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Balancing catalytic activity and durability remains a challenge in the development of high performance, inexpensive and durable electrocatalysts. In this study, fully hydrolyzed composite catalyst V–Fe 2 P@Co 3 (PO 4) 2 /NF with ping-pong daisy-like morphology was synthesized using conventional hydrothermal and chemical vapor deposition (CVD) processes. In alkaline electrolyte, V–Fe 2 P@Co 3 (PO 4) 2 /NF showed excellent electrochemical performance, achieving a current density of 10 mA cm−2 when the driving overpotentials for the hydrogen production reaction (HER) and oxidation reaction (OER) were 56 mV and 178 mV, respectively. Meanwhile, V–Fe 2 P@Co 3 (PO 4) 2 /NF demonstrated good durability in terms of both HER and OER stability. Furthermore, the driving voltage required for the electrolyser assembled with V–Fe 2 P@Co 3 (PO 4) 2 /NF as the electrode is lower than that of the RuO 2 /NF||Pt/C/NF electrode, both of which have driving voltages of 1.503 and 1.562 V (10 mA cm−2), respectively. Meanwhile, it achieves a Faraday efficiency of 95%. This study offers a feasible solution towards synthesizing and applying bifunctional water decomposition electrocatalysts. The synthesized V–Fe 2 P@Co 3 (PO 4) 2 /NF catalyst exhibits excellent catalytic properties for bifunctional electrolysis of water in 1 M KOH solution. [Display omitted] •V doping alters Co3(PO4)2 and Fe2P nanosheets morphology and catalytic properties. • Synthesized samples show superior catalytic activity for total hydrolysis in 1 M KOH. • Ping Pong daisy's shape leads to more pores, larger active area and better stability. [ABSTRACT FROM AUTHOR]

Abnormal combustion is an important factor in the development process of hydrogen engine and it mainly includes pre-ignition, backfire and knocking, among which pre-ignition has the most serious impact on hydrogen engine. In this paper, it is divided into four types: normal combustion, slight pre-ignition, moderate pre-ignition and severe pre-ignition according to different crankshaft rotation angles. In order to identify different combustion types, this paper proposes a fault diagnosis model based on the fusion of SOM neural network and Multi-Agent System (SOM-MAS). Firstly, different combustion types are identified by SOM. Secondly, the abnormal combustion is tracked and located mainly through the Multi-Agent System, and the location of the abnormality is identified. Finally, based on 44 sets of pressure data samples collected from the in-cylinder combustion of a hydrogen engine on the experimental bench, different combustion types were diagnosed and identified, and the location of abnormal combustion faults was tracked, which verifies the effectiveness of the proposed method shows that the method has certain feasibility and superiority for the diagnosis of hydrogen engine pre-ignition. • Research carried out by the 492Q hydrogen engine, close to actual conditions. • The dataset is original and contains data for normal and abnormal combustion. • SOM-MAS can be applied in abnormal combustion of hydrogen fuel engines. • Less relevant dataset, we will publish the dataset for future research. [ABSTRACT FROM AUTHOR]

Because of its superior cold-start effect and lack of pollution, the proton exchange membrane fuel cell (PEMFC) engine has gained a lot of interest as the most common application type of hydrogen fuel cell engines. However, the difficulty in forecasting the remaining life and monitoring the operation state for a lengthy period limits its commercialization. As a result, PEMFC Prognostics and Health Management (PHM) is critical. A method based on bibliometrics is introduced into the research on this topic. In this work, the research in this field is divided into three stages. The characteristics of different stages are summarized through keywords, subject background, and other aspects. We can observe the transformation of the field from the idea based on analytical reduction to systematic theoretical control. Based on the results of bibliometric analysis, we have conducted a literature review, and we can see the typical research results and development direction of each topic clustering. • A bibliometric based approach is used to organize the structure of the review. • The hotspot and driving force of hydrogen fuel cell engine are visualized. • Development direction PHM in the PEMFC was analyzed. • Many fault causes and health management architecture are analyzed. [ABSTRACT FROM AUTHOR]

