Metal Hydroxides Research Articles

IMPROVEMENT OF OPERATION AND RESEARCH METHODOLOGY OF THE HYDRAULIC FLAKE FORMATION CHAMBER FOR DRINKING WATER SUPPLY

Ukraine’s surface water sources are unsatisfactory due to pollution caused by industrial and agricultural activities and the Russian invasion. As the natural water quality deteriorates, the treatment plant’s efficiency in preparing drinking water for the population’s needs decreases. The hydraulic flake formation chamber allows for physicochemical processes that produce large and solid flakes of metal hydroxides with impurities that quickly settle and are then removed from the water. This study aims to develop a methodology for experimental research on the new design of a swirl-vortex flake formation chamber that intensifies the water purification process in the domestic and drinking water supply systems. The proposed design of the swirl-vortex chamber has dimensions of 0.75×2.0 m and a height of 0.65 m. Due to the installation in the first section of 4 fittings with nozzles, two pieces on each pipe, and in the second section, six fittings with nozzles, three pieces on each pipe with a diameter of 6–10 mm, it is possible to increase the effect of water illumination. The authors performed hydraulic modelling following the Reynolds criterion (Re) and the Froude criterion (Fr). We conducted experiments using artificial turbidity water. White-blue clay was used as a turbidant because it contains more small particles than the white-green one. We decided to model flake formation chambers according to the Froude criterion (Fr). Modelling according to the Reynolds criterion leads to such large velocity gradients that it simply does not make sense to talk about flake formation processes. We carried out the second series of experiments to obtain a qualitative assessment of the swirl-vortex chamber’s work in forming flakes by studying the deposition of flakes at different velocity gradients and angles of inclination of the nozzles. The best effect of lightening the water in the flake formation chamber occurs at a nozzle inclination angle of 45° to the bottom. The best effect of water clarification happens at a velocity gradient of about 60 s-1 and the water residence time in the flake formation chamber of 200–300 s. Keywords: water treatment, intensification, flake formation chamber, drinking water supply.

Supramolecular chemistry for the incorporation of multi‐guest molecules into two‐dimensional metal hydroxide hosts

AbstractThe incorporation of functional molecules into the interlayer space of layered double hydroxide (LDH) has been extensively studied for its role in immobilization, stabilization, manipulation of the molecular configuration, and the release from the host. To create dramatically enhanced properties and achieve unexpectedly high performances, it is necessary to incorporate multi‐guests as well as control the guest‐guest interaction. In the present review, we have summarized the multi‐guest incorporation into LDH based on the supramolecular chemistry, which provides insights into non‐covalent molecular interaction through host‐guest chemistry. Four well‐known intercalation methods in LDH, that is, coprecipitation, ion exchange, reconstruction, and exfoliation‐reassembly, are generally applied to multi‐guest intercalation. Combinative methods, in which two different intercalation approaches are combined, are also summarized. The multi‐guest incorporation, despite the difficulty involved in its synthesis design, could provide fine‐tuned and enhanced properties that are useful for a variety of applications.

Reuse and Recovery of Water from Industrial Textile Dyeing Effluent Using High-Performance Electrodes Continuous Flow Electrocoagulation Reactor

