Recent advances and key perspectives of in-situ studies for oxygen evolution reaction in water electrolysis

Electricity-driven water splitting to produce hydrogen is one of the most efficient ways to alleviate energy crisis and environmental pollution problems,in which the anodic oxygen evolution reaction(OER)is the key half-reaction of performance-limiting in water splitting.Given the complicated reaction process and surface reconstruction of the involved catalysts under actual working conditions,unraveling the real active sites,probing multiple reaction intermediates and clarifying catalytic pathways through in-situ characterization techniques and theoretical calculations are essential.In this review,we summarize the recent advancements in understanding the catalytic process,unlocking the water oxidation active phase and elucidating catalytic mechanism of water oxidation by various in-situ characterization techniques.Firstly,we introduce conventionally proposed traditional catalytic mechanisms and novel evolutionary mechanisms of OER,and highlight the significance of optimal catalytic pathways and intrinsic stability.Next,we provide a comprehensive overview of the fundamental working principles,different detection modes,applicable scenarios,and limitations associated with the in-situ characterization techniques.Further,we exemplified the in-situ studies and discussed phase transition detection,visualization of speciation evolution,electronic structure tracking,observation of reaction active intermediates,and monitoring of catalytic products,as well as establishing catalytic structure-activity relationships and catalytic mechanism.Finally,the key challenges and future perspectives for demystifying the water oxidation process are briefly proposed.

Toward a comprehensive hypothesis of oxygen-evolution reaction in the presence of iron and gold

This study investigates the effects of Fe on the oxygen-evolution reaction(OER)in the presence of Au.Two distinct areas of OER were identified:the first associated with Fe sites at low overpotential(~330 mV),and the second with Au sites at high overpotential(~870 mV).Various factors such as surface Fe concentration,electrochemical method,scan rate,potential range,concentration,method of adding K_(2)Fe O_(4),nature of Fe,and temperature were varied to observe diverse behaviors during OER for Fe O_(x)H_(y)/Au.Trace amounts of Fe ions had a significant impact on OER,reaching a saturation point where the activity did not increase further.Strong electronic interaction between Fe and Au ions was indicated by X-ray photoelectron spectroscopy(XPS)and electron paramagnetic resonance(EPR)analyses.In situ visible spectroscopy confirmed the formation of Fe O_(4)^(2-)during OER.In situ Mossbauer and surfaceenhanced Raman spectroscopy(SERS)analyses suggest the involvement of Fe-based species as intermediates during the rate-determining step of OER.A lattice OER mechanism based on Fe O_(x)H_(y)was proposed for operation at low overpotentials.Density functional theory(DFT)calculations revealed that Fe oxide,Fe-oxide clusters,and Fe doping on the Au foil exhibited different activities and stabilities during OER.The study provides insights into the interplay between Fe and Au in OER,advancing the understanding of OER mechanisms and offering implications for the design of efficient electrocatalytic systems.

Dissolution mechanism of a deep-buried sandstone reservoir in a deep water area:A case study from Baiyun Sag,Zhujiang River(Pearl River)Mouth Basin

Dissolution mechanism and favorable reservoir distribution prediction are the key problems restricting oil and gas exploration in deep-buried layers.In this paper,the Enping Formation and Zhuhai Formation in Baiyun Sag of South China Sea was taken as a target.Based on the thin section,scanning electron microscopy,X-ray diffraction,porosity/permeability measurement,and mercury injection,influencing factors of dissolution were examined,and a dissolution model was established.Further,high-quality reservoirs were predicted temporally and spatially.The results show that dissolved pores constituted the main space of the Paleogene sandstone reservoir.Dissolution primarily occurred in the coarse-and medium-grained sandstones in the subaerial and subaqueous distributary channels,while dissolution was limited in fine-grained sandstones and inequigranular sandstones.The main dissolved minerals were feldspar,tuffaceous matrix,and diagenetic cement.Kaolinization of feldspar and illitization of kaolinite are the main dissolution pathways,but they occur at various depths and temperatures with different geothermal gradients.Dissolution is controlled by four factors,in terms of depositional facies,source rock evolution,overpressure,and fault activities,which co-acted at the period of 23.8–13.8 Ma,and resulted into strong dissolution.Additionally,based on these factors,high-quality reservoirs of the Enping and Zhuhai formations are predicted in the northern slope,southwestern step zone,and Liuhua uplift in the Baiyun Sag.

