknesses of CsBr layers in the perovskite absorber exhibited different photovoltaic performance characteristics. The CsBr-modified PSC device with a 50 nm layer of CsBr in the perovskite layer showed a better PCE of 16.19% ± 0.17%, which was about 15% higher than that of the control device, and was able to retain nearly 70% of its initial PCE value after 120 days of storage in an unencapsulated state.

In this work steam methane reforming (SMR) was carried in a palladium-based membrane reactor and its performance was evaluated in terms of methane conversion, hydrogen recovery, hydrogen purity, and CO and CO2 selectivity. The membrane reactor was found to produce ultrahigh purity hydrogen with methane conversions as high as 40% at moderate operating conditions and in the absence of sweep gas. Permeation tests using pure hydrogen and inert gases indicate that the membrane reactor is highly selective toward hydrogen. The SMR reactions were performed at 673 K and operating pressures ranging from 100 to 400 kPa. A gas hourly space velocity of 2,600 hr-1 and a steam-to-carbon ratio of 3.5 were used. Methane conversion increased from approximately 23% at 100 kPa to 42% at 400 kPa while a maximum hydrogen recovery value of 43% was achieved at 400 kPa. Furthermore, the purity of the recovered hydrogen was >99.999%. The carbon capture experiments performed in this work consist of dehydrating the retentate stream and redirecting it to a zeolite 13X packed bed before analyzing the stream via mass spectrometry. The carbon capture studies reveal that approximately 5.96 mmol CO2 (262.25 mg of CO2) can be captured per gram of 13X. This value indicates that approximately 80% of the produced CO2 via the SMR, can be captured before the sorbent bed is completely saturated. SEM-EDS, XRD, and XPS techniques were used to characterize the crystal structure and morphology of the membrane surface. These studies reveal that the surface of the membrane underwent significant oxidation during the SMR reaction. This oxidation is only limited to a few nanometers within the top surface of the palladium.

Hydrochar produced from hydrothermal liquefaction of wastewater-treatment algae has been used as an adsorbent to remove lead(II) from the contaminated water body. The lead-adsorbed hydrochar, that is, a spent adsorbent, is recycled as a carbonaceous anode material prepared for lithium ion batteries. A one-step alkali treatment effectively enhances the electrochemical performance of the adsorbent. After lead adsorption, the spent adsorbent shows high reversible capacity (358 mA h g−1 at 0.1 A g−1 after 100 cycles) and rate capability (383, 312, 261, 214, 175, and 135 mA h g−1 at 0.1, 0.2, 0.4, 0.8, 1.6, and 3.2 A g−1, respectively) as a high-performance carbonaceous anode material. Our work presents a promising strategy to reutilize the spent adsorbent generated from wastewater treatment process as a low-cost and green anode material. Such a waste-to-wealth application could effectively reduce the environmental burden, as well as providing a viable option for transforming heavy metal–enriched carbon waste into high–value-added material, which meanwhile helps to fulfill a growing demand on the electrochemical energy storage devices.