The invention of hydroelectric nanogenerators (HENGs) is a breakthrough technology for green electricity generation. However, the underlying mechanisms driving energy conversion remain largely unknown, impeding the development of HENGs with high energy densities. Here, we develop a new Multiphysics model involving Darcy's law, phase transfer in porous media, and current modules to reveal the mechanisms of electricity generation in HENGs. This is the first model to simulate evaporation as a streaming potential variable with the Robin-type boundary condition that overcomes the shortcomings of Neumann- and Dirichlet-type boundary conditions. Including the streaming potential and electric double layer (EDL) effects, the simulation can be based on actual water flow conditions, which is more convincing and lays a microscopic foundation for future research and exploration into the mechanism of hydroelectric electricity generation. The new model reveals that the concentrations of salt solutions significantly impact the output power density of HENGs by affecting the solution conductivity in the stern layer, while relative humidity has a minimal impact. This model along with experimental validation offers a robust method to improve the electrical output of HENGs.@en

Hydroelectric nanogenerators (HENGs) utilize the synergy between conductive nanomaterials and hydrodynamic flow to generate electricity, but their applications are limited by low output power density. Here, a high-performance HENG is developed by employing single-layer MXene (SMX) nanosheets on wool cloth. The SMX-based HENGs exhibit a maximum energy density of 0.683 mW cm−2, a current of 1.994 mA, and a voltage of 0.687 V, sufficient to power small wearable electronics. Moreover, the hydrophilicity of the HENGs is maintained due to the addition oxidized ketjen black nanoparticles to the SMX matrix. This is attributed to the functional groups (e.g., –COOH and –OH) on OKB, which are important for efficient ion transport and maintaining a high steady-state power density. Important insights into energy generation for the development of high-efficiency HENGs for practical applications have been gained from numerical simulation using COMSOL multiphysics.@en

The ubiquitous and continuous natural processes of water absorption and evaporation have stimulated interest in generating electricity through the creation of a flow of electrical charge, which can then be collected and stored. However, the resultant low output power density as well as the complicated fabrication and operation processes have hindered the practical applications of this technology. Herein, we demonstrate a highly efficient self-operating hydroelectric nanogenerator (HENG) that produces electricity through the absorption and evaporation of seawater. The single HENG consists of a hydrophilic wool cloth stripe functionalized with ketjen black powders and equipped with two electrodes affixed at its ends. The continuous absorption and evaporation of seawater results in the generation of electricity that can be stored in a capacitor. A series of 16 HENGs, each consisting of 10 stacked wool cloth stripes, can generate sufficient power to charge a supercapacitor to 1.6 V within 5 h 30 min under ambient conditions, outperforming most comparable devices reported. The superior performance observed for the HENG is attributable to the hydrophilicity and porosity of wool cloth which can continuously absorb seawater at a desired rate as well as the 2D structure of ketjen black and its high conductivity. This work paves the way to facilitate the development of HENGs for practical applications.

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Wastewater recycling is a solution to address the global water shortage. Phenols are major pollutants in wastewater, and they are toxic even at very low concentrations. Advanced oxidation process (AOP) is an emerging technique for the effective degradation and mineralization of phenols into water. Herein, we aim at giving an insight into the current state of the art in persulfate-based AOP for the oxidation of phenols using metal/metal-oxide and carbon-based materials. Special attention has been paid to the design strategies of high-performance catalysts, and their advantages and drawbacks are discussed. Finally, the key challenges that govern the implementation of persulfate-based AOP catalysts in water purification, in terms of cost and environmental friendliness, are summarized and possible solutions are proposed. This work is expected to help the selection of the optimal strategy for treating phenol emissions in real scenarios.

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Hydroelectric nanogenerators (HENGs) are emerging devices towards sustainable and green energy production. The voltage produced by HENGs varies depending on several variables including the device size and architecture, the type of material used and the ambient conditions. Currently, HENGs have demonstrated the ability to generate voltage up to a few volts, making them well-suited for operating low-power electronics. This work gives a comprehensive review on the various aspects, including the working mechanisms of HENGs based on the phase transitions of water, different working modes (continuous or intermittent), and the materials used/developed to date. Factors that influence the device performance and durability/lifespan are analyzed and the potential applications of HENGs are recommended. Finally, the existing challenges and future trends of HENGs are discussed to guide the development of high-performance HENGs that can help meet the increasing electricity need for charging portable electronics. This review helps identify avenues for enhancing the efficiency and efficacy of HENGs by materials optimization and device design.

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In order to determine the source of the light hydrocarbons in the Kuqa Depression of the Tarim Basin, Northwest China, their geochemical characteristics are documented, and possible influencing factors are discussed in a broad context on the basis of geochemical analyses of natural gas samples from 19 wells in combination with previously reported natural gas components and carbon isotope values from the same depression. The biomarker analytical results show that (a) methyl cyclohexane (37.5–60.3%) of natural gas predominates the C₇ light hydrocarbon series (methyl cyclohexane, heptanes, and dimethyl cyclopentane), and (b) the heptane content (25.0–54.8%) is also relatively high. The C_6–7 light hydrocarbon series (aromatics, normal alkanes, and cycloalkanes) have abnormally high aromatics (benzene and toluene) content (26.2–83.8%). Heptane value (13.31–37.77%) and isoheptane value (2.10–7.64%) indicate that the Kuqa natural gases are of high maturity and typical of coal-derived gas (gas generated by sapropelic source rock). Their light hydrocarbons, however, appear to have some characteristics of mixed-source organic matter. Specifically, the light hydrocarbons in the Dina 2 gas field show characteristics of the coal-derived gas; those in the Dabei gas field show some features of the oil-associated gas (gas generated by humic source rock), whereas those in the Kela 2 and Keshen 2 gas fields and Well Yangtake-101 display characteristics of the mixed source organic matter. The abnormally high content of the aromatics in the Kuqa Depression may have resulted mainly from their high productivity during the thermal maturity of humic type organic matters and the gases accumulation of late stage. The different relative contents of the aromatics in various oil and gas fields may have been accounted by different organic matter types, maturity, and distribution patterns of source rocks.

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