Retention Of Anions Research Articles

Multifunctional polymeric stationary phases with enhanced hydrophilicity grafted with polyethyleneimine and polyglycidol

Two methods for increasing the degree of hydrophilization and screening of the sorbent matrix based on a copolymer of styrene and divinylbenzene grafted with polyethyleneimine quaternized with glycidol are proposed. The first method involves the polymerization of glycidol in the functional layer by varying the pH of the reaction medium, and the second method involves modifying the matrix by oxidizing the double bonds on its surface to obtain anchor epoxy groups. It was demonstrated that in the first method, the optimal approach is the twofold addition of glycidol before and after the addition of alkali, as in this case, the first addition of glycidol is consumed for the quaternization of polyamine, and the second for polymerization in ion-exchange centers. The new method of matrix modification, combined with the developed method of creating hydrophilic layers, significantly reduced the retention of oxyhalides, haloacetic acids, and polarizable anions in ion chromatography with suppressed background conductivity and amino acids in hydrophilic chromatography up to the point of changing the elution order. The obtained stationary phases are suitable for the simultaneous determination of standard inorganic anions, oxyhalides, and anions of haloacetic or alkylphosphonic acids in ion chromatography, as well as for the separation of amino acids, sugars, and vitamins in hydrophilic chromatography.

Novel Highly Hydrophilic Resins with Attached Polymer Layers for Liquid Chromatography

The aim of this work was to the obtaining novel mixed-mode stationary phases with increased hydrophilicity and applying them in ion and hydrophilic interaction liquid chromatography. The resins were obtained by the sequential covalent attachment of branched polyethylenimine and polyelectrolytes synthesized from diepoxide and a secondary amine on the surface of epoxidized polystyrene–divinylbenzene. To increase the shielding degree of the polymer substrate, an additional polymerization of glycidol was carried out in the functional layer of the sorbent at an increased pH of the reaction medium. The synthesized phases possessed increased hydrophilicity compared to most resins based on a styrene–divinylbenzene copolymer with covalently attached layers. This was evidenced in the ion chromatography mode by a decrease in the relative retention of polarizable anions, weakly hydrated oxyhalides (up to a change in the elution order of the bromate), and haloacetic acids. In the hydrophilic interaction liquid chromatography mode, an increased hydrophilicity of the phases was confirmed by an increase in the retention factors of polar analytes, as well as by the reversal of the elution order of ascorbic and nicotinic acids as compared to the phases based on polystyrene–divinylbenzene presented in the literature. The low efficiency of the obtained stationary phases in the ion chromatography mode was noted, which is associated with slow mass transfer in the bulk polymer functional layer. The negative impact of the polymer layer on efficiency in hydrophilic interaction liquid chromatography is less pronounced due to the presumably smaller thickness of the part of the functional layer involved in this mode. The proposed method for the synthesis of resins ensures an increase in the efficiency, selectivity, and separation ability of sorbents in the hydrophilic interaction liquid chromatography mode as compared to phases based on a styrene–divinylbenzene copolymer described previously in the literature. The resulting highly hydrophilic resins makes it possible to separate a mixture of 9 nitrogenous bases and nucleosides in 18 min, 6 vitamins in 24 min, and 8 sugars in 11 min. Thus, the method of substrate hydrophilization proposed in this work is promising for improving the chromatographic characteristics of phases in the hydrophilic interaction liquid chromatography mode and can be used to create sorbents with increased selectivity and efficiency.

Separation of inorganic anions on reversed-phase C18 columns with a phosphomolybdate mobile phase

Reversed-phase high performance liquid chromatography (RP-HPLC) is the most widely used chromatographic method. In addition to hydrophobic interactions, additional interactions such as electrostatic interactions may participate in the retention behaviour of an analyte. This makes it possible to use RP-HPLC for many types of analyte. We describe a simple method for separating inorganic anions on a C18 column, in which retention of inorganic anions is almost entirely due to electrostatic interactions. This leads to rapid separations as well as higher theoretical plate numbers. We used 2 mM phosphoric acid containing a low concentration of disodium molybdate as the mobile phase, which allows UV detection of non-UV-absorbing anions. With this method, we determined eight inorganic anions including several non-UV-absorbing anions photometrically at 220 nm. The detection limits of the examined eight inorganic anions calculated at a signal-to-noise ratio of 3 were between 0.3 and 10 μM. The detector response was linear over three orders of magnitude of inorganic anion concentration. The proposed RP-HPLC/UV method was successfully applied to determine inorganic anions in some water samples.