With the development of new energy, hydrogen fuel engines have become a research boom in the automotive field. But there are abnormal problems such as backfire and pre-ignition during the combustion of hydrogen engines. This paper is based on the Ant Colony Optimization-Back Propagation (ACO-BP) algorithm to study the influence of different speed and load conditions on the ignition advance angle, so as to optimize the control of the hydrogen engine. The experimental system is established on a hydrogen engine converted from a 492Q gasoline engine. The prediction of the optimal ignition advance angle was obtained through experiments, and the optimal ignition MAP diagram of the hydrogen engine is constructed. The optimal ignition advance angle under different working conditions can effectively avoid the occurrence of hydrogen engine pre-ignition. The accuracy reaches 0.0018209 when the training reaches 14 times, the fitness between the actual value and the predicted value of ACO-BP training is 0.99921, the verification accuracy reaches 0.99913, and the test accuracy reaches 0.99932. Compared with the three optimization methods, the convergence speed and error accuracy of ACO-BP are significantly better than the BP neural networks and Genetic Algorithm-Back Propagation (GA-BP). This method realized the model of the nonlinear mapping model from hydrogen engine speed and load to optimal ignition advance angle, which is of great significance for solving the problem of abnormal combustion in hydrogen engine. • Research carried out by the 492Q hydrogen engine, close to actual conditions. • The dataset is original, collected under different speed and load conditions. • ACO-BP can be applied in abnormal combustion of hydrogen fuel engines. • Less relevant dataset, we will publish the dataset for future research. [ABSTRACT FROM AUTHOR]

Co-free La 0.6 Sr 0.4 FeO 3-δ (LSFNb 0) and La 0.6 Sr 0.4 Fe 0.9 Nb 0.1 O 3-δ (LSFNb 0.1) perovskite oxides were prepared by a standard solid-state reaction method. The structural stability and electrochemical performance of La 0.6 Sr 0.4 Fe 0.9 Nb 0.1 O 3-δ as both cathode and anode were studied. Nb dopant in LSFNb 0 significantly enhances the structural and chemical stability in anode condition. At 800 °C, the polarization resistances (Rp) of LSFNb 0.1 symmetric electrode based on YSZ electrolyte are 0.5 and 0.05 Ω cm2 in H 2 and air, respectively. The peak power densities of LSFNb 0.1 based on LSGM electrolyte-supported SSOFCs are 934 and 707 mW cm−2 at 850 °C in H 2 (3% H 2 O) and dry CO, respectively. Moreover, the symmetric cell exhibits reasonable stability in both H 2 and CO fuel, suggesting that La 0.6 Sr 0.4 Fe 0.9 Nb 0.1 O 3-δ may be a potential symmetric electrode material for hydrogen and carbon monoxide SOFCs. • The substitution of Nb improves the structural stability of La 0.6 Sr 0.4 FeO 3 in H 2. • The polarization resistances of LSFNb symmetric cells are 0.5 and 0.05 Ω cm2 in H 2 and air, respectively. • The peak power densities of LSFNb symmetric cell are 934 and 707 mW cm−2 at 850 °C in H 2 (3% H 2 O) and dry CO, respectively. [ABSTRACT FROM AUTHOR]

