Low Production Rates Research Articles

Synergistic Promotion of Direct Interspecies Electron Transfer by Biochar and Fe₃O₄ Nanoparticles to Enhance Methanogenesis in Anaerobic Digestion of Vegetable Waste

When vegetable waste (VW) is used as a sole substrate for anaerobic digestion (AD), the rapid accumulation of volatile fatty acids (VFAs) can impede interspecies electron transfer (IET), resulting in a relatively low biogas production rate. In this study, Chinese cabbage and cabbage were selected as the VW substrates, and four continuous stirred tank reactors (CSTRs) were employed. Different concentrations of biochar-loaded nano-Fe3O4(Fe3O4@BC) (100 mg/L, 200 mg/L, 300 mg/L) were added, and the organic loading rate (OLR) was gradually increased during the AD process. The changes in biogas production rate, VFAs, and microbial community structure in the fermentation tanks were analyzed to identify the optimal dosage of Fe3O4@BC and the maximum OLR. The results indicated that at the maximum OLR of 3.715 g (VS)/L·d, the addition of 200 mg/L of Fe3O4@BC most effectively promoted an increase in the biogas production rate and reduced the accumulation of VFAs compared to the other treatments. Under these conditions, the biogas production rate reached 0.658 L/g (VS). Furthermore, the addition of Fe3O4@BC enhanced both the diversity and abundance of bacteria and archaea. At the genus level, the abundance of Christensenellaceae_R-7_group, Sphaerochaeta, and the archaeal genus Thermovirga was notably increased.

Continuous Flow Photoelectrochemical Reactor with Gas Permeable Photocathode: Enhanced Photocurrent and Partial Current Density for CO2 Reduction.

Photoelectrochemical (PEC) CO2 reduction using a photocathode is an attractive method for making valuable chemical products due to its simplicity and lower overpotential requirements. However, previous PEC processes have often been diffusion-limited leading to low production rates of the CO2 reduction reaction, due to inefficient gas diffusion through the liquid electrolyte to the catalyst surface, particularly at high current densities. In this study, a gas-permeable photocathode in a continuous flow PEC reactor is incorporated, which facilitates the direct supply of CO2 gas to the photocathode-electrolyte interface, unlike dark reaction-based flow reactors. This concept is demonstrated using Ag-TiO2 on carbon paper, illuminated through a quartz window and flowing liquid electrolyte. CO2 supply is managed via pressure and flow control on the non-illuminated side of the carbon paper. The photocurrent density is significantly influenced by the flow rates and pressure of CO2 gas, and the electrolyte flow rates. Compared to the traditional H-cell, the continuous PEC flow reactor achieves ≈10-fold increase in CO faradaic efficiency, 30-fold increase in production rate and 16-fold increase in stability without catalyst modifications. This work provides essential insights into the design and application of continuous gas-liquid flow PEC reactor systems, highlighting their potential for other PEC reactions.

Enhancing Filter Assembly and Printing Efficiency through Automation and Virtual Reality Integration

This paper presents a comprehensive approach to improving the assembly and printing process of filters in a selected company. Currently, the company's process involves significant manual labor, which leads to inefficiencies and potential health risks for employees. The proposed solution integrates the use of pneumatic cylinders to automate the assembly and printing process, reducing manual effort and improving production efficiency. The fixture and filter were modeled using SOLIDWORKS 2022 and simulated in virtual reality with Pixyz Review software. The virtual reality simulation serves as an innovative training tool for new employees, enhancing understanding and accuracy in the assembly process. The study compares the current state, where manual handling results in a time-consuming process with a lower production rate, to the proposed automated system. The proposed solution eliminates unnecessary intermediate storage and manual fixture transfers, significantly reducing the total assembly and printing time from 24 s to 22 s per unit. This results in a 14.16 % increase in production efficiency, allowing the company to produce 1227.3 filters per shift compared to the current 1075 filters.

Bimetallic Fe-Mo Films Deposited via Dynamic Hydrogen Bubble Templating (DHBT) for Electrocatalytic Nitrogen Reduction to Ammonia

