Classification and technical target of water electrolysis for hydrogen production

Continuous efforts are underway to reduce carbon emissions worldwide in response to global climate change.Water electrolysis technology,in conjunction with renewable energy,is considered the most feasible hydrogen production technology based on the viable possibility of large-scale hydrogen production and the zero-carbon-emission nature of the process.However,for hydrogen produced via water electrolysis systems to be utilized in various fields in practice,the unit cost of hydrogen production must be reduced to$1/kg H_(2).To achieve this unit cost,technical targets for water electrolysis have been suggested regarding components in the system.In this paper,the types of water electrolysis systems and the limitations of water electrolysis system components are explained.We suggest guideline with recent trend for achieving this technical target and insights for the potential utilization of water electrolysis technology.

Recent advances and future prospects on Ni_(3)S_(2)-Based electrocatalysts for efficient alkaline water electrolysis

Green hydrogen(H_(2))produced by renewable energy powered alkaline water electrolysis is a promising alternative to fossil fuels due to its high energy density with zero-carbon emissions.However,efficient and economic H_(2) production by alkaline water electrolysis is hindered by the sluggish hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).Therefore,it is imperative to design and fabricate high-active and low-cost non-precious metal catalysts to improve the HER and OER performance,which affects the energy efficiency of alkaline water electrolysis.Ni_(3)S_(2) with the heazlewoodite structure is a potential electrocatalyst with near-metal conductivity due to the Ni–Ni metal network.Here,the review comprehensively presents the recent progress of Ni_(3)S_(2)-based electrocatalysts for alkaline water electrocatalysis.Herein,the HER and OER mechanisms,performance evaluation criteria,preparation methods,and strategies for performance improvement of Ni_(3)S_(2)-based electrocatalysts are discussed.The challenges and perspectives are also analyzed.

Generation of input spectrum for electrolysis stack degradation test applied to wind power PEM hydrogen production

Hydrogen production by proton exchange membrane electrolysis has good fluctuation adaptability,making it suitable for hydrogen production by electrolysis in fluctuating power sources such as wind power.However,current research on the durability of proton exchange membrane electrolyzers is insufficient.Studying the typical operating conditions of wind power electrolysis for hydrogen production can provide boundary conditions for performance and degradation tests of electrolysis stacks.In this study,the operating condition spectrum of an electrolysis stack degradation test cycle was proposed.Based on the rate of change of the wind farm output power and the time-averaged peak-valley difference,a fluctuation output power sample set was formed.The characteristic quantities that played an important role in the degradation of the electrolysis stack were selected.Dimensionality reduction of the operating data was performed using principal component analysis.Clustering analysis of the data segments was completed using an improved Gaussian mixture clustering algorithm.Taking the annual output power data of wind farms in Northwest China with a sampling rate of 1 min as an example,the cyclic operating condition spectrum of the proton-exchange membrane electrolysis stack degradation test was constructed.After preliminary simulation analysis,the typical operating condition proposed in this paper effectively reflects the impact of the original curve on the performance degradation of the electrolysis stack.This study provides a method for evaluating the degradation characteristics and system efficiency of an electrolysis stack due to fluctuations in renewable energy.

Hydrogen generation with acid/alkaline amphoteric water electrolysis

To reduce the energy consumption of the electrolytic hydrogen generation process, we propose a novel approach to generate hydrogen with acidic/alkaline amphoteric water electrolysis, wherein hydrogen is produced inside an acidic solution and oxygen evolved under alkaline condition, and a membrane is employed in the middle of the electrolyzer to restrain neutralization. The electrode polarization is greatly reduced due to the specific arrangement of the acidic/alkaline amphoteric electrolyzer. The rate of hydrogen production achieves over four times higher than that of the alkaline aqueous solution at 2.2 V, and the energy consumption is reduced approximately 30% under the current density of 200 m A/cm ^2. The investigation of transmembrane potential drop indicates water splitting on the membrane surfaces, which compensates for acid or alkaline loss on-site and maintains the concentration approximately constant during electrolysis process. The acidic/alkaline amphoteric water electrolysis is promising as an energy saving, clean and sustainable hydrogen production technology.