Abstract The effect of the addition of hydrogen (H 2) on the combustion process and nitric oxide (NO) formation in a H 2 -diesel dual fuel engine was numerically investigated. The model developed using AVL FIRE as a platform was validated against the cylinder pressure and heat release rate measured with the addition of up to 6% (vol.) H 2 into the intake mixture of a heavy-duty diesel engine with exhaust gas recirculation (EGR). The validated model was applied to further explore the effect of the addition of 6%–18% (vol.) H 2 on the combustion process and formation of NO in H 2 -diesel dual fuel engines. When the engine was at N = 1200 rpm and 70% load, the simulation results showed that the addition of H 2 prolonged ignition delay, enhanced premixed combustion, and promoted diffusion combustion of the diesel fuel. The maximum peak cylinder pressure was observed with addition of 12% (vol.) H 2. In comparison, the maximum peak heat release rate was observed with the addition of 16% (vol.) H 2. The addition of H 2 was a crucial factor dominating the increased NO emissions. Meanwhile, the addition of H 2 reduced soot emissions substantially, which may be due to the reduced diesel fuel burned each cycle. Furthermore, proper combination of adding H 2 with EGR can improve combustion performance and reduce NO emissions. Highlights • Numerical model used to explore effect of H 2 addition on diesel engine performance. • H 2 addition improves combustion, reduces soot, but increases NOx emissions. • Combined H 2 addition/EGR improves combustion performance, reduces NOx emissions. [ABSTRACT FROM AUTHOR]

To research the quality of the hydrogen–air mixture formation and the combustion characteristics of the hydrogen fueled engine under different hydrogen injection timings, nozzle hole positions and nozzle hole diameter, a three-dimensional simulation model for a PFI hydrogen internal combustion engine with the inlet, outlet, valves and cylinder was established using AVL Fire software. In the maximum torque condition, research focused on the variation law of the total hydrogen mass in the cylinder and inlet and the space distribution characteristics and variation law of velocity field, concentration field and turbulent kinetic energy under different hydrogen injection parameters (injection timings, nozzle hole positions and nozzle hole area) in order to reveal the influence of these parameters on hydrogen–air mixture formation process. Then the formation quality of hydrogen–air mixture was comprehensively evaluated according to the mixture uniformity coefficient, the remnant hydrogen percentage in the inlet and restraining abnormal combustion (such as preignition and backfire). The results showed that the three hydrogen injection parameters have important influence on the forming quality of hydrogen–air mixture and combustion state. The reasonable choice of the nozzle hole position of hydrogen, nozzle hole diameter and the hydrogen injection time can improve the uniformity of the hydrogen–air mixing in the cylinder of the hydrogen internal combustion engine, and the combustion heat release reaction is more reasonable. At the end of the compression stroke, the equivalence ratio uniform coefficient increased at first and then decreased with the beginning of the hydrogen injection. When hydrogen injection starting point was with 410–430°CA, equivalence ratio uniform coefficient was larger, and ignition delay period was shorter so that the combustion performance index was also good. And remnant hydrogen percentage in the inlet was less, high concentration of mixed gas in the vicinity of the inlet valve also gathered less, thus suppressing the preignition and backfire. With the increase of the distance between the nozzle and the inlet valve, the selection of the hydrogen injection period is narrowed, and the optimum hydrogen injection time was also ahead of time. The results also showed that it was favorable for the formation of uniform mixing gas when the nozzle hole diameter was 4 mm. [ABSTRACT FROM AUTHOR]

The oxidation behavior of the stainless steel 441 in the initial 2 h was investigated gravimetrically at 600 °C–950 °C under various oxygen pressures. The morphology, composition and the growth stress of the scale on the oxidized alloy were analyzed by SEM/EDS and Raman spectra. It was found that the performances of the scale degraded with the temperature and oxygen pressure increasing. The oxidation of stainless steel 441 presented a multi-stages behavior. It was suggested that the first chemical reaction determining stage was the nonselective oxidation of steel surface. The following stage in pure oxygen ambient was the formation of chromium-oxide-mainly-containing layer. Kinetic mechanism of second stage oxidation changed from diffusion determining step (600–800 °C) to interface chemical reaction (900–950 °C) due to the decline of the protection of the oxides layer. Only linear rate law was obeyed in the lower oxygen pressure atmospheres at 800 and 900 °C within the initial 2 h. [ABSTRACT FROM AUTHOR]

