Amount Of H2 Research Articles

Effective H2O2-Free photo-Fenton processes over ZnSe nanosheets for photocatalytic degradation of dyes and antibiotics

BackgroundTraditional Fenton process depends on adding additional H2O2, which is mainly produced by anthraquinone process involving large amounts of harmful organic solvents and H2, making a secondary pollution. In-situ photocatalytic generation of H2O2 for Fenton-degradation is a promising way to remove pollutants. MethodsZnSe nanosheets was obtained via a simple one-step solvothermal method using diethylenetriamine, hydrazine hydrate and water as reaction medium. Significant FindingsZnSe tends to produce H2O2 under 300 W Xenon light irradiation, which then participates in Fenton reaction with the assistance of Fe2+ to generate active hydroxyl radical for degradation of dyes and antibiotics, leading to the photocatalytic H2O2 evolution rate decreases from 241 μmol·L − 1·h − 1 in pure water to 190 μmol·L − 1·h − 1 in Fe2+-contained solution. The photo-Fenton degradation rate of Methylene blue (MB), Tetracycline hydrochloride (TCH), Ciprofloxacin (CIP) is better than those of corresponding photocatalytic process and Fenton process alone, this is mainly attributed to the continuous generation and activation of H2O2 in the presence of ZnSe and Fe2+based on a series of trapping experiments and related analysis. Besides, ZnSe also displays excellent stability and hydrophilicity in Fe2+-contained solution, which is benefit to the contact of catalyst and pollutants. Further investigation shows the kinetic of photo-Fenton degradation over ZnSe follows the pseudo-first-order kinetic.

Syngas production via chemical looping reforming using methane-based feed and NiO/Al2O3 oxygen carrier

Syngas production based on chemical looping reforming was experimentally studied using a fixed-bead reactor. The 15 wt% NiO/Al2O3 was used as the oxygen carrier. The reaction temperature was fixed as 800 °C. For reactant containing CH4 only, it was termed as chemical looping partial oxidation of methane (CL-POM). With five CL-POM cycles, no decay in oxygen carrier activity was found. A high H2/CO ratio resulted due to dominant H2 production reactions in the reduction stage. Carbon deposition on the oxygen carrier surface can be identified from the CO and CO2 formations in the oxidation stage. With CO2 added in the reactant in addition to CH4, this was referred to as the chemical looping dry reforming of methane (CL-DRM). Near theoretical amounts of H2 and CO yields were obtained. With both H2O and CO2 added in the reactant in addition to CH4, this was referred to as the chemical looping tri-reforming of methane (CL-TRM). Due to coupled steam reforming of methane (SRM), POM, and DRM, higher CH4 conversion, H2 and CO yields resulted compared with the CL-POM and CL-DRM cases. The average H2/CO ratio of 1.2 was obtained with reactant with molar ratio of CH4/CO2/H2O = 1/1/1.

Numerical study on propagation and NO reduction behavior of laminar stratified ammonia/air flames

In recently developed ammonia combustion technologies such as swirl flow and staged combustion, locally rich or lean pockets of unburned mixtures may occur due to insufficient mixing. This results in a premixed flamelet propagating into a gradually leaner or richer mixture. The present study aims to numerically investigate the propagation of laminar ammonia/air premixed flames in compositionally stratified mixtures. Results indicate that the flame speed in a rich-to-lean stratified mixture is increased from that in corresponding homogeneous mixtures at each local equivalence ratio. In contrast, the stratified flame speed is decreased in a lean-to-rich stratified mixture. The response of the stratified flame speed is attributed to variation in the amount of H2 in the burned gas. In the rich-to-lean stratified flame, an extra amount of H2 diffuses into the reaction zone to enhance chain-branching reactions which produce H radicals. The increased H radicals then promote dehydration reactions, resulting in an increased fuel consumption rate. In the lean-to-rich stratified flame, the opposite process takes place. The above mechanism is similar to the so-called back-support effect observed in methane/air stratified flames. Meanwhile, in both rich-to-lean and lean-to-rich stratified flames, additional NO reduction occurs in the stoichiometric region of the burned gas. This is facilitated by unburned ammonia diffusing from the neighboring rich burned gas mixing with O/H radicals diffusing from the neighboring lean burned gas, resulting in a production of extra NHi radicals which readily reduce NO. Therefore, NO emission in stratified flames is expected to be lower than that estimated from the emission characteristics in homogeneous mixtures. Although similar to the well-known thermal DeNOx mechanism, the current NO reduction process occurs under a much higher temperature due to the abundance of radical species. A similar phenomenon is expected to be observed in a triple flame configuration, which requires future investigations.