The dye effluents released from the textile and printing industries contain strong colorants, inorganic salts, and other toxic compounds. The conventional coagulation technique of dye effluent treatment is plagued with issues of low removal rate of color, generation of large quantities of sludge, and toxic end-products. Recently electrocoagulation technique gained immense attention due to its high efficiency. This technique involves the dissolution of the sacrificial anodes to provide an active metal hydroxide as a strong coagulant that destabilizes the pollutants and removes them by precipitation or flocculation. This study is about the efficiency of the electrocoagulation process using titanium coated - aluminum and mild steel electrodes to treat industrial dye wastewater. Effects of parameters such as current density & initial dye concentration were investigated. It was observed that, for the same current density, electrode consumption was higher with TiO2/Al electrode than with mild steel electrode, resulting in more color removal efficiency (CRE) using TiO2/Al electrode. The settling rate of the flocs was higher in the rector having TiO2/Al electrode at the 100 mL with current density (2.5 mL.min-1 to 5.3 mL.min-1), while in the reactor with mild steel electrode, the settling rate was very less. The results showed that dye removal was 95.11% and 92.1% for mild steel and titanium-coated electrodes, respectively. It was observed that 50 % of Aluminum was removed from the treated effluent after the final stage of filtration. Based on the multicriteria analysis to identify the optimum operational parameters to be applied at the field level, it was observed that maximum CRE may be obtained with TiO2/Al electrode and the applied current of 1 Amps with a flow rate of 100 mL.min-1. It can be concluded that electrocoagulation is a highly efficient and the fastest method to treat dye effluents from industries.

Application of tandem heterojunction of metal oxides and hydroxides as robust and repairable moisture-electric generator

Direct conversion of moisture into electricity is emerging as a promising contributor to renewable energy. Having practical utility on sight, we report the development of a robust moisture electric generator (MEG) by creating tandem heterojunctions of oppositely charged layers of metal oxides and hydroxides. The mechanistic insight and great potential utility of metal oxides-hydroxides-based heterojunctions in MEG were first demonstrated by fabricating a bilayer moisture electric generator (BMEG) of exfoliated two-dimensional (2D) sheets of vanadium pentoxide (VO) and β-nickel hydroxide (Ni(OH)2). In contrast to short electric pulses of typical MEGs, BMEG of VO and Ni(OH)2 provides continuous output power 1.06 µW/cm2 (106 µW/cm3 in terms of volume density) for multiple months. The functionality of inorganic materials-based BMEG survived exposure to extreme temperatures (−195 to +200 °C) and prolonged use. The output voltage of overused (80 days) BMEG could be revived by renewing the connections. The single device output potential of BMEG was drastically improved from ∼600 mV to ∼1.02 V upon the incorporation of additional heterojunctions of Al doped ZnO and NiCo2O4. Among continuous power-delivering MEGs, the tandem MEG (TMEG) displayed one of the best power density. Multiple oxide-hydroxide-based BMEGs were connected to obtain output voltage and current up to 40 V and 45 µA, respectively. The output voltage of BMEG can be further improved by 23 % and 34 % by exposing it to white light and waste heat-driven temperature gradient. The sensitivity of BMEG towards atmospheric water molecules is further utilised as self-powered moisture sensors.

Statistical physics of azo reactive dye adsorption by metal hydroxide sludge for water remediation

We performed a theoretical investigation of azo reactive red (RR-120) on metal hydroxide sludge (MHS) using five advanced statistical physics models to interpret thermodynamic equilibrium data for potential water remediation applications. Each model incorporates multiple physicochemical parameters to comprehensively describe the microscopic process through empirical data fitting. The thermodynamic functions (entropy, internal energy and Gibbs free energy) were analyzed using the grand canonical formalism. Our analysis indicated that the single-energy monolayer model represents the most realistic scenario. The adhesion of RR-120 onto MHS was endothermic with an adsorption energy below 40.0 kJ/mol suggesting that Van der Waals interactions and hydrogen bonding are the predominant driving forces. The stereographic analysis demonstrated that as the density of receptor sites (Nm) incremented, there was a corresponding decline in the number of anchored entities per site (n). Moreover, thermodynamic assessment revealed that the disorder increased before half-saturation and decreased after half-saturation while negativity of Gibbs free energy indicated a spontaneous process of RR-120 adsorption in all tested temperatures. The exceptional adsorption capabilities of MHS will open up new avenues in wastewater treatment, soil remediation and air purification.