Ammonia is a very valuable chemical, not only due to its role as a fertilizer precursor in the agricultural sector, but also as an energy storage medium which could potentially substitute oil as the fuel of a society powered by renewable energy[1]. However, it is currently synthesized at the industrial scale by the Haber-Bosch process, which is responsible for around 3% of the global CO2 emissions[2-3]. This fact, coupled with the current global climate crisis caused by the excess emissions of greenhouse gases (GHG) demands that alternative industrial processes be found to produce ammonia that are, at a minimum, GHG neutral. With this perspective in mind, the electrochemical reduction reaction of N2 (NRR) to ammonia becomes an attractive way to make use of the renewable energy to produce ammonia without emitting CO2 in the process.Currently, the electrochemical production of ammonia at an industrial level is unfeasible due to the very low production rates which are observed at the laboratory scale. These lie in the nanomole per second per square centimeter range, and arise from the high stability of the nitrogen molecule due to its triple bond that in turn leads to more competition occurring from the parasitic hydrogen evolution reaction. In our research we attempt to increase the ammonia production rate by using nanostructured and hierarchically porous Gas Diffusion Electrodes (GDEs) produced by the Dynamic Hydrogen Bubble Templating method. The use of GDEs should allow industrially relevant current densities to be reached and the use of Fe and Mo as the catalysts of choice is driven by the fact that these are well-known catalysts for the NRR in the Haber-Bosch process. Additionally, they are also incorporated in the active center of nitrogenases, enzymes that catalyse the conversion of nitrogen at ambient conditions.To take full advantage of the porous nature of the DHBT-deposited metallic foams, it is first necessary to understand how the pore size changes over deposition time. Thus, the first step was to analyse the influence of deposition time and current density on the DHBT deposition of Fe foams, which showed that the average pore diameter on the surface of the Fe foams can reach the order of 20 micrometers within 5 minutes of deposition time.Since pure Fe cannot be used as a NRR catalyst due to its dissolution tendency under typical NRR reaction conditions, the next step was to include Mo in the mix. It was found that the initial electrolyte solution needed only the addition of the Mo salt (its concentration being one tenth of the Fe concentration) and that Fe and Mo co-deposit as expected at a current density of 1.25 A·cm-2. In contrast to the pure Fe foams, the average pore diameter in the presence of Mo decreases to around half of the original value. While the newly deposited foam is more resistant to oxidation in air than the pure Fe foams (pure Fe foams suffer from extensive oxidation after a couple of hours exposed to air), it is still not stable enough in the NRR electrolyte, as it dissolves into the solution already at open circuit potential (OCV) within 30 minutes. To address this stability issue, annealing procedures were implemented in the synthesis routine, with the first tests performed by holding the samples at 400 °C for 1 or 3 hours with a heating ramp of 10 °C·min-1. While this post-treatment reduces the pore sizes even further, initial electrochemical results already reveal that foams annealed for 3h become much more stable in the NRR electrolyte compared to the untreated samples, as evidenced by the more positive OCV that can be observed after 2 hours of immersion in the electrolyte, and the fact that the film did not appear to be damaged. These results are promising to obtain a stable GDE catalyst that can withstand the NRR conditions. Investigations are still pending regarding the effect of annealing at higher temperatures and longer times to allow a fully functional GDE for NRR to be fabricated.

Realizing Superior Durability of Water Electrolyzer Using Anion Exchange Membrane with an Interstitial Alkyl Chain : From a Single Cell to Large-Sized 1-Cell Stack

As the growing utilization of renewable energy continues to grow to address energy and environmental challenges, grid-scale electricity storage technologies are becoming more important. As such, hydrogen has attracted interest over the past few years as an energy carrier for sustainable energy systems. Therefore, water electrolysis is a viable method to mass- produce green hydrogen and can be combined with renewable power generation technologies.The main commercial electrolysis systems currently used to produce hydrogen on a large-scale are alkaline water electrolysis (AWE) and proton exchange membrane water electrolysis (PEMWE). AWE technology has a low hydrogen production rate, typically less than 200 mA cm−2 at a cell voltage of 1.8 V and with an energy efficiency of 75%. Additionally, PEMWE technology suffers from a high unit cost of hydrogen because of the use of platinum group metal (PGM) electrocatalysts and anode plates.Therefore, anion exchange membrane water electrolysis (AEMWE), which can ensure high efficiency and low cost, is considered a promising systems for overcoming the shortcomings of AWE and PEMWE.However, current AEMWE technology has struggled to be commercialized because of poor cell performance and durability, which are directly affected by the membrane electrode assembly (MEA) components. These consist of anion exchange membranes (AEMs), catalyst layers (CLs), and porous transport layers (PTLs). Among the MEA components, AEMs generally have unsatisfactory ionic conductivity, mechanical properties, and alkaline stability, which are directly related to cell performance and durability. These factors limit the widespread implementation of AEMWE.The state-of-the-art cell performance of AEMWEs has advanced dramatically over the past few years and is striving to catch up with the state-of-the-art current density of PEMWEs using a supporting electrolyte (i.e., 1 M KOH). However, the long-term durability of AEMWEs is approximately 10 times lower than that of PEMWEs, which typically operate for 40,000 h; therefore the lifetime of the AEM is currently holding back this technology. When considering only the chemical degradation of an AEM in an alkaline environment (the typical AEMWE operating condition), it can last for more than 1 year. Instead, the factors associated with the durability of AEMWEs are closely related to the alkaline stability of the AEMs as well as the interaction of each component layer, including the ionomer-membrane layer, ionomer-catalyst layer, and ionomer-PTL during cell operation.The contact properties of ionomer-membrane surfaces are largely determined by the number of contact bonds formed by the surface molecular groups across the interface and the entanglement of the surface segments. Therefore, in the present study, we newly designed aryl ether-free PFPBPF-QA AEMs with interstitial alkyl chains in the conducting groups and a polymer backbone. The rationally designed PFPBPF-4-QA not only demonstrated excellent mechanical properties, high alkaline stability and satisfactory hydroxide conductivity, but also improved the contact properties of the Nafion ionomer to ensure excellent durability of the AEMWE. An AEMWE single cell using PFPBPF-4-QA demonstrated superior durability with a voltage decay rate of 2 mV kh−1 at an industrially relevant current density of 1.0 A cm−2. We also demonstrated the commercial viability of PFPBPF-4-QA by evaluating the durability of a large-sized (63.6 cm2 active area) AEMWE 1-cell stack with an energy conversion efficiency (ECE) of 80.2% and voltage decay rate of 1.5 mV kh−1, which is expected to operate for more than 49,095 h based on an initial efficiency of 95%.

