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Alkaline zinc-manganese dioxide (Zn-MnO2) batteries are well suited for grid storage applications because of their inherently safe, aqueous electrolyte and established materials supply chain, resulting in low production costs. With recent advances in the development of Cu/Bi-stabilized birnessite cathodes capable of the full 2-electron capacity equivalent of MnO2 (617 mA h/g), there is a need for selective separators that prevent zincate (Zn(OH)4)2- transport from the anode to the cathode during cycling, as this electrode system fails in the presence of dissolved zinc. Herein, we present the synthesis of N-butylimidazolium-functionalized polysulfone (NBI-PSU)-based separators and evaluate their ability to selectively transport hydroxide over zincate. We then examine their impact on the cycling of high depth of discharge Zn/(Cu/Bi-MnO2) batteries when inserted in between the cathode and anode. Initially, we establish our membranes' selectivity by performing zincate and hydroxide diffusion tests, showing a marked improvement in zincate-blocking (DZn (cm2/min): 0.17 ± 0.04 × 10-6 for 50-PSU, our most selective separator vs 2.0 ± 0.8 × 10-6 for Cellophane 350P00 and 5.7 ± 0.8 × 10-6 for Celgard 3501), while maintaining similar crossover rates for hydroxide (DOH (cm2/min): 9.4 ± 0.1 × 10-6 for 50-PSU vs 17 ± 0.5 × 10-6 for Cellophane 350P00 and 6.7 ± 0.6 × 10-6 for Celgard 3501). We then implement our membranes into cells and observe an improvement in cycle life over control cells containing only the commercial separators (cell lifetime extended from 21 to 79 cycles).

This study was designed to profile the metabolites of Isochrysis galbana, an indigenous and less explored microalgae species. 1H Nuclear Magnetic Resonance (NMR) spectroscopy and Liquid Chromatography-Mass Spectrometry (LCMS) were used to establish the metabolite profiles of five different extracts of this microalga, which are hexane (Hex), ethyl acetate (EtOAc), absolute ethanol (EtOH), EtOH:water 1:1 (AqE), and 100% water (Aq). Partial least square discriminant analysis (PLS–DA) of the generated profiles revealed that EtOAc and Aq extracts contain a diverse range of metabolites as compared to the other extracts with a total of twenty-one metabolites, comprising carotenoids, polyunsaturated fatty acids, and amino acids, that were putatively identified from the NMR spectra. Meanwhile, thirty-two metabolites were successfully annotated from the LCMS/MS data, ten of which (palmitic acid, oleic acid, α-linolenic acid, arachidic acid, cholesterol, DHA, DPA, fucoxanthin, astaxanthin, and pheophytin) were similar to those present in the NMR profile. Another eleven glycerophospholipids were discovered using MS/MS-based molecular network (MN) platform. The results of this study, besides providing a better understanding of I.galbana’s chemical make-up, will be of importance in exploring this species potential as a feed ingredient in the aquaculture industry.

Microalgae can use either ammonium or nitrate for its growth and vitality. However, at a certain level of concentration, ammonium nitrogen exhibits toxicity which consequently can inhibit microalgae productivity. Therefore, this study is aimed to investigate the tolerance of Tetraselmis tetrathele to high ammonium nitrogen concentrations and its effects on growth rate, photosynthetic efficiency (Fv/Fm), pigment contents (chlorophyll a, lutein, neoxanthin, and β-carotene), and fatty acids production. Experiments were performed at different ammonium nitrogen concentrations (0.31–0.87 gL−1) for 6 days under a light source with an intensity of 300 μmol photons m−2 s−1 and nitrate-nitrogen source as the experimental control. The findings indicated no apparent enhancement of photosynthetic efficiency (Fv/Fm) at high levels of ammonium nitrogen (NH4+-N) for T. tetrathele within 24 h. However, after 24 h, the photosynthetic efficiency of T. tetrathele increased significantly (p < 0.05) in high concentration of NH4+-N. Chlorophyll a content in T. tetrathele grown in all of the different NH4+-N levels increased significantly compared to nitrate-nitrogen (NO3-N) treatment (p < 0.05); which supported that this microalgal could grow even in high level of NH4+-N concentrations. The findings also indicated that T. tetrathele is highly resistant to high ammonium nitrogen which suggests T. tetrathele to be used in the aquaculture industry for bioremediation purpose to remove ammonium nitrogen, thus reducing the production cost while improving the water quality.

Significantly high eicosapentaenoic acid (EPA) and fucoxanthin contents with high production rate were achieved in semi continuous culture of marine diatom. Effects of dilution rate on the production of biomass and high value biocompounds such as EPA and fucoxanthin were evaluated in semi-continuous cultures of Chaetoceros gracilis under high light condition. Cellular dry weight increased at lower dilution rate and higher light intensity conditions, and cell size strongly affected EPA and fucoxanthin contents. The smaller microalgae cells showed significantly higher (p < 0.05) value of 17.1 mg g-dw–1 fucoxanthin and 41.5% EPA content per total fatty acid compared to those observed in the larger cells. Chaetoceros gracilis can accumulate relatively higher EPA and fucoxanthin than those reported previously. In addition, maintenance of small cell size by supplying sufficient nutrients and light energy can be the key for the increase production of valuable biocompounds in C. gracilis.

The present study aims to develop a linseed oil coated quartz crystal microbalance sensor to detect trimethylamine (TMA), an important freshness indicating agent of fish. The strong odor of TMA is often termed as “Fish odor”. It is likely to be generated when bacteria starts growing on dead fish. Therefore to detect TMA, a simple approach of vegetable oil film as a receptor element in the quartz crystal transduction platform has been elucidated herein. The developed sensor exhibits a significant sensitivity towards TMA with a sensitivity of 0.1841 kHz/ppm (R2=0.92). Alongside, satisfactory repeatability, reproducibility, and selectivity of the prepared sensor have been studied successfully.