Recent Advances in the Comprehension and Regulation of Lattice Oxygen Oxidation Mechanism in Oxygen Evolution Reaction

Water electrolysis,a process for producing green hydrogen from renewable energy,plays a crucial role in the transition toward a sustainable energy landscape and the realization of the hydrogen economy.Oxygen evolution reaction(OER)is a critical step in water electrolysis and is often limited by its slow kinetics.Two main mechanisms,namely the adsorbate evolution mechanism(AEM)and lattice oxygen oxidation mechanism(LOM),are commonly considered in the context of OER.However,designing efficient catalysts based on either the AEM or the LOM remains a topic of debate,and there is no consensus on whether activity and stability are directly related to a certain mechanism.Considering the above,we discuss the characteristics,advantages,and disadvantages of AEM and LOM.Additionally,we provide insights on leveraging the LOM to develop highly active and stable OER catalysts in future.For instance,it is essential to accurately differentiate between reversible and irreversible lattice oxygen redox reactions to elucidate the LOM.Furthermore,we discuss strategies for effectively activating lattice oxygen to achieve controllable steady-state exchange between lattice oxygen and an electrolyte(OH^(-)or H_(2)O).Additionally,we discuss the use of in situ characterization techniques and theoretical calculations as promising avenues for further elucidating the LOM.

Study on the Operation Mechanism and Effect of the Yellow River Water and Sediment Regulation System

In order to scientifically deal with the problems of less water and more sediment in the Yellow River and the uncoordinated relationship between water and sediment,it is necessary to establish a perfect water and sediment regulation system.Through the calculation of the sediment transport capacity of the Yellow River and the application of the water and sediment regulation system,it is found that the sediment transport efficiency of the Yellow River will increase with the increase of water flow,and there will be an obvious inflection point near the flat discharge.The joint regulation of the backbone reservoir group can discharge the large discharge close to the minimum flat discharge of the downstream river,which improves the sediment transport capacity of the river and alleviates the problem of sediment deposition.In this paper,through the introduction of the Yellow River water and sediment regulation project system,regulation indicators and mechanisms,the author discusses in detail the Yellow River water and sediment regulation scheme and its operation effect,hoping to provide help promote the improvement of the Yellow River governance effect.

Intrinsic correlation between the generalized phase equilibrium condition and mechanical behaviors in hydrate-bearing sediments

The phase equilibrium and mechanical behaviors of natural gas hydrate-bearing sediment are essential for gas recovery from hydrate reservoirs.In heating closed systems,the temperature-pressure path of hydrate-bearing sediment deviates from that of pure bulk hydrate,reflecting the porous media effect in phase equilibrium.A generalized phase equilibrium equation was established for hydrate-bearing sediments,which indicates that both capillary and osmotic pressures cause the phase equilibrium curve to shift leftward on the temperature-pressure plane.In contrast to bulk hydrate,hydrate-bearing sediment always contains a certain amount of unhydrated water,which keeps phase equilibrium with the hydrate within the hydrate stability field.With changes in temperature and pressure,a portion of pore hydrate and unhydrated water may transform into each other,affecting the shear strength of hydrate-bearing sediment.A shear strength model is proposed to consider not only hydrate saturation but also the change in temperature and pressure of hydrate-bearing sediment.The model is validated by experimental data with various hydrate saturation,temperature and pressure conditions.The deformation induced by partial dissociation was studied through depressurization tests under constant effective stress.The reduction in gas pressure within the hydrate stability field indeed caused sediment deformation.The dissociation-induced deformation can be reasonably estimated as the difference in volume between hydrate-bearing and hydrate-free sediments from the compression curves.

Simulation of the Fate of Faecal Bacteria in Estuarine and Coastal Waters Based on A Fractionated Sediment Transport Model

A two-dimensional depth-integrated numerical model is refined in this paper to simulate the hydrodynamics, graded sediment transport process and the fate of faecal bacteria in estuarine and coastal waters. The sediment mixture is divided into several fractions according to the grain size. A bed evolution model is adopted to simulate the processes of the bed elevation change and sediment grain size sorting. The faecal bacteria transport equation includes enhanced source and sink terms to represent bacterial kinetic transformation and disappearance or reappearance due to sediment deposition or re-suspension. A novel partition ratio and dynamic decay rates of faecal bacteria are adopted in the numerical model. The model has been applied to the turbid water environment in the Bristol Channel and Severn estuary, UK. The predictions by the present model are compared with field data and those by non-fractionated model.

