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.

Paleoenvironmental implications of the calcium isotope characteristics in the MD81349 from the Nintyeast Ridge in the Indian Ocean

A δ^（44） Ca curve from shells of the planktonic foraminifera Globigerinoides sacculifer in calcareous biogenic oozes has been extracted from the Nintyeast Ridge in the Indian Ocean since 300 ka. By combining terrigenous inputs（e.g., grain size, magnetic susceptibility, and turbidite frequency） with the oceanic productivity（e.g., biogenic content and Neogloboquadrina dutertrei content）, it is found that the curve＇s variations are closely related to the historical evolution of the oceanic calcium cycle. The δ^（44）Ca value is in lower tendency and has small oscillation during Marine Isotope Stage（MIS） 6, when the supply of terrigenous detrital is highest. In contrast, during MIS 3,5 and 7, the δ^（44） Ca values are in higher tendency, and their fluctuations are consistent with the variations of the productivity proxies. These results suggest that the calcium isotopes are mainly influenced by the input of the Himalayan erosion products to the northern Indian Ocean. In addition, the developmental stages of calcareous planktons may have a secondary impact on the fluctuations of the calcium isotope ratio of sea water.

The relation between modes of lithologic association and interlayer-gliding structures in coal mine

As a case study of the Panji No.1 Coal Mine in Anhui Province, based on thesite measured and statistical data, summarized the lithologic associations, characteristicsand distribution laws of interlayer-gliding structures and tectonic coal in the No.11-2 coalseams.The results show that 9 modes of lithologic association can form interlayer-glidingstructures.It is more easy for rock slip to occur when the lithologic associations are mainroof + coal seam + immediate floor type, compound roof+immediate roof + coal seam +immediate floor type and immediate roof + coal seam + immediate floor type.Lithologicassociations of roof and floor are the precondition to the formation of interlayer-glidingstructures.

Selective conversion of N_(2) to NH_(3) on highly dispersed RuO_(2) using amphiphilic ionic liquid-anchored fibrous carbon structure

Ammonia (NH_(3)) plays a key role in the agricultural fertilizer and commodity chemical industries and is useful for exploring hydrogen storage carriers.The electrochemical nitrogen reduction reaction (NRR) is receiving attention as an environmentally sustainable NH_(3) synthesis replacement for the traditional Haber–Bosch process owing to its near ambient reaction conditions (<100℃ and 1 atm).However,its NH_(3) yield and faradaic efficiency are extremely low because of the sluggish kinetics of N≡N bond dissociation and the hindrance from competitive hydrogen evolution.To overcome these challenges,we herein introduce a dual-functionalized ionic liquid (1-(4-hydroxybutyl)-3-methylimidazolium hydroxide[HOBIM]OH) for a highly dispersed ruthenium oxide electrocatalyst to achieve a biased NRR.The observed uniform distribution of RuO_(2) on the carbon fiber and increase in the surface area for N_(2) adsorption by limiting proton access can be attributed to the presence of imidazolium ions.Moreover,extensive N_(2) adsorption contributes to enhanced NRR selectivity with an NH_(3) yield of 3.0×10^(-10)mol cm^(-2)s^(-1)(91.8μg h^(-1)mg^(-1)) and a faradaic efficiency of 2.2%at-0.20 V_(RHE).We expect our observations to provide new insights into the design of effective electrode structures for electrochemical NH;synthesis.

Boosting the oxygen evolution reaction performance of wrinkled Mn(OH)_(2) via conductive activation with a carbon binder

Electrochemical water splitting is one of the most reliable approaches for environmental-friendly hydrogen production.Because of their stability and abundance,Mn-based materials have been studied as electrocatalysts for the oxygen evolution reaction(OER),which is a more sluggish reaction in the water splitting system.To increase the OER activity of Mn,it is imperative to facilitate the structural change of Mn oxide to the active phase with Mn_(3)+species,known as the active site.Here,we present the relationship between the electronic conductivity in the catalyst layer and the formation of the Mn active phase,δ-MnO_(2),from wrinkled Mn(OH)_(2).Mn(OH)_(2) has poor conductivity,and it disrupts the oxidation reaction toward MnOOH orδ-MnO_(2).Adjacent conductive carbon to Mn(OH)_(2) enabled Mn(OH)_(2) to be oxidized toδ-MnO_(2).Furthermore,after repetitive cyclic voltammetry activation,the more conductive environment resulted in a higher density ofδ-MnO_(2) through the irreversible phase transition,and thus it contributes to the improvement of the OER activity.