Enhancing Hydrogen Storage Capacity of Pd Nanoparticles by Sandwiching between Inorganic Nanosheets

AbstractH2 is regarded to play a crucial role in the transition from a fossil fuel‐based energy economy towards an environmentally friendly one. However, storage of H2 is still challenging, but palladium (Pd) based materials show exciting properties. Therefore, nanoparticulate Pd has been intensely studied for hydrogen storage in the past years. Here, we stabilize Pd nanoparticles by intercalation between inorganic nanosheets of hectorite (NaHec). Compared to nanoparticles stabilized by the polymer polyvinylpyrrolidone (PVP), the H2 storage capacity was found to be 86 % higher for identical Pd nanoparticles being intercalated between nanosheets. We attribute this remarkably enhanced H2 storage capacity to the partial oxidation of Pd, as evidenced by X‐ray photoelectron spectroscopy (XPS). The higher amount of holes in the 4d band leads to a higher amount of H2 that can be absorbed when Pd is stabilized between the nanosheets of hectorite compared to the PVP stabilized nanoparticles.

Direct conversion of almond waste into value-added liquids using carbon-neutral catalysts: Hydrothermal hydrogenation of almond hulls over a Ru/CNF catalyst

The almond industry leaves behind substantial amounts of by-products, with almond hulls being the primary residue generated. Given that one way to improve food security is by decreasing waste to reduce environmental impacts, developing sustainable processes to manage this by-product is necessary. Herein, we report on the hydrothermal hydrogenation of almond hulls over a carbon-neutral Ru supported on carbon nanofibres (Ru/CNF) catalyst, addressing the temperature, H2 pressure, time and catalyst loading. These variables controlled the distribution of the reaction products: gas (0–5%), liquid (49–82%) and solid (13–51%), and ruled the composition of the liquid effluent. This aqueous fraction comprised oligomers (46–81 wt%), saccharides (2–7 wt%), sugar alcohols (2–15 wt%), polyhydric alcohols (1–8 wt%) and carboxylic acids (7–31 wt%). The temperature and reaction time influenced the extension of hydrolysis, depolymerisation, deamination, hydrolysis, hydrogenation and dehydration reactions. Additionally, the initial H2 pressure and catalyst loading kinetically promoted these transformations, whose extensions were ruled by the amount of H2 effectively dissolved in the reaction medium and the prevalence of hydrogenations over dehydration/decarboxylation reactions or vice versa depending on the catalyst loading.Process optimisation revealed that it is feasible to convert up to 67% of almond hulls into merchantable oligomers at 230 °C, 35 bar initial H2, using 1 g catalyst/g biomass (0.4 g Ru/g biomass) for 360 min. Additionally, decreasing the temperature to 187 °C without modifying the other parameters could convert this material into oligomers (31 wt%) and small oxygenates (17 wt% carboxylic acids, 11 wt% sugar alcohols and 6 wt% polyhydric alcohols) concurrently. The theoretical energy assessment revealed that the total and partial combustion of the spent solid material could provide the required energy for the process and allow catalyst recovery and reutilisation. This environmental friendliness and holistic features exemplify a landmark step-change to valorising unavoidable food waste.

Effect of activation conditions and iron loading content on the catalytic cracking of toluene by biochar

Biochar (BC) is a catalyst carrier with a porous structure and low production cost. Herein, a Fe-loaded BC catalyst was prepared by impregnation and calcination, and use toluene to determine the removal efficiency of the catalyst. When the Fe impregnation solution mass fraction was 4%, the removal efficiency for the Fe-loaded BC catalyst was 94.1%. The amount of H2 produced by toluene catalysis is 963.22 ml, which is about three times the total amount of H2 produced by toluene self-pyrolysis and catalyst self-gasification. The effects of steam activation conditions and Fe impregnation mass fraction on the microstructure of BC were studied. The results show that the activation temperature and time can increase the BET surface area. A high concentration of steam volume and impregnation solution decreases the BET surface area. The characterizations of the catalyst before and after the toluene removal experiment shows that C–O bond plays a vital role in the removal process and micropores of BC preferentially adsorb toluene. The adsorption mechanism on BC mainly depends on n–π interaction and pore filling. The electrostatic attraction and π–π interaction on Fe-loaded BC were enhanced. Loading treatment introduces lattice oxygen and leads to increased oxygen vacancies.

