China, People’s Republic

Alloying and structural modification are two effective ways to enhance the hydrogen storage kinetics and decrease the thermal stability of Mg and Mg-based alloys. In order to enhance the characteristics of Mg₂Ni-type alloys Cu and La were added to an Mg₂Ni-type alloy and the sample alloys (Mg₂₄Ni₁₀Cu₂)_100−xLa_x (x = 0 5 10 15 20) were prepared by melt spinning. The influences of La content and spinning rate on the gaseous and electrochemical hydrogen storage properties of the sample alloys were explored in detail. The structural identification carried out by XRD and TEM indicates that the main phase of the alloys is Mg₂Ni and the addition of La results in the formation of the secondary phases LaMg₃ and La₂Mg₁₇. The as-spun alloys have amorphous and nanocrystalline structures and the addition of La promotes glass formation. The electrochemical properties examined by an automatic galvanostatic system show that the samples possess a good activation capability and achieve their maximal discharge capacities within three cycles. The discharge potential characteristics were vastly ameliorated by melt spinning and La addition. The discharge capacities of the samples achieve their maximal values as the La content changes and the discharge capacities always increase with increasing spinning rate. The addition of La leads to a decline in hydrogen absorption capacity but it can effectively enhance the rate of hydrogen absorption. The addition of La and melt spinning significantly increase the hydrogen desorption rate due to the reduced activation energy.

Minimising tailpipe emissions and the decarbonisation of transport in a cost effective way remains a major objective for policymakers and vehicle manufacturers. Current trends are rapidly evolving but appear to be moving towards solutions in which vehicles which are increasingly electrified. As a result we will see a greater linkage between the wider energy system and the transportation sector resulting in a more complex and mutual dependency. At the same time major investments into technological innovation across both sectors are yielding rapid advancements into on-board energy storage and more compact/lightweight on-board electricity generators. In the absence of sufficient technical data on such technology holistic evaluations of the future transportation sector and its energy sources have not considered the impact of a new generation of innovation in propulsion technologies. In this paper the potential impact of a number of novel powertrain technologies are evaluated and presented. The analysis considers heavy duty vehicles with conventional reciprocating engines powered by diesel and hydrogen hybrid and battery electric vehicles and vehicles powered by hydrogen fuel cells and freepiston engine generators (FPEGs). The benefits are compared for each technology to meet the expectations of representative medium and heavy-duty vehicle drivers. Analysis is presented in terms of vehicle type vehicle duty cycle fuel economy greenhouse gas (GHG) emissions impact on the vehicle etc.. The work shows that the underpinning energy vector and its primary energy source are the most significant factor for reducing primary energy consumption and net CO₂ emissions. Indeed while an HGV with a BEV powertrain offers no direct tailpipe emissions it produces significantly worse lifecycle CO2 emissions than a conventional diesel powertrain. Even with a de-carbonised electricity system (100 g CO2/kWh) CO₂ emissions are similar to a conventional Diesel fuelled HGV. For the HGV sector range is key to operator acceptability of new powertrain technologies. This analysis has shown that cumulative benefits of improved electrical powertrains on-board storage efficiency improvements and vehicle design in 2025 and 2035 mean that hydrogen and electric fuelled vehicles can be competitive on gravimetric and volumetric density. Overall the work demonstrates that presently there is no common powertrain solution appropriate for all vehicle types but how subtle improvements at a vehicle component level can have significant impact on the design choices for the wider energy system.

The synthesis of low-cost and highly active electrodes for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is very important for water splitting. In this work the novel amorphous iron-nickel phosphide (FeP-Ni) nanocone arrays as efficient bifunctional electrodes for overall water splitting have been in-situ assembled on conductive three-dimensional (3D) Ni foam via a facile and mild liquid deposition process. It is found that the FeP-Ni electrode demonstrates highly efficient electrocatalytic performance toward overall water splitting. In 1 M KOH electrolyte the optimal FeP-Ni electrode drives a current density of 10 mA/cm2 at an overpotential of 218 mV for the OER and 120 mV for the HER and can attain such current density for 25 h without performance regression. Moreover a two-electrode electrolyzer comprising the FeP-Ni electrodes can afford 10 mA/cm2 electrolysis current at a low cell voltage of 1.62 V and maintain long-term stability as well as superior to that of the coupled RuO2/NF‖Pt/C/NF cell. Detailed characterizations confirm that the excellent electrocatalytic performances for water splitting are attributed to the unique 3D morphology of nanocone arrays which could expose more surface active sites facilitate electrolyte diffusion benefit charge transfer and also favourable bubble detachment behaviour. Our work presents a facile and cost-effective pathway to design and develop active self-supported electrodes with novel 3D morphology for water electrolysis.

Ammonia borane (AB) can be catalytically hydrolyzed to provide hydrogen at room temperature due to its high potentaial for hydrogen storage. Non-precious metal heterogeneous catalysts have broad application in the field of energy catalysis. In this article catalysts precursor is obtained from Co-Ti-resorcinol-formaldehyde resin by sol–gel method. Co/TiO2@N-C (CTC) catalyst is prepared by calcining the precursor under high temperature conditions in nitrogen atmosphere. Co-CoOx/TiO2@N-C (COTC) is generated by the controllable oxidation reaction of CTC. The catalyst can effectively promote the release of hydrogen during the hydrolytic dehydrogenation of AB. High hydrogen generation at a specific rate of 5905 mL min−1 gCo−1 is achieved at room temperature. The catalyst retains its 85% initial catalytic activity even for its fifth time use in AB hydrolysis. The synergistic effect among Co Co3O4 and TiO2 promotes the rate limiting step with dissociation and activation of water molecules by reducing its activation energy. The applied method in this study promotes the development of non-precious metals in catalysis for utilization in clean energy sources.