Formation and water environmental evolution of the Nansihu Lake

Through high-resolution research of sedimental chronology and the sediment environmental indexes, such as graininess, minerals, magnetic parameters, pigment content, organic carbon and chronology in Ds-core and Ws-core in Nansihu Lake, the authors analyze the formation cause of the Nansihu Lake and its water environmental changes. Historical documents are also analyzed here in order to reach the conclusion. Researches indicate that the Nansihu Lake came into being about 2500 aBP and its evolution succession can be divided into four stages. In this evolution process, several scattered lakes merge into one large lake in the east of China. This process is distinctively affected by the overflow of the Yellow River, the excavation of the Grand Canal and other human activities.

Numerical Simulation of Mechanical Compaction of Deepwater Shallow Sediments

To study the compaction law and overpressure evolution in deepwater shallow sediments, a large-strain compaction model that considers material nonlinearity and moving boundary is formulated. The model considers the dependence of permeability and material properties on void ratio. The modified Cam-Clay model is selected as the constitutive relations of the sediments, and the deactivation/reactivation method is used to capture the moving top surface during the deposition process. A one-dimensional model is used to study the compaction law of the shallow sediments. Results show that the settlement of the shallow sediments is large under their own weight during compaction. The void ratio decreases strictly with burial depth and decreases more quickly near the seafloor than in the deeper layers. The generation of abnormal pressure in the shallow flow sands is closely related to the compaction law of shallow sediments. The two main factors that affect the generation of overpressure in the sands are deposition rate and permeability of overlying clay sediments. Overpressure increases with an increase in deposition rate and a decrease in the permeability of the overlying clay sediment. Moreover, an upper limit for the overpressure exists. A two-dimensional model is used to study the differential compaction of the shallow sediments. The pore pressure will still increase due to the inflow of the pore fluid from the neighboring clay sediment even though the deposition process is interrupted.

O-O bond formation mechanisms during the oxygen evolution reaction over synthetic molecular catalysts

Water oxidation is one of the most important reactions in natural and artificial energy conversion schemes.In nature,solar energy is converted to chemical energy via water oxidation at the oxygen-evolving center of photosystem II to generate dioxygen,protons,and electrons.In artificial energy schemes,water oxidation is one of the half reactions of water splitting,which is an appealing strategy for energy conversion via photocatalytic,electrocatalytic,or photoelectrocatalytic processes.Because it is thermodynamically unfavorable and kinetically slow,water oxidation is the bottleneck for achieving large-scale water splitting.Thus,developing highly efficient water oxidation catalysts has attracted the interests of researchers in the past decades.The formation of O-O bonds is typically the rate-determining step of the water oxidation catalytic cycle.Therefore,better understanding this key step is critical for the rational design of more efficient catalysts.This review focuses on elucidating the evolution of metal-oxygen species during transition metal-catalyzed water oxidation,and more importantly,on discussing the feasible O-O bond formation mechanisms during the oxygen evolution reaction over synthetic molecular catalysts.

Hydrogen and Oxygen Isotope Fractionation Mechanism in the Hydrothermal System and Its Geologic Significance

The geochemical behaviors of hydrogen and oxygen isotopes in the hydrothermal system and their inher-ent relationship with the water / rock exchange are discussed in this paper In addition to the temperature con-ditions, the effective W / R ratio is another factor controlling the changes in H and O isotope compositions ofthe altered rock and hydrothermal water. Besides, the application and geological significance of the water-rockexchange theory are also discussed in the light of the H and O isotope compositions and their variation charac-teristics of the mineralizing hydrothermal water and altered rocks from several mineral deposits. Finally, abrief evolutional model of H and O istotope compositions of meteoric and magmatic hydrothermal waters in ahydrothermal system is given.