TiN–LiAlSiO4 powders for hydrogen production under simulated solar light and their relationship between photocatalytic activity and the coefficient of thermal expansion

In the present work, it is reported the synergy effect from TiN with LiAlSiO4 powders for hydrogen production under simulated solar light. TiN–LiAlSiO4 composites were synthesized by solid-state reaction. XRD results showed that conditions of the preparation of the composite did not cause any variation on the crystal structure of materials. By SEM analysis, composites presented a homogeneous distribution of the TiN and LiAlSiO4 particles with similar morphology to TiN or LiAlSiO4, depending on their content in the mixture. Energy band-gap values are within the interval of 2.0 and 3.5 eV, where the presence of TiN in a proportion greater than 30% caused that composite showed Eg values lower than 3.0 eV, which could be favorable for their potential application in photocatalysis under solar light. All samples showed specific surface area close to 2.0 m2/g. TiN–LiAlSiO4 composites presented higher photocatalytic activity than TiN and LiAlSiO4, which is occasioned by synergy effect from, n-type, and p-type semiconductors, respectively. The photocatalytic activity is greater in composites with a major proportion of TiN than those where TiN is less than 50%. TiN–LiAlSiO4 (T60:L40) showed the highest activity, around 306 μmol H2, after 3 h. This activity was corroborated by PL analysis where composite with more than 50% of TiN, presented less intensity in the spectra, indicating that a reduction electron-hole pair recombination rate is occurring during the irradiation. Furthermore, it was found that there is a relation between the coefficient of thermal expansion (CTE) and photocatalytic hydrogen production. Composites with positive thermal expansion (PTE) showed a higher amount of H2 than composites with negative thermal expansion (NTE). Coincidentally, T60:L40 shows the highest activity, but also it is the one that presents the CTE value closest to zero.

A Snowball in Hell: The Potential Steam Atmosphere of TOI-1266c

Abstract TOI-1266c is a recently discovered super-Venus in the radius valley orbiting an early M dwarf. However, its notional bulk density (∼2.2 g cm−3) is consistent with a large volatile fraction, suggesting that it might have volatile reservoirs that have survived billions of years at more than twice Earth’s insolation. On the other hand, the upper mass limit paints a picture of a cool super-Mercury dominated by >50% iron core (∼9.2 g cm−3) that has tiptoed up to the collisional stripping limit and into the radius gap. Here we examine several hypothetical states for TOI-1266c using a combination of new and updated open-source atmospheric escape, radiative−convective, and photochemical models. We find that water-rich atmospheres with trace amounts of H2 and CO2 are potentially detectable (S/N > ∼ 5) in less than 20 hr of James Webb Space Telescope (JWST) observing time. We also find that water vapor spectral features are not substantially impacted by the presence of high-altitude water or ice clouds owing to the presence of a significant amount of water above the cloud deck, although further work with self-consistent cloud models is needed. Regardless of its mass, however, TOI-1266c represents a unique proving ground for several hypotheses related to the evolution of sub-Neptunes and Venus-like worlds, particularly those near the radius valley.

Cavography with hydrogen peroxide. Accidental injection of hydrogen peroxide into the inferior vena cava

Contrast cavography during removal of a vena cava filter in patients treated via thrombectomy for pulmonary embolism is a widely performed procedure, which may involve potentially serious complications if the human factor fails. Accidental injection of hydrogen peroxide (H2O2) after mistaking it for contrast material can have fatal consequences. We present the case of a patient who was accidentally injected with a high quantity of hydrogen peroxide. The preparation of a preoperative checklist, the amount of H2 02 injected and the operator’s skill in aspirating the substance are decisive factors in avoiding such complications.