Engineering a novel zwitterionic polyurethane nanofiltration membrane with enhanced fouling resistance for water reclamation

Design of zwitterionic polymers with feasible methods is rational for grafting membrane surface and enhancing its antifouling property. Herein, we propose a facile and scalable “one-pot” polymerization approach to synthesize a novel thiolated zwitterionic polyurethane (TZP) and graft it onto a polydopamine activated membrane surface via Michael addition for engineering antifouling nanofiltration (NF) membranes. The chemical structure of TZP was confirmed by the 1H nuclear magnetic resonance and it had a weight average molecular weight of 13,000 g mol−1. The Fourier transform infrared and X-ray photoelectron spectra confirm the successful introduction of sulfobetaine groups on membrane surfaces. The TZP grafting neutralized the negative charge of PDA interlayer and further improved membrane hydrophilicity. The pore size and ion selectivity of the NF membranes were optimized by tuning TZP concentrations. Satisfactory divalent anion retention along with a molecular weight cut-off of ∼800 Da was achieved at 30 g L−1 TZP concentration (i.e., TZP-30). During two cycles of synthetic wastewater filtration, the TZP-30 membrane exhibited excellent fouling resistance and satisfactory flux recovery rate compared with a benchmark commercial NF membrane. Our findings shed light on the future design of novel zwitterionic polymers and antifouling NF membranes for sustainable water reclamation.

Planting Anion Channels in a Negatively Charged Polyamide Layer for Highly Selective Nanofiltration Separation.

A nanofiltration (NF) membrane with high salt permeation and high retention of small organics is appealing for the treatment of high-salinity organic wastewater. However, the conventional negatively charged NF membranes commonly show high retention of divalent anions (e.g., SO42-), and the reported positively charged NF membranes normally suffer super low selectivity for small organics/Na2SO4 and high fouling potential. In this work, we propose a novel "etching-swelling-planting" strategy assisted by interfacial polymerization and mussel-inspired catecholamine chemistry to prepare a mix-charged NF membrane. By X-ray photoelectron spectroscopy depth profiling and pore size distribution analysis, it was found that such a strategy could not only deepen the positive charge distribution but also narrow the pore size. Molecular dynamics confirm that the planted polyethyleneimine chains play an important role to relay SO42- ions to facilitate their transport across the membrane, thus reversing the retention of Na2SO4 and glucose (43 vs 71%). Meanwhile, due to the high surface hydrophilicity and smoothness as well as the preservation of abundant negatively charged groups (-OH and -COOH) inside the separation layer, the obtained membrane exhibited excellent antifouling performance, even for the coking wastewater. This study advances the importance of vertical charge distribution of NF membranes in separation selectivity and antifouling performance.

Synthesis and physicochemical characterization of new calcined layered double hydroxide Mg Zn Co Al-CO3; classical modeling and statistical physics of nitrate adsorption

This research focuses on the study of a new material, a layered double hydroxide, which was synthesized using a co-precipitation method at pH constant and, then, tested for its retention of nitrate anions. The LDH was prepared from four metal cations Mg-Zn-Co-Al to produce the quadratic material mentioned, Mg Zn Co Al-CO3, which was calcined to obtain metal oxides. Different techniques of characterization were considered, namely FTIR, X-ray diffraction, BET, SEM and EDX. Adsorption experiments for nitrate were carried out to test the effect of contact time, adsorbent mass, pH values, mass effect, and initial surfactant concentrations. When equilibrium was reached after 300 min (R2 = 0.998), the Pseudo-second order model was found to fit accurately the kinetic data. The intraparticle diffusion model recorded a rate constant of between 0.277 and 0.757 (g/mg. min−0.5) and the Sips adsorption isotherm best fitted the experimental data obtained. Maximum adsorption capacity for nitrate was found to be 55.97 mg g−1 which was in accordance with the experimental results. Thermodynamic parameters indicated that the adsorption process was spontaneous and endothermic. The values of ΔH˚ and ΔS˚ of the adsorption process were 14.81 and 59.04 kJ mol−1, respectively. The low value of ΔH˚ (<40 kJ mol−1) indicated that the adsorption process was associated with physical forces. Finally, for a deeper insight into the nitrate adsorption mechanism, the statistical physics model was considered to quantify the number of adsorbed nitrate molecules per site, the anchorage number, the receptor sites density, the adsorbed quantity at saturation, the concentration at half saturation and the molar adsorption energy. A statistical physics model, with two binding sites, proved to be the best option to characterize and interpret the removal of nitrate on the tested LDH.