Towards high-performance and robust anion exchange membranes(AEMs)for water electrolysis:Super-acid-catalyzed synthesis of AEMs

The increasing demand for hydrogen energy to address environmental issues and achieve carbon neutrality has elevated interest in green hydrogen production,which does not rely on fossil fuels.Among various hydrogen production technologies,anion exchange membrane water electrolyzer(AEMWE)has emerged as a next-generation technology known for its high hydrogen production efficiency and its ability to use non-metal catalysts.However,this technology faces significant challenges,particularly in terms of the membrane durability and low ionic conductivity.To address these challenges,research efforts have focused on developing membranes with a new backbone structure and anion exchange groups to enhance durability and ionic conductivity.Notably,the super-acid-catalyzed condensation(SACC)synthesis method stands out due to its user convenience,the ability to create high molecular weight(MW)polymers,and the use of oxygen-tolerant organic catalysts.Although the synthesis of anion exchange membranes(AEMs)using the SACC method began in 2015,and despite growing interest in this synthesis approach,there remains a scarcity of review papers focusing on AEMs synthesized using the SACC method.The review covers the basics of SACC synthesis,presents various polymers synthesized using this method,and summarizes the development of these polymers,particularly their building blocks including aryl,ketone,and anion exchange groups.We systematically describe the effects of changes in the molecular structure of each polymer component,conducted by various research groups,on the mechanical properties,conductivity,and operational stability of the membrane.This review will provide insights into the development of AEMs with superior performance and operational stability suitable for water electrolysis applications.

NiCoP nanoleaves array for electrocatalytic alkaline H2 evolution and overall water splitting

The development of non-precious, high-efficient and durable electrocatalysts for H2 evolution in alkaline media is highly desirable. Herein we report NiCoP nanoleaves array vertically grown on Ni foam for H2 evolution and overall water splitting via simple hydrothermal treatment and phosphorization. The selfsupported NiCoP nanoleaves architecture contributes to more exposed active sites, the smaller contact resistance between catalyst and substrate, faster ion diffusion and electron transfer. As a result, the optimized electrode requires only overpotentials of 98 and 173 mV to achieve current densities of 10 and100 m A cm-2 in 1.0 M KOH,respectively. Besides, used as both anode and cathode simultaneously, the electrode delivers current densities of 100 and 200 m A cm-2 at cell voltages of only 1.8 and 1.87 V, respectively. Moreover, the relatively high efficiency of about 11.4% for solar-driven water splitting further illustrates the application of our catalyst to sustainable development based on green technologies.

Effect of supercritical water on the stability and activity of alkaline carbonate catalysts in coal gasification

The stability and activity of alkaline carbonate catalysts in supercritical water coal gasification has been investigated using density functional theory method. Our calculations present that the adsorption of Na2CO3 on coal are more stable than that of K2CO3, but the stability of Na2CO3 is strongly reduced as the cluster gets larger. In supercritical water system, the dispersion and stability of Na2CO3 catalyst on coal support is strongly improved. During coal gasification process, Na2CO3 transforms with supercritical water into NaOH and NaHCO3, which is beneficial for hydrogen production. The transformation process has been studied via thermodynamics and kinetics ways. The selectively catalytic mechanism of NaOH and the intermediate form of sodium-based catalyst in water-gas shift reaction for higher hydrogen production has also been investigated. Furthermore, NaOH can transform back to Na2CO3 after catalyzing the water-gas shift reaction. Thus, the cooperative effects between supercritical water and Na2CO3 catalyst form a benignant circle which greatly enhances the reaction rate of coal gasification and promotes the production of hydrogen.

Ternary layered double hydroxide oxygen evolution reaction electrocatalyst for anion exchange membrane alkaline seawater electrolysis

Anion exchange membrane(AEM)water electrolyzers are promising energy devices for the production of clean hydrogen from seawater.However,the lack of active and robust electrocatalysts for the oxygen evolution reaction(OER)severely impedes the development of this technology.In this study,a ternary layered double hydroxide(LDH)OER electrocatalyst(NiFeCo-LDH)is developed for high-performance AEM alkaline seawater electrolyzers.The AEM alkaline seawater electrolyzer catalyzed by the NiFeCo LDH shows high seawater electrolysis performance(0.84 A/cm^(2)at 1.7 Vcell)and high hydrogen production efficiency(77.6%at 0.5 A/cm^(2)),thus outperforming an electrolyzer catalyzed by a benchmark IrO_(2)electrocatalyst.The NiFeCo-LDH electrocatalyst greatly improves the kinetics of the AEM alkaline seawater electrolyzer,consequently reducing its activation loss and leading to high performance.Based on the results,this NiFeCo-LDH-catalyzed AEM alkaline seawater electrolyzer can likely surpass the energy conversion targets of the US Department of Energy.