Given the limited sources of fossil fuels mankind should find new ways to meet its energy demands. In this regard geothermal and solar energy are acknowledged as reliable safe promising and clean means for this purpose. In this research study a comparative analysis is applied on geothermal and solar-driven multi-generation systems for clean electricity and hydrogen production through energy and exergy assessments. The system consists of an organic Rankine cycle a proton electrolyte membrane electrolyzer and a thermoelectric generator subsystem. The Engineering Equation Solver software has been utilized in order to model the system and obtain the output contours sensitivity analysis and exergy destruction. The results were calculated considering the ambient temperature of Bandar Abbas city as a case study considering the geothermal system due to better performance in comparison to the solar system. According to the sensitivity analysis the turbine efficiency evaporator inlet temperature thermoelectric generator suitability criterion pump efficiency and evaporator inlet mass flow rate are the most influential parameters. Also the exergy analysis showed that the utmost system's exergy destruction is pertinent to the evaporator and the least is related to the pump. In addition the system produces 352816 kWh and 174.913 kg of electrical power and hydrogen during one year.

Density functional theory (DFT) calculations have been performed to investigate the hydrogen dissociation and diffusion on Mg (0001) surface with Ni incorporating at various locations. The results show that Ni atom is preferentially located inside Mg matrix rather than in/over the topmost surface. Further calculations reveal that Ni atom locating in/over the topmost Mg (0001) surface exhibits excellent catalytic effect on hydrogen dissociation with an energy barrier of less than 0.05 eV. In these cases the rate-limiting step has been converted from hydrogen dissociation to surface diffusion. In contrast Ni doping inside Mg bulk not only does little help to hydrogen dissociation but also exhibits detrimental effect on hydrogen diffusion. Therefore it is crucial to stabilize the Ni atom on the surface or in the topmost layer of Mg (0001) surface to maintain its catalytic effect. For all the case of Ni-incorporated Mg (0001) surfaces the hydrogen atom prefers firstly immigrate along the surface and then penetrate into the bulk. It is expected that the theoretical findings in the present study could offer fundamental guidance to future designing on efficient Mg-based hydrogen storage materials.

In recent years photocatalytic technology driven by solar energy has been extensively investigated to ease energy crisis and environmental pollution. Nevertheless efficiency and stability of photocatalysts are still unsatisfactory. To address these issues design of advanced photocatalysts is important. Cadmium sulphide (CdS) nanomaterials are one of the promising photocatalysts. Among them hollow-structured CdS featured with enhanced light absorption ability large surface area abundant active sites for redox reactions and reduced diffusion distance of photogenerated carriers reveals a broad application prospect. Herein main synthetic strategies and formation mechanism of hollow CdS photocatalysts are summarized. Besides we comprehensively discuss the current development of hollow-structured CdS nanomaterials in photocatalytic applications including H₂ production CO₂ reduction and pollutant degradation. Finally brief conclusions and perspectives on the challenges and future directions for hollow CdS photocatalysts are proposed.

Developing non-precious catalysts as Pt substitutes for electrochemical hydrogen evolution reaction (HER) with superior stability in acidic electrolyte is of critical importance for large-scale low-cost hydrogen production from water. Herein we report a CoCrFeNiAl high-entropy alloy (HEA) electrocatalyst with self-supported structure synthesized by mechanical alloying and spark plasma sintering (SPS) consolidation. The HEA after HF treatment and in situ electrochemical activation for 4000 cycles of cyclic voltammetry (HF-HEAa2) presents favourable activity with overpotential of 73 mV to reach a current density of 10 mA cm⁻² and a Tafel slope of 39.7 mV dec⁻¹. The alloy effect of Al/Cr with Co/Fe/Ni at atomic level high-temperature crystallization as well as consolidation by SPS endow CoCrFeNiAl HEA with high stability in 0.5 M H₂SO₄ solution. The superior performance of HF-HEAa2 is related with the presence of metal hydroxides/oxides groups on HEA.

In the current study the effect of hydrogen atoms on the intergranular failure of α-iron is examined by a molecular dynamics (MD) simulation. The effect of hydrogen embrittlement on the grain boundary (GB) is investigated by diffusing hydrogen atoms into the grain boundaries using a bicrystal body-centered cubic (BCC) model and then deforming the model with a uniaxial tension. The Debye Waller factors are applied to illustrate the volume change of GBs and the simulation results suggest that the trapped hydrogen atoms in GBs can therefore increase the excess volume of GBs thus enhancing intergranular failure. When a constant displacement loading is applied to the bicrystal model the increased strain energy can barely be released via dislocation emission when H is present. The hydrogen pinning effect occurs in the current dislocation slip system <111>{112}. The hydrogen atoms facilitate cracking via a decrease of the free surface energy and enhance the phase transition via an increase in the local pressure. Hence the failure mechanism is prone to intergranular failure so as to release excessive pressure and energy near GBs. This study provides a mechanistic framework of intergranular failure and a theoretical model is then developed to predict the intergranular cracking rate

The Paris Agreement has set the goal of carbon neutrality to cope with global climate change. China has pledged to achieve carbon neutrality by 2060 which will strategically change everything in our society. As the main source of carbon emissions the consumption of fossil energy is the most profoundly affected by carbon neutrality. This work presents an analysis of how China can achieve its goal of carbon neutrality based on its status of fossil energy utilization. The significance of transforming fossils from energy to resource utilization in the future is addressed while the development direction and key technologies are discussed.