High Alkalinity Concentrations Research Articles

Study on the Adsorption Performance of Lead Ions in Water by Phosphate Base Polymer with Different Ratio

Red mud, a by-product of the aluminum industry, poses a threat to the environment with its high alkalinity and heavy metal content and may seep into the soil and groundwater, endangering ecology and health. Effective utilization of red mud can reduce pollution and achieve resource recycling. In this study, a metakaolin/red mud geopolymer was prepared by phosphoric acid excitation to investigate its adsorption capacity for lead ions. The ratio of metakaolin to red mud and the additions of phosphoric acid and water were optimized, and the optimal formulations were 3/7 mass ratio of metakaolin to red mud, 2.2 molar ratio of H3PO4/Al2O3, and 0.5 water-solid ratio, which demonstrated good stability and operability.

A Comparative Study of the Oxygen Reduction Reaction on Pt and Ag in Alkaline Media

AbstractInvestigating the ORR under practical conditions is vital for optimizing metal–air batteries and alkaline fuel cells. Herein, we characterized Pt and Ag gas diffusion electrodes (GDE) in a GDE half‐cell in high alkaline concentrations at elevated temperatures by polarization curves and electrochemical impedance spectroscopy (EIS) combined with the distribution of relaxation times (DRT) analysis. The Pt catalyst's polarization curve displays substantial losses below 0.82 V vs. RHE. The DRT analysis reveals significantly increased charge transfer resistance and a decelerated ORR at that potential. RRDE measurements attributed the polarization loss observed for Pt catalysts to increased peroxide formation in this potential region triggered by the desorption of oxygenated species. Therefore, the ORR activity of Ag exceeds some of the here‐used Pt catalysts at high current densities. This work combines the benefits of the RRDE and the GDE half‐cell to study catalysts and identify the reaction mechanisms under conditions relevant to practical fuel cells and batteries. Moreover, the DRT analysis is introduced as an analytical tool to determine the charge transfer resistance contribution and the corresponding frequency of the ORR.

Groundwater remediation techniques around Kodungaiyur dump yard

Abstract The groundwater around the Kodungaiyur dump yard, in Tamil Nadu, India, is polluted due to the percolation of leachate from the dumpsite. This paper proposes three remedial techniques to make the groundwater drinkable for the people living near the Kodungaiyur trash yard. Twelve bore wells around the Kodungaiyur dumpsite provided water samples for which the physicochemical parameters were measured. Moderately high concentrations of Total Hardness (TH), Total Alkalinity (TA), Chloride, Sulphate, Nitrate, Sodium, and Total Dissolved Solids (TDS) are present in the groundwater around the dump yard. The Physicochemical parameters of the samples tend to deviate from the standards prescribed by WHO and BIS. Therefore, remedial measures such as solar distillation, Activated Charcoal, and the Phytoremediation process are suggested to reduce the contaminants in the groundwater. The activated charcoal removes the unpleasant color of the water completely and makes the water clear and transparent through filtration. The solar distillation process does not affect the pH value and is reduced by 4.5% in the phytoremediation technique. Similarly, the level of chlorides is reduced by 99% in solar distillation and by 56% in the phytoremediation technique. Total hardness is reduced by 89.88% in the solar still process and 56.65% in the phytoremediation technique. Sodium is reduced by 99.88% in solar still and 57.03% in the phytoremediation technique. The economical and eco-friendly nature of the suggested techniques makes it sustainable for future generations.

Design, Operation and Simulation of a Passive Osmosis-Integrated Electrolyzer for Seawater Electrolysis

Utilizing abundant seawater for green hydrogen production through electrolysis is a promising pathway to produce a sustainable energy carrier. However, modern seawater electrolyzers have shown insufficient durability due to electrode corrosion and/or competitive production of chlorinated products that result from the presence of Cl−. In this work, a new cell, driven by osmotic separation, was designed and operated that can passively draw fresh water from seawater into compartments with high acid and/or alkaline concentration for electrolysis, thereby eliminating the need for an external energy source for desalination. The work focuses first on demonstrating the passive transport of water through membranes over a wide range of acid and base concentrations. Then, electrodes are integrated, and the cells are operated under multiple configurations and current densities. It is observed that some co-ion diffusion occurs, which is quantified through pH measurements and quantitative Cl− titration. Water transport and ion crossover experiments are supported by comprehensive continuum-level modeling. Finally, strategies for improving future performance are discussed. The findings in this work, a first step in the development of an osmosis-driven electrolyzer cell (ODEC), showcase the promise of this novel electrolyzer design for future direct seawater electrolysis.