The role of proton dynamics on the catalyst-electrolyte interface in the oxygen evolution reaction

The development of non‐precious metal catalysts that facilitate the oxygen evolution reaction(OER)is important for the widespread application of hydrogen production by water splitting.Various perovskite oxides have been employed as active OER catalysts,however,the underlying mechanism that occurs at the catalyst‐electrolyte interface is still not well understood,prohibiting the design and preparation of advanced OER catalysts.Here,we report a systematic investigation into the effect of proton dynamics on the catalyst‐electrolyte interfaces of four perovskite catalysts:La_(0.5)Sr_(0.5)CoO_(3‐δ)(LSCO),LaCoO_(3),LaFeO_(3),and LaNiO_(3).The pH‐dependent OER activities,H/D kinetic isotope effect,and surface functionalization with phosphate anion groups were investigated to elucidate the role of proton dynamics in the rate‐limiting steps of the OER.For oxides with small charge‐transfer energies,such as LSCO and LaNiO_(3),non‐concerted proton‐coupled electron transfer steps are involved in the OER,and the activity is strongly controlled by the proton dynamics on the catalyst surface.The results demonstrate the important role of interfacial proton transfer in the OER mechanism,and suggest that proton dynamics at the interface should carefully be considered in the design of future high‐performance catalysts.

Monitoring and Analysis on Impact of Gezhouba Hydroproject on Downstream River Course

Gezhouba hydroproject was impounded and put into operation in 1981. In order to analyse the impact on the downstream river course, Jingjiang Hydrologic and Water Resources Survey Bureau of Changjiang Water Resources Commission has conducted prototype observation on the Yichang-Chenglingji river stretch. On basis of the observed data, the change in river regime and scour-sedimentation evolution and water surface profile below the dam are analysed systematically. The results show that the scouring of downstream river course mainly stretches from Yichang to Ouchikou, mainly occurring in 1980～1987; the scourring mainly takes place in the river channel and the water surface profile drops significantly in dry season,but not quite in high flood season.

缺水胁迫区水系统优化调控理论与模式

开展水系统优化调控是实现缺水胁迫区人-水-生态和谐可持续发展的关键措施之一,对于保障地区经济社会稳定发展和生态健康具有重要意义。本文以京津冀作为典型缺水胁迫区案例,通过解析水系统内涵,总结得出缺水胁迫区水系统存在深度耦合、强烈竞争和系统失衡三大现象,发现水系统呈现非稳态和稳态之间交替演进的模式,并通过构建水系统稳态指数,研判了京津冀地区水系统状态变化发展过程。研究以实现自然社会水系统健康为调控目标,提出缺水胁迫区水系统“高内聚-低耦合”解耦式调控模式,结合京津冀现实状态,在需求侧开展“保障刚需-压缩弹性-抑制奢侈”层次化调控,在供给侧进行“自然水网-人工水网-虚拟水网”适配性优化,提出京津冀“三线七河、四区八源”一体化水网布局,进而实现水系统的整体健康。

我国江河演变新格局与系统保护治理

系统治理是我国新时期治水实践的根本遵循。近几十年来,受自然气候演变与强人类活动影响,我国江河“量-质-域-流-生”过程,特别是水沙通量及其过程发生了显著变化,导致河流水沙来源变化、河道冲淤转换、河床与河势形态演变、江湖关系变化及河口三角洲造陆减缓与蚀退等。我国江河演变呈现新的格局,给江河湖库防洪安全、生态安全和沿岸经济发展带来新的挑战。面对治水新形势,提出需从生态系统整体性和流域系统性出发,科学认知江河水沙情势变化规律与发展趋势,统筹确定流域适宜治理度与水沙调控临界阈值体系,系统推进流域“量-质-域-流-生”协同修复,优化布局水土流失治理格局,持续提升水沙调控及优化配置利用体系整体合力,保护河口生境系统,保障江河长久安澜,筑牢国家水安全防线。

取水工程对松花江悦来河段影响研究

为了研究引水工程的建设对松花江悦来河段水沙变化的影响,构建了松花江干流悦来河段的平面二维水沙数学模型,分析了引水工况对松花江悦来河段的流速、水位、分流比和冲淤分布的影响。研究结果表明:松北引渠引水入松花江致使入江处水位抬升为0.03~0.04 m,由于松南引渠引水,致使取水口附近的主河道水位下降约0.03 m;在天然条件下,松南下口引渠位置分流量为78 m~3/s,分流比为8.8%,在取水方案下,松南上口引渠分流量为104 m~3/s,分流比为8.5%,松南下口引渠分流量为323 m~3/s,分流比为28.9%;在天然条件下,悦来河段主河道呈现冲刷状态,冲刷深度为1.0 m左右,双口引渠导致取水口附近的泥沙淤积较天然条件有所增加,其中松南引渠下口淤积更为显著,引渠口门处淤积厚度可达1.0 m以上。

