Alkaline Solution Research Articles

Unraveling the Electrocatalytic Activity in HMF Oxidation to FDCA by Fine-Tuning the Degree of NiOOH Phase Over Ni Nanoparticles Supported on Graphene Oxide.

The development of an efficient electrocatalyst for HMF oxidation to FDCA has been in the early stages. Herein, the NiNPs/GO-Ni-foam is fabricated as an electrocatalyst for FDCA production. However, the electrocatalytic performance of the untreated NiNPs/GO-Ni-foam is observed with moderate Faradaic efficiency (FE) (73.0%) and FDCA yield (80.2%). By electrochemically treating the NiNPs/GO-Ni-foam in an alkaline solution with positive potential at different treatment durations, the degree of NiOOH on metal surfaces is changed. The distinctive electrocatalytic activity obtained when using the different NiOOH degrees allows to understand the crucial impact of NiOOH species in HMF electrooxidation. Enhancing the portion of the NiOOH phase on the electrocatalyst surface improves electrocatalytic activity in terms of FE and FDCA yield up to 94.8±4.8% and 86.9±4.1%, respectively. Interestingly, as long as the NiOOH portion on the electrocatalyst surface is preserved or regenerated, the electrocatalyst performance can be intact even after several catalytic cycles. The theoretical study via density functional theory (DFT) also agrees with the experimental observations and confirms that the NiOOH phase facilitates the electrochemical transformation of HMF to FDCA through the HMFCA pathway, and the potential limiting step of the overall reaction is the oxidation of FFCA to FDCA.

The impact of supplementary cementitious materials on the rheological and mechanical properties of mortars based on quarry waste sand

Mineral substances used as additives in cement plants or as additives in the making of concrete contribute through their physical, hydraulic, and pozzolanic activity to improving the behavior of cements in both the fresh and hardened states. Several types of additions are well known, such as natural pozzolans, fly ash, blast furnace slag, and silica fume. These products become more active in the alkaline solutions of cement and give rise to new hydrates that impart greater mechanical strength and better durability to concretes. Through their surface activity and granular distribution, they play a fundamental role in the rheological and mechanical behavior of mortars and concretes. Quarry waste sand (QWS) is generally stockpiled to be eventually sold at very low prices. For this reason, its use in the production of concrete and mortar is increasingly becoming a necessity to protect the environment and meet the needs of the construction and public works sector.This study aims to investigate the effect of using both supplementary cementitious materials (SCM) and quarry waste sand(QWS) to improve some properties of mortar. Ordinary cement is replaced by 10%, 20% and 30% of silica fume (SF), natural pozzolan (NP) or ground blast-furnace slag (GBFS) by weight and the properties of the QWS sand -based mortar are compared to those of natural sand (NS) based mortar. In this study, the slump, superplasticizer requirement, rheological parameters, mechanical strength, and water absorption are investigated. The results obtained show that QWS sand mix has the best workability and requires less superplasticizer dosage. When SCM were used, a drop-in workability is shown and more superplasticizer is required. Also, QWS sand makes the mortar strength 2 and 1.5 times higher than that of NS and becomes 42% higher with 10% SF. Adequate relationships have been established to predict mechanical strengths as a function of test parameters with high correlation coefficient and low root mean square error.

The synergistic effect of periodate/ferrate (VI) system on disinfection of antibiotic resistant bacteria and removal of antibiotic resistant genes: The dominance of Fe (IV)/Fe (V)