The Use of Waste Materials Red Mud and Fly Ash as Road Embankment Fill

This study provides a comprehensive evaluation of red mud as a sustainable material for road base construction, particularly in combination with bottom ash. Red mud, a by-product of the Bayer process used in alumina extraction, is known for its high alkalinity and heavy metal content. For this reason, this waste material causes environmental challenges. Red mud sourced from the Eti Aluminum Factory in Seydişehir, Konya (Turkey), was stabilized with bottom ash. Then, these waste materials were tested through a number of experiments, such as in relation to their Atterberg limits, compaction characteristics, unconfined compressive strength (UCS), California bearing ratio (CBR), and microstructure through a scanning electron microscopy (SEM) analysis. The results highlight that the UCS of stabilized red mud samples significantly improved with the addition of bottom ash and longer curing periods. Specifically, the UCS values increased from 0.5 MPa to 2.5 MPa after 28 days of curing. Moreover, RM specimens stabilized with 25% bottom ash achieved a CBR value of 146.64% after 28 days, far exceeding Turkey’s road fill material requirement, which mandates a minimum unsoaked CBR value of 15%. These findings indicate that red mud stabilized with bottom ash not only meets but exceeds the structural requirements for road base materials. This approach provides a sustainable solution for the environmental management of red mud while contributing to infrastructure development. Through the recycling of these industrial by-products, this study presents a viable method to reduce waste and support economic and environmental sustainability in road construction projects.

Zero-Gap Liquid Alkaline Water Electrolyzers: Challenges in Benchmarking and Directions for Development

Green hydrogen is expected to play a central role in the replacement of fossil energy sources, especially in difficult to decarbonize sectors of the economy. Currently, low temperature methods of electrolysis are the only commercially realized sources of green hydrogen. Liquid alkaline water electrolysis (LAWE) is the most widely utilized method of electrolysis, with a 100-year history of use. Given this lengthy history one could be forgiven for assuming that there is little development left. However, standard LAWE materials and cell designs do not achieve the production, efficiencies, and durability necessary to meet the anticipated demand for green hydrogen.To spur development in this neglected area of hydrogen production, the US Department of Energy, Hydrogen and Fuel Cell Technology Office (DOE-HFTO) added LAWE to its Hydrogen from Next-generation Electrolyzers of Water (H2NEW) Consortium. One of the main tasks for this part of the consortium is to benchmark and validate materials and cell components for LAWE. This includes the development of lab-scale cell hardware and test protocols that can be widely disseminated in the research community. The result of this work will be the development of the methods and materials necessary to achieve robust and reproducible datasets for the improvement of catalysts, separators, cell architecture and operation.We will present the status of the benchmarking effort. This will include a description and explanation of a lab-scale LAWE test station, electrolyte handling, and hydrogen safety. The requirements for the safe operation of an electolyzer using high concentration alkaline electrolytes differs significantly from more typical proton exchange, or anion exchange membrane systems. We will also discuss common sources of error that can significantly influence cell performance and result in poor reproducibility. Acknowledgement:This research is supported by the U.S. Department of Energy (DOE) Hydrogen and Fuel Cell Technologies Office through the Hydrogen from Next-generation Electrolyzers of Water (H2NEW) consortium.

Electricity-driven dealkalization of bauxite residue based on thermodynamics, kinetics, and mineral transformation.

High alkalinity content of bauxite residue is a major factor that hinders resource reutilization and pollutes the environment. Although acid neutralization is a direct and effective method, the amount of acid and secondary waste of sodium salt are still difficult problems to solve. Herein, we innovatively integrated an electric field into the acid neutralization dealkalization of bauxite residue and analyzed the dealkalization behavior by thermodynamics, kinetics, and mineral transformation. The results show that the pH of the anode chamber was maintained at the acidic levels of 3-6 after 30min of galvanostatic electrolysis, and bauxite residue can realize dealkalization by acid neutralization. In the anode chamber, Na+ was released into the leachate via the reactions of Na3Al3Si3O12 and the removal of encapsulated soluble alkali. The stainless steel wire mesh anode exhibited its superiority and decreased the Na2O content in bauxite residue from 9.48 to 3.13% through convective mass transfer driven by the electric field and steady-state diffusion under stirring. This research provides a promising method for the electricity-driven dealkalization of bauxite residue, thus facilitating the development of multifield coupling theory and the application of electric fields in the alumina industry.