Wood-derived continuously oriented channels coupled with tunable built-in electric fields for efficient oxygen evolution

Interface engineering has emerged as a promising strategy for efficiently enhancing catalytic performance. Herein, we present a built-in electric field (BEF) strategy to assemble Co9S8/Ni3S2 heterojunctions confined in S-doped carbon matrix (SC) and anchored S-doped carbide wood framework (SCW). Leveraging BEF, Co-S-Ni charge transfer channels and the superior mass transfer properties inherent in wood’s unique structure, (Co9S8/Ni3S2)@SC/SCW exhibits a low overpotential of 220 mV at 50 mA cm−2, and remarkable stability. The experimental characterizations and theoretical simulation indicate that the constructed BEF can induce the directional transfer of electrons from Co9S8 to Ni3S2, which is beneficial for the adsorption of OH- owing to the electrostatic interaction, thereby promotes the formation of the highly active amorphous metal hydroxide oxides at lower OER potentials. This work provides a new perspective for exploring the design of energy storage and conversion catalysts based on renewable wood substrates.

Electrocoagulation process for phosphate recovery of agricultural wastewater: effect of calcium adding, voltage, and time.

Recovery of valuable resources, such as phosphate recovery from wastewater, can help close the nutrient cycle and is interesting to investigate. This study aims to evaluate phosphate recovery and set aside TOC, OC, and IC in agricultural wastewater using electrocoagulation with a helix electrode configuration. This study employed the Response Surface Methodology (RSM) for statistical analysis and modeling, utilizing a central composite design (CCD). Variation of calcium concentration (2-7mg/L), voltage (15-45V), and electrocoagulation time (5-15min) was applied in an electrocoagulation reactor with a helix-shaped stainless steel cathode and a solid cylindrical Mg anode. Based on RSM analysis, electrocoagulation with a helical electrode configuration significantly affects phosphate recovery and the removal of TOC, OC, and IC when treating agricultural wastewater. Under operating conditions of 15V, 15min time, and 2mg/L calcium concentration, we achieved the lowest phosphate concentration of 0.003mg/L (99.74% reduction). The highest TOC allowance is > 100% of the initial concentration, the TC allowance is 55.79%, and the IC allowance is 30.91%. The formation of metal hydroxides affects the efficiency of TOC removal in the electrocoagulation process, and higher electrolysis times lead to higher TOC removal efficiency. Higher voltages also improve the coagulation and flotation processes in the reactor. Calcium concentration plays a role in enhancing the flocculation process and binding phosphonates from wastewater.

Quantitative study on the selective depressing effect of polysaccharides on some polar minerals

This study presents a systematic summary on the depressing effect of polysaccharides on some polar minerals, revealing that the order of their depressing strength on some polar minerals was primarily associated with the surface properties of the minerals, showing a limited correlation with the structure of polysaccharides. Subsequently, the selective depressing mechanism of polysaccharides on polar minerals was quantitatively explained from the perspective of acid–base interaction mechanism, and a criterion system for determining the depressing effect of polysaccharide on minerals was proposed. Specifically, it was found that the hydroxylation reaction of metal sites on mineral surface was a prerequisite for polysaccharide adsorption. Under the above–mentioned conditions, the selective depressing effect of polysaccharides on these minerals with different metal sites could be assessed through a parameter system in which the ion potential φ of surface metal sites served as the primary determinant, and the solubility product constant of metal hydroxides played a secondary role. In cases where minerals shared identical surface metal sites, the selective depressing effect of polysaccharides was analyzed by comparing the coordination numbers of these sites. Specifically, minerals with a higher number of coordinated surface metal sites tend to show a weaker response to depressing effect of polysaccharide. Consequently, this study theoretically elucidated the selective depressing effect of polysaccharides on polar minerals, and the criterion system proposed in this study outperforms the prediction results based on the isoelectric point (pHiep). These research findings have important guiding significance for a deeper understanding of the selective depressing mechanism of polysaccharides and the regulation of flotation.

