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Overall seawater splitting driven by regenerable electricity is an ideal pathway for mass production of green hydrogen. Nonetheless, its anodic oxygen evolution half‐reaction (OER) confronts sluggish kinetics, competitive chlorine evolution, and chloride corrosion or poisoning problems, needing to develop high‐efficient and robust electrocatalysts toward those challenges. Herein, novel defect‐rich single‐phase (NiCoMnCrFe)3O4 high‐entropy spinel oxide (HEO) is fabricated by low‐temperature annealing of high‐entropy layered double hydroxide precursor. Due to the presence of abundant defects, unique “cocktail” effect, and efficient electronic structure regulation, such (NiCoMnCrFe)3O4 can deliver 500 mA cm−2 current density at the overpotentials of 268/384 mV in alkaline freshwater/seawater, outperforming its counterparts, commercial IrO2, and most reported OER catalysts. Moreover, it manifests exceptional OER durability and anticorrosion capability. Theoretical calculations reveal that the eg occupancies of surface Mn atoms are closer to 1.0, which may be the activity origin of such HEO. Importantly, the constructed (NiCoMnCrFe)3O4||Pt/C electrolyzer only requires 1.57 V cell voltage for driving overall seawater splitting to reach 500 mA cm−2 current under real industrial conditions. This work may spur the development of advanced OER electrocatalysts by combining entropy and defect engineering and accelerate their applications in seawater splitting, metal–air batteries, or marine biomass electrocatalytic conversion fields. Defect‐rich (NiCoMnCrFe)3O4 high‐entropy oxide is fabricated, which shows unprecedented activity toward oxygen evolution in alkaline seawater, outperforming (NiCoMnCrZnFe)3O4, (NiCoMnCrZnAlFe)3O4, (NiCoMnFe)3O4, well‐crystallized (NiCoMnCrFe)3O4‐H, IrO2, and the‐state‐of‐art reported electrocatalysts. Moreover, it manifests exceptional durability and chlorine‐resistant corrosion ability. Remarkably, the assembled (NiCoMnCrFe)3O4||Pt/C electrolyzer only requires 1.57 V voltage to attain 500 mA cm−2 overall seawater‐splitting current under real industrial conditions.

The thermodynamic properties of seawater have recently been redefined as the International Thermodynamic Equation of Seawater—2010 (TEOS-10 for short), and here we summarize the changes to oceanographic practices that are needed to take advantage of this new international standard. A key feature of TEOS-10 is that the thermodynamic quantities are functions of a new salinity variable, Absolute Salinity, which incorporates the effects of spatial differences in seawater composition. TEOS-10 also treats the “heat content” of seawater in a more consistent and natural fashion through the introduction of a new temperature variable, Conservative Temperature, which replaces potential temperature. Since TEOS-10 includes fundamental equations of state also for ice and for humid air, thermodynamically consistent and complete relationships now exist between all the thermodynamic properties of fresh water, seawater, ice and humid air.

In the twenty-first century, the ramifications of human civilization on natural resources are immense, which has led to water quantity, quality and environmental problems across the globe. Groundwater is a vital resource for ensuring water, food and environmental securities. This study focuses on in-depth hydrogeochemical characterization, and assessment of seawater intrusion and groundwater suitability in a coastal alluvial basin of eastern India. The groundwater-quality data of pre-monsoon season (April) for the 2012–2021 period were used in this study. The results of different analyses revealed that the comparative order of ionic concentrations in groundwater is: Na +  > Ca 2+  > Mg 2+  > K +  > Fe 2+ , and HCO 3 –  > Cl –  > SO 4 2–  > NO 3 –  > F – . The Piper and Chadha’s Diagrams revealed that the major groundwater types are: ‘Ca–Mg–HCO 3 ’, ‘Mixed Ca–Mg–Cl’, ‘Na–K–Cl–SO 4 ’, ‘Ca–Mg–Cl–SO 4 ’ and ‘Mixed Ca–Na–HCO 3 ’. Based on the USSL Diagrams, groundwater from the irrigation viewpoint is characterized as ‘C2–S1’ type, followed by ‘C1–S1’, ‘C3–S1’ and ‘C3–S2’ types, which suggest that groundwater should be utilized carefully for irrigation in the study area. The Gibb’s Diagrams indicated that mainly ‘Rock-Water Interaction Dominance (Weathering)’ is responsible for controlling groundwater chemistry. The HFE Diagrams suggested that groundwater in ~ 22% of the observation wells is influenced by the ‘Reverse Cation-Exchange (Intrusion Phase)’ process. The ‘Seawater Mixing Index’ values of > 1 in the unconfined aquifer (~ 84% of observation wells) and the confined aquifer (~ 69% of observation wells) indicate that the freshwater-seawater mixing phenomenon considerably influences the groundwater. Furthermore, the Entropy Groundwater Quality Index for unconfined and confined aquifers indicated that the groundwater in 4–18% of the study area is of ‘Good’ to ‘Excellent’ quality, followed by ‘Medium’ quality (36–58% of the area), ‘Poor’ quality (17–36% of the area), and ‘Extremely Poor’ quality (6–24% of the area). On the other hand, the Irrigation Groundwater Quality Index of unconfined and confined aquifers suggested that the groundwater is suitable for irrigation (‘Good’ to ‘Excellent’ quality) in 95–97% of the study area.