Background and Aim: Malachite green (MG) is an effective antiparasitic and antifungal chemical for treatment of fish. However, MG is reported to be a potential carcinogen. Yet, it is widely used in aquaculture despite its prohibition for use in food-producing animals by the EU and USFDA. The present study quantified MG residues and evaluated the oxidative stress in red tilapia when exposed to subacute and sublethal concentrations of MG. Materials and Methods: Red tilapia exposed to subacute (0.105 mg/L for 20 days) and sublethal (0.053 mg/L for 60 days) concentrations were evaluated for total plasma protein, total immunoglobulin, nitroblue tetrazolium activity, malondialdehyde, reduced glutathione (GSH), and catalase (CAT) activity levels. The residues of MG and leuco-MG (LMG) were also quantified in the fish muscles using liquid chromatography-tandem mass spectrometry. Results: Fish exposed to subacute concentration showed higher CAT on day 10 in the liver and days 5 and 15 in the spleen, whereas in fish exposed to the sublethal concentration, higher levels of GSH were observed on day 1 in the kidney and day 50 in the spleen. Fish muscle was able to accumulate the sum of MG and LMG of 108.04 μg/kg for subacute (day 20) and 82.68 μg/kg for sublethal (day 60). Conclusion: This study showed that red tilapia was able to adapt to the stress caused by exposure to MG at sublethal concentration.

Malachite green (MG) is still being used as an antiparasitic and antifungal agent in aquaculture. This is due to the fact that many stakeholders are not aware of the potential genotoxic and carcinogenic properties of MG. Since the consumption of fish in Malaysia was recorded to be the highest in Southeast Asia in 2013, it is therefore important to ensure that fish sold in the market are free of MG and its metabolite, leucomalachite green (LMG). In this study, MG and LMG residues in muscle tissue of commonly consumed fish such as red tilapia (Oreochromis hybrid), African catfish (Clarias gariepinus), barramundi (Lates calcarifer), hybrid grouper (Epinephelus fuscoguttatus × Epinephelus lanceolatus) and striped catfish (Pangasius hypophthalmus) were analysed using liquid chromatography-tandem mass spectrometry. The fish were purchased from 11 different markets in the state of Selangor, Malaysia. The results showed that the sum residues of MG and LMG in the present study ranged from 0.53 to 4.10 μg/kg with the highest residue detected in domestic striped catfish. This study indicates that MG is still being used and aquaculture stakeholders should be made aware of the judicious use of MG for the benefit of public health.

MnO2 is one of the safest and most abundant electrochemical materials available. It exhibits polymorphism, which has been exploited in many applications especially batteries. In alkaline batteries, γ-MnO2 is widely used because its proton insertion reaction yields one e− (1st) per Mn at high voltages. It also gives a second (2nd) e− during dissolution-precipitation reactions that occur at lower voltages than the proton insertion; however, these 2nd e− reactions are highly irreversible. In this communication, we explore the reversibility of the 2nd e− reactions with bismuth oxide (Bi2O3) and copper (Cu) additives, and cycling in specific potential regions where δ-MnO2 is the polymorph synthesized electrochemically in-situ from γ-MnO2. The use of Bi2O3 and Cu add complexation and intercalation reactions, where presence and/or electrochemical activation of both are essential for reversibility and for capacity retention (50–100%). Attaining 300–610Wh kg−1 against a zinc anode is possible for these batteries, which could promote its use for many applications.

We report for the first time the creation of 2.45 and 2.8 V aqueous manganese dioxide (MnO2)|zinc (Zn) batteries without the use of expensive ion-selective membranes separating the anodes and catho...

In this study, an efficient, simple and eco-friendly biological method, immobilized Tetraselmis chuii beads (TetraBeads) were tested for its efficacy in maintaining water quality to improve the survival and growth of Penaeus monodon postlarvae. Results showed that the tanks, treated with Tetrabeads, were able to significantly (p

Birnessite (δ-MnO 2 ) is a layered polymorph of manganese dioxide used in a number of applications because of its low cost and non-toxic characteristics. In organic electrolyte battery chemistry's it has been considered as an insertion electrode for lithium, magnesium and other ions. In an alkaline environment, however, it undergoes conversion reactions. It has a high theoretical specific capacity of 617 mAh/g based on two electron reactions making it an energy dense electrode. However, its implementation in practice has been limited due to complicated, time cumbersome synthesis methods, and formation of electrochemical irreversible phases after a few cycles. In this article, we report the rapid synthesis and study of the electrochemical synthesis of δ-MnO 2 from cheap and commercially available electrolytic manganese dioxide (EMD, γ-MnO 2 ), where we find the formation to proceed from γ-MnO 2 to groutite (α-MnOOH) and pyrochroite [Mn(OH) 2 ] on the first discharge and follow the reverse transition on the immediate charge to form δ-MnO 2 in alkaline electrolyte. The formation process takes only one cycle to completely form δ-MnO 2 . The electrochemical reversibility of δ-MnO 2 formed through this process is also addressed, where we find that avoiding hydrophobic binders, use of appropriate carbons, addition of certain metallic additives and possibly porosity/pore structure play an important role in unleashing its energy-dense electrochemical performance.

Microalgae are natural producers of various biochemical compounds such as protein, lipid, carotenoids and fatty acids. However, the biochemical composition of microalgae can vary depending on species, culture conditions as well as composition of culture media. This research aims to compare the growth and proximate composition of Scenedesmus obliquus and Selenastrum bibraianum cultured in different media and culture conditions. In the present study, S. obliquus and S. bibraianum were cultured in two different media (BBM and Bristol) under control and natural conditions. Results revealed the highest growth of S. obliquus when cultured in BBM under control condition. Nonetheless, S. obliquus accredited the highest lipid (42.6 ± 0.01%) and carbohydrate content (27.7 ± 0.02%) when cultured in Bristol media under control condition. On the other hand, the highest protein content (44.7 ± 0.00%) was obtained in S. bibraianum when cultured in Bristol media under natural condition. The findings from this study can be used in cultivation of S. obliquus and S. bibraianum using the optimum growth condition for specific purposes of either to obtain a higher biomass growth or better biochemical conformation.