The proliferation of antibiotic resistant genes (ARGs) and antibiotic resistant bacteria (ARB) caused by antibiotic abuse has raised concerns about the global infectious-disease crisis. This study employed periodate (PI)/ferrate (VI) (Fe (VI)) system to disinfect Gram-negative ARB (Escherichia coli DH5α) and Gram-positive bacteria (Bacillus subtilis ATCC6633). The PI/Fe (VI) system could inactivate 1 × 108 CFU/mL of Gram-negative ARB and Gram-positive bacteria by 4.0 and 2.8 log in 30 min. Neutral and acidic pH, increase of PI dosage and Fe (VI) dosage had positive impacts on the inactivation efficiency of ARB, while alkaline solution and the coexistence of 10 mM Cl-, NO3-, SO42- and 20 mg/L humic acid had slightly negative impacts. The reactive species generated by PI/Fe (VI) system could disrupt the integrity of cell membrane and wall, leading to oxidative stress and lipid peroxidation. Intracellular hereditary substance, including DNA and ARGs (tetA), would leak into the external environment through damaged cells and be degraded. The electron spin resonance analysis and quenching experiments indicated that Fe (IV)/Fe (V) played a leading role in disinfection. Meanwhile, PI/Fe (VI) system also had an efficient removal effect on sulfadiazine, which was expected to inhibit the ARGs transmission from the source.

NiS-modified zeolite imidazolic acid frame-67 as a bi-functional catalyst: A non-enzymatic lactic acid sensor and supercapacitor

The ZIF-67/NiS composite electrode was prepared on nickel foam (NF) matrix by hydrothermal method. NiS has been widely studied in sensors and supercapacitors due to its good electron transfer ability and good pseudocapacitor performance. Therefore, we prepared ZIF-67/NiS composite electrode. The synthesised ZIF-67/NiS composite electrode not only has certain electrochemical performance of battery type electrode, but also is sensitive to lactic acid (LA), and can be used as a non-enzymatic LA sensor and a dual-function material for supercapacitors. The detection limit of LA concentration in alkaline solution is 0.8 μM, and the sensitivity is 1.34 μA μM−1 cm−2. Indicating that the electrode has good electrochemical sensing performance. The GCD test results show that the charging capacity of the ZIF-67/NiS is 2.5 times that of the ZIF-67. The ZIF-67/NiS composite has good cyclic performance, and the capacitance retention rate of the ZIF-67/NiS composite is 87% at 10 A/g current density.

Embeddable Chloride Sensor for Monitoring Chloride Penetration into Cement Mortar.

A composite solid chloride sensor consisting of two single sensors, i.e., Ag/AgCl working electrode and Mn/MnO2 reference electrode, was developed. The Ag/AgCl electrode was prepared by the anodic polarization method, while the Mn/MnO2 reference electrode was prepared using the powder compaction technique. Then, the electrochemical performances such as stability, reproducibility, and sensitivity of the composite and single sensors were investigated in a saturated Ca(OH)2 solution and mortar specimen. A current density of 0.5 mA/cm2 and polarization time of 2.5 h were the optimal preparation parameters of the Ag/AgCl selective electrode. The Ag/AgCl selective electrode showed a linear potential response with the logarithm of chloride ion content in solution and had good stability, reproducibility, and anti-polarization performances. In addition, the Mn/MnO2 electrode exhibited potential stability after being activated in an alkaline solution for 60 days. The composite sensor demonstrated exceptional sensitivity to the Cl- content, boasting a slope of approximately 51.1 mV/decade, and showcased excellent stability in both solution and mortar specimens. In every measurement, the time needed for the potential of a composite sensor to become stable was less than 30 s. The sensor enables non-destructive in situ monitoring of the chloride ion content in cement mortar, thus realizing early warning of deterioration of reinforcement and guaranteeing long service life of the structure.

Photocatalytic Hydrogen Production with A Molecular Cobalt Complex in Alkaline Aqueous Solutions.