Impact of Organic Anions on Metal Hydroxide Oxygen Evolution Catalysts.

Structural metamorphosis of metal-organic frameworks (MOFs) eliciting highly active metal-hydroxide catalysts has come to the fore lately, with much promise. However, the role of organic ligands leaching into electrolytes during alkaline hydrolysis remains unclear. Here, we elucidate the influence of organic carboxylate anions on a family of Ni or NiFe-based hydroxide type catalysts during the oxygen evolution reaction. After excluding interfering variables, i.e., electrolyte purity, Ohmic loss, and electrolyte pH, the experimental results indicate that adding organic anions to the electrolyte profoundly impacts the redox potential of the Ni species versus with only a negligible effect on the oxygen evolution activities. In-depth studies demonstrate plausible reasons behind those observations and allude to far-reaching implications in controlling electrocatalysis in MOFs, mainly where compositional modularity entails fine-tuning organic anions.

Construction of iron-doped nickel cobalt phosphide nanoparticles via solvothermal phosphidization and their application in alkaline oxygen evolution

Multi-metallic phosphides offer the possibility to combine the strategies of surface reconstruction, electronic interaction and mechanistic pathway tuning to achieve high electrocatalytic oxygen evolution activity. Here, iron-doped nickel cobalt phosphide nanoparticles (FexCoyNi2-x-yP) with the crystalline NiCoP phase are for the first time synthesized by the solvothermal phosphidization method via the reaction between metal–organic frameworks and white phosphorus. When used to electrochemically catalyze oxygen evolution reaction (OER), the Fe0.4Co0.8Ni0.8P supported by nickel foam requires only 248 mV overpotential to achieve 10 mA cm−2 current densities, and is robust towards the long-term OER in 1 M KOH. The higher number of electrochemically active sites can account for the good OER activity, along with the improved intrinsic activity which is caused by the electron interaction that optimizes the adsorption energy of hydroxyl intermediates, and that increases the acidity of high-valent metal centers. The OER mechanistic pathway involves both adsorbate and lattice oxygen. Surface conversion is observed after OER in alkaline solution, and metal phosphide layer transforms to metal oxides and (oxy)hydroxides.

Optimisation of Mo doping to form NiCoMo ternary sulphides for high performance charge storage.

Multi-component synergy and the rational design of structures are effective methods for preparing electrode materials for high-performance energy storage devices. Transition metal-based hydroxides offer advantages such as a large specific surface area, large interlayer spacing, multiple redox states, and high theoretical capacity, making them commonly used as positive materials for supercapacitors. However, challenges like low conductivity and severe agglomeration limit their practical application. This study focuses on the preparation of Ni, Co, and Mo ternary transition metal hydroxides by incorporating the Mo element to optimize their structure. Furthermore, sulfide ions were utilized in an ion exchange process to replace hydroxides, resulting in the formation of NiCoMo ternary sulfide electrode materials. By adjusting the amount of Mo added, a spherical nanoneedle-shaped N2C1MS0.2-2 electrode material was successfully synthesized. This electrode exhibited a specific capacity of 2094 F g-1 at a current density of 1 A g-1. In addition, an asymmetric supercapacitor was assembled with activated carbon as the negative electrode and N2C1MS0.2-2 as the positive electrode, which had an energy density of 46.2 W h kg-1 at a power density of 800 W kg-1, a capacity retention of 89.7% and a coulombic efficiency of 97.8% after 10 000 cycles. This study provides a reference for the design and preparation of ternary sulphide electrode materials.

