Magnesium-based hydrogen storage materials,such as MgH_(2),have attracted considerable attention because of its superior hydrogen storage capacities,inexpensive,and excellent reversibility.However,their high thermodyn...Magnesium-based hydrogen storage materials,such as MgH_(2),have attracted considerable attention because of its superior hydrogen storage capacities,inexpensive,and excellent reversibility.However,their high thermodynamic stabilities and slow kinetics lead to relatively high desorption temperatures,which severely limit the wide application of MgH_(2).In this study,the inclusion of vanadium induced the formation Ni-Co metal-organic frameworks(MOF)from a NiCo layered double hydroxide(LDH),thereby increasing the number of defects and vacancies,and improving the hydrogen storage properties of MgH_(2).The synthesized NiCo-MOF/V-O-doped MgH_(2) system demonstrates excellent hydrogen storage capacity.More specifically,5 wt.%of H_(2) was released over 20 min at a relatively low dehydrogenation temperature of 250℃,and almost complete dehydrogenation was achieved at 300℃ for 5 min.In addition,at 125℃,the hydrogen storage material absorbed 5.5 wt.%H_(2) in 10 min.Furthermore,the activation energy of dehydrogenation was determined to be 69.588±6.302 k J·mol^(-1)which is significantly lower than that of the ball-milled MgH_(2)(i.e.,118.649±2.825 kJ·mol^(-1)).It was therefore inferred that during dehydrogenation process,a Mg_(2)Ni/Mg_(2) NiH_4 hydrogen pump is formed by Ni,while the V-H and Co-H bonds formed by Co and V during the reaction act synergistically to catalyze the absorption and desorption of hydrogen,thereby increasing the hydrogen storage capacity of MgH_(2).These experiments provide new perspectives on the commercial application of MgH_(2).展开更多
为解决激光定向能量沉积(laser-directed energy deposition,L-DED)成型工艺制备的镍钴基功能梯度材料(NiCo-FGMs)磨削后表面质量一致性较差这一问题,基于正交试验分析了磨削工艺参数对NiCo-FGMs的磨削力和表面粗糙度的影响规律,并建立...为解决激光定向能量沉积(laser-directed energy deposition,L-DED)成型工艺制备的镍钴基功能梯度材料(NiCo-FGMs)磨削后表面质量一致性较差这一问题,基于正交试验分析了磨削工艺参数对NiCo-FGMs的磨削力和表面粗糙度的影响规律,并建立相应的预测模型.针对粗加工与精加工的不同加工目标,利用第二代非支配排序遗传算法(NSGA-Ⅱ)结合熵权法与逼近理想解的排序方法即熵权TOPSIS(technique for order proference by similarity to ideal solution)法进行了多目标磨削工艺参数优化,并进行验证.结果表明:粗加工磨削参数采用a_(p)=53.61μm,v_(s)=29.99 m/s,v_(w)=311.89 mm/min;精加工磨削参数采用ap=14.96μm,v_(s)=29.99 m/s,v_(w)=300.92 mm/min.经两道工序加工,表面粗糙度标准差从0.195μm降至0.101μm,有效提高NiCo-FGMs的表面粗糙度一致性.展开更多
The imperative quest for renewable energy sources and advanced energy storage technologies has arisen amidst the escalating perils of climate change and dwindling fossil fuel reserves.In the realm of energy storage te...The imperative quest for renewable energy sources and advanced energy storage technologies has arisen amidst the escalating perils of climate change and dwindling fossil fuel reserves.In the realm of energy storage technologies,asymmetric supercapacitor(ASC)has garnered significant attention owing to its high energy density and power density.In the quest for advanced electrode materials for ASC,the integration of 2D layered heterostructures on hierarchical porous carbon(HPC)substrates has emerged as a promising approach to enhance the electrochemical performance.Herein,a highly innovative hierarchical NiCo LDH/MoS_(2)/HPC heterostructure was successfully synthesized using a simple two-step hydrothermal method for the electrode materials of ASC.Benefiting from the unique hierarchical heterostructure of NiCo LDH/MoS_(2)/HPC composite and the synergistic effect between the components,it reveals an exceptional specific capacitance of 2368 F/g at 0.5 A/g in a three-electrode system,which significantly exceeds that of conventional supercapacitor electrodes.Additionally,the ASC device of NiCo LDH/MoS_(2)/HPC//HPC achieves remarkable specific capacitance of 236 F/g at 0.5 A/g and an impressive energy density of 84Wh/kg at a power density of 400 W/kg,as well as superior cyclic stability.This study not only demonstrates the effectiveness of incorporating MoS_(2) and NiCo LDH into a carbon-based framework for supercapacitor applications but also opens avenues for designing more efficient energy storage devices.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.U24A2044,52071092).