Molten Salt Electrolysis for Sustainable Iron Metal Production

Iron and steel production, comprising approximately 95% of the global metal output annually1, are integral to modern industrialization, with steel serving as a critical material across various sectors, including construction and automotive industries. However, the industry's significant environmental impact is evident in the escalating CO2 emissions observed over the last decade. Due to this massive environmental burden, efforts to develop cleaner alternatives that benefit from advantages of electrochemistry have grown.Existing and emerging electrochemical processes ideally aim for emission-free operations by utilizing energy extracted from renewable sources. While processes operating at high temperatures (using molten oxides at 1600°C) show promise, they face some challenges related to complex materials choices2, resulting in increased production costs. Conversely, processes operating at low temperatures using aqueous electrolytes (60-100°C) suffer from significantly lower production rates and efficiency3,4.In this study, we present a novel approach—moderate temperature, chloride-based molten salt electrolysis (MSE) of iron—under development at CWRU. This method combines the advantages of both high and low-temperature electrolytic processes, offering a clean, cost-effective, and practical solution for sustainable iron metal production. During chloride MSE, iron is electrodeposited from a binary (NaCl+FeCl3) or ternary (LiCl+KCl+FeCl3) chloride mixture at moderate temperatures ranging from 300-500°C. Electrowinning in these molten salts capitalizes on their several attractive properties, including low viscosity, high ionic conductivity, high diffusivity, high solubility for electroactive species, electrochemical stability over a wide potential range, and fast electrochemical kinetics.5 Figure 1 illustrates the overall process flow of iron production via chloride MSE, including the upstream non-carbothermic chlorination of ore to FeCl3 resulting in the separation of ore impurities and the subsequent electrolytic deposition process. Initial findings indicate promising outcomes for sustainable iron electrowinning at lower operational costs, attributed to the moderate temperatures, high electrolyte conductivity (1-2 S/cm), and adequate FeCl3 concentrations (>2 M), allowing for high current efficiencies (>85%) at high electrodeposition rates (approaching 1 A/cm2). Furthermore, the chloride MSE process enables the incorporation of a proprietary dimensionally stable anode (DSA) to catalyze the chlorine evolution reaction at the anode. This innovation significantly reduces cell voltage, thereby enhancing the overall process energy efficiency.Figure 1. Iron metal production from ore via chloride-based Molten Salt Electrolysis (MSE) process.

The extent of formation of organic molecules in the comae of comets showing relatively high activity

Comets are a rich reservoir of complex organic molecules. Ground and space-based observatories have recently greatly enhanced the cometary molecular inventory. Although these molecules’ origin is believed to be the cometary nucleus, they can be partially synthesized in the coma. We studied organic molecules’ nucleus versus coma origins for various initial conditions, using a multifluid chemical-hydrodynamical model and an updated chemical network. For the study, we considered four comets [C/1996 B2 (Hyakutake), C/2012 F6 (Lemmon), C/2013 R1 (Lovejoy), and C/2014 Q2 (Lovejoy)] due to their relatively high activity and observation of large number of organic species. We emphasized on the C-H-O and N-bearing species, including the simplest amino acid, glycine. We discuss the formation pathways of the organics and the conditions for their formation in the coma and find that the abundance varies from one comet to another due to differences in the initial conditions, relative abundances of the reactants and temperature. We compare the organic abundances when they are present as parent volatiles to their formation solely due to gas-phase chemistry. Their abundance purely due to the coma chemistry is moderately to significantly lower compared to that when they are parent volatiles. However, we find that the production rates of some of the coma-synthesized organic molecules can reach peak values of ∼1022−1026 molecules s−1, which is in the realm of detection by in situ/space-based observations, and can therefore be important considering future missions to comets. We also compare our modeled abundances with those observed in 67P/C-G by Rosetta, which detected several organics at a large heliocentric distance and low production rate.