Abstract: Preignition or backfire occurs easily in hydrogen internal combustion engines (HICE) of manifold injection type, especially, the bigger equivalence ratio is, the more serious backfire happens. And decreasing equivalence ratio will reduce engine''s power output. So to analyze and resolve the contradiction between abnormal combustion and power output in HICE is the key of promoting the progress of research on HICE. Postponing ignition timing is helpful to reducing the occurrence degree or inclination of pre-ignition, and water injection of intake manifold can be used to eliminate backfire. But postponement of ignition has a lesser effect on power output and brake thermal efficiency than water injection of intake manifold, That is to say water injection would bring power output to drop obviously, and water injection will also has many disadvantages, such as, the worse corrosion degree of cylinder and deteriorated lubrication performance. It is necessary to combine postponing ignition timing with water injection of intake manifold to give full play to their advantages, and avoid their disadvantages to the greatest extent. In the paper, the concept of pre-ignition strength and backfire strength were presented, and the inhibition degree of pre-ignition and the elimination degree of backfire was introduced. The functional relationship between inhibition degree of pre-ignition and ignition timing was established, and the functional relationship between the elimination degree of backfire and water injection rate was also established for quantitative analysis and research into inhibiting pre-ignition and eliminating backfire. A optimal control method was put forward about resolving contradiction between eliminating backfire and improving performance of HICE, which not only eliminates backfire, but also take into account the power output and economy. [Copyright &y& Elsevier]

Abstract: With its obvious advantages, hydrogen is expected to be greatly used as a new energy, which can reduce vehicle emissions effectively and efficiently. Besides, it can be adopted as an alternative fuel for petroleum fuel of internal combustion engine. However, due to its unique physical and chemical characteristics, hydrogen often leads to abnormal combustion and decay of power, which can be effectively dealt with by optimal control. In this paper, thermodynamic analysis methods, like mass transfer and energy transfer, is combined with state space analysis methods of nonlinear control system, so that an optimal control model of nonlinear combustion control system for hydrogen fueled engines can be established. Through illustrating the inner relations between combustion and energy transfer of hydrogen fueled engines and operating parameter, state parameter and performance index, this paper provides theoretical analysis and found experimental research for promoting abnormal combustion and performance index after controlling operating parameters optimally and changing state parameters of the cylinder. Based on nonlinear programming theory and multi-objective genetic algorithm, the methods of establishing the optimal control model and carrying out the optimal value of operating parameters are shown in this paper. What’s more, some new ways are proposed to integrate the optimal control aspects of multi-variate, multiple targets and multiple constraints for hydrogen fueled engines by changing the multi-objective and multi-constraint optimal control into the single-target integrated optimal control. [Copyright &y& Elsevier]

Abstract: An optimization control model which is about the relationship between power, economy, emission performances and operating parameters of hydrogen-fueled engines is established in the text, and optimality of the solution''s Pareto is realized through multi-objective optimization algorithm which is combined with Pareto rank and partial decision-making, and the optimization process of multi-objective is carried out parallelly in the searching process, the solution converges to the direction of decision partiality, and the convergence speed is improved; at the same time, dynamic adjustment of partial decision-making changes as the operating condition of hydrogen-fueled engines can be realized through weighting function, thus the control of multi-variable, multi-objective, multi-working status is unified to single-objective integrated optimal control technique. This develops a new avenue to solve the controlling problem of optimization objective''s diversification and complication in hydrogen-fueled engines and improve the controlling precise further. [Copyright &y& Elsevier]

Abstract: Hydrogen fuel is regarded as one of the most promising alternative fuels for automobiles in future. Technology of the optimum control on hydrogen-fueled engines is a key to improve its performances in every respect. In this paper, based on the experiments, the policy of optimum control on hydrogen-fueled engines has been shown. Moreover, a new optimizing control model on hydrogen-fueled engines has been constructed, in which ignition timing, injection timing and injection duration were separately selected as control variation, and output power and rate of fuel consumption are separately chosen as performance index function. Further, a new method ingeniously adopting fuzzy-neural network (FNN) system to calculate the optimizing control laws for the optimizing control model has been designed, and a series connection control system has been set up, which is composed of FNN controllers combined with an adaptive controller for ignition timing to realize open-loop or closed-loop control pattern with stepping regulation of ignition timing. Last, the calculated results of the control variations with an improved FNN system were contrasted with experimental results; the contrasting result has shown that the maximum absolute error is less than 1°CA, the maximum relative error is less than 5%, mean square error is 0.381°CA. Therefore, the calculation method with FNN system is practical and satisfactory. [Copyright &y& Elsevier]