黑龙江干流黑河市城区段河床演变研究

黑龙江黑河市城区河段河道受自然及人为因素影响,河床演变复杂。采用Mann-Kendall趋势检验法和双累积曲线法分析了水沙变化趋势。基于实测水文和泥沙资料,对河床稳定性及冲淤变化进行了定量研究。研究结果表明,该河段属于少沙河流,结雅河口以上年径流和输沙量随时间呈减小趋势,结雅河口以下年径流没有明显的趋势性变化,年输沙量呈减小趋势。自然状态下,河段岸线和深泓线位置基本稳定,河床冲淤变化不大,以约10年为一个周期,基本可以达到冲淤平衡。在人类活动及支流汇入影响下,黑河水位站至长发岛段纵向不稳定,预测会引起该段未防护岛屿洲滩的岸线变迁。

黄河下游高村-孙口段冲淤变化及影响因素定量分析

为探究黄河过渡段河道滩槽演变规律,采用实测水沙和大断面数据,分析近年来高孙段河床冲淤、水沙条件和河床形态的演变,以年和汛期为时间尺度,用灰色关联度分析河槽冲淤量与水沙条件及河床形态的关联程度。结果表明,近年来高孙段以冲刷为主,汛期是年内输沙的主要时期;高村断面来沙系数可以分为波动减小(2002~2017年)和快速增加(2018~2019年)两大阶段,而河床形态中水力半径和宽深比变化趋势完全相反,糙率存在增大趋势;高村断面的水沙条件及河床形态与高孙段河道冲淤具有较高的关联程度,河床形态比水沙条件具有更高的相关性。

黄河下游游荡性河段心滩形态特征与水沙过程响应关系

黄河下游游荡性河段素以调整速度快与幅度大著称,河道心滩复杂多变,探究心滩形态特征与水沙过程之间的响应关系对于解析下游游荡性河段的河床演变机制具有重要的意义。围绕黄河下游铁谢至高村游荡性河段的心滩面积与数量等形态特征指标,结合下游水沙及冲淤特性,采用遥感影像和数值模拟相结合的研究方法厘清游荡性河段水沙过程与心滩面积及数量之间的响应关系,揭示水沙变化对心滩形态特征的影响机制。结果表明:自小浪底水库运用以来,下游河道发生剧烈冲刷,游荡性河段累计冲刷量15.37亿m^(3),占下游累计冲刷量的68%;在小浪底水库运用以前,游荡性河段的心滩面积与数量年际变化剧烈,存在着明显的增长与降低变化过程,而小浪底水库运用以后,该河段的心滩面积与数量呈现先减小后增大再减小的变化趋势;随着4 a滑动汛期平均流量和4 a滑动汛期平均来沙系数的增加,游荡性河段的心滩面积及数量分别呈现出减小和增大的变化趋势。数值模拟方法不仅可以较好地再现心滩发育及演变过程,还可以定性地表征特定水动力学因素对心滩形态特征塑造的影响,为阐明游荡性河段的心滩演变理论提供了一种新的研究方法。研究成果不仅有助于阐明河流平面形态的调整过程,还可为今后河道整治工程的布局提供理论支撑。

机械力活化方解石复合硫酸亚铁去除水中镉/砷复合污染研究

水体中的镉、砷等重金属污染严重威胁人类的健康安全,其中镉/砷复合污染去除难度更大。通过水中镉/砷复合污染去除试验,探究机械力活化方解石复合硫酸亚铁去除镉/砷复合污染的性能,发现机械力活化方解石可显著提升水中镉/砷复合污染的去除效果。试验结果表明,活化方解石复合硫酸亚铁在30 min内对溶液中镉、砷离子的去除率可达到99%以上。采用SEM-EDS、XRD、XPS等方法对活化方解石复合硫酸亚铁高效去除水中镉/砷复合污染机理进行研究,结果表明,方解石在机械力活化的作用下改变了自身的结晶度和溶解活性,其在水体中溶解水解产生CO_(3)^(2-)与OH^(-)的性能明显提升,OH^(-)促进硫酸亚铁在溶液中与砷形成稳定的铁氧结合态沉淀,CO_(3)^(2-)与溶液中的镉结合形成稳定的碳酸镉沉淀。