Terraced (K, Na)NbO3 piezocatalysts with superior H2O2 production

Piezocatalytic hydrogen peroxide (H2O2) production is an emerging and green technology, but complex preparation process of piezocatalyst and low production rate limit its practical application. Herein, we propose a straightforward and efficient strategy, that is, fabricating a novel terraced potassium sodium niobate (KNN-H) by integrating high-energy pendulum ball-milling into the conventional solid-state method, to control the morphology of piezocatalyst and boost its piezocatalytic activities. By exposing a large number of edge sites with higher piezoelectric response and more active sites, KNN-H sample exhibits an extremely high H2O2 production rate of 47 μmol/h, about 35 times higher than that of previously reported potassium niobate piezocatalyst. Besides, KNN-H sample also has good effects on dye degradation and bacterial inhibition. Therefore, our strategy provides a paradigm for large-scale fabrication of high-performance perovskite piezocatalysts.

Prediction of waxing degree in oil wells based on the frost optimizer algorithm

Abstract Monitoring wax deposition in oil wells becomes increasingly difficult in the complex and extended downhole working conditions, where direct measurement is often impractical. Over time, wax buildup intensifies, affecting oil production and equipment functionality. The degree of wax deposition in oil wells is difficult to measure. This paper proposes a predictive strategy for rod pumping well operations. It integrates the Crested Porcupine Optimizer (CPO) optimization algorithm with Variational Mode Decomposition (VMD) decomposition, selecting suitable K and α values for the electrical power of oil wells. The Rime improves Long Short-Term Memory (RIME-LSTM) network forecasts each mode component, and the final prediction is obtained by summing these values. The method’s performance was validated using real power time series data from four wells over a specific period. The coefficient of determination (R²) and mean absolute percentage error (MAPE) evaluated the models, confirming effectiveness. Finally, a rating strategy for wax deposition predicts when to perform shutdown cleaning before severe accumulation occurs, thus protecting the oil pump and preventing low production rates. This article studies the prediction of downhole technology and wax deposition degree in oil wells, and proves its effectiveness through experiments.

Novel dual-enhanced stimulation for safe and efficient marine hydrate production

The commercial exploitation of natural gas hydrates is currently facing several challenges, including low production rates, limited recovery areas, and brief periods of continuous production. To address these issues, we propose a novel dual-enhanced stimulation (DES) method for marine hydrate reservoirs. This method involves injecting a special slurry that solidifies into porous, high-permeability, and high-strength slurry veins. These veins not only enhance permeability, allowing for faster gas and water flow, but also improve reservoir stability. This study experimentally investigated the split grouting of clayey-silty sediments with dual-enhanced slurry to assess the feasibility of DES and to explore the slurry diffusion mechanism and micro-pore structure of the veins. The results showed that split grouting with dual-enhanced slurry exhibited frequent fracture initiation with quick pressure spikes and sharp declines, suggesting shorter fractures in clayey-silty sediments. As vertical stress increased, the primary diffusion direction of the dual-enhanced slurry shifted from horizontal to vertical, aligning with fracture propagation patterns observed during fracturing. Unlike hydraulic fracturing in hard rocks, split grouting in clayey-silty sediments encountered more difficult conditions. These veins formed through a recurring cycle of splitting into fractures and filling with slurry, occurring more frequently in weaker sediments with slower injection rates and higher vertical stress. Increased vertical stress hindered slurry vein diffusion, easily resulting in compaction grouting near the grouting pipe. Additionally, three-dimensional laser scanning of the veins showed that those formed through split grouting were continuous and stable, with their thickness decreasing as diffusion distance increased. The morphology of these veins was shaped by factors such as grouting rate, formation stress, and elastic modulus, with higher rates and elastic moduli facilitating the formation of complex vein networks. Mercury intrusion porosimetry demonstrated that the DES method resulted in veins with consistent effective porosity between 65% and 70% and median pore sizes of 11–15 μm across different locations. These veins formed a well-connected porous network of smaller pores, significantly enhancing both permeability and sand control. The research findings validate the effectiveness of the DES method for marine hydrate reservoirs, providing a strategy for the safe and efficient exploitation of NGH resources.