When hydrogen internal combustion engine works using the intake manifold injection mode to provide the hydrogen, it has to face a contradiction between the abnormal combustion (preignition, backfire, etc.). Currently, most researches on abnormal combustion in hydrogen internal combustion engines have focused primarily on backfire and detonation, with limited investigation of pre-ignition, particularly when initiated by in-cylinder hot spots. In order to explore the relationship between the hot spot and the pre-ignition of hydrogen internal combustion engine, the influence of characteristic parameters of hot spot, such as hot spot area, initial temperature, duration of hot spot and temperature change rate, on pre-ignition of hydrogen internal combustion engines were analyzed. On the basis of using the isolated factor method to research the influence of each characteristic parameter on the occurrence time of pre-ignition of hydrogen internal combustion engines, the comprehensive effect of these characteristic parameters on the occurrence moment of pre-ignition in hydrogen internal combustion engines was also investigated with the orthogonal test method. It is found that the occurrence of pre-ignition of hydrogen internal combustion engines is the result of multi-factor interaction. Pre-ignition is most affected by hot spot area, and when the hot spot area is the same, the order of influence of pre-ignition timing is initial temperature > temperature change rate > duration of hot spot. The research results can promote the practical application of hydrogen fuel in internal combustion engines and provide guidance for the structural design of hydrogen internal combustion engines. • Hydrogen engine pre-ignition results from combined effects of several parameters such as the area, initial temp. • Strategies to control temp change rates could mitigate pre-ignition risks and optimize combustion performance. • Compared to initial temp, the moment of pre-ignition is more sensitive to changes in the area of the hot spot. • With equal hot spot area: initial temp > temp change rate > duration influence hydrogen engine pre-ignition. [ABSTRACT FROM AUTHOR]

For the port injection hydrogen-fueled spark ignition (SI) engine modified from the Jialing JH600 gasoline engine, the hydrogen injection timing and ignition timing of the hydrogen SI engine are comprehensively optimized on the AVL-FIRE software based on the combination of design of experiment (DOE) and multiple population genetic algorithm (MPGA). Firstly, the effects of hydrogen injection timing and ignition timing on the performance of the hydrogen engine are investigated through the full factors design of experiment scheme, and then the optimum intervals of them are determined respectively. Secondly, the uniform design of experiments scheme is arranged, and the regression functions of indicated power, indicated thermal efficiency and emissions of the hydrogen engine under different working conditions are fitted. Then, the comprehensive optimization model is constructed. Finally, the optimum hydrogen injection timing and ignition timing of the hydrogen engine under different working conditions are solved based on MPGA. The results show that, compared with the standard genetic algorithm (SGA), the MPGA has faster convergence speed and higher convergence accuracy. In addition, as the load increases from low to high, the optimum hydrogen injection timing is advanced and the rate of variation increases from 0.6% to 1.1%, the optimum ignition timing is delayed and the rate of variation decreases from 29.1% to 17.8%. • The uniform design can substantially reduce experimental study effort and cost. • Optimization models obtained by regression analysis based on the uniform design. • Solving optimization models with MPGA instead of SGA. • Providing a new idea for optimizing hydrogen SI engine. [ABSTRACT FROM AUTHOR]

