Alkaline Water Research Articles

Yttrium-doped NiMo-MoO2 heterostructure electrocatalysts for hydrogen production from alkaline seawater

Active and stable electrocatalysts are essential for hydrogen production from alkaline water electrolysis. However, precisely controlling the interaction between electrocatalysts and reaction intermediates (H2O*, H*, and *OH) remains challenging. Here, we demonstrate an yttrium-doped NiMo-MoO2 heterogenous electrocatalyst that efficiently promotes water dissociation and accelerates the intermediate adsorption/desorption dynamics in alkaline electrolytes. Introducing yttrium into the NiMo/MoO2 heterostructure induces lattice expansion and optimizes the d-band center of NiMo alloy component, enhancing water dissociation and H* desorption. Yttrium doping also increases the concentration of oxygen vacancies in MoO2−x, which in turn accelerates the charge kinetics and the swift evacuation of *OH intermediates from the active sites. Consequently, the Y-NiMo/MoO2−x heterostructure exhibits notable performance by requiring only 189 and 220 mV overpotentials to achieve current density of 2.0 A cm−2 in alkaline water and seawater, respectively. This work provides a strategy to modulate heterostructure catalysts for scalable, economically viable hydrogen production from low-quality waters.

Decoding the Hume-Rothery Rule in a Bifunctional Tetra-metallic Alloy for Alkaline Water Electrolysis.

The 90-year-old Hume-Rothery rule was adapted to design an outstanding bifunctional tetra-metallic alloy electrocatalyst for water electrolysis. Following the radius mismatch principles, Fe (131 pm) and Ni (124 pm) are selectively incorporated at the Pd (139 pm) site of Mo0.30Pd0.70 nanosheets. Analogously, Cu (132 pm) alloys with only Pd, while Ag (145 pm) alloys with both Pd and Mo (154 pm). The face-centered cubic Mo0.30Pd0.35Ni0.23Fe0.12 nanosheets with 10-12 atomic layers, featuring in-plane compressive strain along the {111} basal plane, show 1/3 (422) reflection from local hexagonal symmetry. The more electronegative Pd attracts electron density from Ni/Fe in Mo0.30Pd0.35Ni0.23Fe0.12, synergistically boosting the mass activities for hydrogen and oxygen evolution reactions to 89 ± 5 and 38.6 ± 3.1 A g-1 at ±400 mV versus RHE, respectively. Full water electrolysis continues for ≥550 h, requiring cell voltages of 1.51 and 1.63 V at 10 and 100 mA cm-2, delivering 45 mL h-1 green H2.

Ameliorative role of camel protein hydrolysates diet against alkaline stress in Oreochrmis niloticus: Hematology, immune responses and their regulating genes expression, and histopathological assays.

This investigation looked at the ameliorative role of camel whey protein hydrolysates-diet (PH) in Oreochromis niloticus stocked under alkaline conditions. One hundred sixty fish (16.02 ± 0.14g) were allocated equally into four groups with four replications for 30 days. The first (control) and second (alkaline) groups were fed basal diets and maintained in fresh and alkaline water, respectively. The third and fourth groups were fed on a PH diet (basal diet containing 75g PH/kg) and maintained in fresh water and alkaline water, respectively. The hematology, immune-antioxidant indices, immune-regulatory genes, histopathological investigation of the spleen, and resistance to Aeromonas sobria were investigated. The results showed that the alkaline condition induced hematological disorders (lowered red blood cells, hemoglobin, packed cell volume, and white blood cell count) and immunosuppression (lowered phagocytic activity and index, lysozyme, nitric oxide, and complement 3) in the exposed fish. Alkaline exposure induced oxidative stress through elevation of the malondialdehyde and reduction in the antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase, glutathione S-transferase, glutathione S-reductase, and reduced glutathione). The immune modulatory genes (tolls like receptor-5, interleukin-1beta, interleukin-6, interleukin-8, interleukin-10, interleukin-17, nuclear factor kappa beta, and tumor necrosis factor-alpha) were down-regulated by exposure to alkaline conditions. The microscopic section of the spleen of the fish subjected to alkaline conditions showed notable hyperplasia of the melanomacrophage centers, besides vascular congestion, endothelial cell hypertrophy, and mild hypercellularity in the erythroid and lymphoid elements. In addition, few sections manifested more pronounced erythroid hyperplasia than the lymphoid one. The survival of the fish subjected to alkaline conditions was reduced during the A. sobria challenge. Feeding on a PH diet, the hematology was restored and the immune-antioxidant functions were modulated. Modulation of the immune-regulatory genes and increased survivability of the alkaline-exposed fish were noticed when fed on the PH diet. Consequently, we can recommend enriching the Nile tilapia diet with a 75g PH/kg diet especially when reared under alkaline conditions to support the immune functions of the fish.

Delayed onset of ocean acidification in the Gulf of Maine

The Gulf of Maine holds significant ecological and economic value for fisheries and communities in north-eastern North America. However, there is apprehension regarding its vulnerability to the effects of increasing atmospheric CO2. Substantial recent warming and the inflow of low alkalinity waters into the Gulf of Maine have raised concerns about the impact of ocean acidification on resident marine calcifiers (e.g. oysters, clams, mussels). With limited seawater pH records, the natural variability and drivers of pH in this region remain unclear. To address this, we present coastal water pH proxy records using boron isotope (δ11B) measurements in long-lived, annually banded, crustose coralline algae (1920–2018 CE). These records indicate seawater pH was low (~ 7.9) for much of the last century. Contrary to expectation, we also find that pH has increased (+ 0.2 pH units) over the past 40 years, despite concurrent rising atmospheric CO2. This increase is attributed to an increased input of high alkalinity waters derived from the Gulf Stream. This delayed onset of ocean acidification is cause for concern. Once ocean circulation-driven buffering effects reach their limit, seawater pH decline may occur swiftly. This would profoundly harm shellfisheries and the broader Gulf of Maine ecosystem.