Bioreactors are of interest for value-upgrading of stranded or waste industrial gases. Reactor intensification requires development of low cost bioreactors with fast gas–liquid mass transfer rate. Here we assess published reactor technology in comparison with a novel downward bubble flow created by a micro-jet array. Compared to known technology, the advanced design achieves higher volumetric gas transfer efficiency (kLa per power density) and can operate at higher kLa. We measure the effect of four reactor heights (height-to-diameter ratios of 12, 9, 6, and 3) on the gas transfer coefficient kL, total interfacial area a, liquid residence time distribution, energy consumption, and turbulent hydrodynamics. Leading models for predicting kL and a are appraised with experimental data. The results show kL is governed by “entrance effects” due to Higbie penetration dominate at short distances below the micro-jet array, while turbulence dominates at intermediate distances, and finally terminal rise velocity dominates at large distances. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1399–1411, 2018

Zinc poisoning of the cathode is a leading failure mechanism for rechargeable alkaline Zn/MnO2 batteries, as it leads to the formation of an electrochemically inactive zinc manganese spinel phase. In this communication, we report the use of calcium hydroxide sheets interlayered between zinc anodes and separators, which trap zincate ions through a complexing mechanism. Cells with such interlayers show favorable characteristics as compared with regular cells, such as lower zincate ion concentration in the bulk electrolyte, absence of undesirable spinel phase, and capacity retention above 90mAh/g-MnO2 after 60cycles at 100% depth of discharge (DOD) of the 1st electron of MnO2. Keywords: Rechargeable alkaline Zn/MnO2 battery, Separator, Calcium zincate

Microbubbles dispersed in bubble column reactors have received great interest in recent years, due to their small size, stability, high gas-liquid interfacial area concentrations and longer residence times. The high gas-liquid interfacial area concentrations lead to high mass transfer rates compared to conventional bubble column reactors. In the present work, experiments have been performed in a downflow bubble column reactor with microbubbles generated and dispersed by a novel mechanism to determine the gas-liquid interfacial area concentrations by measuring the void fraction and bubble size distributions. Gamma-ray densitometry has been employed to determine the axial and radial distributions of void fraction and a high speed camera equipped with a borescope is used to measure the axial and radial variations of bubble sizes. Also, the effects of superficial gas and liquid velocities on the two-phase flow characteristics have been investigated. Further, reconstruction techniques of the radial void fraction profiles from the gamma densitometry's chordal void fraction measurements are discussed and compared for a bubble column reactor with dispersed microbubbles. Empirical correlations are also proposed to predict the Sauter mean bubble diameter. The results demonstrate that the new bubble generation technique offers high interfacial area concentrations (1000–4500 m 2 /m 3 ) with sub-millimeter bubbles (500–900 µm) and high overall void fractions (10–60%) in comparison with previous bubble column reactor designs.

Shrimp is an important traded fishery commodity. When subjected to stress, shrimp usually suffers from oxidative stress, which leads to cell injury, senescence, and death. To maintain shrimp good health, performance and production, antioxidant and immune systems are important. Natural antioxidants found in microalgae may be used to increase the cell protection against oxidative damage, being a promising alternative to the carcinogenic synthetic antioxidants. In this study, Tetraselmis chuii was evaluated for its effect on survival, growth and oxidative stress biomarkers on Litopenaeus vannamei postlarvae (PL). The antioxidant properties of the formulated feed with T. chuii inclusion were determined using four antioxidant chemical assays. Meanwhile, the oxidative stress biomarkers on PL were analyzed by hydrogen peroxide, membrane stability and lipid peroxidation assays. Results showed that PL reared on diets supplemented with 50% T. chuii had a significantly higher (P ≤ 0.05) survival (97.6 ± 1.4%) and lower oxidative stress in terms of hydrogen peroxide content (10.08 ± 0.4 mM g−1 FW) and electrolyte leakage (10.8 ± 0.3%). The result of this study also showed that shrimp PL reared on diets supplemented with microalgal, T. chuii have high resistance to reverse salinity stress test (76.7–100%). However, no significant differences (P ≥ 0.05) were found in the growth and lipid peroxidation. Due to the positive effect on oxidative stress status, survival and resistance to salinity stress, the feeding of L. vannamei PL with diet containing at least 50% of T. chuii is recommended as a natural source of antioxidant for PL.

Zinc alkaline anodes command significant share of consumer battery markets and are a key technology for the emerging grid-scale battery market. Improved understanding of this electrode is required for long-cycle deployments at kWh and MWh scale due to strict requirements on performance, cost, and safety. Here we give a modern literature survey of zinc alkaline anodes with levelized performance metrics and also present an experimental assessment of leading formulations. Long-cycle materials characterization, performance metrics, and failure analysis are reported for over 25 unique anode formulations with up to 1500 cycles and ∼1.5 years of shelf life per test. Statistical repeatability of these measurements is made for a baseline design (fewest additives) via 15 duplicates. Baseline design capacity density is 38 mAh per mL of anode volume, and lifetime throughput is 72 Ah per mL of anode volume. We then report identical measurements for anodes with improved material properties via additives and other pertu...

Manganese dioxide cathodes are inexpensive and have high theoretical capacity (based on two electrons) of 617 mAh g−1, making them attractive for low-cost, energy-dense batteries. They are used in non-rechargeable batteries with anodes like zinc. Only ∼10% of the theoretical capacity is currently accessible in rechargeable alkaline systems. Attempts to access the full capacity using additives have been unsuccessful. We report a class of Bi-birnessite (a layered manganese oxide polymorph mixed with bismuth oxide (Bi2O3)) cathodes intercalated with Cu2+ that deliver near-full two-electron capacity reversibly for >6,000 cycles. The key to rechargeability lies in exploiting the redox potentials of Cu to reversibly intercalate into the Bi-birnessite-layered structure during its dissolution and precipitation process for stabilizing and enhancing its charge transfer characteristics. This process holds promise for other applications like catalysis and intercalation of metal ions into layered structures. A large prismatic rechargeable Zn-birnessite cell delivering ∼140 Wh l−1 is shown., Manganese oxide cathodes in alkaline solutions combine low cost and high capacity for energy storage, but it has been challenging to combine high capacity and stable cycling in this system. Here authors demonstrate reversible, high-capacity cycling when copper additives are introduced and investigate the transformations involved.

Asphaltenes are a solubility class of crude oils comprising polyaromatic and heterocyclic molecules with different interfacial activities. The previously neglected effects of compositional mixture on dilatational rheology are discussed in the light of diffusional relaxation models. It is demonstrated that the reported deviations from the Lucassen-van den Tempel model for a single-component solution could largely originate from a distribution in adsorption coefficients within the asphaltenes class. This particularly applies to the peculiar gel point rheology previously ascribed to asphaltenes cross-linking at the interface. Furthermore, an extensive bibliographical review shows that asphaltenes dilatational rheology data always verify the main features of diffusional relaxation, including a decrease in modulus at high bulk concentrations and phase shift values always lower than 45°. Using diffusional relaxation concepts, the reanalysis of the most extensive dataset so far confirmed recently published studies, showing that asphaltenes exhibit a unique equation of state (EOS) irrespective of adsorption conditions. This EOS proves to be very similar for bitumen and petroleum asphaltenes. Finally, a numerical application of a binary diffusional model proved efficient to capture both dynamic interfacial tension and dilatational rheology, with the same parameters. It appears that a minority of asphaltenes (less than 10%) have a much stronger interfacial activity than the bulk of them, as previously demonstrated by fractionation. These results open up the need for a reinterpretation of the physical mechanisms of asphaltenes adsorption in terms of classical amphiphilic behavior, with a potential impact on emulsion breaking and enhanced oil recovery strategies.

