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Due to its slow kinetics, the oxygen evolution reaction (OER) is a key limiting reaction in electrocatalytic water separation and fuel cells. Transition metal sulphides with high intrinsic activity, outstanding stability and excellent electrical conductivity have been considered as promising electrocatalysts for OER. In this study, we develop a green and general strategy for the synthesis of nitrogen, sulphur co-doped honeycomb like carbon nanosheets coupled with binary metal sulfides ((M 1 , M 2) x S y @SNC, (M 1 , M 2) = Fe, Co, Ni) derived from chitosan (nitrogen sources) and lignosulfonate (sulphur sources) with NaCl as template. At the same time the sulphonate group in the lignosulphonate as a sulphur source sulphurises the transition metal to binary metal sulfides. The (M 1 , M 2) x S y @SNC has a large specific surface area (171.5 m2g −1), abundant defects and honeycomb-like hierarchical porosity with interconnected pore structures. The overpotential (at 10 mA cm −2) of the prepared (Fe, Ni) 9 S 8 @SNC was only 207 mV in 1 mol KOH. In this study, we provide a green and novel fabrication method for the synthesis of binary metal sulphides and achieves a high-value utilization of biomass. [Display omitted] • The synthesized (M 1 , M 2) x S y @SNC has honeycomb-like hierarchical porosity with interconnected pore structures. • Lignosulfonates were first used to prepare metal sulphides without other sulphur sources which is harmful to environment. • The prepared (M 1 , M 2) x S y @SNC has a lower overpotential than commercial IrO 2. [ABSTRACT FROM AUTHOR]

This paper proposes a coordinated power control method with virtual inertia (VI) for fuel cell-based DC microgrids (MGs) cluster based on the multi-agent system (MAS) control frame. In the primary control layer, a local energy management strategy with virtual inertia is adopted to suppress the bus voltage disturbance, smooth the output power of fuel cell, as well as manage the power flow in the DC MG. In the secondary and tertiary control layers, a coordinated power control method based on MAS frame is implemented for the power flow among the sub-MGs. More specifically, the secondary voltage control loop is used for the bus voltage smooth control at the moment of microgrids interconnection, and the power flow tertiary control regular is applied for the battery SoC converge uniformly in finite time. Also, a fuel cell-based DC microgrids cluster real-time simulation platform is established to verify the control performance of the proposed coordinated power control method on the bus voltage smooth control, the SoC consistency control, load abrupt response and 'plug and play' capability. • A primary control layer with virtual inertia is adopted to enhance power quality of DC MG. • A MAS-based supervisory control method is proposed for coordinated management in FC-based MGC. • The overall performance of the coordinated power control method is verified in a real-time simulation platform. [ABSTRACT FROM AUTHOR]

With the fast development of DC Microgrid (MG) technology, its operating economy and reliability are getting more and more concern. The traditional distributed control method is aimed at power balance and system stability, and is difficult to meet the requirement of energy management system for multi-source hybrid DC MG. This paper provides a two-level energy management strategy for PV-fuel cell-battery-based DC MG, which is divided into device control level and system control level. At the device control level, the distributed control methods based on MPPT-droop dual-mode control and droop control are proposed to enhance system reliability; at the system control level, the equivalent consumption minimization strategy (ECMS) is used to distribute system net power between battery pack and fuel cell system. A lab-scale DC microgrid platform is developed to verify the proposed energy management strategy in this paper. Moreover, the analysis and compare of the results show that the proposed two-level energy management strategy can achieve lower equivalent hydrogen consumption than classical PI control and state machine control method. • Developing a lab-scale PV-fuel cell-battery-based DC microgrid platform. • Proposing a two-level energy management strategy for DC microgrid. • The analysis and compare of the results among various management strategies. [ABSTRACT FROM AUTHOR]

Abstract This research presents an optimum design scheme and a hierarchical energy management strategy for an island PV/hydrogen/battery hybrid DC microgrid (MG). In order to efficiently utilize this DC MG, the optimum structure and sizing scheme are designed by HOMER pro (Hybrid Optimization of Multiple Energy Resources) software. The designed structure of hydrogen MG includes a PV generation, a battery as well as a hydrogen subsystem which composes a fuel cell (FC) system, an electrolyzer and hydrogen tank. To improve the robustness and economy of this DC MG, this study schedules a hierarchical energy management method, including the local control layer and the system control layer. In the local control layer, the subsystems in this DC MG are controlled based on their inherent operating characteristics. And the equivalent consumption minimization strategy (ECMS) is applied in the system control layer, the power flow between the battery and FC is allocated to minimum the fuel consumption. An island DC MG hardware-in-loop (HIL) Simulink platform is established by RT-LAB real-time simulator, and the simulation results are presented to validate the proposed energy management strategy. Highlights • An optimum design scheme for PV/hydrogen/battery DC microgrid. • A hierarchical energy management strategy based on ECMS. • DC MG HIL experimental platform based on RT-LAB real-time simulator. [ABSTRACT FROM AUTHOR]