Evidence for the formation of 6PPD-quinone from antioxidant 6PPD by cytochrome P450

N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) as a rubber antioxidant has attracted global concern, since its ozone-oxidation product 6PPD-quinone (6PPDQ) was found to be the primary toxicant responsible for urban runoff mortality syndrome in coho salmon. However, the biotransformation fate and associated toxicological mechanism of 6PPD have not received much study yet. In this work, the in vitro assays showed 6PPD can be transformed into 6PPDQ by cytochromes P450 (CYP450) in human liver microsomes (HLMs) with 0.98 % production rate, and the adducts of 6PPDQ with calf thymus DNA and the N-N coupling product between 6PPD and 6PPDQ were further identified after 6PPD incubation in HLMs. Further evidence for the 6PPDQ formation can be obtained from the in vivo assays that the 6PPDQ-DNA adducts and 6PPD-N-N-6PPDQ dimer were detected in mice by oral gavage with 6PPD, and the latter dimer species was detected as well in 6PPD exposure to zebrafish larvae. Especially, the bioaccumulation property and high reactivity of 6PPDQ result in the continuous formation of the significant DNA adducts and 6PPD-N-N-6PPDQ dimer even in case of low production rate of biotransformation of 6PPD to 6PPDQ, which may provide potentially effective biomarkers for such process. DFT computations revealed the formation mechanism of 6PPDQ is the (N)H-abstraction of 6PPD by CYP450, followed by amino radical rebound at the nearby ortho-carbon, yielding a quinol intermediate due to spin delocalization, that might readily undergo further oxidation by CYP450 into 6PPDQ.

Geological and Engineering Integration Fracturing Design and Optimization Study of Liushagang Formation in Weixinan Sag

The Weixinan Sag in the Beibuwan Basin is rich in shale oil resources. However, the reservoirs exhibit rapid phase changes, strong compartmentalization, thin individual layers, and high-frequency vertical variations in the thin interbedded sandstone and mudstone. These factors can restrict the height of hydraulic fracture propagation. Additionally, the low-porosity and low-permeability shale oil reservoirs face challenges such as low production rates and rapid decline. To address these issues, the Plannar3D full 3D fracturing model was used to simulate hydraulic fracture propagation and to study the main controlling factors for fracture propagation in the second member of the Liushagang Formation. Based on the concept of geological–engineering integration, a sweet spot evaluation was conducted to identify reservoirs with relatively better brittleness, reservoir properties, and oil content as the fracturing targets for horizontal wells. The UFM model was then applied to optimize fracturing parameters. This study indicates that the matrix-type oil shale has a high clay mineral content, resulting in a low Young’s modulus and poor brittleness. This makes hydraulic fracture propagation difficult and leads to less effective reservoir stimulation. In contrast, hydraulic fractures propagate more easily in high-brittleness interlayer-type oil shale. Therefore, it is recommended to prioritize the extraction of shale oil from interlayer-type oil shale reservoirs. The difference in interlayer stress is identified as the primary controlling factor for cross-layer fracture propagation in the study area. Based on the concept of geological–engineering integration, a sweet spot evaluation standard was established for the second member of the Liushagang Formation, considering both reservoir quality and engineering quality. Four sweet spot zones of interlayer-type oil shale reservoirs were identified according to this evaluation standard. To achieve uniform fracture initiation, a differentiated segment and cluster design was implemented for certain high-angle sections of well WZ11-6-5d. Interlayer-type oil shale was selected as the fracturing target, and the UFM was used for hydraulic fracture propagation simulation. Fracturing parameters were optimized with a focus on hydraulic fracture characteristics and the estimated ultimate recovery (EUR). The optimization results were as follows: a single-stage length of 50 m, cluster spacing of 15 m, pump injection rate of 10 m3/min, fluid intensity of 25 m3/m, and proppant intensity of 3.5 t/m. The application of these optimized fracturing parameters in field operations resulted in successful fracturing and the achievement of industrial oil flow.