Aquaculture sector shows the fastest growth among the global food production industries. However, nutrition and diseases are two important hurdles that need to be addressed to propel the industry forward. Consistent supply of high-quality feed for growing larvae of important aquaculture species is one of the bottlenecks of the local larviculture industry. Microalgal pigments containing carotenoids, phycobiliproteins and chlorophylls are highly nutritious functional foods containing high antioxidant biomolecules associated with fast growth, high immunity, enhanced pigmentation and high productivity. Their high contents of lipids and fatty acids make them valuable alternatives for replacement of fish meals in livestock and fish feeds. Polyunsaturated fatty acids (PUFAs), functional amino acids, vitamins and other biomolecules associated with health are also found in many microalgae species. Major pigments such as astaxanthin, lutein, beta-carotene, chlorophylls, and phycobiliproteins have been proven as valuable sources for the development of functional, nutritional and therapeutic commodities to enhance pigmentation, survival, disease resistance and health of cultured organisms. In spite of their well-known applications, commercial production of pigment supplies such as astaxanthin, fucoxanthin, canthaxanthin, β-carotene and phycobiliproteins are still limited by production technologies. More research and innovation for cost-effective pigments production and applications in improving growth and health in aquatic organisms are important for a sustainable aquaculture industry.

Redistribution of zinc over the electrode surface, also known as shape change, is a major problem and a cause of failure in alkaline zinc anode batteries. To mitigate this phenomenon, we propose a scalable approach based on an in situ formed, highly porous electrochemically synthesized ZnO matrix with uniformly electrodeposited zinc particles. This results in ∼70% improvement in cycle life performance at a rate of 10 mA cm−2 compared to control Zn anodes, which have not gone through the formation process. A quantitative electrolyte analysis revealed under-saturated zincate ion concentration in the electrochemically synthesized ZnO/Zn cells indicating reduced zincate movement. Post mortem analysis of the anodes indicated higher retention of both Zn and ZnO on the electrochemically synthesized ZnO anodes signifying reduced redistribution of active material. Image analysis of the cycled anodes revealed a narrower Zn particle size distribution (62−79 μm) in contrast to a wider particle size distribution of 51–96 μm observed in the control anodes. The formation approach results in electrochemically synthesized ZnO/Zn anodes providing a stable ZnO matrix in which Zn particles retain their localized distribution on cycling better than control electrodes conventionally made by pasting zinc particles together with a binder.

Manganese dioxide (MnO2)–zinc (Zn) batteries are cheap and environmentally benign and have sufficient theoretical energy density to be used as an energy storage device for the grid; however, they have been relegated to primary systems, where the complete energy is delivered in a single discharge, due to the irreversibility of their active materials. Until recently, rechargeable MnO2–Zn batteries have only been able to cycle ∼10% of MnO2's theoretical 2-electron capacity (617 mA h g−1), thus delivering significantly reduced energy density. In a recent paper from our group, we reversibly accessed the full theoretical 2-electron capacity of MnO2 for >6000 cycles by using a layered polymorph of MnO2 mixed with bismuth oxide (Bi2O3) called Bi-birnessite (Bi–δ-MnO2) intercalated with Cu2+ ions. This discovery highlighted the possibility of achieving very high energy densities from inexpensive aqueous batteries; however, a full-cell demonstration with Zn as the anode was not studied. Here we report for the first time the effect of Zn anodes on the cycle life and energy density of a full cell, where we observe that 15% depth-of-discharge (DOD) of the Zn's theoretical capacity (820 mA h g−1) creates a cell energy density of ∼160 W h L−1; however, this causes a drastic shape change and formation of irreversible zinc oxide (ZnO) at the anode, which ultimately causes cell failure after ∼100 cycles. A drop in energy density is also observed as a result of the interaction of dissolved Zn ions with the cathode, which forms a resistive Zn-birnessite compound in the early cycles, and then forms a highly resistive haeterolite (ZnMn2O4) in the later cycles, and ultimately causes cathode failure. A possible solution using a calcium hydroxide layer as a separator is presented, where the layer blocks the interaction of zinc ions through a complexing mechanism to obtain >900 cycles with >80% retention of MnO2 DOD.

Electrochemical behavior of Ag, Bi, Cu, Fe, Ni and Sn substrates on zinc deposition was evaluated over battery cycling by cyclic voltammetry and electrochemical impedance spectroscopy. The effect of Bi, Cu, Ni, and Sn substrates on zinc electrodeposition during battery cycling was investigated using scanning electron microscopy and X-ray diffraction. The corrosion behavior of each metal in 9 M KOH and the corrosion rates of zinc plated on each substrate were analyzed by Tafel extrapolation method from the potentiodynamic polarization curves and electrochemical impedance spectroscopy. Although the charge-transfer resistance (Rct) of zinc electrodeposition is lowest on Sn, Sn eventually corrodes on cycling in alkaline media. Use of Ni as a substrate causes zinc to deteriorate on account of rapid hydrogen evolution. Bi and Cu substrates are more suitable for use as current collectors in zinc-anode alkaline rechargeable batteries because of their low corrosion rate and compact zinc deposition over battery cycling.

The rechargeability of γ-MnO2 cathodes in alkaline batteries is limited by the formation of the [Mn2]O4 spinels ZnMn2O4 (hetaerolite) and Mn3O4 (hausmannite). However, the time and formation mechanisms of these spinels are not well understood. Here we directly observe γ-MnO2 discharge at a range of reaction extents distributed across a thick porous electrode. Coupled with a battery model, this reveals that spinel formation occurs at a precise and predictable point in the reaction, regardless of reaction rate. Observation is accomplished by energy dispersive X-ray diffraction (EDXRD) using photons of high energy and high flux, which penetrate the cell and provide diffraction data as a function of location and time. After insertion of 0.79 protons per γ-MnO2 the α-MnOOH phase forms rapidly. α-MnOOH is the precursor to spinel, which closely follows. ZnMn2O4 and Mn3O4 form at the same discharge depth, by the same mechanism. The results show the final discharge product, Mn3O4 or Mn(OH)2, is not an intrinsic property of γ-MnO2. While several studies have identified Mn(OH)2 as the final γ-MnO2 discharge product, we observe direct conversion to Mn3O4 with no Mn(OH)2.