Abstract The effect of Ni/Co ratio on the catalytic performance of Ni Co/ceramic foam catalyst for hydrogen production by steam reforming of real coal tar was studied. The Ni Co/ceramic foam catalyst was synthesized by deposition-precipitation (DP) method and characterized with different methods. The experiments were conducted in a two-stage fixed-bed reactor. The results showed that the reducibility of the metallic oxides in bimetallic Ni Co/ceramic foam catalysts was influenced obviously by the Ni/Co ratio. Both gas and hydrogen yield increased first and then decreased with the decline of Ni/Co ratio, and the highest hydrogen yield of 31.46 mmol g−1 was obtained when the Ni/Co ratio was 5/5. The lowest coke deposition of 0.34 wt% was generated at the same Ni/Co ratio. The lifetime test showed the catalyst maintained catalytic activity after 14 cycles (28 h), indicating the coal tar steam reforming on Ni Co/ceramic foam catalyst is a promising method for hydrogen production. Highlights • Comparison of Ni Co/ceramic foam catalysts with different Ni/Co ratios was studied. • The highest H 2 yield of 31.46 mmol g−1 coal tar was obtained as the Ni/Co = 5/5. • The catalyst exhibited a stable catalytic behavior during a 28-h lifetime test. [ABSTRACT FROM AUTHOR]

The structure and hydrogen storage capacities of a sandwich-type binuclear complex Al 4 Ti 2 Al 4 are studied using first-principles calculations. It is found that the aromatic Al 4 2− unit can be incorporated to sandwich the transition metal Ti atoms forming a stable all-metal binuclear compound Al 4 Ti 2 Al 4 . One Al 4 Ti 2 Al 4 molecule can adsorb 28 hydrogen atoms, which corresponds to a gravimetric storage capacity of 8.24 wt%. This hydrogen storage capacity is above the 2015 target of 5.5% set by the US Department of Energy (DOE) in 2009. Furthermore, the average binding energy is in the ideal range of 0.2–0.6 eV/H 2 and the conjugation between H and Al 4 Ti 2 Al 4 differs according to the adsorbed sites. Meanwhile, we found that multicenter bond is formed between H atoms and Al or Ti atoms during the process of hydrogen adsorption through AdNDP analysis, and it is characterized by specific vibration frequency. Therefore, mode selective vibrational excitation of the IR intense bands may lead to desorption of the absorbed hydrogen form Al 8 Ti 2 , enabling efficient reversible hydrogen storage. Last but not least, the binding energies of the multicenter bond between adsorbed H atoms and pure Ti atoms are much larger than those of the multicenter bonds related to both Ti and Al atoms. Thereby, the inter-doping of Ti and Al can modulate the binding energy between Ti Al cluster and adsorbed hydrogen. [ABSTRACT FROM AUTHOR]

The hydrogen storage capacities of the two sandwich-type Cp 2 TM 2 [Cp = cyclopentadienyl (C 5 H 5 ); TM = V or Cr)] dimetallocenes were studied using first-principles calculations. According to the B3PW91 method in density functional theory (DFT), Cp 2 V 2 and Cp 2 Cr 2 could adsorb up to seven and six hydrogen molecules, respectively. The predicted hydrogen storage densities of Cp 2 V 2 and Cp 2 Cr 2 were 5.73 and 4.91 wt%, respectively. Additionally, because hydrogen binding energies bound by Kubas model were 0.39 and 0.43 eV/H 2 , respectively, both the Cp 2 V 2 and Cp 2 Cr 2 dimetallocenes were proven to be favourable for reversible adsorption and desorption of hydrogen molecules under ambient conditions. [ABSTRACT FROM AUTHOR]

The hydrogen storage capacities of a sandwich-type ethylene dimetallocene complex (Cp 2 Ti 2 C 2 H 4 ) are studied using first-principles calculations. It is found that the TiC 2 H 4 Ti molecule can intercalate into the two cyclopentadienyl (Cp) rings and form a stable sandwich-type complex. Each Ti atom can adsorb a maximum of three H 2 molecules, which corresponds to a gravimetric storage capacity of 4.73 wt%. This hydrogen storage capacity is close to the 2015 target of 5.5% set by the US Department of Energy (DOE) in 2009. Furthermore, the Cp 2 Ti 2 C 2 H 4 molecule proposed in this paper is favorable for both adsorption and desorption of hydrogen molecules at room temperature and ambient pressure because its average binding energy of 0.34 eV/H 2 . [ABSTRACT FROM AUTHOR]