Management history and mixture evenness affect the ecosystem services from a crimson clover-rye cover crop

Cover crop mixtures of functionally distinct species may increase multiple ecosystem services, depending on their productivity and composition. We assessed how unique management legacies, and resulting soil fertility properties, influenced the functions provided by a cover crop mixture. We used the Kellogg Biological Station’s long-term Main Cropping Systems Experiment to test the legacy effects of four management systems (ranging from conventional to organic) on the production and function of crimson clover and cereal rye cover crops grown alone and in mixture, with a focus on their potential for improving agroecosystem N retention and supply. We applied bromide as a conservative tracer of solute flow in the soil profile to assess management legacy and cover crop treatment effects on potential anion leaching. A history of ecological nutrient management practices, including long-term cover crop use, increased soil fertility. Higher soil fertility, in turn, increased spring cover crop biomass and mixture evenness, and percent recovery of bromide, an estimate of soil anion retention. Mixture evenness was positively related to higher cover crop C/N ratios, N retention in corn biomass, and percent of clover N from fixation. In legacies with lower soil fertility, clover was more competitive than rye in the mixtures. Our results show that the benefits from cover crop mixtures depend on the management context into which they are adopted. In lower fertility soils with higher nutrient leaching potential, we suggest increasing crop functional diversity by including single species cover crops at different points within a crop rotation to build soil fertility. Once background soil fertility has been developed, farmers could include mixtures in their agroecosystems to maximize the functions provided by cover crops.

Improved Fire Retardancy of Cellulose Fibres via Deposition of Nitrogen-Modified Biopolyphenols.

Driven by concerns over the health and environmental impacts of currently used fire retardants (FRs), recent years have seen strong demand for alternative safer and sustainable bio-based FRs. In this paper, we evaluated the potential of nitrogen-modified biopolyphenols as FRs for cellulosic natural fibres that could be used in low-density cellulose insulations. We describe the preparation and characterisation of nitrogen-modified lignin and tannin containing over 10% nitrogen as well as the treatment of cellulose pulp fibres with combinations of lignin or tannin and adsorption-enhancing retention aids. Combining lignin or tannin with a mixture of commercial bio-based flocculant (cationised tannin) and anionic retention chemical allowed for a nearly fourfold increase in lignin adsorption onto cellulosic pulp. The nitrogen-modified biopolyphenols showed significant improvement in heat release parameters in micro-scale combustion calorimetry (MCC) testing compared with their unmodified counterparts. Moreover, the adsorption of nitrogen-modified lignin or tannin onto cellulose fibres decreased the maximum heat release rate and total heat release compared with cellulose reference by 15–23%. A further positive finding was that the temperature at the peak heat release rate did not change. These results show the potential of nitrogen-modified biopolyphenols to improve fire-retarding properties of cellulosic products.

Partially Reduced Graphene Oxide Membranes Crosslinked by an Anionic Porphyrin: Green Fabrication for High‐Performance Ion Sieving

AbstractGO membranes crosslinked by planar cation (e. g. TMPyP, a cationic porphyrin) meet the requirements of green fabrication, because TMPyP can pre‐assemble on GO sheets. However, their ion sieving performance are unsatisfactory. With shortened water channels, reduced graphene oxide (rGO) membranes owe high water flux, yet the retention of multivalent anions may goes down distinctly on account of Donnan effect decreasing obviously. Herein, we focus on the assembly between partially reduced graphene oxide (p‐rGO) and Anionic planar molecule (tetrasulfonic tetraphenyl porphyrin, TPPS), and then fabricate p‐rGO/TPPS composite membranes via assembling p‐rGO/TPPS sheets on base membrane. Anionic planar molecule is firstly used as crosslinking agent for graphene‐based membranes, which has the advantage of 100% atomic efficiency. The fabricated p‐rGO/TPPS membranes show better sieving performance than GO/TMPyP membranes on both side of rejection of Na2SO4 and water flux. Moreover, water flux go up to around another double though rejection decline slightly as the polyther sulfone (PES) base membrane with large surface pores is used.

Retention of inorganic anions using mesoporous zirconia spheres modified with anion-exchange groups as the stationary phase for ion chromatography.