Steam activation of Fe-N-C catalyst for advanced power performance of alkaline hydrazine fuel cells

Alkaline hydrazine liquid fuel cells(AHFC) have been highlighted in terms of high power performance with non-precious metal catalysts.Although Fe-N-C is a promising non-Pt electrocatalyst for oxygen reduction reaction(ORR),the surface density of the active site is very low and the catalyst layer should be thick to acquire the necessary number of catalytic active sites.With this thick catalyst layer,it is important to have an optimum pore structure for effective reactant conveyance to active sites and an interface structure for faster charge transfer.Herein,we prepare a Fe-N-C catalyst with magnetite particles and hierarchical pore structure by steam activation.The steam activation process significantly improves the power performance of the AHFC as indicated by the lower IR and activation voltage losses.Based on a systematic characterization,we found that hierarchical pore structures improve the catalyst utilization efficiency of the AHFCs,and magnetite nanoparticles act as surface modifiers to reduce the interracial resistance between the electrode and the ion-exchange membrane.

Rapid determination of lithium-ion battery degradation: High C-rate LAM and calculated limiting LLI

Herein,incremental capacity-differential voltage (IC-DV) at a high C-rate (HC) is used as a non-invasive diagnostic tool in lithium-ion batteries,which inevitably exhibit capacity fading caused by multiple mechanisms during charge/discharge cycling.Because battery degradation modes are complex,the simple output of capacity fading does not yield any useful data in that respect.Although IC and DV curves obtained under restricted conditions (<0.1C,25℃) were applied in non-invasive analysis for accurate observation of degradation symptoms,a facile,rapid diagnostic approach without intricate,complex calculations is critical in on-board applications.Herein,Li Ni_(0.5)Mn_(0.3)Co_(0.2)O_(2)(NMC532)/graphite pouch cells were cycled at 4 and 6C and the degradation characteristics,i.e.,loss of active materials (LAM) and loss of lithium inventory (LLI),were parameterized using the IC-DV curves.During the incremental current cycling,the initial steep LAM and LLI slopes underwent gradual transitions to gentle states and revealed the gap between low-and high-current measurements.A quantitative comparison of LAM at high and low C-rate showed that a IC;revealed the relative amount of available reaction region limited by cell polarization.However,this did not provide a direct relationship for estimating the LAM at a low C-rate.Conversely,the limiting LLI,which is calculated at a C-rate approaching 0,was obtained by extrapolating the LLI through more than two points measured at high C-rate,and therefore,the LLI at 0.1C was accurately determined using rapid cycling.

Optimistic performance of carbon-free hydrazine fuel cells based on controlled electrode structure and water management

In this study, we first attempted to discover the optimal configuration of membrane-electrode assemblies(MEAs) used to achieve a high performance of direct hydrazine fuel cells(DHFCs). We have investigated the effect of water management and the electrode thickness on the performance of DHFCs, depending on the hydrophobicity of the gas diffusion layers in the cathode and the catalyst loading in the anode with the carbon-supported Ni, synthesized by a polyol process. With the optimal water management and electrode thickness, the MEA constructed using the as-prepared Ni/C anode catalyst containing the metallic and low oxidative state and ultra-low Pt loading cathode reduced the ohmic resistance and mass transfer limitation in the current-voltage curves observed for the alkaline DHFC, achieving an impressive power performance over 500 mW cm^(–2).

A Simulation Study of Support Break-Off and Water Inrush during Mining under the High Confined and Thick Unconsolidated Aquifer

The thick Cenozoic unconsolidated aquifer is deposited under Sunan syncline core in Huaibei coalfield, the water yield property of unconsolidated bottom aquifer is strong and water pressure is high in some areas (up to 4 MPa in some areas). Water inrush accident often occurs during mining under unconsolidated aquifer, the biggest characteristic is abnormal mine pressure and support break-off during water inrush accident comparing with normal condition. In order to study mechanism of?support break-off and water inrush during mining under the high confined thick unconsolidated aquifer, a simulation of similar material was designed. The experimental results indicated that, under normal condition, the compound breakage sequence of water-resisting key strata between coal seam and high confined thick unconsolidated aquifer is from top to bottom and the basic reason of synchronous fracture is the load of bottom key strata increased suddenly when the breakage of top key strata happened. Because of high confined thick unconsolidated aquifer, surface acts on the bottom key strata soil layer in the form of uniformly distributed load, which is the load-transfer mechanism of confined thick unconsolidated aquifer. Once the overlying key strata compound breaks, the height of unstable strata will reach far more than 30 meters and exceed support capability of current fully-mechanized mining supporter, which leads to support break-off accident during mining process under confined unconsolidated aquifer.