Nutritional Value, Phytochemical Properties of Different Parts of Dill (Anethum graveolens L.) and Their Effects on in vitro Digestibility in Ruminants

Introduction: At the interface between man, animal and environment, the use of phytobiotics in agroecology practices has been developed as one of the most effective nutritional strategies for animal performance, health, and well-being. This study aimed to determine the effect of extracts from different parts (leaves, flowers and fruits) of a medicinal and food plant, dill ( Anethum graveolens L.) on in vitro digestibility in small ruminants. Methods: Chemical and parietal composition and antioxidant activity were determined, and nutritional and energy values were predicted. Substrate fermentation was studied using in vitro gas production techniques in sheep and goat intestines. Results: Flowers were rich in secondary metabolites, while fruits were rich in fiber and showed the best antioxidant activity against DPPH (IC50 = 41.71 μg/ml). The studied dill plant parts were digestible and nutritious, mainly fruits, with lower gas production rates compared to leaves and flowers in sheep and goats. The methane gas produced by fermentation was not significant in the leaves of either species. Conclusion: In summary, A. graveolens fruits can be considered a natural source of antioxidants that improve animal nutrition and health. Moreover, A. graveolens leaves can play an ecological role in the environment.

Analysis on a five-spot well for enhancing energy recovery from silty natural gas hydrate deposits in the South China Sea

The five-spot well is a promising technique for enhancing the inherent low gas production rate from silty natural gas hydrate (NGH) reservoirs with low permeability in the South China Sea (SCS). However, the production characteristics and the responses to key geological and engineering factors are still unclear and warrants investigation. Herein, we first establish a three-dimensional reservoir model based on the SH2 NGH deposits at SCS with the implementation of a five-spot well. We systematically examine the gas production enhancement effect and the unexpected well-to-well interaction induced by long-term depressurization. A sensitivity analysis on the effects of bottomhole pressure (Pbtm), permeability (k) and hydrate saturation (SH) is conducted to elucidate the key factors controlling the gas production enhancement. Our results reveal that the five-spot well significantly improves the gas productivity with cumulative gas production increased to 4.12 times that of a single well over 10 years. The well interference on gas production is not significant in the early stage but becomes more significant as depressurization sustains. Due to the relatively slow pressure propagation at the inner well, contribution to gas production from the inner well decreases over time while the outer wells increase. Based on the sensitivity analysis, gas production increases with decreasing Pbtm, increasing k, and decreasing SH with Pbtm and k as the key controlling factors. The findings provide valuable design basis for the adoption of a multi-well system in enhancing gas production for targeted NGH reservoirs in the next field production trial at SCS.

Present status and future prospects of fisheries of Tehri dam reservoir

Fisheries in India are a burgeoning industry with immense potential and opportunities. Ironically, because of its enormous but untapped potential, reservoir fisheries are called as "a sleeping giant". The average productivity from these reservoirs in India is about 30 kg/ha compared to the production potential of 250 kg/ha. Inadequate management leads to low rate of fish production in Indian reservoirs. A major impediment to science-based fish productivity in reservoirs is the lack of authentic data on target stocks. Inland fisheries, like those in reservoirs, are particularly affected. Investigators generally rely on simple catch statistics and hypothesis statements to assess fish production and potential yields due to inadequate resources, population data, and experts in the area. The present paper emphasizes the quintessential 44sq km huge Tehri hydro-power dam reservoir, located in the Bhagirathi and Bhilangana valleys of the lesser Himalayas in the Garhwal hills. On average the fish productivity from Tehri reservoir in the year 2021-2022 is reported as 13.75 kg/ha but, this is significantly lower than its actual productivity. Thus, the current technical paper addresses this issue by condensing and synthesizing the current status of fisheries in the Tehri Dam reservoir with past status in terms of fish species diversity. It provides baseline information on fish production and various data shortfalls in fisheries activity management. The paper also describes the ecological and economic aspects that affect fish catch to utilize the reservoir resources and mired the cold-water fishery management in the Tehri reservoir.

Electrocatalytic Conversion of Plasma-Activated CO2 Toward Multicarbon Products

Renewable electricity-powered CO2 reduction reaction (CO2RR) toward chemicals and fuels has been gaining significant attention not only for achieving net-zero carbon emissions but also for enabling long-term energy storage. In electrochemical conversion, CO2 can be upgraded into single- or multicarbon products such as carbon monoxide, formate, and ethylene with remarkable selectivity. However, challenges still exist in terms of high overpotential, limited product range, and low production rates. Moreover, most reported CO2RR to multicarbon products which used Cu as catalysts have predominantly generated C2 products like ethylene or ethanol. However these systems require further performance improvement to target C3+ products which have higher energy density and market price. Another electrified conversion technique involves non-thermal plasma, which can activate CO2 into radical, ionized, and vibrationally excited species at atmospheric pressure and near-ambient temperature. However, plasma processes are non-selective, which poses limitations for controlling reaction pathways and necessitates H2 or light alkanes as co-reactants to produce hydrocarbons.We synergized plasma and electrocatalytic conversion to demonstrate a combined CO2RR process that overcomes the limitations of each individual method. Through the integration of a dielectric barrier discharge plasma and an electrochemical flow reactor, pre-activated CO2 was electrochemically converted on a Cu electrode to produce multicarbon products. The combination enhanced the faradaic efficiency and reaction rate of desirable products and opened new reaction pathways by increasing the activity of CO2 prior to adsorption. The production rates of ethanol, propanol, and acetaldehyde were significantly increased, and new products such as methanol, acetylene, and ethane that were formed only in the combined reaction were detected. The product distribution was studied according to plasma-activated states of CO2 and the electrochemical applied potential. To elucidate the synergistic effects in the combined system, the selectivity and production rates were compared with those in the plasma-only and electrochemical-only reactions. Further control experiments using ground-state reactants were conducted, and the excited states during plasma activation were identified by optical electron spectroscopy. This work represents not only electrocatalysis of pre-activated reactants for enhanced generation of multicarbon products during electrified conversion of CO2, but also demonstrates synergistic convergence of plasma and electrocatalysis for converting reactants possessing strong chemical bonds.