A zirconia (ZrO2) stationary phase with a chemically fixed silane coupling agent (trimethyl [3-(trimethoxysilyl)propyl]ammonium chloride; TMA), which possesses quaternary ammonium functional groups, is evaluated as a separation column for ion chromatography (IC) of anions. The selectivity for anions varies depending on the amount of TMA immobilized on the ZrO2. The TMA-ZrO2, with an anion-exchange capacity of 17 ± 3µeq/g, shows an anion-exchange reaction that involves the specific retention of fluoride ion on ZrO2. The TMA-ZrO2 exhibits a decrease of the anion resolution with an increase of the eluent pH and an enhancement of the selective separation of fluorideion with an increase of the column temperature. Through this study, the TMA-ZrO2 stationary phase shows potential as a new medium for ion separation.

Characterization of a highly stable zwitterionic hydrophilic interaction chromatography stationary phase based on hybrid organic-inorganic particles.

We have characterized a sulfobetaine stationary phase based on 1.7 μm ethylene‐bridged hybrid organic–inorganic particles, which is intended for use in hydrophilic interaction chromatography. The efficiency of a column packed with this material was determined as a function of flow rate, demonstrating a minimum reduced plate height of 2.4. The batch‐to‐batch reproducibility was assessed using the separation of a mixture of acids, bases, and neutrals. We compared the retention and selectivity of the hybrid sulfobetaine stationary phase to that of several benchmark materials. The hybrid sulfobetaine material gave strong retention for polar neutrals and high selectivity for methyl groups, hydroxy groups, and configurational isomers. Large differences in cation and anion retention were observed among the columns. We characterized the acid and base stability of the hybrid sulfobetaine stationary phase, using accelerated tests at pH 1.3 and 11.0, both at 70°C. The results support a recommended pH range of 2–10. We also investigated the performance of columns packed with this material for metal‐sensitive analytes, comparing conventional stainless steel column hardware to hardware that incorporates hybrid surface technology to mitigate interactions with metal surfaces. Compared to the conventional columns, the hybrid surface technology columns showed a greatly improved peak shape.

Laboratory Scale Evaluation of Fertiliser Factory Wastewater Treatment through Membrane Distillation and Reverse Osmosis.

The incumbent water stress scenario imposes wastewater valorisation to freshwater, promoting technology for its effective treatment. Wastewater from fertiliser factories is quite problematic because of its relevant acidity and solute content. Its treatment through vacuum membrane distillation (VMD) was evaluated through laboratory scale tests at 40 °C and 25 mbar vacuum pressure with polytetrafluoroethylene and polypropylene flat-sheet porous membranes. The wastewater from a partially disused Italian industrial site was considered. VMD distillate fluxes between 22 and 57.4 L m−2 h−1 (LMH), depending on the pore size of the membranes, along with very high retention (R > 99%) for anions (Cl−, NO3−, SO42−, PO43−), NH4+, and chemical oxygen demand (COD) were observed. Laboratory scale reverse osmosis (RO) tests at 25 °C and increasing of the operating pressure (from 20 bar to 40 bar) were carried out with a seawater desalination membrane for comparison purposes. Permeability values around 1.1 LMH/bar almost independently of the operating pressure were observed. Lower retentions than those measured from VMD tests were found. Finally, for any given RO operating pressure, the flux recovery ratio (FRR) calculated from permeate fluxes measured with pure water before and after wastewater treatment was always much lower that evaluated for VMD membranes.

Hydrophobicity of polymer based anion-exchange columns for ion chromatography

The regularities of the retention of alkanoic and alkanesulfonic acids homologues were investigated for the set of 36 anion-exchange columns produced by various manufacturers. The role of hydrophobic and electrostatic interactions in the retention and separation of organic anions was studied. The methylene selectivity increments α(CH2) were measured for the studied columns with 10 mM sodium hydroxide eluent. The influence of matrix, surface area, polar group structure, ion-exchange capacity, the density of charged functional groups on the surface and other characteristics of anion-exchangers on resin hydrophobicity was considered.A unified approach for the measurements of hydrophobic properties of anion-exchange resins is proposed and the ratio of chloride retention factor (kCl) to α(CH2) was introduced as mixed-mode factor. The synergetic effect of electrostatic and hydrophobic interactions was observed.

Characterization of a highly stable mixed-mode reversed-phase/weak anion-exchange stationary phase based on hybrid organic/inorganic particles.