Heteroatom-Induced Accelerated Kinetics on Nickel Selenide for Highly Efficient Hydrazine-Assisted Water Splitting and Zn-Hydrazine Battery

Hydrazine-assisted water electrolysis is a promising energy conversion technology for highly efficient hydrogen production.Rational design of bifunctional electrocatalysts,which can simultaneously accelerate hydrogen evolution reaction(HER)/hydrazine oxidation reaction(HzOR)kinetics,is the key step.Herein,we demonstrate the development of ultrathin P/Fe co-doped NiSe_(2) nanosheets supported on modified Ni foam(P/Fe-NiSe_(2)) synthesized through a facile electrodeposition process and subsequent heat treatment.Based on electrochemical measurements,characterizations,and density functional theory calculations,a favorable“2+2”reaction mechanism with a two-step HER process and a two-step HzOR step was fully proved and the specific effect of P doping on HzOR kinetics was investigated.P/Fe-NiSe_(2) thus yields an impressive electrocatalytic performance,delivering a high current density of 100 mA cm^(−2) with potentials of−168 and 200 mV for HER and HzOR,respectively.Additionally,P/Fe-NiSe_(2) can work efficiently for hydrazine-assisted water electrolysis and Zn-Hydrazine(Zn-Hz)battery,making it promising for practical application.

Strong electronic coupling of CoNi and N-doped-carbon for efficient urea-assisted H2 production at a large current density

Exploiting efficient urea oxidation reaction(UOR)and hydrogen evolution reaction(HER)catalysts are significant for energy-saving H2 production through urea-assisted water electrolysis,but it is still challenging.Herein,carbon-encapsulated CoNi coupled with CoNiMoO(CoNi@CN-CoNiMoO)is prepared by solvothermal method and calcination to enhance the activity/stability of urea-assisted water electrolysis at large current density.It exhibits good activity for UOR(E10/1,000=1.29/1.40 V)and HER(E-10/-1000=-45/-245 mV)in 1.0 M KOH+0.5 M urea solution.For the UOR||HER system,CoNi@CN-CoNiMoO only needs 1.58 V at 500 mA cm-2 and shows good stability.Density functional theory calculation suggests that the strong electronic interaction at the interface between NiCo alloy and N-doping-carbon layers can optimize the adsorption/desorption energy of UOR/HER intermediates and accelerate the water dissociation,which can expedite urea decomposition and Volmer step,thus increasing the UOR and HER activity,respectively.This work provides a new solution to design UOR/HER catalysts for H2 production through urea-assisted water electrolysis.

Efficiency of Aluminium and Copper Coated Aluminium Electrode in Hydrogen Fuel Generation from Rain Water

Water electrolysis is considered as the most capable and old technology for hydrogen fuel preparation. Electrolysis needs external electrical energy through electrodes to split water into hydrogen and oxygen. An efficient electrolysis requires suitable electrodes to minimize potential drop. In this study Aluminium and Copper Coated Aluminium were used as different combination of Anodes and Cathodes to find out more efficient electrodes combination. NaCl solution in rain water was taken as electrolyte. Rain water was taken to avoid ionic impedance of tap water and expenses of distilled water. In this study, the most efficient electrode combination was Copper Coated Aluminium (anode)-Aluminium (cathode) and gave the highest efficiency of hydrogen production to about 11% at normal temperature for very low concentration of NaCl (0.051 M) which increased with temperature, up to 29% upon rising of temp to 60°C. It was showed that higher concentration of electrolyte would surge the efficiency significantly. If the supplied heat could be provided from any waste heat sources then this study would be more efficient. However, current research evaluated the technical feasibility of this electrode combination for producing hydrogen with electrolysis of rain water utilizing electricity and modified electrodes.

Molybdenum disulfide as hydrogen evolution catalyst:From atomistic to materials structure and electrocatalytic performance