100 W-class green hydrogen production from ammonia at a dual-layer electrode containing a Pt-Ir catalyst for an alkaline electrolytic process

Ammonia allows storage and transport of hydrogen over long distances and is an attractive potential hydrogen carrier.Electrochemical decomposition has recently been used for the conversion of ammonia to hydrogen and is regarded as a future technology for production of CO_(2)-free pure hydrogen.Herein,a heterostructural Pt-Ir dual-layer electrode is developed and shown to achieve successful long-term operation in an ammonia electrolyzer with an anion exchange membrane(AEM).This electrolyzer consisted of eight membra ne electrode assemblies(MEAs)with a total geometric area of 200 cm~2 on the anode side,which resulted in a hydrogen production rate of 25 L h~(-1).We observed the degradation in MEA performance attributed to changes in the anode catalyst layer during hydrogen production via ammonia electrolysis.Furthermore,we demonstrated the relationship between the ammonia oxidation reaction(AOR)and the oxygen evolution reaction(OER).

Iridium oxide fabrication and application: A review

Despite the scarcity and cost of iridium oxide,it is still the material of choice in numerous fields of science and applications,including capacitors,electrochromism,sensors,and various oxidation electrocatalysis(e.g.,chlorine evolution reaction,detoxification,and oxygen evolution reaction).Such versatility is attributed to the distinct features of iridium oxides,such as their activity,biocompatibility,conductivity,and durability.The features and properties of iridium oxides are strongly dependent on the fabrication method.In this review,methodologies relating to the synthesis and fabrication of solid-state iridium oxides have been thoroughly collected and discussed.Structuring and crystallization techniques for iridium oxides are also noted.At the end of the review,the effects of utilizing a certain fabrication method on the characteristics of the iridium oxide product are recapitulated,together with the recommended application of the product in various fields.

Analysis on geological structures influencing gas occurrence at Qidong coalmine

The occurrence state of methane is mostly controlled by coalfield geologicalstructures.The coal-bearing strata at Qidong coalmine experienced many tectonic cyclessince their formation.The gas content made by the complicated structural geologic systemat the coalfield is very different, which is obviously higher on the north side of the Weimiaofracture belt than that on the south side and near itself.This thesis discussed the gas occurrenceregularity based on the geometric characteristics of the geological structure andits regional tectonic evolution.This study can provide a foundation for coalfield exploitationand deal with coal and gas outburst.

Preparation of Ag@AgCl-doped TiO_2/sepiolite and its photocatalytic mechanism under visible light

A cube-like Ag@Ag Cl-doped TiO2/sepiolite（denoted Ag@Ag Cl–TiO2/sepiolite） was successfully synthesized via a novel method. X-ray diffraction, scanning electron microscopy, energy dispersion X-ray fluorescence, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and diffuse reflectance ultraviolet–visible spectroscopy were performed to determine the structure and physicochemical properties of Ag@Ag Cl–TiO2/sepiolite. SEM micrographs revealed that Ag@Ag Cl nanoparticles and TiO2 film are well deposited on the surface of tube-like sepiolite. As a result, Ag@Ag Cl–TiO2/sepiolite exhibits a red shift relative to TiO2/sepiolite. Photocatalytic experiments demonstrated that the dosage of catalysts plays an important role during photocatalysis. The photoelectrochemical activities of Ag@Ag Cl–TiO2/sepiolite and TiO2/sepiolite were also investigated. Photocurrent responses confirmed that the ability of Ag@Ag Cl–TiO2/sepiolite to separate photo-generated electron–hole pairs is stronger than that of TiO2/sepiolite. Methylene Blue degradation is also improved under alkaline conditions and visible light irradiation because more UOH is produced by visible light excitation.This excellent catalytic ability is mainly attributed to the formed Ag nanoparticles and the Schottky barrier at the Ag/TiO2 interface. Active species analysis indicated that UO2-and h＋are implicated as active species in photocatalysis. Therefore, catalysts are excited to produce abundant electron–hole pairs after they absorb photons in photocatalysis.