We have characterized Atlantis ethylene‐bridged hybrid C18 anion‐exchange, a mixed‐mode reversed‐phase/weak anion‐exchange stationary phase designed to give greater retention for anions (e.g., ionized acids) compared to conventional reversed‐phase materials. The retention and selectivity of this stationary phase were compared to that of three benchmark materials, using a mixture of six polar compounds that includes an acid, two bases, and three neutrals. The compatibility of the ethylene‐bridged hybrid C18 anion‐exchange material with 100% aqueous mobile phases was also evaluated. We investigated the batch‐to‐batch reproducibility of the ethylene‐bridged hybrid C18 anion‐exchange stationary phase for 27 batches across three different particle sizes (1.7, 2.5, and 5 μm) and found it to be comparable to that of one of the most reproducible C18 stationary phases. We also characterized the acid and base stability of the ethylene‐bridged hybrid C18 anion‐exchange stationary phase and the results show it to be usable over a wide pH range, from 2 to 10. The extended upper pH limit relative to silica‐based reversed‐phase/weak anion‐exchange materials is enabled by the use of ethylene‐bridged hybrid organic/inorganic particles. The improved base stability allows Atlantis ethylene‐bridged hybrid C18 anion‐exchange to be used with a wider range of mobile phase pH values, opening up a greater range of selectivity options.

Poly(ethylene glycol) Methyl Ether Methacrylate-bonded Stationary Phase in Ion Chromatography and Its Application to Seawater Samples.

A fast and simple ion chromatographic method for the determination of iodide in seawater is reported using poly(ethylene glycol) methyl ether methacrylate-bonded stationary phase. Poly(ethylene glycol) methyl ether methacrylate was reacted with primary amino groups of aminopropylsilica in N,N-dimethylformamide at 80°C. The prepared stationary phases were evaluated by analyzing several inorganic anions and the retention behavior was observed. Various chromatographic parameters were optimized for the separation of these anions. Although there were no ion-exchange sites on the resulted stationary phases, the results obtained suggested that an ion-exchange mechanism was involved in the retention of analyte anions. With 0.15 μL injection, the limit of quantitation of iodide was 26 μg L-1 when 200 mM NaCl was selected as the eluent. This stationary phase was applied to the analysis of direct and fast determination of iodide in real seawater samples successfully with the recovery rates of 98.1 and 104.9%.

Rapid Saturation–Diffusion Method to Determine Cation- and Anion-Exchange Capacities in Soil

ABSTRACT Soils have long been recognized for electrostatic retention of anions as well as cations, although this property is usually characterized by measuring cation- but not anion-exchange capacity. A technique is described that determines effective cation- and anion-exchange capacities (CECe and AECe) for a single soil sample. In this technique, 0.5 g of soil is saturated by treatment with 1 or 0.006 M ammonium nitrate (NH4NO3) using a vacuum manifold equipped with disposable syringes, the excess NH4NO3 is removed by leaching with 2-propanol, and sequential diffusions are performed to determine ammonium-nitrogen (NH4 +-N) as CECe and nitrate (NO3 ‒)-N as AECe. In evaluative studies, complete saturation of cation- and anion-exchange resins was achieved with 1 but not 0.006 M NH4NO3, and neither CECe nor AECe measurements were affected by entrapment of excess saturating reagent, cross-contamination of NO3 ‒-N diffused following 15NH4 +-N, or interference due to soil organic N. Good agreement was obtained in comparing CEC data collected with 1 M NH4NO3 and ammonium acetate for 10 soils dominated by permanent charge but not for seven highly weathered soils. For all soils studied, both CECe and AECe were significantly reduced by the use of 0.006 M NH4NO3, and the AECe data thereby obtained agreed closely with compulsive exchange measurements using 0.002 M barium chloride. The rapid saturation-diffusion method described measures CECe and AECe when using 1 M NH4NO3, and can also be performed to estimate electrostatic ion retention at a low ionic strength (μ = 0.006) that approximates field conditions.

Fundamental Insights into the Covalent Silane Functionalization of NiFe Layered Double Hydroxides.