Fabrication of hierarchical 3D layered yttrium hydroxide nanocomposites: Their use for enzyme immobilization and catalysis of H2O2

3D layer metal hydroxides (LMHs) have attracted significant interest due to their distinctive structural features. Unfortunately, the limited electrical conductivity hinders the potential utilization of LMHs in electrochemical analysis. To address this issue, herein, gold nanoparticles (AuNPs) were introduced to layered yttrium hydroxides by a facile in-situ electrodeposition method. Subsequently, the hierarchical AuNPs/LYH nanocomposite was employed as solid supports for immobilization of horseradish peroxidase, generating an enzymatic biosensor for hydrogen peroxide detection. As a result, a linear range of 1–500 μM with a remarkably low detection limit of 0.33 μM (S/N=3) was achieved. Moreover, the biosensor also demonstrated excellent selectivity, reproducibility and stability. The superior electrochemical responses of the HRP/AuNPs/LYH nanocomposite towards H2O2 can be ascribed to the synergistic effect arising from the flower-like structures of LYHs and the high conductivity of AuNPs. Our study provides a significant approach for the development of enzyme immobilized supports through the construction of layer metal hydroxide nanocomposites.

Recent Development of Transition Metal‐based Amorphous Electrocatalysts for Water Splitting

AbstractElectrochemical water splitting, including the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), is a promising hydrogen production technology. However, in practice, the high overpotentials and sluggish reaction kinetics associated with the anode OER process are the major obstacles to the smooth progress of electrocatalytic water splitting. Amorphous electrocatalysts, a crucial family of functional materials, exhibit unexpected performance due to their special short‐range ordered and long‐range disordered atom arrangement, abundant defect sites and adjustable composition. To date, while numerous recent publications showcase promising results for transition metal‐based amorphous electrocatalysts, including amorphous metal phosphide and metal hydroxide electrocatalysts with remarkable HER and OER properties respectively, the utilization of single‐function HER or OER catalysts tends to augment system complexity for water electrolysis, thereby escalating the cost of hydrogen production. In this regard, amorphous HER/OER bifunctional electrocatalysts are desired. In this review, we summarize the recent development on transition metal‐based amorphous catalysts for electrochemical water splitting. The design strategies for constructing HER/OER bifunctional transition‐metal‐based amorphous electrocatalysts are highlighted here, also including the exploration of relationship between catalyst structures and their remarkably improved performance. Finally, the possibilities of amorphous bifunctional catalysts for practical industrial applications are evaluated and future research direction are suggested.

Recycling Spent Ternary Cathodes to Oxygen Evolution Catalysts for Pure Water Anion-Exchange Membrane Electrolysis.

Recycling spent lithium-ion batteries (LIBs) to efficient water-splitting electrocatalysts is a promising and sustainable technology route for green hydrogen production by renewables. In this work, a fluorinated ternary metal oxide (F-TMO) derived from spent LIBs was successfully converted to a robust water oxidation catalyst for pure water electrolysis by utilizing an anion-exchange membrane. The optimized catalyst delivered a high current density of 3.0 A cm-2 at only 2.56 V and a durability of >300 h at 0.5 A cm-2, surpassing the noble-metal IrO2 catalyst. Such excellent performance benefits from an artificially endowed interface layer on the F-TMO, which renders the exposure of active metal (oxy)hydroxide sites with a stabilized configuration during pure water operation. Compared to other metal oxides (i.e., NiO, Co3O4, MnO2), F-TMO possesses a higher stability number of 2.4 × 106, indicating its strong potential for industrial applications. This work provides a feasible way of recycling waste LIBs to valuable electrocatalysts.

Preparation of CMC-MF/FeO(OH) by growing ferric nanoparticles on melamine foam in-situ for effective phosphate removal