(Invited) Electrochemical Engineering Approaches for High-Performing Electrosynthesis of Polymer Precursors

The chemical industry accounts for ~5% of the US energy utilization and >30% of the US energy-derived industrial CO2 emissions. Amongst these processes, the production of organic chemical commodities, many of which are used as polymer precursors, account for the majority of the energy utilization (>1200 TBTU/y). The electrification of these processes via the implementation of electro-organic reactions could accelerate the decarbonization of the chemical industry, and bring additional sustainability advantages over their thermo-chemical counterparts. Currently, however, two major challenges prevent the deployment of electro-organic reactions: their low selectivity and their low production rates. To circumvent these barriers, our group deploys electrochemical reaction engineering principles to engineer electrode/electrolyte interfaces and design high-performing electro-organic processes. In this presentation, I will discuss how we implement this approach to understand and improve the performance of electro-organic reactions for the production of large-scale precursors for the production of Nylon 6,6 and polyethylene.The production of Nylon 6,6 involves the step-growth polymerization of 1,6-hexanediamine (HMDA) with adipic acid. HMDA is currently produced by the hydrogenation of adiponitrile (ADN). Here, I will present our insights into the electrohydrodimerization of acrylonitrile (AN) to adiponitrile (ADN). This is one of the largest electro-organic reaction deployed in industry and serves as a model process for the development of practical organic electrochemical processes. Our investigations on ADN uncovered relationships between the microenvironment at and near the electrical double layer (EDL) and reaction performance metrics (i.e., selectivity, efficiency, and productivity). I will discuss general guidelines for electrolyte formulation, dynamic electrochemical operation, the implementation of convective forces to mitigate transport limitations, ultimately leading in the conversion of AN to ADN at Faradaic efficiencies >80% and current densities of 100’s mA/cm2. Our learnings on ADN electrosynthesis helped us to engineer the electrocatalytic hydrogenation of ADN to HMDA, achieving the highest reported selectivity to date for this reaction (>95%). I will also show how similar electrochemical engineering approaches allowed us to elucidate factors that control performance in the electrochemical production of ADN from glutamic acid, an abundant and inexpensive bio-based feedstock, and of ethylene from bio-derived propionic acid. Through our studies, we aim to electrify and bring sustainability to chemical manufacturing, one reaction at a time.

Multiphase Modeling of Enhanced Bubble Evacuation in Alkaline Water Electrolysis Cells Based on Laterally-Graded 3-D Electrodes