Metallic zinc (Zn) is an attractive negative electrode material for rechargeable batteries because it is a non-toxic, non-flammable, earth abundant metal that is compatible with aqueous electrolytes. Zinc metal is also energy dense, exhibiting a high gravimetric discharge capacity of 820 mAh/g, a high volumetric discharge capacity of 5850 mAh/mL, and a low equilibrium potential of -1.35 V vs. mercury-mercuric oxide (Hg|HgO) in concentrated alkaline electrolyte. Rechargeable aqueous Zn alkaline batteries have thus recently been the subject of intense investigations for safe, low-cost, stationary electrochemical energy storage. Our research aims to achieve Zn depth-of-discharge (DOD) of 20% that is sustainable for 500 or more charge-discharge cycles, corresponding to an overall battery energy density of 200 Wh/L at the cell level. However, the cycle life of the porous Zn electrode in concentrated alkaline electrolyte is observed to decrease strongly with increasing Zn DOD. For example, we recently demonstrated that metallic Zn electrodes cycled in the range of 1% to 16% Zn DOD had an exponential decrease in cycle life with Zn DOD, which was attributed mostly to the loss of active Zn material. Here, we study the effect of additives to increase the Zn DOD and cycle life of Zn electrodes. Zinc oxide (ZnO) was used as a starting material from which metallic Zn was formed in zinc-nickel (Zn-Ni) batteries. Additives were incorporated into the ZnO electrodes for the tests done on Zn-Ni batteries and these electrodes were cycled in the range of 15% to 30% Zn DOD. The potential values of the Zn electrodes vs. Hg|HgO reference electrodes were recorded to identify failure due to Zn. At 15% Zn DOD, ZnO electrodes with certain additives or combinations of additives achieved an increased cycle life compared to Zn electrodes without additives. This highlights the need to perform electrochemical and spectroscopic studies to determine the effects of the additives on the mechanisms of the Zn electrode. These additives, with further understanding, could be implemented in low-cost, energy-dense, rechargeable Zn alkaline batteries for grid-scale energy storage.

For energy storage to become ubiquitous in the electric grid, safe, reliable low-cost electrochemical storage technologies manufactured at high volumes with low capital expenditures are needed. Alkaline batteries based on high capacity multi-electron conversion electrodes from low cost, abundant and safe materials, such as a Zn/MnO2 are a promising technology. These batteries have a theoretical specific energy rivaling that of Li-ion systems (Zn @820 mAh/g and MnO2 @617 mAh/g, with ~400 Wh/L) and costs reducible to et al.). While recent advances by Yadav et al. have demonstrated highly reversible Bi- and Cu-stabilized MnO2 electrodes that can achieve the full 2e- capacity of MnO2 in alkaline electrolyte, the ability to pair this electrode with Zn over 5000+ cycles, which equates to ~10-15 years of battery life, remains a difficult challenge. Zn anodes suffer from irreversible shape change, the redistribution of active material, and passivation over repeated charge and discharge, limiting their achievable capacity and lifetime. Pre-saturating the electrolyte with zincate [Zn(OH)4 2-], which minimizes dissolution of Zn from the anode and reduces the rate of hydrogen evolution, has recently been shown to enhance cycle life for ~10-35% depth-of-discharge (DOD) Zn anodes by ~100-200% (M. Lim et al.); however, Zn(OH)4 2- saturated electrolyte is incompatible with high DOD MnO2, and exacerbates the formation of electrochemically inactive phases, such as ZnMn2O4 at the cathode. Hence, using zincate-blocking separators, able to entrap the zincate within the anode and effectively isolate the MnO2 cathode from Zn(OH)4 2- crossover, while maintaining hydroxide/cation conductivity, is one approach to improve the reversible cycling of a Zn/MnO2 cell at high DOD of both MnO2 and Zn. More recently we have developed a series of permselective polymeric separators (Kolesnichenko et al.) and screened them using our newly-developed anodic stripping voltammetry crossover assay (Duay et al.) to identify those with Zn(OH)4 2- blocking ability. A primary discharge of MnO2 was used to demonstrate that a sustained 2nd e- discharge plateau, indicative of the absence of zinc species at the cathode, was observed only for Zn/MnO2 batteries that utilized our selective polymeric separators. Finally, application of these polymeric separators in rechargeable Zn/MnO2 batteries increased cycle life with higher coulombic efficiencies. Various aspects involved in improving the cycle life of Zn anodes at increased DOD, and of the application of polymeric separators in isolating the MnO2 cathode from soluble zincate and their ability to enable higher DOD cycling in Zn, will be discussed. This work was supported by the U.S. Department of Energy, Office of Electricity, and the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia National Laboratories is a multi-program laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525. The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government. References [1] S. Banerjee S. Banerjee, Alkaline Zn-MnO2 Battery Development: A University-Private-Public Partnership, in Department of Energy Office of Electricity and Energy Reliability Peer Review, Santa Fe, NM, September 25-27th, 2018., https://eesat.sandia.gov/ wp-content/uploads/2018/10/1_SanjoyBanerjee_Presentation.pdf [2] G. G. Yadav, J. W. Gallaway, D. E. Turney, M. Nyce, J. Huang, X. Wei and S. Banerjee, Nat. Commun., 8, 14424 (2017). [3] M. B. Lim, T. N. Lambert and E. I. Ruiz “Effect of ZnO-Saturated Electrolyte on Rechargeable Alkaline Zinc Batteries at Increased Depth-of-Discharge” J. Electrochem. Soc. 2020, 167, 060508. DOI:10.1149/1945-7111/ab7e90. [4] J. Duay, M. Kelly and T. N. Lambert J. Power Sources, 395, 430-438 (2018). [5] I. Kolesnichenko et al. manuscript submitted. [6] J. Duay, T. N. Lambert and R. Aidun Electroanal 29, 2261-2267 (2017).

Rechargeable zinc alkaline batteries are of great interest for stationary storage applications because they are inherently safe, energy dense, environmentally friendly, and low-cost. However, these batteries have not been commercialized on a large scale because of their low cycle life at high depths of discharge. One cause is the buildup of ZnO on the electrode. It has been shown recently that ZnO produced in zinc alkaline electrodes inserts protons and electrons and undergoes electrochromic color changes as a function of electrode potential. This dynamic behavior increases hydrogen catalysis, contributes capacity to the electrode, and changes oxide conductivity as a function of electrode potential. In this work we investigate the disorder and nonstoichiometry of ZnO that allow the material to become electrochemically active. We used 1H, 2H, and 67Zn solid-state MAS NMR to better understand structure, defects, order, and the hydrogen insertion mechanism of the ZnO. Understanding the physical properties of the ZnO will enable better design of electrodes and additives for zinc alkaline batteries in the future.