General and Efficient C–P Bond Formation by Quantum Dots and Visible Light

General and Efficient C–P Bond Formation by Quantum Dots and Visible Light

A novel sludge pyrolysis and biomass gasification integrated method to enhance hydrogen-rich gas generation

A novel sludge pyrolysis and biomass gasification (SPBG) integrated method is proposed to facilitate the efficient utilization of sludge and biomass. The transformation of gas, especially hydrogen, and the migration of N in SPBG were investigated. The H2 proportion increased by 6.22 vol% due to the involvement of sludge steam (S-steam) and sludge volatiles (S-volatiles). S-steam was beneficial to gasification, reforming, and the water–gas shift (WGS) reaction of biomass, which was conducive to hydrogen production. Moreover, in the gasification stage, S-volatiles were heated and then cracked to form gases and free radicals. The latter changed the original system to facilitate dehydrogenization with condensation and the formation of new functional groups. In the range of 30–70%, when the moisture content of the wet sludge was 50%, a relatively higher amount of H2 and a higher calorific value were obtained. To further enhance hydrogen production, a modified calcium-based additive (MCA) was added. At 800 °C, the addition of MCA promoted steam reforming and the WGS reaction, resulting in a higher H2 concentration of 268.31 mL/g (based on dehydrated feeding including sludge volatiles and biomass). Nitrogen-containing functional groups such as amines, N-PAH, and nitriles from tar also decreased after the addition of MCA.

Nature and evolution of the ore‐forming fluids in the Shazhou volcanic‐related hydrothermal uranium deposit, Xiangshan ore field, SE China

The Xiangshan uranium (U) ore field in South‐east China has been recognized as the largest volcanic‐related hydrothermal U deposit in China since its discovery in the 1950s. The U mineralization at Xiangshan is mostly hosted in felsic volcanic and sub‐volcanic rocks and occurs mainly in veins, which are controlled by high‐angle normal faults in association with haematite, quartz, fluorite, apatite, and pyrite. Likewise, diverse hydrothermal alterations such as haematitization, silicification, fluoritization, and illitization have been identified adjacent to the ore‐bearing faults and outward for tens to hundreds of metres into the volcanic rocks. Situated to the west in the Xiangshan ore field, the Shazhou deposit is the second‐largest U deposit in the Xiangshan volcanic basin. Based on geological field evidence and petrographic observations, the ore‐forming fluids in the Shazhou U deposit can be classified and separated into three stages (early, main, and late): (a) fluids associated with the early mineralization stage are characterized by the oxidizing feature with U‐O hydroxide complexes as the dominant species; (b) fluids from the main mineralization stage were reducing fluids with black–purple fluorite and sulphide complexes of U‐Ti‐O; and (c) fluids from the late‐stage were weakly oxidizing fluids with light purple fluorite and light red calcite complexes of U‐O as the dominant species in the fluid. Fluid inclusions in alteration minerals from the main and late mineralization stage recorded homogenization temperatures (Th) of 280–340°C and 200–260°C, with salinities of 5–17 and 6–10% NaCleqv, respectively. Ore‐forming fluids contain variable amounts of CO2, O2, and H2, in which the volatile content in the main mineralization stage is higher than that in the late stage. The temperature and salinity of the ore‐forming fluids were fluctuating and gradually decreased as the geologic history of the deposit progressed. The δDW‐SMOW values calculated for the ore‐forming fluids range from −97.4 to −65.1‰. The δ18O values of syn‐ore quartz occur mainly between 5.9 and 15.7‰; calculated δ18OW‐SMOW values are between −1.5 and +8.3‰. The δ34SCDT values of syn‐ore pyrite and galena range from 9.7 to 19.7‰. The ore‐forming fluids in the Shazhou U deposit are derived from different sources with a complex geological evolution history. The ore‐forming fluids from the early mineralization stage with high O2 contents may have been primarily derived from post‐volcanic hydrothermal activity. Subsequently, fluids from the main mineralization stage (with lower O2 and high H2 contents) might have originated from the deep‐sourced fluids, where sulphur was carried from the metamorphic basement. Finally, ore‐forming fluids from the late mineralization stage could have been produced by mixing meteoric hydrothermal fluids. Large‐scale fluid immiscibility and boiling occurred during the main mineralization stage, followed by fluid mixing during the late mineralization stage. Boiling and mixing of fluids were the two dominant mechanisms for the deposition of U in the Shazhou deposit.

Molecular Photocatalytic Water Splitting by Mimicking Photosystems I and II.