Nanocomposite adsorbents composed of a bulk matrix and metal nanoparticles have garnered significant attention for phosphorus (P) removal. However, many nanocomposite adsorbents have been synthesized in harsh environments involving high temperature or high energy consumption, which do not meet industrial requirements; on the other hand, lots of adsorbents are synthesized by directly depositing metal hydroxides on bulk matrixs, leading to the active components shedding from the matrix due to the lack of chemical anchoring sites to immobilize metal oxide. To overcome the limitations of the existing methods, we synthesized a nanocomposite adsorbent named CMC-MF/FeO(OH) using a facile method in a mild environment. It involved coating an anchoring film prepared with carboxymethyl cellulose sodium (CMCNa) on melamine foam (MF) for in-situ growth of ferric nanoparticles. Our results demonstrated that the CMC-MF/FeO(OH) adsorbent showed promising efficiency in phosphate removal. The adsorption process was effectively described by Elovich kinetic model and Freundlich isotherm model. The adsorption mechanism was ascribed to the chemisorption by inner-sphere complex along with physical adsorption. A maximum adsorption capacity of 31.579 mg P/g which calculated by Langmuir isotherm model was achieved at 45 °C and natural pH condition in experimental range. The adsorbent exhibited effective P adsorption even in harsh environments, with the process being spontaneous and exothermic. In column applications, the CMC-MF/FeO(OH) adsorbent reduce the P content of wastewater from 4 mg P/L to 0.5 mg P/L within a short empty bed contact time of 190.95 s. Furthermore, the adsorption capacity reached 8.87 mg P/g in a column study, and trace P levels in lake water decreased to undetectable levels in a lake experiment, effectively inhibiting algae growth.

Exploring the Phase Transformation of Tri-Metallic Prussian Blue Analogue Pre-Catalyst for Improved Oxygen Evolution Reaction

The development of non-noble metal electrocatalyst with high-efficiency and clear underlying of the related reaction mechanism towards the sluggish oxygen evolution reaction (OER) is critical for large-scale hydrogen production. In this study, tri-metallic Prussian blue analogue (PBA) of FeCoNi-PBA was synthesized using a facile and low-energy consumption co-precipitation method. The FeCoNi-PBA was found to be etched by the high-pH 1 M KOH electrolyte such that under anodic applied potential during electrolysis the formation of metal (oxy)hydroxide is accelerated. Operando Raman and post-mortem characterizations reveal that the applied anodic potential promotes the phase transformation so that the PBA undergoes self-reconstruction to form metal (oxy)hydroxide embedded in a carbon matrix with fully exposed active sites. The metal (oxy)hydroxide serves as the real active sites while the carbon matrix is believed to enhance the conductivity and hydrophilicity, which facilitates the electron transfer and electrolyte diffusion to improve the OER performance. In alkaline media, FeCoNi-PBA demonstrates excellent OER performance with a low overpotential of 236 mV at 10 mA cm−2, small Tafel slope of 43.8 mV dec-1, and long-term durability.

(Invited) Achieving Circularity in the Battery Industry through Salt Splitting Electrolysis

In an era focused on sustainability, Aepnus Technology introduces a transformative approach in electrochemical engineering that enables circularity in the manufacturing of battery chemicals. Aepnus’ innovation centers on advanced gas diffusion electrodes (GDEs), engineered to significantly boost efficiency and lower the costs of electrolytic salt splitting processes. GDEs offer a cost-effective alternative to traditional planar electrodes, and open new reaction pathways for versatile product generation. For example, GDE’s can improve on the incumbent technologies capable of converting sodium sulfate waste into useful chemicals such as sodium hydroxide and sulfuric acid. Aepnus’ GDEs are poised to revolutionize the recycling of sodium sulfate, the largest waste product of the lithium battery supply chain.The application of these GDE’s can extend into the synthesis of various metal hydroxides and other essential commodity chemicals. Aligning with the principles of circular economy and eco-manufacturing, our project addresses challenges in electrolyzer design, catalyst advancement, and reactor optimization. We underscore the translation from academic research to scalable solutions, integrating our technology seamlessly into existing industrial processes.This presentation will delve into the environmental and operational advantages of Aepnus GDEs, their role in reducing the ecological footprint of chemical manufacturing for the battery industry, and our journey to manufacture chemicals in ways that are circular and carbon neutral. Additionally, we will provide insights into the setbacks of existing electrochemical technologies such as membrane electrolysis and bi-polar electrodialysis (BPED), while demonstrating the real-world applicability of our technology through performance data at lab and pilot-scales.

