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Hydrogen and its unique properties pose major challenges to the development of innovative combustion engines, while it represents a viable alternative when it is based on renewable energy sources. The present paper deals with the holistic approach of hydrogen combustion modeling from a 0D/1D reactor evaluation with Cantera up to complete engine simulations in the 3D-CFD tool QuickSim. The obtained results are referenced to the current literature and calibrated with experimental data. In particular, the engine simulations are validated against measurements of a single-cylinder research engine, which was specifically adapted for lean hydrogen operation and equipped with port fuel injection and a passive pre-chamber system. Special attention is hereby given to the influence of different engine loads and varying lambda operation. The focus of this work is the complementary numerical investigation of the hydrogen flame speed and its self-ignition resistance under the consideration of various reaction mechanisms. A detailed transfer from laminar propagation under laboratory conditions to turbulent flame development within the single-cylinder engine is hereby carried out. It is found that the relatively simple reaction kinetics of hydrogen can lead to acceptable results for all mechanisms, but there are particular effects with regard to the engine behavior. The laminar flame speed and induction time vary greatly with the inner cylinder conditions and significantly affect the entire engine’s operation. The 3D-CFD environment offers the opportunity to analyze the interactions between mixture formation and combustion progress, which are indispensable to evaluate advanced operating strategies and optimize the performance and efficiency, as well as the reliability, of the engine.

Ultrafine W powder is a key material for manufacturing high-performance W-based products. In this study, ultrafine W powder was prepared via the H2 reduction of carbon-containing WO3, and the parameters of reduction temperature (740–830 °C) and C/WO3 molar ratio (0.5–2.5) were mainly considered. The results demonstrated that, with the increase in reduction temperature, the reaction rate gradually increased, while the particle size of W powder exhibited a trend showing an initial decrease and then increase, with a minimum value of 146 nm at 770 °C. The results also showed that, with the increase in C/WO3 molar ratio, the reaction rate gradually decreased, while the particle size of W powder also first decreased and then increased, with its minimum value at a C/WO3 molar ratio of 1.0. The reduction pathways of H2 reduction of WO3 to W was given as WO3→WO2.9→WO2.72→WO2→W. Due to the co-actions of nucleating agent and the synergistic reduction effect, the particle size of W powder obtained by reducing carbon-containing WO3 was smaller than that obtained by reducing pure WO3, and a possible reaction mechanism was proposed.

Nowadays, the rapid development of the social economy inevitably leads to global energy and environmental crisis. For this reason, more and more scholars focus on the development of photocatalysis and/or electrocatalysis technology for the advantage in the sustainable production of high-value-added products, and the high efficiency in pollutants remediation. Although there is plenty of outstanding research has been put forward continuously, most of them focuses on catalysis performance and reaction mechanisms in laboratory conditions. Realizing industrial application of photo/electrocatalytic processes is still a challenge that needs to be overcome by social demand. In this regard, this review comprehensively summarized several explorations in the field of photo/electrocatalytic reduction towards potential industrial applications in recent years. Special attention is paid to the successful attempts and the current status of photo/electrocatalytic water splitting, carbon dioxide conversion, resource utilization from waste, etc., by using advanced reactors. The key problems and challenges of photo/electrocatalysis in future industrial practice are also discussed, and the possible development directions are also pointed out from the industry view. This review summarized the potential industrial applications of representative catalysts in various photo/electrocatalytic processes. The key problems and challenges of photo/electrocatalysis in future practical industrial applications are also discussed, and the possible development direction is pointed out. [Display omitted] •The various photo/electrocatalysis processes toward potential industrial applications are summarized.•Several large-scale integrated processes for holistic renewable energy production and utilization are reviewed.•The current problems and challenges of photo/electrocatalysis industrialization are evaluated.

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.

Molecular hydrogen (H2) is now considered among the most prominent substitute for fossil fuels. The environmental impacts of a hydrogen economy have received more attention in the last years, but still, the knowledge is relatively poor. In this work, the reaction of H2 with NO3 radical (the dominant night-time detergent of the atmosphere) is studied for the first time using high-level composite G3B3 and modification of high accuracy extrapolated ab initio thermochemistry (mHEAT) methods in combination with statistical kinetics analysis using non-separable semi-classical transition state theory (SCTST). The reaction mechanism is characterized, and it is found to proceed as a direct H-abstraction process to yield HNO3 plus H atom. The reaction enthalpy is calculated to be 12.8 kJ mol−1, in excellent agreement with a benchmark active thermochemical tables (ATcT) value of 12.2 ± 0.3 kJ mol−1. The energy barrier of the title reaction was calculated to be 74.6 and 76.7 kJ mol−1 with G3B3 and mHEAT methods, respectively. The kinetics calculations with the non-separable SCTST theory give a modified-Arrhenius expression of k(T) = 10−15 × T0.7 × exp(−6120/T) (cm3 s−1) for T = 200–400 K and provide an upper limit value of 10−22 cm3 s−1 at 298 K for the reaction rate coefficient. Therefore, as compared to the main consumption pathway of H2 by OH radicals, the title reaction plays an unimportant role in H2 loss in the Earth’s atmosphere and is a negligible source of HNO3.