Recycling and reusing of exhaust gas from solid oxide fuel cell (SOFC) could enhance the fuel utilization of methane. In the present work, the effects of two main components of exhaust gas, viz. hydrogen and carbon dioxide, on the performance of exhaust gas reforming methane fueled cell were investigated. The cell with Ni/8 mol% Y 2 O 3 doped zirconia (Ni/YSZ) as the anode was exposed to H 2 CO 2 CH 4 atmospheres at 800 °C. DC techniques and impedance spectroscopy was used for characterization. Two kinds of cells with different fuel utilization factors ( U f ) were used in experiments, which represented different relationship of power density/voltage with current density. The results indicated that electrooxidation of H* dominated the electrochemical reaction on the anode of the cell at low U f value, while electrooxidation of C* becomes important at high U f value. In the case of CO 2 H 2 mixtures, CO 2 improved the exchange current density, raised the value of U f , and depressed anodic activation polarization. As for H 2 CH 4 CO 2 system, H 2 , partly replacing CH 4 , reduced the heat loss in dry reforming, improved the exchange current density, raised U f value, and depressed the activation and concentration polarization resistances of Ni/YSZ anode. But it had limited effect on the power density of the cell with high U f value. [ABSTRACT FROM AUTHOR]

La-doped Sr 2-x La x Fe 1.5 Mo 0.5 O 6-δ perovskite oxides are synthesized and used as a symmetric electrode to evaluate the effect of La on the crystal structure, conductivity, and catalytic activity for O 2 reduction and H 2 oxidation reaction. The electronic doping effect dominates the oversize effect in Sr 2-x La x Fe 1.5 Mo 0.5 O 6-δ oxide, resulting in unit cell volume expansion and decreased conductivity in air. In addition, the introduction of La increases the chemical structural stability of Sr 2 Fe 1.5 Mo 0.5 O 6-δ in reducing condition due to the higher La–O bond compared with Sr–O bond, leading to high catalytic activity for the H 2 oxidation reaction. At 800 °C, the R p values of Sr 1.9 La 0.1 Fe 1.5 Mo 0.5 O 6-δ symmetric cell in air and wet H 2 are as low as 0.075 and 0.21 Ω cm2, respectively. Moreover, the peak power densities of 769, 561, 439, and 653 mW cm−2 at 850 °C are obtained when wet H 2 , CO, CH 4, and C 3 H 8 are used as fuels on Sr 1.9 La 0.1 Fe 1.5 Mo 0.5 O 6-δ /LSGM/Sr 1.9 La 0.1 Fe 1.5 Mo 0.5 O 6-δ cell. The symmetric cell also shows excellent stability (>100 h) in wet H 2 /air, implying Sr 1.9 La 0.1 Fe 1.5 Mo 0.5 O 6-δ oxide is a promising symmetric electrode material. [Display omitted] • The substitution of La improves the stability of Sr 2 Fe 1.5 Mo 0.5 O 6-δ in reducing atmosphere. • La enhances the catalytic activity for H 2 oxidization reaction (HOR). • High electrochemical performance is obtained for SLFM symmetric cell under carbon-based fuels. [ABSTRACT FROM AUTHOR]

Abstract: To accelerate the start-up process and enhance the efficiency of a hydrogen production system, piggery anaerobic digested residues (PADRs) were subjected to several different treatment methods to enrich the hydrogen-producing bacteria. Eight treatment methods were performed on the PADRs, including acid, alkali, heat, drying, ultrasound, aeration, sodium 2-bromoethanesulfonate (BES), and chloroform. The best method was found to be drying at 60 °C for 48 h, which maximised the total biogas production and the hydrogen fraction without causing any methane production. The volatile fatty acids (VFAs) found after the drying treatment were acetate and butyrate, which together accounted for 91.9% of all VFAs, indicating that butyric acid fermentation was established. Due to the drying treatment, the metabolites produced from the biodegradable DOM were utilised more rapidly, more completely, and with the least amount of hard-degradation organic matter content obtained, according to EEM fluorescence spectra. This drying treatment offers a promising method to1 improve bio-hydrogen production. [Copyright &y& Elsevier]