The thermodynamic favorability of an alkaline solution for the oxidation of water suggests the need for developing hydrogen evolution reaction (HER) catalysts that can function in basic aqueous solutions so that both of the half reactions in overall water splitting can occur in mutually compatible solutions. Although photocatalytic HERs have been reported mostly in acidic solutions and a few at basic pHs in mixed organic aqueous solutions, visible-light driven HER catalyzed by molecular metal complexes in purely alkaline aqueous solutions remains largely unexplored. Here, we report a new cobalt complex with a tetrapyridylamine ligand that catalyzes photolytic HER with turnover number up to 218 000 in purely aqueous solutions at pH 9.0. Density functional theory (DFT) calculations suggested a modified electron transfer (E)-proton transfer (C)-electron transfer (E)-proton transfer (C) (mod-ECEC) pathway for hydrogen production from the protonation of CoII-H species. The remarkable catalytic activity resulting from subtle structural changes of the ligand scaffold highlights the importance of studying structure-function relationships in molecular catalyst design. Our present work significantly advances the development of a molecular metal catalyst for visible-light driven HER in more challenging alkaline aqueous solutions that holds substantial promise in solar-driven water-splitting systems.

Carbon-captured sodium hydroxide solution for sustainable alkali-activated slag

The escalating impact of climate change, primarily driven by greenhouse gas emissions, has prompted global efforts to achieve carbon neutrality. Ordinary Portland cement production contributes approximately 7% to global carbon dioxide (CO2) emissions, necessitating innovative approaches for its sustainable production. A novel method is introduced that utilizes a sodium hydroxide (NaOH) solution captured with CO2 as an alkali activator for ground granulated blast furnace slag (GGBFS); it can substitute for the cement in producing construction materials. The method integrates CO2-dissolved alkaline solutions into the activation process of GGBFS, which results in the production of sustainable alkali-activated slag materials. Various concentrations of dissolved CO2 in the NaOH-based activator were used to evaluate their impact on compressive strength, setting time, and changes in phase composition. The results demonstrate that higher CO2 concentrations lead to increased compressive strength, but an excess hinders early-age strength development. X-ray diffraction and thermogravimetry analyses explain the phase changes during carbonation, emphasizing the role of CO2 in forming calcite and enhancing C-S-H production. Additionally, the study quantifies CO2 uptake, revealing a linear relationship with dissolved CO2 concentrations.

Fast microwave synthesis of high-silica natural soil based porous geopolymer

This study describes a simple microwave process for fabricating porous geopolymer-polymer based Shirasu soil. The porous geopolymer samples were synthesized using sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) solution as alkaline solution in range of 0.5 M to 9 M. After mixing process, the geopolymer slurry was heated and stimulated geopolymerization reaction by different microwave powers at 200 W, 500 W and 700 W for 30 s, 60 s, 90 s and 120 s. The influence of NaOH concentration, microwave powers and heating times on the apparent bulk density, the water adsorption was focused. Results showed that the microwave powers and heating time affected the apparent bulk density, the water adsorption, and the densification of geopolymer matrix. Higher microwave power can promote higher water adsorption related to lower apparent bulk density. Moreover, the results revealed that the porosity and the nitrogen adsorption of geopolymers at 120 s of heating time increased with an increment of the NaOH from 1 M to 4 M. On the other hand, geopolymers activated by 200 W at 30 s could not be hardened. This work provides the feasibility of porous geopolymer synthesis based natural soil.

Recovery of alkali in Gracilaria agar production by electrodialysis and membrane concentration

Industrial Gracilaria agar extraction consumes a large amount of alkali. The previous strategy was to directly reuse the alkali to extract agar. It eventually led to the accumulation of chemical oxygen demand (COD) in the alkali solution, resulting in the failure of alkali functions. The large amount of COD and alkali from alkali-treated Gracilaria results in resource waste and environmental damage. For this reason, electrodialysis and membrane concentration were used to recover the low-concentration alkali in alkali-treated Gracilaria, and the physicochemical properties of Gracilaria agar extracted by recovered alkali from different methods were evaluated. Results shown that the COD removal rate and the alkali recovery rate of the recovered alkaline solution by electrodialysis reached 69.97 % and 45.31 %, respectively. Furthermore, the optimal conditions for low-concentration alkali membrane concentration were pressure of 0.50 MPa, flow rate of 40 L/h, and pore size of 1000 Da. Under these conditions, the highest COD removal rate and the alkali recovery rate of recovered alkaline solution by membrane concentration reached 68.46 % and 11.20 %, respectively. The gel strength of agar extracted by electrodialysis and from a low-alkaline solution after five times of membrane concentration increased by 18.2 % and 15.7 %, respectively, compared with those extracted by the traditional method. The X-ray fluorescence spectra indicated that elemental K and Ca from the recovered alkali could improve the gel strength of agar. Electron microscopy analysis and Fourier transform infrared spectroscopy revealed no significant differences in the gel skeleton and functional group structure between the recovered alkali-extracted agar and traditional method-extracted agar. After electrodialysis and membrane concentration, the cumulative alkali recovery rate of alkali-treated Gracilaria could reach 37.14 %. This study provided new ideas for the clean production of agar and other marine polysaccharides.