Electro-oxidation of 5-hydroxymethylfurfural in a low-concentrated alkaline electrolyte by enhancing hydroxyl adsorption over a single-atom supported catalyst

Electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA), a sustainable strategy to produce bio-based plastic monomer, is always conducted in a high-concentration alkaline solution (1.0 mol L−1 KOH) for high activity. However, such high concentration of alkali poses challenges including HMF degradation and high operation costs associated with product separation. Herein, we report a single-atom-ruthenium supported on Co3O4 (Ru1-Co3O4) as a catalyst that works efficiently in a low-concentration alkaline electrolyte (0.1 mol L−1 KOH), exhibiting a low potential of 1.191 V versus a reversible hydrogen electrode to achieve 10 mA cm−2 in 0.1 mol L−1 KOH, which outperforms previous catalysts. Electrochemical studies demonstrate that single-atom-Ru significantly enhances hydroxyl (OH−) adsorption with insufficient OH− supply, thus improving HMF oxidation. To showcase the potential of Ru1-Co3O4 catalyst, we demonstrate its high efficiency in a flow reactor under industrially relevant conditions. Eventually, techno-economic analysis shows that substitution of the conventional 1.0 mol L−1 KOH with 0.1 mol L−1 KOH electrolyte may significantly reduce the minimum selling price of FDCA by 21.0%. This work demonstrates an efficient catalyst design for electrooxidation of biomass working without using strong alkaline electrolyte that may contribute to more economic biomass electro-valorization.

Highly alkaline electrokinetic extraction: Characteristics of chromium mobilization, conversion and transport in high alkalinity soil

In site chromium (Cr) contaminated soil characterized by high alkalinity and carbonate content, protons are not effectively targeted for Cr(III) mobilization but rather accelerate the reduction of easily transportable Cr(VI) within the acidification electrokinetic (EK) system. As an alternative, the highly alkaline extraction conditions (HAECs) maintained by anolyte regulation are explored owing to the ability to desorb strong binding Cr(VI) and form anionic Cr(III)-hydroxides (Cr(OH)4−, Cr(OH)52−). The results demonstrate that HAECs were more efficient in mobilizing ions in severe alkalinity and electrical conductivity soil compared to organic acid acidifying extraction conditions (OAECs). Simultaneously, a limited amount of soluble Cr(III) was produced; however, its transportation was hindered and more noticeable in the case of Cr(VI), displaying a distinct retention phase within the intermediate soil chamber. The antagonistic interplay between electromigration and electroosmotic flow was considered the main responsible factor. The conversion intensity of Cr(VI) to Cr(III) was inhibited at HAECs. The promising mobilization and low conversion intensity contributed to total Cr removal. At HAECs, enhanced electromigration and electroosmotic flow combined with a favorable oxidation environment may facilitate in situ delivery of oxidants, offering practical implications for the EK detoxification of high alkalinity site soil contaminated with Cr. The practicability of HAECs is likely to be enhanced when the cost-benefit balance of providing a simultaneous energy supply during site treatment is resolved.

Zero Voltage-Degradation of Li2MnO3 with Ultrathin Amorphous Li─Mn─O Coating.

Manganese-based lithium-rich layered oxides (Mn-LLOs) are promising candidate cathode materials for lithium-ion batteries, however, the severe voltage decay during cycling is the most concern for their practical applications. Herein, an Mn-based composite nanostructure constructed Li2MnO3 (LMO@Li2MnO3) is developed via an ultrathin amorphous functional oxide LixMnOy coating at the grain surface. Due to the thin and universal LMO amorphous surface layer etched from the lithiation process by the high-concentration alkaline solution, the structural and interfacial stability of Li2MnO3 are enhanced apparently, showing the significantly improved voltage maintenance, cycle stability, and energy density. In particular, the LMO@Li2MnO3 cathode exhibits zero voltage decay over 200 cycles. Combining with ex situ spectroscopic and microscopic techniques, the Mn2+/4+ coexisted behavior of the amorphous LMO is revealed, which enables the stable electrochemistry of Li2MnO3. This work provides new possible routes for suppressing the voltage decay of Mn-LLOs by modifying with the composite functional unit construction.