In nature, water is oxidized by plastoquinone to evolve O2 and form plastoquinol in Photosystem II (PSII), whereas NADP+ is reduced by plastoquinol to produce NADPH and regenerate plastoquinone in Photosystem I (PSI), using homogeneous molecular photocatalysts. However, water splitting to evolve H2 and O2 in a 2:1 stoichiometric ratio has yet to be achieved using homogeneous molecular photocatalysts, remaining as one of the biggest challenges in science. Herein, we demonstrate overall water splitting to evolve H2 and O2 in a 2:1 ratio using a two liquid membranes system composed of two toluene phases, which are separated by a solvent mixture of water and trifluoroethanol (H2O/TFE, 3:1 v/v), with a glass membrane to combine PSI and PSII molecular models. A PSII model contains plastoquinone analogs [p-benzoquinone derivatives (X-Q)] in toluene and an iron(II) complex as a molecular oxidation catalyst in H2O/TFE (3:1 v/v), which evolves a stoichiometric amount of O2 and forms plastoquinol analogs (X-QH2) under photoirradiation. On the other hand, a PSI model contains nothing in toluene but contains X-QH2, 9-mesityl-10-methylacridinium ion (Acr+-Mes) as a photocatalyst, and a cobalt(III) complex as an H2 evolution catalyst in H2O/TFE (3:1 v/v), which evolves a stoichiometric amount of H2 and forms X-Q under photoirradiation. When a PSII model system is combined with a PSI model system with two glass membranes and two liquid membranes, photocatalytic water splitting with homogeneous molecular photocatalysts is achieved to evolve hydrogen and oxygen with the turnover number (TON) of >100.

Alternatif Yakıt Hidrojen Üretiminde Mezogözenekli Alüminosilikat Destekli Katalizörler

In the present study, Ni-containing mesoporous aluminosilicate (Al2(SiO2)3) supported catalysts, which are resistant to carbon formation, were developed for hydrogen production from acetic acid. Commercial aluminosilicate (Al2(SiO2)3) was used as catalyst support. Furthermore, to improve the catalyst stability, Mg, La, Ce, Ca, Ru metals, and Ni (5% by mass) were incorporated by the wet impregnation method into the catalyst supports’ structure. The synthesized catalysts were characterized to define their physical and chemical properties. N2 adsorption-desorption results reveal that the resulting isotherm behavior of all the prepared catalysts is consistent with type IV isotherm with plate-like wall structures. The catalytic activity test of the prepared catalysts was investigated at a reaction temperature of 750 C and a feed molar ratio of 1/2.5 (AA/H2O) in a packed bed continuous reactor system. Activity test results showed that catalyst composition has profound effects on product distribution. Hydrogen-rich syngas was produced over 5Ni-3Ru@Al2(SiO2)3 and 5Ni-3CeO2@Al2(SiO2)3 (about % 44 and % 46, respectively) catalysts. However, the addition of MgO over the 5Ni@Al2(SiO2)3 catalyst strongly influenced the selectivity of hydrogen. Syngas, which contains an equimolar amount of H2, and CO is a quite important feedstock for the Fischer-Tropsch process (about 35% each), was obtained with the 5Ni-3MgO@Al2(SiO2)3 catalyst.

Constructing S-Scheme Heterojunction of CoAlLa-LDH/g-C3N4 through Monolayer Ti3C2-MXene to Promote Photocatalytic CO2 Re-forming of Methane to Solar Fuels

Multi-heterostructure interfaces of CoAlLa-LDH with porous g-C3N4 on monolayer Ti3C2-MXene was designed to get double-S-scheme heterojunction through in situ grown titania nanoparticles using a single-step ultrasonic assisted hydrothermal approach. The Ti3C2 MXene nanotexture embedded TiO2 NPs provides 3D nanotexture for promoting the interface interaction of g-C3N4 with CoAlLa-LDH. The g-C3N4/Ti3C2T/CoAlLa-LDH dual-S-scheme assembly possesses merits of conductive and semiconductive components with higher charges separation. The photoactivity test was conducted for CO2 reduction through different re-forming systems such as dry re-forming of methane (DRM) and bi-re-forming of methane (BRM), whereas acidic and basic sites over the composite enabled the attachment of both the CO2 and CH4 molecules for their activation under solar energy. The electron rich composite resulted in CO and H2 production of 55.25 and 54.72 μmol g–1 h–1, respectively under visible light during DRM process. These amounts of CO and H2 were many folds higher than the pristine g-C3N4 and LDH samples. This significant performance was ascribed to the strong interfacial interaction with a dual-step-scheme formation and electron rich linkers of oxygen defective La/Ti sites for superior charge-transfer separation. More importantly, by introducing water to CO2/CH4, a further efficiency was enhanced due to more utilization of holes. The hydrogen rich syngas production through feed ratio and reducing agents with tremendous stability further endorses good sorption characteristics of newly developed nanotextures. This electrostatic attraction approach presented a promising route for the rational design of layered multicomponent heterojunctions with 2D/2D/2D architecture for CO2 reduction to solar fuels.