Hydrogen production via water electrolysis defines the novel energy vector for achieving a sustainable society.However,the true progress of the given technology is hindered by the sluggish and complex hydrogen evolution reaction(HER)occurring at the cathodic side of the system where overpriced and scarce Pt-based electrocatalysts are usually employed.Therefore,efficient platinum group metals(PGMs)-free electrocatalysts to carry out HER with accelerated kinetics are urgently demanded.In this scenario,molybdenum disulfide(MoS_(2))owing to efficacious structural attributes and optimum hydrogen-binding free energy(ΔG_(H*))is emerging as a reliable alternative to PGMs.However,the performance of MoS_(2)-based electrocatalysts is still far away from the benchmark performance.The HER activity of MoS_(2)can be improved by engineering the structural parameters i.e.,doping,defects inducement,modulating the electronic structure,stabilizing the 1 T phase,creating nanocomposites,and altering the morphologies using appropriate fabrication pathways.Here,we have comprehensively reviewed the majority of the scientific endeavors published in recent years to uplift the HER activity of MoS_(2)-based electrocatalysts using different methods.Advancements in the major fabrication strategies including hydrothermal synthesis methods,chemical vapor deposition,exfoliation techniques,plasma treatments,chemical methodologies,etc.to tune the structural parameters and hence their ultimate influence on the electrocatalytic activity in acidic and/or alkaline media have been thoroughly discussed.This study can provide encyclopedic insights about the fabrication routes that have been pursued to improve the HER performance of MoS_(2)-based electrocatalysts.

降低可再生能源水电解制氢时氧中氢安全风险的措施

可再生能源水电解制氢在低负荷运行时氧中氢含量超标容易导致安全风险,针对碱液互混、隔膜两侧气体分压差和运行负荷对氧中氢含量的影响,分析认为主要是分离罐后的碱液互混所导致,其对指标影响的占比超过50%,提出了降低氧中氢安全风险的改进措施,在普遍使用的碱水电解制氢流程中,增加碱液脱气罐,同时对补水泵进行适应性增容改造,可消除碱液互混对氧中氢的影响,即使在10%的低负荷下运行也可实现副产氧气中氢含量1%以下,满足降低安全风险的同时,可更充分地适应可再生能源发电不稳定的能源特性。

面向海上风电的碱性电解水制氢系统热力学分析与优化设计

[目的]为了最大化利用电能与海水资源,针对海上风电的碱性电解水(AWE)制氢系统进行热力学分析和优化设计,研究工作压力、工作温度、碱液流量等对系统运行特性的影响。[方法]基于热力学、电化学及质量平衡模型,通过Aspen Plus软件建立碱性电解水制氢的热力学平衡模型,并与实验结果进行对比验证。[结果]结果表明,此方案碱性电解水制氢系统最佳工作压力和工作温度分别为9 bar和70℃,最佳碱液流量为1600 t/h。系统能量损失和㶲损随输入电流密度的增加而增加。碱性电解输入电流密度为3000 A/m^(2)时,系统能量效率和㶲效率分别为63.58%和57.27%,系统能量损失占总能量投入的26%,其中电解槽㶲损最高,占系统总㶲损的93.39%。[结论]通过该参数优化方法,可以得到合适的工作参数范围,能够为海上风电制氢参数选择提供参考。

基于多物理场耦合模型的碱性水电解槽工作特性

风电制氢系统将富余的风电用于电解水制取氢气,有效提高了风电的消纳能力。碱性水电解槽是电制氢的重要设备,通过数值方法研究其工作特性对于提高制氢效率具有重要意义。然而,现有电解槽模型通常只关注其电学性能,难以对各工况下设备运行状态进行准确预测。为此,提出了碱性水电解槽电场-流场-浓度场多物理场耦合模型。首先对碱性水电解槽进行了几何建模;接着建立电解槽电场、流场、浓度场数学模型,并基于COMSOL平台进行多物理场模型搭建;在验证模型有效性后,分析了电压、温度、压力、电解液浓度与流速对电解槽稳态、瞬态工作特性的影响。模拟结果表明:升高温度与降低压力减小了单位电流所需电压;降低电流、升高温度与压力增大了电解效率。单位电流所需电压随电解液浓度增加先减小后增大,而电解效率随浓度增加而先升后降,50℃时在质量分数为30%处达到最大电解效率。电压突变会产生电流过冲现象;流速突变不会发生电流过冲现象。研究成果可为碱性水电解槽设计与性能预测提供理论指导。

Recent advances in hybrid water electrolysis for energy-saving hydrogen production

Electricity-driven water splitting to convert water into hydrogen(H_(2)has been widely regarded as an efficient approach for H_(2)production.Nevertheless,the energy conversion efficiency of it is greatly limited due to the disadvantage of the sluggish kinetic of oxidation evolution reaction(OER).To effectively address the issue,a novel concept of hybrid water electrolysis has been developed for energy–saving H_(2)production.This strategy aims to replace the sluggish kinetics of OER by utilizing thermodynamically favorable organics oxidation reaction to replace OER.Herein,recent advances in such water splitting system for boosting H_(2)evolution under low cell voltage are systematically summarized.Some notable progress of different organics oxidation reactions coupled with hydrogen evolution reaction(HER)are discussed in detail.To facilitate the development of hybrid water electrolysis,the major challenges and perspectives are also proposed.