Identification of prevalent leachate percolation of municipal solid waste landfill: a case study in India

Landfill leachate forms when waste-inherent water and percolated rainfall transfer are highly toxic, corrosive, acidic, and full of environmental pollutants. The release of leachate from municipal solid waste (MSW) landfill sites poses a severe hazard to human health and aquatic life. This study examined the impact of leachate from Delhi’s Ghazipur landfill on the nearby groundwater quality. Analysis of leachate samples was done to determine various parameters such as total dissolved solids (TDS), hardness, alkalinity, electrical conductivity, pH, BOD5, COD, nitrate, sulphate, chloride and iron, and presence of coliform bacteria. Significant dissolved elements (22,690–34,525 mg/L) were observed in the samples, indicated by the high conductivity value (1156–1405 mho/cm). However, a stable pH range (6.90–7.80) of leachate samples was observed due to high alkalinity concentrations between 2123 and 3256 mg/L. The inverse distance weighing (IDW) interpolation tool from QGIS 3.22.7 developed spatial interpolated models for each parameter across the Ghazipur area. The IDW interpolated graphs of various parameters over the whole study area confirmed these contaminations. In addition, leachate and groundwater samples were physio-chemically analyzed, and temporal fluctuation in landfill waste has also been studied. The temporal fluctuation results showed that when heat is produced, transmitted, and lost throughout the waste system, the maximum temperature position fluctuates over time. The findings of this study highlight the critical importance of landfill management in reducing groundwater contamination from MSW leachate.

Efficient Recovery of Lithium from Spent Lithium Ion Batteries Effluent by Solvent Extraction Using 2-Ethylhexyl Hydrogen {[Bis(2-Ethylhexyl) Amino]methyl} Phosphonate Acid

In order to overcome the interface emulsification problem of TBP-FeCl3 systems and the instability of β-diketone systems in high-concentration alkaline medium, it is necessary to design and synthesize some new extractants. By introducing amino groups into a phosphorus extractant, a new 2-ethylhexyl hydrogen {[bis(2-ethylhexyl)amino]methyl} phosphonate acid (HA) extractant was synthesized. In this study, an efficient method of recovering lithium from the effluent of spent lithium-ion batteries (LIBs) is proposed. Experiments were conducted to assess the influential factors in lithium recovery, including the solution pH, saponification degree, extractant concentration, and phase ratio. Over 95% of lithium in the effluent was extracted into the organic phase, and nearly all lithium in the organic phase could be stripped into the aqueous phase using a 3 mol/L HCl solution. There was no significant decrease in extraction capacity after 10 cycles. The experimental results indicated that the extraction mechanism was a cation exchange process, and the extractive complex was proposed as LiA. Importantly, after three months of stable operation, the process demonstrated excellent stability and extraction efficiency, with rapid phase separation and a clear interface. This study offers an efficient, cost-effective, and environmentally friendly method for lithium extraction from the effluent of spent LIBs.

Sustainable Management of Red Mud: Life Cycle Assessment and Treatment Techniques

Red mud is a strongly alkaline leaching solid hazardous waste material generated in the Bayer process of alumina production. India ranks 4th place in alumina production. According to the Ministry of Mines (Oct 2022), India produces 9 million tonnes of red mud annually. In nature, red mud is highly alkaline. The high alkalinity and caustic content of red mud will contaminate the groundwater and fertile soil, and also there is a limitation on the utilization of red mud. Due to its low utilization ratio, large amounts of red mud are stacked in disposal areas, which may cause water pollution, soil salinization and heavy metal pollution. Red mud contains toxic metals such as arsenic, chromium, lead, nickel, zinc and radioactive elements such as thorium, potassium, and uranium, which cause severe effects on the environment and also on our health. The objective is to examine the environmental impact, utilization methods and treatment process of the red mud (bauxite residue). Also, scrutinize the biodegradation of heavy metals in red mud.

Quaternary Ammonium‐Free Membranes for Water Electrolysis with 1 m KOH

AbstractWhile anion exchange membrane (AEM) water electrolysis has many advantages, its commercialization is impeded by the low alkaline stability of most AEM, due to the fragility of quaternary ammonium groups. Ion solvating membranes (ISM) can be an alternative, but so far require high alkaline concentrations. Here, it is shown that sulfonation of polybenzimidazole results in ISM which swell strongly in 1 m KOH. Crosslinking with dibromoxylene controls the swelling, and after activation conductivities of >100 mS cm−1 can be reached in 1 m KOH. Stability in 1 m KOH at 80 °C is excellent: Conductivity remains unchanged and tensile strength and Young's modulus remains high over the test period of a half year. In an electrolyzer operating with 1 m KOH feed solution at 80 °C, a stable performance is achieved for over 500 h test without failure, suggesting that the high alkaline stability observed in ex situ tests is also achieved in the electrolyzer.