Malachite green (MG) is not permitted by the EU and FDA to be used in animals intended for human consumption due to its potential carcinogenesis. However, recent findings have shown residues of MG in fish sold to consumers. Therefore, the presence of MG residues is of concern. In this study, MG and its primary metabolite leucomalachite green (LMG) in red tilapia (Oreochromis hybrid) muscle tissue was quantified by a simplified method for sample preparation using liquid chromatography-tandem mass spectrometry. The decision limit and detection capability for MG was 0.05 μg/kg and 0.09 μg/kg and for LMG was 0.05 μg/kg and 0.08 μg/kg, respectively. In addition, accuracy, precision, recovery, and matrix effects were also performed. To evaluate the persistence of MG and LMG, fish were exposed to dip (A) (66.7 mg/L; 30 s), dips (B) (66.7 mg/L; 30 s repeated for 5 days), short-term bath (C) (6.7 mg/L; 15 min), short-term bath (D) (6.7 mg/L; 15 min repeated for 5 days) and long-term bath (E) (0.5 mg/L; 6 days) treatments using MG. The MG and LMG residues were quantified at the following intervals; immediately after treatment, 1st, 2nd, 3rd, 4th, 10th, 20th and 30th day post-exposure. Long-term bath (E) showed the highest accumulation of total MG and LMG immediately after treatment (441.38 μg/kg) and at day 30 (13.30 μg/kg). Whereas, all other treatments (day 30) were below 0.26 μg/kg.

In recent studies of asphaltenes from the Norwegian continental shelf at water–oil interfaces, adsorption from largely aliphatic oils appeared to be governed at early times by molecular diffusion and at later times by molecular random sequential adsorption. In addition, the interfacial tension of asphaltenes at the oil–water interface was a a unique function of interfacial coverage, and no apparent rearrangement of asphaltenes at the interface was observed within an experimental time frame of up to 12 h. Confirmation of this result was obtained by showing that high frequency elasticity is a unique function of asphaltene interfacial tension. Both interfacial tension versus coverage and elasticity versus interfacial tension data have been successfully captured by the Langmuir Equation of State (EoS), which also allows estimates of the sizes of the asphaltene polyaromatic cores to be made. The value obtained in experiments with asphaltenes from a Norwegian crude oil is 0.32 nm2/molecule, which corresponds to...

Asphaltenes are "n-alkane insoluble" species in crude oil that stabilize water-in-oil emulsions. To understand asphaltene adsorption mechanisms at oil-water interfaces and coalescence blockage, we first studied the behavior in aliphatic oil-water systems in which asphaltenes are almost insoluble. They adsorbed as monomers, giving a unique master curve relating interfacial tension (IFT) to interfacial coverage through a Langmuir equation of state (EoS). The long-time surface coverage was independent of asphaltene bulk concentration and asymptotically approached the 2-D packing limit for polydisperse disks. On coalescence, the surface coverage exceeded the 2-D limit and the asphaltene film appeared to become solidlike, apparently undergoing a transition to a soft glassy material and blocking further coalescence. However, real systems consist of mixtures of aliphatic and aromatic components in which asphaltenes may be quite soluble. To understand solubility effects, we focus here on how the increased bulk solubility of asphaltenes affects their interfacial properties in comparison to aliphatic oil-water systems. Unlike the "almost irreversible" adsorption of asphaltenes where the asymptotic interfacial coverage was independent of the bulk concentration, an equilibrium surface pressure, dependent on bulk concentration, was obtained for toluene-water systems because of adsorption being balanced by desorption. The equilibrium surface coverage could be obtained from the short- and long-term Ward-Tordai approximations. The behavior of the equilibrium surface pressure with the equilibrium surface coverage was then derived. These data for various asphaltene concentrations were used to determine the EoS, which for toluene-water could also be fitted by the Langmuir EoS with Γ∞ = 3.3 molecule/nm(2), the same value as that found for these asphaltenes in aliphatic media. Asphaltene solubility in the bulk phase only appears to affect the adsorption isotherm but not the EoS. Further support for these observations is provided by dilatational rheology experiments for the EoS and contraction experiments in which desorption to the equilibrium surface pressure was observed.

During crude oil recovery, asphaltene-stabilized water-in-oil emulsions are formed. Asphaltenes is the component of crude oil, which is insoluble in n-alkane and is considered to be largely responsible for the stability of water-in-crude oil emulsions. To avoid wide range of problems, water has to be removed from these emulsions by using chemical ‘demulsifiers’. How demulsifiers act is still poorly understood. As the real crude oil system is extremely complex, system consisting of model oil with 100 ppm asphaltenes concentration is used as this concentration corresponds to nanoaggregation in the bulk fluid as shown in previous work. The surface pressure values appear to be a result of both asphaltenes and demulsifier competing to adsorb at the interface. The fractional interfacial coverage achieved by each appears to depend on their respective bulk concentrations. Thus demulsifier-asphaltene systems exhibit an equilibrium surface pressure, reached at higher demulsifier concentrations possibly due to adsor...

Microalgae are the major photosynthesizers on earth and produce important pigments that include chlorophyll a, b and c, β-carotene, astaxanthin, xanthophylls, and phycobiliproteins. Presently, synthetic colorants are used in food, cosmetic, nutraceutical, and pharmaceutical industries. However, due to problems associated with the harmful effects of synthetic colorants, exploitation of microalgal pigments as a source of natural colors becomes an attractive option. There are various factors such as nutrient availability, salinity, pH, temperature, light wavelength, and light intensity that affect pigment production in microalgae. This paper reviews the availability and characteristics of microalgal pigments, factors affecting pigment production, and the application of pigments produced from microalgae. The potential of microalgal pigments as a source of natural colors is enormous as an alternative to synthetic coloring agents, which has limited applications due to regulatory practice for health reasons.