电解制氢产业的基础研究

文章从政策、技术、市场三个方面对电解制氢产业进行介绍,同时对我国氢能产业支持政策进行了介绍,通过对比现有的电解制氢工艺,对技术特性、优缺点及应用现状进行了总结,最后整理了国内外绿氢项目的发展现状,旨为同行了解电解制氢产业提供参考。

碱性水电解制氢装置模型研究综述

在大规模绿色制氢方面,碱性水电解制氢是一种相对成熟的技术,对碱性水电解制氢装置进行建模是理解、分析和优化碱性水电解制氢过程及相关设备的有效途径。目前,虽然存在多种研究碱性水电解制氢装置的模型,但缺乏对模型发展现状及其存在问题的总结。针对碱性水电解制氢装置模型的研究进展进行了综述,首先对3种主要的水电解制氢技术进行了对比,并对碱性水电解制氢装置采用的电解槽的工作原理进行了介绍;然后从稳态模型和动态模型的角度总结了基于碱性水电解制氢装置建立的模型;最后针对碱性水电解制氢装置组成部分的研发现状进行了介绍。分析结果显示:1)3种主要的水电解制氢技术分别为碱性水电解制氢、质子交换膜水电解制氢和固体氧化物水电解制氢。2)目前商业上碱性水电解制氢装置采用的电解槽的制氢效率在59%~70%之间,许多研究都集中在通过改变电解槽运行条件和创新其相关部件来提高其制氢效率方面。3)碱性水电解制氢装置的稳态模型主要包括热力学模型和电化学模型,动态模型一般包括气体纯度模型和热模型。研究结果可为进一步改进碱性水电解制氢装置建模提供理论和技术支撑。

海上风电制氢技术及氢能产业发展现状与建议

利用海上风电制氢是未来重要的制氢方式,也是实现“双碳”目标的重要途径。对不同水电解制氢技术的优缺点、海上风电制氢装置的运行方式进行了介绍,从氢气的存储与运输、加氢站、氢能应用领域这3个方面对氢能产业发展现状进行了分析,并对氢能产业发展提出了建议。研究结果显示:1)碱性水电解制氢装置的整体造价低,单台装置的产氢量大,但难以快速启动和调节负荷,适用于输出功率波动较小的集中式风力发电电源。2)PEM水电解制氢装置可以更好地耦合输出功率波动较大的电源,未来其将向大功率、低成本制氢的方向发展,以适应大规模海上风电制氢项目的需求。3)从短期来看,高压气态储氢技术是发展重点;而从长期来看,低温液态储氢技术是未来重要发展方向。氨储氢、甲醇储氢和有机液态储氢等新型化合物储氢技术的发展为氢能存储提供了更多选择。4)目前中国日加注能力在200 kg的加氢站属于示范运营站,未来加氢站有望从500 kg的日加注量起步,大日加注量的加氢站将会成为未来1~2年内建设的主流加氢站。5)目前氢能在化工、交通、天然气掺氢等领域均有应用,且未来发展潜力巨大。

钼-钴-钒多金属复合材料设计及碱性电解水制氢性能

为制备高效碱性电解水催化剂,先通过水浴共沉淀法在80℃下反应4 h获得钴钒双金属氧化物基底,再通过在200℃下反应8 h负载含钼化合物制得钼-钴-钒多金属复合材料Co_(2)V_(2)O_(7)@MoS_(2)。该复合材料的微观形貌和物相分析表明,钴钒双金属氧化物基底为六边形片状形貌,表面负载的含钼化合物为纳米片状且呈现无定型结构。电化学测试结果表明,所得钼-钴-钒多金属复合材料Co_(2)V_(2)O_(7)@MoS_(2)-8在驱动电解水阳极析氧反应中表现出优异的电催化活性,当驱动电流密度为10 mA/cm2时,所需过电势为241 mV,相较于单独组分Co_(2)V_(2)O_(7)和MoS_(2)分别提升29.1%和22.8%。此外,Co_(2)V_(2)O_(7)@MoS_(2)-8材料在进行80 h恒电流密度测试后,过电势降低3.8%,表明该复合材料具有良好的长寿命循环稳定性。Co_(2)V_(2)O_(7)@MoS_(2)复合材料催化活性的提升,与其本身的界面结构有关,内部丰富的微孔通道和界面异质结均有利于界面电子的快速传递,最终加速碱性电解水的动力学过程。