Pioneering minimum liquid discharge desalination: A pilot study in Lampedusa Island

Minimum Liquid Discharge (MLD) and Zero Liquid Discharge (ZLD) schemes have been widely proposed in the recent scientific literature not only as a possible solution to brine disposal but also as a non-conventional sustainable source of raw materials. Nevertheless, very few works have pushed the idea towards a real demonstration activity, and this somehow limits the reliability that such schemes have with respect to the real implementation potential at the industrial scale. In this work, for the first time in the literature, an integrated treatment chain for the sustainable production of freshwater and minerals has been demonstrated at a pre-industrial scale, in the island of Lampedusa (Italy). The treatment chain included a Nanofiltration (NF) step to separate monovalent and bivalent ions, followed by a Multi-Effect Distillation (MED) unit, powered by waste heat from a Thermal Power plant, generating high-quality water (<30 μS/cm) and an ultra-concentrated brine. The latter was treated in Evaporation Ponds (EPs) to generate high purity NaCl (>99 %). On the other side, the NF retentate was treated to selectively recover magnesium and calcium hydroxides (Mg(OH)2 purity up to 98 %) in a novel Multiple Feed-Plug Flow Reactor (MF-PFR). The resulting brine fed an ElectroDialysis with Bipolar Membranes unit (EDBM), generating in-situ alkaline and acidic solutions: chemicals needed for internal usage in the plant. All units were successfully tested, reaching satisfactory performance indicators. Furthermore, the stability of each unit during the daily operational run was assessed and successfully achieved, demonstrating not only the technical feasibility of the proposed demo plant, but also the feasibility of MLD as a sustainable alternative for minerals recovery.

Sol-gel synthesis, physicochemical characteristics and in vitro pH-responsive metformin drug release of uniformly polydopamine coated mesoporous silica nanospheres

A recent attention has been paid to the repurposing potential of metformin drug for cancer chemotherapy. Herein, pH-responsive metformin drug delivery nanocarriers were achieved using sol-gel synthesized mesoporous silica nanospheres (MSN) uniformly coated with polydopamine (PDA) shell. The PDA coating shell around the MSN surface was in situ formed through oxidative self-polymerization of dopamine monomers in an alkaline solution at room temperature. The microstructure, structural and textural characteristics of PDA@MSN were examined and compared to uncoated MSN. Furthermore, PDA coated metformin (MET) drug-loaded MSN were used to study the pH-responsive MET drug release behaviour under neutral and acidic conditions. The in vitro release test showed that the PDA coating shell not only protects MET drug leakage under normal physiological conditions (pH 7.4) but also allows for its controlled/sustained release in acidic conditions (pH 4.5 and pH 5.5) which closely mimic the intracellular acidity (pH 4.5–5.5) of endosomes/lysosomes formed around drug-loaded nanocarriers after their endocytosis by cancer cells.