Batteries based on manganese dioxide (MnO2) cathodes are good candidates for grid-scale electrical energy storage, as MnO2 is low-cost, relatively energy dense, safe, water-compatible, and non-toxic. Alkaline Zn–MnO2 cells, if cycled at reduced depth of discharge (DOD), have been found to achieve substantial cycle life with battery costs projected to be in the range of $100 to 150 per kWh (delivered). Commercialization of rechargeable Zn–MnO2 batteries has in the past been hampered due to poor cycle life. In view of this, the work reported here focuses on the long-term rechargeability of prismatic MnO2 cathodes at reduced DOD when exposed to the effects of Zn anodes and with no additives or specialty materials. Over 3000 cycles is shown to be obtainable at 10% DOD with energy efficiency >80%. The causes of capacity fade during long-term cycling are also investigated and appear to be mainly due to the formation of irreversible manganese oxides in the cathode. Analysis of the data indicates that capacity loss is rapid in the first 250 cycles, followed by a regime of stability that can last for thousands of cycles. A model has been developed that captures the behavior of the cells investigated using measured state of charge (SOC) data as input. An approximate economic analysis is also presented to evaluate the economic viability of Zn–MnO2 batteries based on the experiments reported here.

Energy dispersive X-ray diffraction (EDXRD) with photons of high energy and high flux is used to map crystalline discharge products within alkaline AA cells following discharge at various rates: C/160, C/80, C/40, C/20, C/10, and C/5. During the study, the sealed cells are never opened and thus never exposed to air. The technique’s resolution allows the various manganese oxide discharge products to be distinguished, which has previously proven difficult. In particular, colocalized Mn3O4 (hausmannite) and ZnMn2O4 (hetaerolite) phases are resolved at C/160, C/80, and C/40 rates. Following more rapid discharge at C/20, no hausmannite is observed: instead, two well-defined zones result, one consisting only of hetaerolite, and the other only of α-MnOOH (groutite), withasmalltransitionregionwherebothphasesaredetected.Modelingsuggeststheobservedhetaerolite-groutiteboundarypositions are consistent with hetaerolite formation in regions of greater active material utilization. Radial hetaerolite and hausmannite profiles are calculated and found to be a function of the discharge current, which also determines discharge capacity. Results also show formation of a α-MnOOH phase from oxidation states MnO1.7 to MnO1.53 with relatively little γ-MnOOH character.

In previous studies, the adsorption kinetics of asphaltenes at the water-oil interface were interpreted utilizing a Langmuir equation of state (EOS) based on droplet expansion experiments.1-3 Long-term adsorption kinetics followed random sequential adsorption (RSA) theory predictions, asymptotically reaching ∼85% limiting surface coverage, which is similar to limiting random 2D close packing of disks. To extend this work beyond this slow adsorption process, we performed rapid contractions and contraction-expansions of asphaltene-laden interfaces using the pendant drop experiment to emulate a Langmuir trough. This simulates the rapid increase in interfacial asphaltene concentration that occurs during coalescence events. For the contraction of droplets aged in asphaltene solutions, deviation from the EOS consistently occurs at a surface pressure value ∼21 mN/m corresponding to a surface coverage ∼80%. At this point droplets lose the shape required for validity of the Laplace-Young equation, indicating solidlike surface behavior. On further contraction wrinkles appear, which disappear when the droplet is held at constant volume. Surface pressure also decreases down to an equilibrium value near that measured for slow adsorption experiments. This behavior appears to be due to a transition to a glassy interface on contraction past the packing limit, followed by relaxation toward equilibrium by desorption at constant volume. This hypothesis is supported by cycling experiments around the close-packed limit where the transition to and from a solidlike state appears to be both fast and reversible, with little hysteresis. Also, the soft glass rheology model of Sollich is shown to capture previously reported shear behavior during adsorption. The results suggest that the mechanism by which asphaltenes stabilize water-in-oil emulsions is by blocking coalescence due to rapid formation of a glassy interface, in turn caused by interfacial asphaltenes rapidly increasing in concentration beyond the glass transition point.

An economic design for an alkaline zinc-anode flow-assisted battery without membrane separators was tested at grid-scale of 25 kWh with a string of thirty 833 Wh cells in series, and also at bench scale with individual 28 Wh cells. The bench-scale tests allowed optimization of parameters such as electrolyte flow, choice of hardware material, electrolyte composition, and charge/discharge protocol. The best-performing bench scale cell cycled for over 3300 cycles with energy efficiency above 80%, and was selected as the design basis for scale-up to the 25 kWh battery string. Testing of the grid-scale string demonstrated 1000+ cycles with round trip energy efficiency above 80%. Two challenges observed at the bench scale were overcome for successful scale-up, namely a) passivation of the anode surface, which occurred when the anode experienced voltages 100 mV above zinc's rest voltage, and b) zinc particulates that jammed the gap between the electrodes and caused cathode degradation and passivation of the anode surface. Best practices to overcome these challenges and achieve long cycle life are presented.

Preferred orientation of zinc deposits during charging is shown to significantly improve performance and cycle life in flow-assisted alkaline zinc batteries, which has not been demonstrated earlier. The preferred orientation of zinc deposits was investigated using X-ray diffraction (XRD). Compact zinc is found to have ( 11 2 ¯ 2 ) preferred orientation on brass, which contributes to ∼60% of the texture. The effect of charging current and zincate concentration on morphology was investigated in a rotating hull cell and correlated with anodic efficiency. Compact zinc deposits are found to have a fine-grained, bright finish and the highest anodic efficiency. Electrochemical impedance spectroscopy (EIS) proves that compact zinc corresponds to the minimum in the half-cell resistance. Morphological control using compact zinc could be accomplished using innovations such as pulse charging or enhanced mass-transfer to improve anode performance without affecting the cathode.

Cyclic voltammetry of zinc plated from flowing alkaline zincate electrolyte with a bismuth additive showed a marked mass transport effect during metal layer deplating. This bismuth was added as Bi2O3 and had a saturated concentration of 26 ppm bismuth. Using a small, transparent window flow cell the mechanism was studied in situ using synchrotron X-rays. X-ray microdiffraction revealed that the metal-electrolyte interface was bismuth rich, and bismuth behaved in a manner similar to a surfactant. Transmission X-ray microscopy revealed that in the presence of bismuth additive, 5 μm raised features on the metal layer were preferentially dissolved during deplating. However, macro-morphology experiments demonstrated that at 26 ppm a detrimental bismuth buildup occurred over many cycles. By reducing additive concentration to 3 ppm a metal layer was planarized compared to a no-additive control, while avoiding the bismuth buildup. These findings suggested that 3 ppm bismuth could be used to planarize zinc metal layers such as those in flow-assisted zinc batteries. However, concentration will need to be well-controlled.