Layered double hydroxides (LDHs) are a class of 2D anionic materials exhibiting wide chemical versatility and promising applications in different fields, ranging from catalysis to energy storage and conversion. However, the covalent chemistry of this kind of 2D materials is still barely explored. Herein, the covalent functionalization with silanes of a magnetic NiFe-LDH is reported. The synthetic route consists of a topochemical approach followed by anion exchange reaction with surfactant molecules prior to covalent functionalization with the (3-aminopropyl)triethoxysilane (APTES) molecules. The functionalized NiFe-APTES was fully characterized by X-ray diffraction, infrared spectroscopy, electron microscopy, thermogravimetric analysis coupled with mass spectrometry and 29 Si solid-state nuclear magnetic resonance, among others. The effect on the electronic properties of the functionalized LDH was investigated by a magnetic study in combination with Mössbauer spectroscopy. Moreover, the reversibility of the silane-functionalization at basic pH was demonstrated, and the quality of the resulting LDH was proven by studying the electrochemical performance in the oxygen evolution reaction in basic media. Furthermore, the anion exchange capability for the NiFe-APTES was tested employing CrVI , resulting in an increase of 200 % of the anion retention. This report allows for a new degree of tunability of LDHs, opening the door to the synthesis of new hybrid architectures and materials.

Influence of counterion charge on the electrochemistry and impedance of polypyrrole

Polypyrroles doped with multiply charged anions are becoming increasingly important in a wide range of energy, environmental and biomedical applications. The increased counterion charge promotes anion binding and retention and can significantly increase stability and performance. The electrochemical properties of polypyrrole films prepared galvanostatically in Na2SO4 (PPySO4) where found to be similar those of PPyClO4 prepared in NaClO4, although there was significantly more anion retention during potential cycling. In contrast, PPyPO4 films prepared in Na3PO4 under the same conditions were over-oxidised and more dense, which is beneficial for corrosion protection and electroanalysis. Paradoxically, the low mobility of SO42− counterions results in more facile charging and discharging of the film, as observed with large and polymeric counterions. This can create significant benefits in applications that require fast cycling, such as supercapacitors and high-rate batteries. These conclusions are corroborated by electrochemical impedance measurements in various aqueous electrolytes. Ionic conductivity was dominated by anion transport for both PPyClO4 and PPySO4, whilst PPyPO4 was predominantly a cation conductor.

Ion and organic transport in Graphene oxide membranes: Model development to difficult water remediation applications

The role of steric hindrance and charge interactions in governing ionic transport through reduced graphene oxide (rGO) and commercial (DOW-Filmtec NF270) membranes was elucidated by a comprehensive study of experimental and established mathematical analysis based on Nernst-Planck equation. A charge-dominated salt exclusion mechanism was observed for the rGO membranes, which exhibited retention from low (7%) to moderate (70%) extent depending on the nature of ions (5 mM). Swelling of GO (1.2 nm interlayer distance) in water beyond the hydrated diameter of ions was attributed as a primary cause for lowering steric hindrance effects. The influence of parameters affecting charge interactions, such as pH and ionic strength, on the extent of salt rejection was modelled. The potential impact of the membrane's charge density, GO loading and interlayer spacing on salt retention was quantified by performing sensitivity analyses. For a high TDS produced water sample, the rGO membranes partially retained divalent cations (Ca:13%) and exhibited high dissolved oil rejection. The membranes were found to be suitable for the treatment of high TDS water with the goal of selectively removing organic impurities, and thus minimizing the impact of osmotic pressure effect. Performance of the membranes was also investigated for retention of water remediation related organic anions, using perfluoro octanoic (PFOA) acid as a model compound. rGO membranes exhibited a charge-dominated exclusion mechanism for retention (90%) of PFOA (1 ppm).

Retention of anions in cobalt hydroxide with Ni substitution to emphasize the role of anions and cations for high current density in oxygen evolution reactions.

Herein, we report the fabrication of remarkably fine nickel-substituted α-Co(OH)2 sheets using an ingenious co-precipitation method at a lower pH value. An α-CoNiOOH sheet retains the parent α-Co(OH)2 structure consisting of both tetrahedral (Td) and octahedral (Oh) sites with the retention of interlayer chloride ions, which is in contrast to the previous reports. The as-synthesized α-CoNiOOH sheet exhibits excellent oxygen evolution reactions (OERs) and produces a current of 10 mA cm-2 at an overpotential of merely 190 mV in an alkaline environment. Moreover, the α-CoNiOOH sheet attains an exceptionally high current density of 100 mA cm-2 at a low overpotential of only 270 mV. Additionally, this electrocatalyst possesses a 33 mV dec-1 Tafel slope with higher values of TOF (11 s-1) and double-layer capacitance (7.76 mF cm-2). This enhancement is attributed partially to the substitution of Ni during the conversion of α-Co(OH)2 to α-CoNiOOH and partially to the exceptionally thin sheets allowing potential octahedral sites for improved oxygen evolution reactions.