Comparative toxicity of silver nanoparticles and silver ions to Escherichia coli

With the increase in silver（Ag）-based products in our lives, it is essential to test the potential toxicity of silver nanoparticles（Ag NPs） and silver ions（Ag ions） on living organisms under various conditions. Here, we investigated the toxicity of Ag NPs with Ag ions to Escherichia coli K-12 strain under various conditions. We observed that both Ag NPs and Ag ions display antibacterial activities, and that Ag ions had higher toxicity to E. coli K-12 strain than Ag NPs under the same concentrations. To understand the toxicity of Ag NPs at a cellular level, reactive oxygen species（ROS） enzymes were detected for use as antioxidant enzymatic biomarkers. We have also studied the toxicity of Ag NPs and Ag ions under various coexistence conditions including： fixed total concentration, with a varied the ratio of Ag NPs to Ag ions; fixed the Ag NPs concentration and then increased the Ag ions concentration; fixed Ag ions concentration and then increasing the Ag NPs concentration.Exposure to Ag NPs and Ag ions clearly had synergistic toxicity; however, decreased toxicity（for a fixed Ag NPs concentration of 5 mg/L, after increasing the Ag ions concentration） to E. coli K-12 strain. Ag NPs and Ag ions in the presence of L-cysteine accelerated the bacterial cell growth rate, thereby reducing the bioavailability of Ag ions released from Ag NPs under the single and coexistence conditions. Further works are needed to consider this potential for Ag NPs and Ag ions toxicity across a range of environmental conditions.Environmental Significance Statement： As silver nanoparticles（Ag NPs）-based products are being broadly used in commercial industries, an ecotoxicological understanding of the Ag NPs being released into the environment should be further considered. Here, we investigate the comparative toxicity of Ag NPs and silver ions（Ag ions） to Escherichia coli K-12 strain, a representative ecotoxicological bioreporter. This study showed that toxicities of Ag NPs and Ag ions to E. coli K-12 strain display different relationships when existing individually or when coexisting, and in the presence of L-cysteine materials. These findings suggest that the toxicology research of nanomaterials should consider conditions when NPs coexist with and without their bioavailable ions.

Vulnerability of inland and coastal aquaculture to climate change: Evidence from a developing country

Developing countries,which contribute 90%of global aquaculture production,are considered global climate risk hotspots.However,no study focuses on measuring district-or sub-national-level aquaculture vulnerability to climatic hazards or disasters.This study has measured the level of aquaculture vulnerability to climate variability and change in all 64 districts of Bangladesh using a composite vulnerability index approach(using 19 climatic,environmental and socio-economic indicators)and geographical information system(GIS).The results reveal that aquaculture in 12 districts namely Satkhira,Mymensingh,Panchagarh,Lalmonirhat,Nilphamari,Thakurgaon,Sunamganj,Dinajpur,Kurigram,Noakhali,Lakshmipur,and Cox's Bazar have very high vulnerability(in order of highest to lowest vulnerability),which are explained by their higher level of exposure,moderate level of sensitivity,and lower to moderate level of adaptive capacity.Among these,8 districts belong to inland and 4 districts to coastal regions of the country.Three districts,namely Dhaka,Chittagong,and Bandarban,have the lowest level of aquaculture vulnerability(in order of lowest to highest vulnerability)mainly because of very high adaptive capacity and moderate or low level of sensitivity and exposure.This study will punctuate the vulnerability of inland aquaculture and develop and prioritize actions to reduce the climatic impacts.

Versioned geoscientific workflow for the collaborative geosimulation of human-nature interactions-a case study of global change and human activities

Global change refers to changes in the relationship between humans and nature.It is desirable to actively integrate human social activities into the unified framework of global change so that their mutual relations and functional mechanisms can be understood.This complicated issue necessitates an appropriate method allowing domain experts to collaboratively contribute their knowledge to geoscientific research.Also,an efficient approach to optimize experimentation is of great importance.The reproducibility of research methods and results needs to be improved to boost the sharing of geographic knowledge and resources.This paper proposes a versioned geoscientific workflow and characterizes its full lifecycle using Virtual Geographic Environments,intending to facilitate and improve research related to the interactions between global change and human activities.The geoscientific workflow management is realized using the concept of version management,making geographic simulation methods and computational results easily reproducible and extendable.The sharing and reuse of geographic knowledge in various forms are archived through version management of geoscientific workflows.A versatile prototype system is implemented which enables the visual modeling of geoscientific workflows,the interactive optimization and collaborative evaluation of geoscientific workflows at runtime,the multi-dimensional dynamic visualization of geo-workflow outputs,and role-based access control for data security.

Recent advances in water-splitting electrocatalysts based on manganese oxide

The oxygen evolution reaction(OER)of electrochemical water splitting represents a source of hydrogen(H_(2))energy.Precious-metal-based RuO_(x)and IrO_(x)are expensive and degrade in the presence of electrolyte;thus,the development of low-cost and eco-friendly OER electrocatalysts is needed.This review summarizes the recent status of the nonprecious manganese metal-oxide-based electrocatalysts with reference to nanostructure,defect engineering,hybrid composite formation,and core-shell formation to achieve efficient OER performance.In particular,we focus on the strategies used to lower the onset potential and the Tafel slope of the water oxidation process.Future prospects for the development of manganese-oxide-based electrocatalysts are discussed.