An effective alkaline solid electrolyte with magnetic field-aligned Fe3O4–GO nanofillers in a polybenzimidazole membrane for methanol fuel cells

In this work, alkaline-doped polybenzimidazole/magnetite–graphene oxide (PBI/Fe3O4–GO) nanocomposite membranes are successfully synthesized for enhanced ion conduction and suppressed alcohol permeation for use in direct methanol alkaline fuel cells (DMAFCs). The structural, morphological, and magnetic properties of Fe3O4–GO nanofillers are thoroughly investigated. During the membrane drying step, the Fe3O4–GO nanofillers are aligned in a polymeric PBI matrix using an applied magnetic field (MF). Without an MF, the nanofillers are randomly distributed in the PBI matrix. The composite membrane with the MF demonstrates a 2- to 3-fold increase in hydroxide conductivity (7.6 × 10−2 S cm−1) and a one-order of magnitude reduction in fuel permeability (9.96×10−7 cm2 s−1) compared to the other samples. The potassium hydroxide (KOH)-doped PBI/Fe3O4–GO composite with MF achieves a higher maximum power density (Pmax) of 226 mW cm−2 at 80 °C than the other samples. The composite membrane with an MF demonstrates good long-term durability of 107 h with low voltage decay (6.5 × 10−4 V h−1) at high alkaline concentrations (6 M KOH). The results indicate that a small amount (0.5 wt%) of Fe3O4–GO nanofillers has an extensive effect on membrane properties in DMAFCs.

Flux of NH3 release from dew evaporation in downtown and suburban Changchun, China.

Ammonia, as the only high-concentration alkaline gas in the atmosphere, plays an extremely important role in the initial nucleation process of aerosols. A rise in the concentration of NH3 after sunrise has been observed in many areas, known as the "morning peak phenomenon", which is likely related to the dew evaporation process because of the considerable amount of NH4+ present in dew. To investigate and compare the flux and rate of NH3 release from dew evaporation in downtown (WH) and suburban areas (SL), the dew amount and chemical makeup were measured and analyzed in Changchun, in northeastern China, from April to October 2021. The differences in the fraction of NH4+ released as NH3 gas and the NH3 emission flux and rate during the process of dew evaporation between SL and WH were identified. The results showed that the daily dew amount in WH (0.038 ± 0.017mm) was lower than that in SL (0.065 ± 0.032mm) (P < 0.01), and the pH in SL (6.58 ± 0.18) was approximately 1 pH unit higher than that in WH (5.60 ± 0.25). SO42-, NO3-, Ca2+ and NH4+ were the main ions in WH and SL. The ion concentration in WH was significantly higher than that in SL (P < 0.05), which was influenced by human activities and pollution sources. A total of 24%-48% NH4+ was released as NH3 gas during dew evaporation in WH, which was lower than the conversion fraction of SL dew (44%-57%). The evaporation rate of NH3 was 3.9-20.6ng/m2·s (9.9 ± 5.7ng/m2·s) in WH and 3.3-15.9ng/m2·s (8.6 ± 4.2ng/m2·s) in SL. The dew evaporation process makes an important contribution to the NH3 morning peak phenomenon, but it is not the only contributor.

Resource recycling and carbon sequestration by carbonizing concrete washing wastewater of ready-mix concrete plant

Recycling the concrete washing wastewater (CWW) of ready-mix concrete plants is significantly important for saving hundreds of millions of tons of water and avoiding water and soil pollution. However, to directly recycle CWW to mix fresh concrete is particularly difficult due to its high alkalinity and high solid content with unstable compositions. To respond these challenges, a feasible approach involving carbonation treatment of CWW and subsequent recycling of the carbonized CWW (CCWW) for concrete mixing is proposed in this paper. To this end, the CWW carbonation test was firstly carried out and the compositional analysis showed that the CCWW became a stable suspension with uniform distribution of fine CaCO3 particles, stable ions contents and neural pH value. The effects of CWW, CCWW and the tap water on the fresh cement pastes hydration and the mechanical and deformation properties of hardened cement pastes were then comparatively analyzed. The results supported that CCWW contributed to the improvement of workability of fresh paste, the increase of strength, the decrease of dry shrinkage and the pore refinement of harden paste. Approximate 16.6 million tons of CO2 per year was estimated to be captured by this approach wemix concrete plants. Benefiting from the improved mechanical properties and extraordinary CO2 sequestration capability, recycling CCWW for concrete mixing resulted in nearly half reduction in CO2 emission.