Rapid economic development in coastal areas has gradually increased the risk of coastal water quality deterioration. The assessment methods of coastal water quality are multifarious, but many depend on either subjective judgment or objective calculation. We proposed a weighted sum methodology by integrating the subjective analytic hierarchy process and objective entropy theory (AHP-entropy weight methodology) to obtain an overall evaluation of coastal water quality. The mathematical models to transform the biochemical and physical parameter values and soluble substance concentrations into index scores have been formulated in comparison to the national water quality classification scheme. The application of the AHP-entropy weight methodology was demonstrated in the nearshore area of Yangjiang city, China, based on 23 seawater sampling stations in autumn 2017 and spring 2018. Datasets including biochemical and physical parameters, nutrients, and heavy metals have been converted into water quality index scores based on the proposed mathematical model. Results revealed that the overall water quality fell into the “good” class in both sampling seasons. The spatial distribution of the water quality index scores demonstrated that the relatively worse water quality occurred in estuarine and nearshore areas, signifying the negative effect of coastal anthropogenic activities. The statistical analyses like the hierarchical cluster analysis interpreted that the river input acted as a main source of pollutants in the study area. The AHP-entropy weight methodology could be a preferred way to assist decision-makers in properly evaluating the current state of coastal water quality in an unbiased, objective manner.

The seawater circulation pump represents the pump product with the largest flow rate within nuclear power plants. Its energy consumption accounts for a substantial portion of the energy consumed by nuclear power plants. To investigate the internal flow characteristics of the seawater circulation pump and optimize the performance while reducing energy consumption, taking the seawater circulation pump as the research object, the entropy production of each flow passage component of the pump under different flow conditions are analyzed by employing numerical simulation based on the entropy production theory. Additionally, the entropy production mechanisms of the impeller and volute are specifically analyzed. The results demonstrate that under different flow conditions, the impeller and volute are the main flow components contributing to entropy production losses for the entire pump. The leading and trailing edges of the blade and the shroud are the main locations where entropy production occurs in the impeller. Excessive attack angle and circulation are the main factors leading to entropy production. The throat area of the volute is the main entropy production area of the volute, and the secondary flow and vortex caused by flow separation are the main causes of entropy production.

Environment can impact the wear behavior of metals and alloys substantially. The tribological properties of Al0.6CoCrFeNi high-entropy alloys (HEAs) were investigated in ambient air, deionized water, simulated acid rain, and simulated seawater conditions at frequencies of 2–5 Hz. The as-cast alloy was composed of simple face-centered cubic and body-centered cubic phases. The wear rate of the as-cast HEA in the ambient air condition was significantly higher than that in the liquid environment. The wear resistance in seawater was superior to that in ambient air, deionized water, and acid rain. Both the friction coefficient and wear rate in seawater were the lowest due to the formation of oxidation film, lubrication, and corrosion action in solution. The dominant wear mechanism in the ambient air condition and deionized water was abrasive wear, delamination wear, and oxidative wear. By contrast, the wear mechanism in acid rain and seawater was mainly corrosion wear, adhesive wear, abrasive wear, and oxidative wear.