Artificial Intelligence Approach in Gasification Integrated Solid Oxide Fuel Cell Cycle

With the growing world population and industrial developments, the supply of energy from an economically feasible and widely available source is important. Biomass gasification is a promising technology that produces lower emissions and allows efficient conversion. The gas obtained from the gasification process, especially in steam gasification, consists of a considerable amount of H2 and is used in fuel cells, especially solid oxide fuel cells (SOFC), to generate electricity. SOFC can convert the chemical energy into electricity and is considered as the most suitable fuel cell type for biomass gasification derived fuels. There are numerous research studies on integrated gasification-SOFC systems in the literature. However, these systems are still under development and studies are being conducted on the appropriate design parameters and operating conditions to achieve high energy efficiency.Modeling of the integrated gasification and SOFC system using the thermodynamic method is the simplest way to determine the process behavior. Nowadays, artificial neural networks (ANN) are one of the most popular modeling methods to represent the thermodynamic based gasification and SOFC systems. In this study, an integrated bubbling fluidized bed gasifier and SOFC model was created to generate data for training the ANN models with Aspen Plus simulation. The ANN models predicted the performance parameters in terms of electrical efficiency, net voltage and current density successfully using the varying operating conditions and 30 different biomass types as input parameters. The results showed that the developed ANN models estimated the output parameters with high accuracy by means of R2 greater than 0.999, MAPE < 0.053 and RMSE < 0.751 for training test and validation data sets.

Design strategies for oxy-combustion power plant captured CO2 purification

Abstract This study presents a novel design and techno-economic analysis of processes for the purification of captured CO2 from the flue gas of an oxy-combustion power plant fueled by petroleum coke. Four candidate process designs were analyzed in terms of GHG emissions, thermal efficiency, pipeline CO2 purity, CO2 capture rate, levelized costs of electricity, and cost of CO2 avoided. The candidates were a classic process with flue-gas water removal via condensation, flue-gas water removal via condensation followed by flue-gas oxygen removal through cryogenic distillation, flue-gas water removal followed by catalytic conversion of oxygen in the flue gas to water via reaction with hydrogen, and oxy-combustion in a slightly oxygen-deprived environment with flue-gas water removal and no need for flue gas oxygen removal. The former two were studied in prior works and the latter two concepts are new to this work. The eco-technoeconomic analysis results indicated trade-offs between the four options in terms of cost, efficiency, lifecycle greenhouse gas emissions, costs of CO2 avoided, technical readiness, and captured CO2 quality. The slightly oxygen-deprived process has the lowest costs of CO2 avoided, but requires tolerance of a small amount of H2, CO, and light hydrocarbons in the captured CO2 which may or may not be feasible depending on the CO2 end use. If infeasible, the catalytic de-oxygenation process is the next best choice. Overall, this work is the first study to perform eco-technoeconomic analyses of different techniques for O2 removal from CO2 captured from an oxy-combustion power plant.

Decreasing extents of Archean serpentinization contributed to the rise of an oxidized atmosphere

At present, molecular hydrogen (H2) produced through Fe(II) oxidation during serpentinization of ultramafic rocks represents a small fraction of the global sink for O2 due to limited exposures of ultramafic rocks. In contrast, ultramafic rocks such as komatiites were much more common in the Early Earth and H2 production via serpentinization was a likely factor in maintaining an O2-free atmosphere throughout most of the Archean. Using thermodynamic simulations, this work quantifies the global O2 consumption attributed to serpentinization during the past 3.5 billion years. Results show that H2 generation is strongly dependent on rock compositions where serpentinization of more magnesian lithologies generated substantially higher amounts of H2. Consumption of >2 Tmole O2 yr−1 via low-temperature serpentinization of Archean continents and seafloor is possible. This O2 sink diminished greatly towards the end of the Archean as ultramafic rocks became less common and helped set the stage for the Great Oxidation Event.