Because of its high efficiency, low pollution and good stability, proton exchange membrane fuel cell (PEMFC) is considered as one of the most promising technologies for a wide range of applications, such as distributed power generation, transportation, portable power source and automobile. In a PEMFC grid-connected system, the proportion integration (PI) regulator can achieve zero error for the dc components in the rotating frame, but cannot achieve zero error for the ac components in the rotating frame. Hence, the PEMFC grid-connected system will produce a large number of harmonics. In order to overcome this shortcoming, a proportion integration resonant (PIR) controller is utilized to realize zero magnitude error and selective disturbance rejection. Instead of the PIR controller, a vector proportion integration (VPI) controller is designed to quickly and accurately regulate current which achieve zero both amplitude and phase frequency response at the resonant frequency simultaneously. In this paper, the PEMFC grid-connected system based on PIR and VPI controllers are developed according to the operating characteristics of a PEMFC generation system, then analyze and compare the performance of compensation harmonics between them. The total harmonic distortion (THD) of grid-connected voltage and current are measured by means of the criterion of IEEE Std1547-2003. This proposed grid-connected method will provide a novel approach for the design of advanced PEMFC grid-connected control system. [ABSTRACT FROM AUTHOR]

A multi-stack fuel cell system (MFCS) comprises multiple individual fuel cell systems (FCSs). The allocation of power among these FCSs significantly impacts the overall system performance, which is influenced by various factors, including ambient conditions. To effectively distribute power and enhance the efficiency and fuel economy of the Multi-Fuel Cell System (MFCS) at high altitudes, this work presents a coordinated optimal distribution strategy based on the concept of the maximum efficiency range (MER) of the MFCS. The configuration of the MFCS includes three fuel cell systems, and a model is developed to account for the altitude effect on the MFCS. In addition, an efficiency analysis of the MFCS is conducted for various altitudes. In this study, the coordinated optimal distribution strategy, based on the MER, is employed to achieve optimal power allocation among the various fuel cell systems within the MFCS. The results demonstrate that the proposed strategy yields higher average efficiency of the MFCS and consumes less hydrogen compared to the equal distribution strategy at three altitude levels: 0 m, 3000 m, and 4000 m. Furthermore, the proposed strategy effectively improves the efficiency of the MFCS at different altitudes by adjusting the MER, yielding satisfactory outcomes, particularly in high-altitude regions. • A coordinated optimal power distribution strategy based on maximum efficiency range is proposed. • The maximum efficiency range of multi-stack fuel cell system at different altitudes is proposed. • The proposed strategy could improve multi-stack fuel cell system efficiency and fuel economy. [ABSTRACT FROM AUTHOR]

In order to efficiently absorb more regenerative braking energy which sustains much longer compared with the conventional vehicle, and guarantee the safety of the hybrid system under the actual driving cycle of locomotive, an energy management control based on dynamic factor strategy is proposed for a scale-down locomotive system which consists of proton exchange membrane fuel cell (PEMFC) and battery pack. The proposed strategy which has self-adaption function for different driving cycles aims to achieve the less consumption of hydrogen and higher efficiency of the hybrid system. The experimental results demonstrate that the proposed strategy is able to maintain the charge state of battery (SOC) better than Equivalent Consumption Minimization Strategy (ECMS), and the proposed strategy could keep the change trend of SOC, which the final SOC is closed to the target value regardless of the initial SOC of battery. Moreover, the hydrogen consumption has been reduced by 0.86g and the efficiency of overall system has been raised of 2% at least than ECMS under the actual driving cycle through the proposed strategy. Therefore, the proposed strategy could improve the efficiency of system by diminishing the conversion process of energy outputted by fuel cell. [ABSTRACT FROM AUTHOR]

In this paper, a hybrid powertrain configuration which consists of multiple proton exchange membrane fuel cell (PEMFC) systems, batteries and supercapacitors (SCs) is developed for LF-LRV tramway. A state machine strategy based on droop control is proposed to coordinate multiple power sources, avoid the transients and rapid changes of power demand, and achieve high efficiency without degrading the mechanism performance for an energy management system of hybrid tramway. A hybrid system model of tramway is established with commercially available devices, and then the proposed energy management strategy is evaluated with a real driving cycle of tramway from Turkey. The results demonstrate that the proposed strategy is able to coordinate multiple power sources based on their natural characteristics, satisfy rapid changes of the power demand and achieve high efficiency of overall tramway. Hence, the proposed energy management strategy for high-power hybrid tramway will improve the hydrogen consumptions of overall hybrid system and the efficiencies of each power source. [ABSTRACT FROM AUTHOR]

In this study, the catalytic steam reforming of biomass tar for hydrogen production was carried out in a fixed-bed reactor with NiO/ceramic foam catalyst. The ceramic foam used as catalyst carrier was a three-dimensional porous material with high porosity and high specific heat capacity. The effects of reaction temperature, steam to carbon ratio (S/C) and equivalence ratio (ER) on gas quality parameters were investigated. And the fresh, coked and regenerated NiO/ceramic foam catalysts were characterized by SEM and XRD analyses. It was found that, when the temperatures varied from 500 to 900 °C and S/C ratio from 0 to 4, H 2 yields were in the range of 28.29–105.28 g H 2 /kg tar. With increasing ERs, the concentrations of H 2 decreased from 63.13 to 18.96%. SEM and XRD analyses showed that the catalyst was in situ activated by reducing nickel oxide to the active nickel metal during a reducing atmosphere in steam reforming process. [ABSTRACT FROM AUTHOR]