To mitigate the challenges posed by anthropogenic climate interference, substantial efforts are imperative in order to limit the rise in global average temperature. One major declaration made by the international community through various climate agreements [1,2] calls for an elimination of greenhouse gas emissions, necessitating a shift from fossil fuels to sustainable renewable energy sources. Hydrogen and hydrogen-based fuels emerge as promising candidates to decarbonize a wide range of sectors – including transport, industry and chemical manufacture – due to hydrogen’s remarkable flexibility and storage capacity. At present, water electrolysis conducted by renewable electricity is considered as the most sustainable technology to produce green hydrogen.Among the various approaches for water electrolysis, two commercially available methods stand out: alkaline and proton exchange membrane (PEM) [3]. Alkaline water electrolysis (AWE) has the advantage of presenting the lowest cost per kilowatt of electricity but yields lower hydrogen production rates. In contrast, PEM electrolysis achieves superior performance, thanks to the use of costly and scarce electrocatalytic materials like Ir and Pt. Considering the unique strengths of each system, it is appealing to try to integrate the best of these two technologies, yielding high production rates per electrode area while benefiting from more cost-effective electrode materials.To this end, recent experimental work in our group has focused on the conception and analysis of flow-engineered 3-D electrodes into a novel laterally-graded cell configuration to allow alkaline water electrolysis to become PEM-like [4,5]. More specifically, 3-D electrodes such as foams were integrated into a zero-gap cell using a bi-layer configuration in which a fine foam (450 µm pore size) working as a catalytic electrode is put in contact with a coarser foam (3000 µm pore size) acting as a porous transport layer (PTL). Because of the high production rate in the 450 µm foam, a high forced upstream electrolyte flow is used to favour bubble removal and hence decrease the Ohmic resistance of the system. Thanks to the use of a bi-layer configuration in flow-through upstream flow mode, the many bubbles generated near the diaphragm were believed to be evacuated laterally towards the coarser foam, keeping the catalytic surface of the finer foam active throughout the process. The enhanced performance of this PEM-like system was confirmed experimentally and current densities of 2 A/cm2 were observed at cell voltages lower than 2 V (for 2 x 2 x 0.56 cm3 electrodes).The aim of this work is to use Computational Fluid Dynamics (CFD) simulations in order to assess flow behaviour into the bi-layer and validate the assumptions that were made based on the experimental results. First of all, a single-phase model (i.e. considering only the electrolyte) was used to solve the incompressible Navier-Stokes equations in OpenFOAM. The objective is to shift towards multiphase simulations by considering a simple mixture model to account for the presence of gas bubbles. The driftFluxFoam solver will be used to solve the general mixture model equations, in which velocity, density and viscosity are weight-averaged based on gas fraction and on the properties of both phases. This work also highlights two ways of incorporating porous media in the numerical simulations. The first way, called explicit, is based on the exact geometry of the foams, obtained thanks to high-resolution micro-CT (computed tomography) scanned data, but is extremely costly from a numerical point of view. The other method, called implicit, uses the Darcy-Forchheimer approximation to spatially average porosity over a given domain, which is less representative of the exact foam structure but generally allows to get first useful insights of the flow behaviour in porous media.An example of a laterally graded bi-layer configuration and some initial multiphase results are shown in Figure 1. The velocity vectors and the lateral velocity profile confirm that hydrogen bubbles can indeed be expected to be evacuated from the fine catalytic 450 µm into the coarser 3000 µm PTL foam. The main objective of our modeling approach is to demonstrate the relation between the observed electrochemical performance enhancement with multiphase mass transport phenomena occurring inside the 3-D electrodes in order to show the intrinsic interest of using such laterally graded bi-layer approach in all future alkaline water electrolysers. Figure 1

Bioconversion of industrial wastes to hydrogen: A review on waste-to-wealth technologies.

Energy plays a significant role in attaining the sustainable growth of the industrial sector of any nation. The resources for getting energy are limited and cannot fulfill the huge demand for energy supply in the near future. Generating fuels from various waste materials and biomass is widely viewed as a sustainable energy source and a viable option for the future. Currently, researchers are particularly interested in synthesizing hydrogen (H2) without emitting CO2 and other greenhouse gases (GHGs). Hydrogen is recognized as a pristine and environmentally friendly energy source, presenting an optimal substitute for fossil fuels due to its high energy content of 122 kJg-1. The traditional methods for the production of H2 are cost-intensive and heavy input requirements are needed. Thus, the synthesis of H2 through biological approaches is cost-effective and eco-friendly alternating with easy operational requirements with ambient reaction conditions. The most common drawback of the biological production of H2 is the low yield and production rates of gas during scale-up conditions. This review is focused on different processes used to convert the wastes into H2 energy along with their pattern of utilization and the effect on the environment.

Floatable Termination-Vacant MXene Architecture for High-Performance and Cost-Effective Photothermal Dehydrogenation.

Liquid hydrogen carriers have garnered considerable interest in long-distance and large-scale hydrogen storage owing to their exceptional hydrogen storage density, safety, and compatibility. Nonetheless, their practical application is hampered by the low hydrogen production rate and high cost, stemming from poor thermal utilization and heavy reliance on noble metals in solar bulk dehydrogenation platforms. To conquer these challenges, we devise an economical all-in-one architecture comprising the photothermal catalytic termination-vacant MXene and a highly insulated melamine substrate. This design floats on the air-reactant interface to efficiently drive solar interfacial dehydrogenation. The melamine enables interfacial heat localization to improve the thermal utilization, providing a high reaction temperature. Meanwhile, the MXene with termination vacancies exposes rich active sites for formic acid dehydrogenation, and simultaneously high performance and cost-effectiveness can be realized. This work offers fresh perspectives on the design and application of photothermal catalytic MXene, broadening the prospects for hydrogen storage using liquid hydrogen carriers.