Quaternization of cassava starch and determination of antimicrobial activity against bacteria and coronavirus

This study describes the novel development of quaternized cassava starch (Q-CS) with antimicrobial and antiviral properties, particularly effective against the MHV-3 coronavirus. The preparation of Q-CS involved the reaction of cassava starch (CS) with glycidyltrimethylammonium chloride (GTMAC) in an alkaline solution. Q-CS physicochemical properties were determined by FTIR, NMR, elemental analysis, zeta potential, TGA, and moisture sorption. FTIR and NMR spectra confirmed the introduction of cationic groups in the CS structure. The elemental analysis revealed a degree of substitution (DS) of 0.552 of the cationic reagent on the hydroxyl groups of CS. Furthermore, Q-CS exhibited a positive zeta potential value (+28.6 ± 0.60 mV) attributed to the high positive charge density shown by the quaternary ammonium groups. Q-CS demonstrated lower thermal stability and higher moisture sorption compared to CS. The antimicrobial activity of Q-CS was confirmed against Escherichia coli (MIC = 0.156 mg mL−1) and Staphylococcus aureus (MIC = 0.312 mg mL−1), along with a remarkable ability to inactivate 99% of MHV-3 coronavirus after only 1 min of direct contact. Additionally, Q-CS showed high cell viability (close to 100%) and minimal cytotoxicity effects, guaranteeing its safe use. Therefore, these findings indicate the potential use of Q-CS as a raw material for antiseptic biomaterials.

Titanium Dioxide and N-Doped Carbon Hybrid Nanofiber Modulated Ru Nanoclusters for High-Efficient Hydrogen Evolution Reaction Electrocatalyst.

The designing and fabricating highly active hydrogen evolution reaction (HER) electrocatalysts that can superior to Pt/C is extremely desirable but challenging. Herein, the fabrication of Ru/TiO2/N-doped carbon (Ru/TiO2/NC) nanofiber is reported as a novel and highly active HER electrocatalyst through electrospinning and subsequent pyrolysis treatment, in which Ru nanoclusters are dispersed into TiO2/NC hybrid nanofiber. As a novel support, experimental and theoretical calculation results reveal that TiO2/NC can more effectively accelerate water dissociation as well as optimize the adsorption strength of *H than TiO2 and NC, thus leading to a significantly enhanced HER activity, which merely requires an overpotential of 18mV to reach 10mAcm-2, outperforming Pt/C in an alkaline solution. The electrolytic cell composed of Ru/TiO2/NC nanofiber and NiFe LDH/NF can generate 500 and 1000mAcm-2 at voltages of 1.631 and 1.753V, respectively. Furthermore, the electrolytic cell also exhibits remarkable durability for at least 100h at 200mAcm-2 with negligible degradation in activity. The present work affords a deep insight into the influence of support on the activity of electrocatalyst and the strategy proposed in this research can also be extended to fabricate various other types of electrocatalysts for diverse electrocatalytic applications.

Effect of the triangular prism dent on stress corrosion cracking behavior of alloy 690TT heat transfer tube in a lead-containing alkaline solution

In this paper, the microstructural changes and mechanical characteristics of alloy 690TT heat transfer tube with a triangular prism dent are investigated by combining experimental and simulation methods, and subsequently examines their influence on stress corrosion cracking (SCC) behavior. The results indicate that the deformation mechanism caused by impact dent is slip and twinning. The structural transformation of high-density dislocations, as well as Copper and Brass deformation textures, are formed at dent bottom, resulting in stress concentration through work hardening, which greatly increases SCC sensitivity. Oxidation preferentially occurs along grain boundaries and dislocations, and the corrosion products are formed, which exhibit a semi-coherent orientation relationship with the matrix. Oxidation is essentially a de-alloying process in which oxygen diffuses inward and Cr migrates towards the oxidation zone. The wedge force generated by corrosion products provides another driving force for initiation and propagation of SCC cracks, in addition to external loads and residual stress. SCC cracks propagate in the form of intergranular stress corrosion cracking and transgranular stress corrosion cracking in a high temperature lead-containing alkaline solution.