Development of Bifunctional Electrocatalyst for Overall Water Electrolysis: Vanadium and Phosphorus Dual-Doping Strategy on Ni3S2 Nanoneedle

Along with the rapid consumption of fossil fuels and serious environmental pollution, the development of renewable and clean energy has been receiving a lot of attention recently. Among the various renewable energy sources, hydrogen (H2) is considered as most promising substance in future energy society owing to its high gravimetric energy density and environmental friendliness. Electrochemical water electrolysis system is powerful strategy for high-purity hydrogen production without emission of any pollutants. It consists of two electrocatalytic reactions: oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). However, the practical efficiency of water electrolysis is limited due to the intrinsically sluggish reaction kinetics of OER and HER. To date, the precious metal-based electrocatalysts such as RuO2 and Pt/C for OER and HER, respectively, were employed as state-of-the-art electrocatalyst to enhance the performance of water electrolysis. However, due to the high expense, mono-functionality, and unsatisfactory stability of the precious metal-based materials, research on bifunctional electrocatalysts with low cost and high activity has become an urgent topic. To date, numerous scientific endeavors have been dedicated to the advancement of highly efficient non-noble metal-based bifunctional electrocatalysts such as transition metal oxides, hydroxides, sulfides, carbides, nitrides, and phosphides. Among these, Ni3S2 has emerged as a particularly promising electrocatalyst for water splitting, garnering substantial attention owing to its high electric conductivity, rich redox property, abundance in the Earth's crust, and environmentally friendly characteristics. Nevertheless, the electrocatalytic activity of Ni3S2 lags behind that of noble metal counterparts. Therefore, elaborate modification of Ni3S2 catalyst should be conducted to further improve its intrinsic activity toward OER and HER. Among the various strategies, heteroatom doping into Ni3S2 structure could be adopted as powerful technique for enhancement of electrocatalytic performance. The homogeneously incorporated dopants not only generate lattice disorders but elaborately modulate the surface electronic property. Specifically, high-valent cation dopants such as vanadium and molybdenum can effectively mediate the change of chemical states of Ni active sites during the step-wise electrocatalytic procedure. Meanwhile, additionally introduced anion dopants, which have lower electronegativity compared with sulfur, can reduce the electron trapping phenomenon induced by excessive electron transfer from nickel to sulfur. Inspired by above features, we synthesized V and P co-doped Ni3S2 nanoneedles directly grown on nickel foam (V-Ni3S2-P/NF) through facile two-step preparation method. First, V doped Ni3S2 nanoneedles were homogeneously grown on NF (V-Ni3S2/NF) by hydrothermal process without use of nickel precursor. The vanadium ions promote the nucleation of Ni3S2 species and lead the preferential growth toward 1D direction during the hydrothermal reaction. After that, the V-Ni3S2/NF was annealed in the tube furnace with the NaH2PO2 as a phosphorus precursor under the Ar flow. Under the mild annealing condition, the PH3 gases generated from thermal decomposition of NaH2PO2 reacted with the V-Ni3S2 species. Consequently, the V-Ni3S2 was partially phosphidated into V-Ni3S2-P throughout anion exchange process. As a result, the V-Ni3S2-P/NF electrocatalyst exhibited excellent bifunctional activity toward both OER and HER compared with mono-doped and un-doped counterparts and precious metal-based electrocatalysts. Furthermore, the outstanding electrocatalytic performance of V-Ni3S2-P/NF was well-maintained over the 100 h of continuous operation under alkaline condition. This study will contribute to the development of efficient and cost-effective electrocatalysts for future energy conversion and storage technologies.