In an earlier study, oil-water interfacial tension was measured by the pendant drop technique for a range of oil-phase asphaltene concentrations and viscosities. The interfacial tension was found to be related to the relative surface coverage during droplet expansion. The relationship was independent of aging time and bulk asphaltenes concentration, suggesting that cross-linking did not occur at the interface and that only asphaltene monomers were adsorbed. The present study extends this work to measurements of interfacial rheology with the same fluids. Dilatation moduli have been measured using the pulsating droplet technique at different frequencies, different concentrations (below and above CNAC), and different aging times. Care was taken to apply the technique in conditions where viscous and inertial effects are small. The elastic modulus increases with frequency and then plateaus to an asymptotic value. The asymptotic or instantaneous elasticity has been plotted against the interfacial tension, indicating the existence of a unique relationship, between them, independent of adsorption conditions. The relationship between interfacial tension and surface coverage is analyzed with a Langmuir equation of state. The equation of state also enabled the prediction of the observed relationship between the instantaneous elasticity and interfacial tension. The fit by a simple Langmuir equation of state (EOS) suggests minimal effects of aging and of nanoaggregates or gel formation at the interface. Only one parameter is involved in the fit, which is the surface excess coverage Γ∞ = 3.2 molecules/nm(2) (31.25 Å(2)/molecule). This value appears to agree with flat-on adsorption of monomeric asphaltene structures consisting of aromatic cores composed of an average of six fused rings and supports the hypothesis that nanoaggregates do not adsorb on the interface. The observed interfacial effects of the adsorbed asphaltenes, correlated by the Langmuir EOS, are consistent with the asphaltene aggregation behavior in the bulk fluid expected from the Yen-Mullins model.

The immobilization of nitrifying bacteria in alginate has been used to evaluate the performance of ammonia reduction. In this research, bacteria were screened and observed for their ability to reduce ammonia. Consortium M1, isolated from the mangrove area (Morib, Selangor) showed the most effective reduction of ammonia from an initial concentration of 2.17±0.10 to 0.06±0.01 mg L-1 in 14 days. The consortium was then identified to consist of Pseudomonas aeruginosa (99%), Pseudomonas stutzeri (98%) and Nocardioides albus (98%) using the 16S rDNA gene sequences via Polymerase Chain Reaction (PCR) technique and identified by phylogenetic analysis based on their partial 16S rDNA sequences comparison in NCBI GenBank. The consortium M1 was then immobilized into alginate beads each containing 1.79x103 CFU mL-1 bacteria cells before being tested for its efficacy in reducing ammonia under laboratory conditions using 10, 20, 30, 40, 50, 100, 150 and 200 beads. The fastest reduction rate of Total Ammonia Nitrogen (TAN) was observed in flasks containing 150 beads which on day 6, drastically reduced TAN from 2.50±0.10 to 0.090±0.059 mg L-1 followed by treatment with 200 beads (0.104±0.07 mg L-1). However, at the end of experiment at day 14, the lowest TAN level (0.083±0.063 mg L-1) was observed in flasks with 200 beads which was not significantly different (p>0.05) from flasks with 150 beads (0.106±0.034 mg L-1). The present study reveals that the immobilization of bacterial consortium consisting of ammonia oxidizing bacteria could be used as an alternative for reduction of high TAN concentration in shrimp or fish hatchery system.

Changes in electrodeposited zinc morphology were experimentally investigated in a flowing alkaline electrolyte. Deposition of zinc on flat sheets as well as on new mesh-type reduced-area current collectors was studied. Zincate concentration in the electrolyte, flow velocity, and current density was varied over a wide range. The results show that the ratio between the effective current density and the limiting current density (current density ratio) which is directly related to the zincate concentration at the electrode surface determines the zinc morphology. Zinc morphology is mossy and porous when the current density ratio is below 0.4, whereas it is a mixture of mossy and crystalline structures when it is between 0.4 and 0.9. Only when the current density ratio is above 0.9, does zinc deposition become just crystalline and compact. This finding holds for both flat sheet and mesh-type reduced-area current collectors.

Asphaltenes constitute high molecular weight constituents of crude oils that are insoluble in n-heptane and soluble in toluene. They contribute to the stabilization of the water-in-oil emulsions formed during crude oil recovery and hinder drop-drop coalescence. As a result, asphaltenes unfavorably impact water-oil separation processes and consequently oil production rates. In view of this there is a need to better understand the physicochemical effects of asphaltenes at water-oil interfaces. This study elucidates aspects of these effects based on new data on the interfacial tension in such systems from pendant drop experiments, supported by results from nuclear magnetic resonance (NMR) and dynamic light scattering (DLS) studies. The pendant drop experiments using different asphaltene concentrations (mass fractions) and solvent viscosities indicate that the interfacial tension reduction kinetics at short times are controlled by bulk diffusion of the fraction of asphaltenes present as monomer. At low mass fractions much of the asphaltenes appear to be present as monomers, but at mass fractions greater than about 80 ppm they appear to aggregate into larger structures, a finding consistent with the NMR and DLS results. At longer times interfacial tension reduction kinetics are slower and no longer diffusion controlled. To investigate the controlling mechanisms at this later stage the pendant drop experiment was made to function in a fashion similar to a Langmuir trough with interfacial tension being measured during expansion of a droplet aged in various conditions. The interfacial tension was observed to depend on surface coverage and not on time. All observations indicate the later stage transition is to an adsorption barrier-controlled regime rather than to a conformational relaxation regime.

An experimental study on hydrogen and oxygen evolution was carried out in a sealed zinc–nickel oxide battery. The effects of flowing electrolyte on gas evolution were quantitatively evaluated. The results show that both the hydrogen and oxygen evolution are suppressed by making the electrolyte flow on a regular cycle. This is due to increased cell polarization in the non-flowing case attributed to the concentration boundary layer of zinc (zincate) ion near the anode surfaces. Though the Coulombic efficiency in the flowing case was higher than that in the non-flowing case, the fraction of gas evolution against Coulombic loss was the same for both the cases. When deeply discharging the cell, more hydrogen is evolved in the flowing case than in the non-flowing case.

The zinc morphology on repeated charging and discharging in flow-assisted zinc–nickel oxide cells was studied. The results show that higher charge rates cause more dendritic growth of zinc deposition on charging and tend to cause deterioration of battery cells. However, when the electrolyte velocity is higher than 15 cm s −1 , the direction of dendrites was distorted toward the flow direction and the internal short circuit was suppressed. Good cycle life was obtained – 1500 cycles at 100% depth of discharge and C /2 charge and discharge rate. Also, the battery was scaled up to a 100 Wh prismatic cell, and more than 200 cycles were obtained.