Iodide retention characteristics on oxidized Cu coupon in saline and alkaline environments: Perspectives on high-level radioactive waste disposal

Radioactive iodine, particularly 129I, is one of the most hazardous radioisotopes found in deep geological repositories for high-level radioactive waste (HLW). This study investigated the iodide retention capacity of Cu coupons, simulating Cu canisters, under potential repository conditions. In saline environments (0.1 M NaCl + 0.01 M MgSO4), iodide was immobilized through CuI(s) formation on the oxidized surface of Cu coupons. This process was facilitated by the favorable affinity between Cu+ oxidized from the Cu coupons and I−. The iodide retention capacity of Cu coupons exhibited notable sensitivity to the pH and chemical composition of the solutions. Cu+ remained stably complexed with Cl− under saline conditions, leading to the CuI(s) formation. However, in distilled water, iodide retention decreased over time due to the transformation of CuI to CuO through Cu oxidation. In an alkaline solution (0.1 M KOH), iodide retention was negligible. These results indicate that radioactive iodide ions, released in the event of canister failure, can be effectively immobilized, and their migration to the ecosystem can be impeded through CuI(s) formation on oxidized Cu canisters in saline conditions. Consequently, Cu canisters can serve as an effective barrier against radioactive iodide migration and as a long-term isolation medium for HLW, particularly under saline conditions.

Biodegradable Mg-Mo2C MXene Air Batteries for Transient Energy Storage.

Primary batteries are the fundamental power sources in small electronic gadgets and bio/ecoresorbable batteries. They are fabricated from benign and biodegradable materials and are of interest in environmental sensing and implants because of their low toxicity toward the environment and human body during decomposition. However, current bio/ecoresorbable batteries suffer from low operating voltages and output powers because of the occurrence of undesired hydrogen evolution reactions (HERs) at cathodes. Herein, Mo2C MXene was used as a cathode to achieve high operating voltage and areal power. Mo2C provides energy barriers for HERs in alkaline solutions, and such barriers suppress HERs and allow the oxygen reduction reaction to dominate at the cathode. The fabricated battery exhibits an operating voltage and areal power of 1.4 V and 0.92 mW cm-2, respectively. Degradation tests show that the full cell completely degrades within 123 days, leaving only Mo fragments from the electrode and biodegradable encapsulation. This study provides insights into bio/ecoresorbable batteries with high power and operating voltage, which can be used for environmental sensing.

Material design of geopolymers using calcined allophane

As kaolinite, the main material of geopolymers, is not produced in East Asia and elsewhere, it is necessary to find alternative materials to replace kaolinite. The authors therefore investigated the preparation conditions and optimum curing temperature of geopolymers using allophane, which is not used as a cementitious material. Based on compressive strength and internal temperature history results, specimens were prepared by mixing allophane calcined at 800 °C for 3 h with an alkaline solution adjusted to a Na2O/SiO2 ratio of one at a water-to-powder ratio of two. Powder X-ray diffraction and nuclear magnetic resonance spectral analyses of specimens indicated that amorphous geopolymers with a three-dimensional structure were produced from calcined allophane. As for the optimum curing temperature, the samples cured at 20 °C showed the best strength development properties. On the other hand, specimens cured at 80 °C showed a temporary decrease in compressive strength as zeolite formation progressed with increasing curing time. Since 20 °C is the optimal curing condition, we conclude that geopolymers that can be used for on-site curing can be produced by using calcined allophane.

Fabrication and Mechanical Evaluation of Eco-Friendly Geopolymeric Mortars Derived from Ignimbrite and Demolition Waste from the Construction Industry in Peru