Effect of high replacement ratio of lime mud as a filler on mechanical and hydration properties of high-strength mortar

Lime mud (LM) is a solid industrial byproduct with high alkalinity and calcium carbonate (CaCO3) content produced by the paper industry. LM has been used and investigated as a supplementary cementitious material (SCM). However, using LM with a high replacement ratio causes agglomeration, which reduces the material’s strength and has a detrimental effect on other properties. In addition to agglomeration, LM is unreactive; thus, in this work, a high replacement ratio (70%) of sand with raw LM was investigated in a mortar mixture containing silica fume (SF), considering the fast SF hydration properties of cement in a high alkaline environment, and river sand is used to reduce the agglomeration of LM. The effects of the replacement were then evaluated using compressive strength, X-ray diffraction, thermogravimetric analysis, mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM). The hydration kinetics were investigated using isothermal calorimetry. The experimental results showed that combining SF with a high replacement ratio (70%) of LM improves compressive strength and flexural strength by 16% and 59.7%, respectively. This is due to the filler nature of LM, which refines the pore structure. Furthermore, the highly alkaline environment provided by LM increased the secondary hydration of SF with cement, which also improved the strength.

Valorization of a Steel Industrial Co-Product for the Development of Alkali-Activated Materials: Effect of Curing Environments

Abstract While natural resources are becoming scarce and climate change is accelerating, the recovery and recycling of wastes and by-products is an effective way to deal with the economic and ecological constraints of recent decades. The valorization of industrial by-products in civil engineering is a common practice either by their incorporation during the manufacture of Portland cements or as a partial replacement of cement during the production of concrete. The present work aims to develop waste-based alkali-activated materials WAAMs intended for civil engineering applications as a potential alternative to cement-based materials. A steel industrial by-product called commonly granulated blast furnace slag GBFS was used alone as a solid CaO-rich precursor; two alkaline activators such us sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) were used separately for the production of two-part alkali-activated materials. Besides the microstructure analysis of the hardened samples, the influence of activator/precursor mass ratio, NaOH molarity, and two curing environments (Room temperature and 60°C) on the compressive strength, water accessible porosity, mass loss, and drying shrinkage were assessed. The results showed that a high Liquid/Solid ratio leads to a decrease in the compressive strength of the samples, while high NaOH molarity significantly improves the mechanical properties by reducing the porosity of the specimens. Moreover, alkaline silicate activator provides higher compressive strengths compared to the alkaline hydroxide activator, especially when the samples were cured at room temperature where a maximum 28days-compressive strength value of 105.28 MPa was achieved. For the samples activated using sodium hydroxide solution, the results revealed that their curing at 60°C promotes obtaining high initial-compressive strengths (7 days) before decreasing subsequently as a function of the curing time. As an indication, at high alkaline concentration (NaOH = 9M), a mechanical strength decline of 21% was recorded between a curing time of 7 to 28 days. Moreover, curing at 60°C induced high porosity, significant mass loss and high drying shrinkage. SEM analysis highlighted a dense, homogeneous microstructure without apparent defects, in particular for the samples where the alkali silicate activator was used.

Ni-B-P micro spheres for superior water splitting OER electrocatalyst satisfying industrial operational requirement

To satisfy the global energy demands and deal with the climate crisis, it is necessary to develop an advanced alternative electrocatalyst for hydrogen generation by water electrolysis, which meets the industrial operational requirements. Herein, the nickel-boride-phosphide (Ni-B-P) micro spheres are fabricated by a hydrothermal approach and significantly improved OER/HER catalytic activities are demonstrated through optimizations of various synthesis parameters. The Ni-B-P sphere electrode demonstrates significantly higher OER performance over the RuO2 benchmark electrode due to the improved charge transfer capacity and large ECSA with the micro spherical morphology and excellent stability and corrosion resistance. The Ni-B-P micro spheres demonstrate the OER overpotential of 360 mV at 300 mA/cm2 as compared to 460 mV of RuO2 benchmark. The bifunctional Ni-B-P sphere electrode readily reaches the high current of 2,000 mA/cm2 with 3.62 and 3.42 V in 1 M and 6 M KOH and demonstrates excellent durability for over 5 days (120-hr) of continuous operation at the high alkaline concentration at elevated temperature, meeting the industrial operation requirement. In addition, coupling with Pt/C (Pt/C ‖ Ni-B-P), the hybrid configuration demonstrates super-low cell voltages of 2.89 and 2.72 V at 2,000 mA/cm2 in 1 M and 6 M KOH with the superior stability, indicating the feasibility of commercial OER application.