In the terrestrial climate system, water is a key player in the form of its different ambient phases of ice, liquid and vapour, admixed with sea salt in the ocean and with dry air in the atmosphere. For proper balances of climatic energy and entropy fluxes in models and observations, a highly accurate, consistent and comprehensive thermodynamic standard framework is requisite in geophysics and climate research. The new Thermodynamic Equation of Seawater – 2010 (TEOS-10) constitutes such a standard for properties of water in its various manifestations in the hydrological cycle. TEOS-10 was recommended internationally in 2009 by the Intergovernmental Oceanographic Commission (IOC) to replace the previous 1980 seawater standard, EOS-80, and in 2011 by the International Union of Geodesy and Geophysics (IUGG) as the official description for the properties of seawater, of ice and of humid air. This paper briefly reviews the development of TEOS-10, its novel axiomatic properties, the new oceanographic tools it offers and the important tasks that still await solutions by ongoing research. Among the latter are new definitions and measurement standards for seawater salinity and pH in order to establish their metrological traceability to the International System of Units (SI) for the first time after a century of widespread use. Of similar climatological relevance is the development and recommendation of a uniform standard definition of atmospheric relative humidity that is unambiguous and rigorously based on physical principles.The leading thermodynamic properties of a fluid are determined by the relations which exist between volume, pressure, temperature, energy, and entropy … But all the relations existing between these five quantities for any substance …may be deduced from the single relation existing for that substance between volume, energy, and entropy. Josiah Willard Gibbs, 1873b

Owing to their multi-elemental compositions and unique high-entropy mixing states, high-entropy alloy (HEA) nanoparticles (NPs) displaying tunable activities and enhanced stabilities thus have become a rapidly growing area of research in recent years. However, the integration of multiple elements into HEA NPs at the nanoscale remains a formidable challenge, especially when it comes to the precise control of particle size, elemental composition and content. Herein, a simple and universal high-energy laser assisted reduction approach is presented, which achieves the preparation of HEA NPs with a wide range of multi-component, controllable particle sizes and constitution on different substrates within seconds. Laser on carbon nanofibers induced momentary high-temperature annealing (>2000 ​K and ramping/cooling rates > 105 ​K ​s−1) to successfully decorate HEA NPs up to twenty elements with excellent compatibility for large-scale synthesis (20.0 ​× ​20.0 ​cm2 of carbon cloth). The IrPdPtRhRu exhibit robust electrocatalytic hydrogen evolution reaction (HER) activities and low overpotentials of 16, 28, and 12 ​mV at a current density of 10 ​mA ​cm−2 in alkaline (1.0 ​M KOH), alkaline simulated seawater (1.0 ​M KOH ​+ ​0.5 ​M NaCl), and acidic (0.5 ​M ​H2SO4) electrolytes, respectively, and excellent stability (7 days and >2000 cycles) at the alkaline HER.

Potentiostatic electrodeposition was used to obtain CoCrFeMnNi high-entropy alloy (HEA) thin films on copper substrate. An electrolyte based on a DMSO (dimethyl sulfoxide)-CH3CN (acetonitrile) organic compound was used for the HEA deposition. The microstructure of the high-entropy deposits before and after corrosion in artificial seawater was investigated by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) investigation. SEM analysis revealed that compact and uniform film consists of compact and uniform 50 nm–5 μm particles that form the HEA films. The successful co-deposition of all five elements was highlighted by the energy dispersive spectrometry investigation (EDS). Electrochemical measurements carried out in an aerated artificial seawater solution under ambient conditions demonstrated the promising potential for application in the field of anti-corrosion protection, due to the protective behavior of the HEA thin films.

The lack of corrosion resistance limits the application of most conventional soft magnetic materials (SMMs) in a corrosive environment, especially in seawater. Hence, enhancing the corrosion resistance of SMMs is critically important. However, a severe contradiction exists between magnetic properties and corrosion resistance as the main anticorrosion element Cr has strong anti-ferromagnetism that deteriorates the magnetism of alloys. This study aimed to report a novel single body-centered cubic high-entropy alloy (HEA) (Fe 2.25 Co 1.25 Cr) 94 Al 6 with an optimal combination of soft magnetic properties, corrosion resistance, and mechanical properties. The saturation magnetization of the HEA was as high as 141.88 emu g −1 and the coercivity was only 2.9 Oe, which were superior to most of the reported magnetic HEAs and conventional alloys. The corrosion resistance of the HEA was better than that of the 304 stainless steel, all of soft magnetic HEAs, and most of the reported HEAs in simulated seawater medium. In addition, the novel HEA exhibited excellent mechanical properties with a yield strength of 1100 MPa, a compressive fracture strain of more than 33%, and an outstanding Vickers hardness value of 469 HV. Thus, this novel (Fe 2.25 Co 1.25 Cr) 94 Al 6 HEA is a promising SMM for marine environment applications.