文摘Magnesium-based hydrogen storage materials,such as MgH_(2),have attracted considerable attention because of its superior hydrogen storage capacities,inexpensive,and excellent reversibility.However,their high thermodynamic stabilities and slow kinetics lead to relatively high desorption temperatures,which severely limit the wide application of MgH_(2).In this study,the inclusion of vanadium induced the formation Ni-Co metal-organic frameworks(MOF)from a NiCo layered double hydroxide(LDH),thereby increasing the number of defects and vacancies,and improving the hydrogen storage properties of MgH_(2).The synthesized NiCo-MOF/V-O-doped MgH_(2) system demonstrates excellent hydrogen storage capacity.More specifically,5 wt.%of H_(2) was released over 20 min at a relatively low dehydrogenation temperature of 250℃,and almost complete dehydrogenation was achieved at 300℃ for 5 min.In addition,at 125℃,the hydrogen storage material absorbed 5.5 wt.%H_(2) in 10 min.Furthermore,the activation energy of dehydrogenation was determined to be 69.588±6.302 k J·mol^(-1)which is significantly lower than that of the ball-milled MgH_(2)(i.e.,118.649±2.825 kJ·mol^(-1)).It was therefore inferred that during dehydrogenation process,a Mg_(2)Ni/Mg_(2) NiH_4 hydrogen pump is formed by Ni,while the V-H and Co-H bonds formed by Co and V during the reaction act synergistically to catalyze the absorption and desorption of hydrogen,thereby increasing the hydrogen storage capacity of MgH_(2).These experiments provide new perspectives on the commercial application of MgH_(2).
文摘为解决激光定向能量沉积(laser-directed energy deposition,L-DED)成型工艺制备的镍钴基功能梯度材料(NiCo-FGMs)磨削后表面质量一致性较差这一问题,基于正交试验分析了磨削工艺参数对NiCo-FGMs的磨削力和表面粗糙度的影响规律,并建立相应的预测模型.针对粗加工与精加工的不同加工目标,利用第二代非支配排序遗传算法(NSGA-Ⅱ)结合熵权法与逼近理想解的排序方法即熵权TOPSIS(technique for order proference by similarity to ideal solution)法进行了多目标磨削工艺参数优化,并进行验证.结果表明:粗加工磨削参数采用a_(p)=53.61μm,v_(s)=29.99 m/s,v_(w)=311.89 mm/min;精加工磨削参数采用ap=14.96μm,v_(s)=29.99 m/s,v_(w)=300.92 mm/min.经两道工序加工,表面粗糙度标准差从0.195μm降至0.101μm,有效提高NiCo-FGMs的表面粗糙度一致性.
文摘研究探讨了NiCo合金阳极催化甲烷助氧电解水制氢的性能,评估了其电催化活性、稳定性、耐久性及能效。在长时间循环测试中,NiCo合金阳极表现出良好的稳定性,电流密度在100 h内几乎没有明显下降。能效评估结果表明,NiCo合金阳极在1.8 V的电解电压下达到最高能效0.87 k Wh/m^(3),证明其能够高效地将电能转化为化学能。该研究表明,NiCo合金阳极在甲烷助氧电解水制氢中表现出优异的性能,具有广泛的应用前景,尤其在绿色氢气生产和能源节约方面具有重要意义。
基金supported by the National Key Research and Development Program of China(No.2021YFB3801200)the National Natural Science Foundation of China(Nos.22278051,22178044,and 22308043)the Science and Technology Innovation foundation of CNPC(No.2022DQ02–0608).
文摘The imperative quest for renewable energy sources and advanced energy storage technologies has arisen amidst the escalating perils of climate change and dwindling fossil fuel reserves.In the realm of energy storage technologies,asymmetric supercapacitor(ASC)has garnered significant attention owing to its high energy density and power density.In the quest for advanced electrode materials for ASC,the integration of 2D layered heterostructures on hierarchical porous carbon(HPC)substrates has emerged as a promising approach to enhance the electrochemical performance.Herein,a highly innovative hierarchical NiCo LDH/MoS_(2)/HPC heterostructure was successfully synthesized using a simple two-step hydrothermal method for the electrode materials of ASC.Benefiting from the unique hierarchical heterostructure of NiCo LDH/MoS_(2)/HPC composite and the synergistic effect between the components,it reveals an exceptional specific capacitance of 2368 F/g at 0.5 A/g in a three-electrode system,which significantly exceeds that of conventional supercapacitor electrodes.Additionally,the ASC device of NiCo LDH/MoS_(2)/HPC//HPC achieves remarkable specific capacitance of 236 F/g at 0.5 A/g and an impressive energy density of 84Wh/kg at a power density of 400 W/kg,as well as superior cyclic stability.This study not only demonstrates the effectiveness of incorporating MoS_(2) and NiCo LDH into a carbon-based framework for supercapacitor applications but also opens avenues for designing more efficient energy storage devices.