Understanding the Reaction Activity of Ni(1-x)FexOH Towards Oxygen Evolution Reaction

The development of electrocatalysts towards the oxygen evolution reaction based on earth-abundant and cheap materials, such as transition metal oxide and hydroxide, is crucial to reduce the emission of CO2 and slowdown the global warming [1]. Among these transition metal compounds, ferromagnetic electrocatalysts usually exhibit promising activities towards OER due to their unique electron spin properties [2]. Applying an external magnetic field can further tune the electron spin polarization of ferromagnetic materials and, therefore, improve the OER activity. However, evaluating the activity of these electrocatalysts towards OER remains challenging. For example, the electrocatalysts will undergo activation under reaction conditions (frequently due to Fe insertion), which brings difficulties in determining the real reaction sites as well as establishing the “structure-activity” relationship [3]. In addition, the overall measure activity (current density) is contributed by multiple factors such as intrinsic kinetics, mass transfer, conductivity, etc., which strongly depend on operation conditions. In this talk, I will present our recent study of OER on Ni(1-x)FexOH [4]. Electrochemical impedance spectroscopy (EIS) and quasi-in situ XPS will be applied to obtain the contribution from different reaction parameters and understand the intrinsic activity.[1] McCrory, C. C. L. et al. Benchmarking Hydrogen Evolving Reaction and Oxygen Evolving Reaction Electrocatalysts for Solar Water Splitting Devices. Am. Chem. Soc. 137, 4347–4357 (2015).[2] Ren, X. et al. Spin-polarized oxygen evolution reaction under magnetic field. Commun. 12, 1–12 (2021).[3] Jung, S., McCrory, C. C. L., Ferrer, I. M., Peters, J. C. & Jaramillo, T. F. Benchmarking nanoparticulate metal oxide electrocatalysts for the alkaline water oxidation reaction. Mater. Chem. A 4, 3068–3076 (2016)[4] Wei Chen, Laura Donk, Tiago Fernandes, Anna Kitayev, ErvinTal Gutelmacher, Yury V. Kolen’ko, Marta C. Figueiredo*, in preparation.

Compact Energy Storage Devices Developed from Waste-Derived Electrodes via Facile Recycling Technology

Indeed, the development of sustainable and renewable energy technologies is a critical aspect of addressing the challenges posed by pollution and climate change. Electrochemical energy storage devices, such as batteries and supercapacitors, play a crucial role in this transition by enabling the efficient storage and utilization of energy. The mention of nanomaterials-based electrodes highlights a fascinating area of research and innovation. Nanomaterials offer unique properties and advantages due to their small size, high surface area, short-diffusion path, rapid kinetics, enhanced conductivity, making them highly desirable for energy storage applications.Recycling waste to electrodes in compact energy storage device represents a particularly exciting frontier. Integrating energy storage into advance technology can enhance the portability and convenience of power sources, especially in the context of emerging technologies like wearable electronics and smart devices. However, challenges such as scalability, cost-effectiveness, and environmental impact must also be addressed to ensure the widespread adoption of these technologies. The emphasis on carbon-based nanomaterials, including graphene, carbon quantum dots, and activated carbon, as electrode materials is noteworthy. These materials show promise not only as negative electrodes but also as positive electrodes when combined with metal oxides, hydroxides, or sulphides, demonstrating their versatility in energy storage applications. Additionally, the innovative use of waste recycling, such as tires, shoots, and dry cells, for extracting carbon aligns with the broader goal of creating an eco-friendly environment. The focus on developing carbon-based electrodes from recycled waste for energy storage devices is commendable, as it not only addresses environmental concerns but also contributes to the creation of stable and efficient energy storage systems. In conclusion, this work on the generation of efficient carbon-based electrodes (graphene derived from different waste materials) for energy storage devices, showcases a multidisciplinary approach that considers both environmental sustainability and technological advancement. This research has the potential to contribute significantly to the ongoing efforts to create a more sustainable and efficient energy landscape.Key words: Recycling, Electrochemical, Carbon, Metal oxides, Energy storage, Compact devices