Rationally designed novel multifunctional poly(ionic liquid)s for ultra-selective valorization of Yiwu lignite to monocyclic aromatic compounds

The selective valorization of lignite into monocyclic aromatic compounds (MCACs) is extremely challenging due to its chemical inertness and geometrical complexity. The catalytic efficiency of lignite valorization into MCACs over solid acids is significantly reduced by the presence of H2O resulting in the leaching and deactivation of acid sites. Moreover, the precise fabrication of poly(ionic liquid)s (PILs) containing Brønsted-Lewis acidic sites, well-defined mesoporous channels, and hydrophobicity remains a considerable challenge. Herein, a novel hydrophobic mesoporous PILs with strong Brønsted-Lewis acid sites was successfully constructed by a synergistic regulation-induced copolymerization strategy for the first time. More exotically, the resultant multifunctional PILs was found to be ultra-efficient catalyst for the selective valorization of Yiwu lignite (YL) into MCACs with 23.5 wt.% yield, which is the highest yield reported for lignite catalytic valorization by precious metal-free catalysts under mild conditions. The co-catalysis mechanisms of YL valorization into MCACs over the multifunctional PILs are confirmed by characterization methods and the synergistic catalysis mechanisms are as follows: (1) hydrophobic micro-environment: the hydrophobic micro-environment created by hydrophobic block is favorable for preventing the leaching and deactivation of Brønsted-Lewis acid sites; (2) mesoporous confinement: the well-defined mesoporous channels strengthen the adsorption amount of H2 and increases the concentration of substrates; (3) synergistic catalytic active hydrogen transfer of Brønsted-Lewis acid sites: Brønsted-Lewis acid sites synergistically promote H2 heterolysis to the mobile H+ and immobile H−, and then the resulting mobile H+ transfers to oxygen atom in lignite to produce MCACs via C–O bond cleavage. This work not only sheds some light on developing the multifunctional solid acid catalysts, but also demonstrates an efficient catalyzing method to produce lignite-based MCACs by co-catalysis of Brønsted-Lewis acidic sites, mesoporous confinement, and hydrophobic micro-environment.

Boosting the H2 Production Efficiency via Photocatalytic Organic Reforming: The Role of Additional Hole Scavenging System

The simultaneous photocatalytic H2 evolution with environmental remediation over semiconducting metal oxides is a fascinating process for sustainable fuel production. However, most of the previously reported photocatalytic reforming showed nonstoichiometric amounts of the evolved H2 when organic substrates were used. To explain the reasons for this phenomenon, a careful analysis of the products and intermediates in gas and aqueous phases upon the photocatalytic hydrogen evolution from oxalic acid using Pt/TiO2 was performed. A quadrupole mass spectrometer (QMS) was used for the continuous flow monitoring of the evolved gases, while high performance ion chromatography (HPIC), isotopic labeling, and electron paramagnetic resonance (EPR) were employed to understand the reactions in the solution. The entire consumption of oxalic acid led to a ~30% lower H2 amount than theoretically expected. Due to the contribution of the photo-Kolbe reaction mechanism, a tiny amount of formic acid was produced then disappeared shortly after the complete consumption of oxalic acid. Nevertheless, a much lower concentration of formic acid was generated compared to the nonstoichiometric difference between the formed H2 and the consumed oxalic acid. Isotopic labeling measurements showed that the evolved H2, HD, and/or D2 matched those of the solvent; however, using D2O decreased the reaction rate. Interestingly, the presence of KI as an additional hole scavenger with oxalic acid had a considerable impact on the reaction mechanism, and thus the hydrogen yield, as indicated by the QMS and the EPR measurements. The added KI promoted H2 evolution to reach the theoretically predictable amount and inhibited the formation of intermediates without affecting the oxalic acid degradation rate. The proposed mechanism, by which KI boosts the photocatalytic performance, is of great importance in enhancing the overall energy efficiency for hydrogen production via photocatalytic organic reforming.