Ignimbrite rock is a volcanic material located in the Arequipa region (Peru), and for centuries, it has been used as a construction material, giving a characteristic light pastel, white to pink color to the city of Arequipa, with white being the most common. In the present study, the potential use of three types of Arequipa raw materials (ignimbrite rock powder, calcined clay powder, and demolition mortar powder) as the main source of new binders or the manufacture of environmentally friendly mortars, without the addition of ordinary Portland cement (OPC) is discussed. In this work, an in-depth characterization of the materials used was carried out. The proposed fabrication route for geopolymeric materials was considered for the manufacture of binders and mortars using an alkaline solution of NaOH with values between 12 and 18 molar, as a trigger for the geopolymerization process. Geopolymeric mortars were obtained by adding a controlled amount of fine sand to the previously prepared mixture of binder raw material and an alkaline solution. Conventional OPC and geopolymeric mortars manufactured under the same conditions were mechanically evaluated by uniaxial compression tests at a constant compression rate of 0.05 mm/min and under normal conditions of temperature and atmosphere, where the most optimal values were obtained for 15 molar alkaline solutions of ignimbrite without the addition of aggregates, with values of compressive strength of 42 MPa and a modulus elastic of 30 GPa. The results revealed a significant increase in the maximum strength and modulus of elasticity values when the volumetric fractions of OPC are completely replaced with geopolymeric binders in the study conditions of this work, demonstrating the enormous potential of the ignimbrite rock and construction waste studied, as raw material of alternative mortar binders without the addition of OPC. With this work, the ignimbrite rock, of great value in the region and also found in other areas of the Earth’s geography, was characterized and valued, in addition to the calcined clay and demolition mortar of the region.

Enhanced electrochemical performance of MoSe2 nanosheets on CoAl- layered double hydroxide for oxygen evolution reaction

The design of high-efficiency electrocatalysts for water electrolysis has attracted much attention. A crucial half-reaction in electrochemical water splitting is the oxygen evolution reaction (OER), which suffers from sluggish reaction kinetics due to the high-energy barrier of the complex electron transfer process. This study presents a MoSe2@CoAl-layered double hydroxide (LDH) hybrid nanostructure prepared using the facile hydrothermal method and investigated as a potential OER electrocatalyst. Morphological analysis indicated that the MoSe2 formed in very thin nanosheet structures containing multiple defects on the LDH platelets, increasing the number of catalytic active sites. Compared with pristine MoSe2 and CoAl-LDH, the obtained MoSe2@CoAl-LDH catalyst exhibited enhanced electrocatalytic activity for the OER in an alkaline solution. The MoSe2@CoAl-LDH electrocatalyst showed an overpotential of 360 mV at a current density of 10 mA cm−2 and a small Tafel slope of 53 mV dec−1. In addition, it demonstrated good electrochemical stability. The MoSe2@CoAl-LDH exhibited a lower Tafel slope than commercial RuO2, indicating faster electron transfer on the MoSe2@CoAl-LDH electrode.

Rational Design of FeCo-S/Ni2P/NF Heterojunction as a Robust Electrocatalyst for Water Splitting.

The rational design of nonnoble-metal-based catalysts with high electroactivity and long-term stability, featuring controllable active sites, remains a significant challenge for achieving effective water electrolysis. Herein, a heterogeneous catalyst with a FeCo-S and Ni2P heterostructure (denoted FeCo-S/Ni2P/NF) grown on nickel foam (NF) was synthesized by a solvothermal method and low-temperature phosphorization. The FeCo-S/Ni2P/NF catalyst shows excellent electrocatalytic performance and stability in alkaline solution. The FeCo-S/Ni2P/NF catalyst demonstrates low overpotentials (η) for both the hydrogen evolution reaction (HER) (49 mV@10 mA cm-2) and the oxygen evolution reaction (OER) (279 mV@100 mA cm-2). Assembling the FeCo-S/Ni2P/NF catalyst as both cathode and anode in an electrolytic cell for overall water splitting (OWS) needs an ultralow cell voltage of 1.57 V to attain a current density (CD) of 300 mA cm-2. Furthermore, it demonstrates excellent durability, significantly outperforming the commercial Pt/C∥IrO2 system. The results of experiments indicate that the heterostructure and synergistic effect of FeCo-S and Ni2P can significantly enhance conductivity, facilitate mass/ion transport and gas evolution, and expose more active sites, thereby improving the catalytic activity of the electrocatalyst for the OWS. This study provides a rational approach for the development of commercially promising dual-functional electrocatalysts.