Self-Reconstruction of High Entropy Alloys for Efficient Alkaline Hydrogen Evolution.

Alkaline water (H2O) electrolysis is currently a commercialized green hydrogen (H2) production technology, yet the unsatisfactory hydrogen evolution reaction (HER) performance severely limits its energy conversion efficiency and cost reduction. Herein, PtRu2.9Fe0.15Co1.5Ni1.3 high entropy alloys (HEAs) is synthesized and subsequently exploited electrochemically induced structural oxidation processes to construct self-reconfigurable HEAs, as an efficient alkaline HER catalyst. The optimized self-reconstructed PtRu2.9Fe0.15Co1.5Ni1.3 HEAs with the HEAs and cobalt rutheniate interface (HEAs-Co2RuO4) exhibits excellent alkaline HER performance, requiring just 11.8mV to obtain a current density (j) of 10 mA cm-2 in 1m KOH. And the j on HEAs-Co2RuO4 is 41.8 mA cm-2 at 0.07 VRHE, 2.0 and 6.1 times higher than PtRu2.9Fe0.15Co1.5Ni1.3 HEAs and 20% Pt/C. Mechanism studies reveal that the improved alkaline HER performance of HEAs-Co2RuO4 is due to the formation of HEAs-Co2RuO4, which significantly shrinks the Helmholtz layer, provides a new fast material transport channel, boosts H2O adsorption, and reduces hydrogen adsorption, and thus accelerates the alkaline HER. This research not only throws new light on the self-reconstruction of catalysts but also provides guidance for the rational design of efficient electrocatalysts.

Identifying the Bifunctional Mechanism in Alkaline Water Electrolysis by Lewis Pairs at the Single-Atom Scale.

The bifunctional mechanism, involving multiactive compositions to simultaneously dissociate water molecules and optimize intermediate adsorption, has been widely used in the design of catalysts to boost water electrolysis for sustainable hydrogen energy production but remains debatable due to difficulties in accurately identifying the reaction process. Here, we proposed the concept of well-defined Lewis pairs in single-atom catalysts, with a unique acid-base nature, to comprehensively understand the exact role of multiactive compositions in an alkaline hydrogen evolution reaction. By facilely adjusting active moieties, the induced synergistic effect between Lewis pairs (M-P/S/Cr pairs, M = Ru, Ir, Pt) can significantly facilitate the cleavage of the H-OH bond and accelerate the removal of intermediates, thereby switching the rate-determining step from the Volmer step to the Heyrovsky step. Moreover, the representative Ru-P Lewis pairs deliver an impressive 266 h durability at a high industrial current density of 2 A cm-2 without activity decay in anion-exchange membrane water electrolysis, and the concept can be extended to modify commercial noble-metal-based catalysts for performance enhancement. This work not only sheds light on the important effect of the bifunctional mechanism in alkaline water electrolysis at the single-atom scale but also offers a universal descriptor for the rational design of advanced catalysts.

Atomic Gap-State Engineering of MoS2 for Alkaline Water and Seawater Splitting.

Transition-metal dichalcogenides (TMDs), such as molybdenum disulfide (MoS2), have emerged as a generation of nonprecious catalysts for the hydrogen evolution reaction (HER), largely due to their theoretical hydrogen adsorption energy close to that of platinum. However, efforts to activate the basal planes of TMDs have primarily centered around strategies such as introducing numerous atomic vacancies, creating vacancy-heteroatom complexes, or applying significant strain, especially for acidic media. These approaches, while potentially effective, present substantial challenges in practical large-scale deployment. Here, we report a gap-state engineering strategy for the controlled activation of S atom in MoS2 basal planes through metal single-atom doping, effectively tackling both efficiency and stability challenges in alkaline water and seawater splitting. A versatile synthetic methodology allows for the fabrication of a series of single-metal atom-doped MoS2 materials (M1/MoS2), featuring widely tunable densities with each dopant replacing a Mo site. Among these (Mn1, Fe1, Co1, and Ni1), Co1/MoS2 demonstrates outstanding HER performance in both alkaline and seawater alkaline media, with overpotentials at a mere 159 and 164 mV at 100 mA cm-2, and Tafel slopes at 41 and 45 mV dec-1, respectively, which surpasses all reported TMD-based nonprecious materials and benchmark Pt/C catalysts in HER efficiency and stability during seawater splitting, which can be attributed to an optimal gap-state modulation associated with sulfur atoms. Experimental data correlating doping density and dopant identity with HER performance, in conjunction with theoretical calculations, also reveal a descriptor linked to near-Fermi gap state modulation, corroborated by the observed increase in unoccupied S 3p states.

Alkaline Water Electrolysis Beyond 3 A/cm2 Using Catalyst Coated Diaphragms

Alkaline water electrolysis using catalyst coated diaphragms (Zirfon UTP 500 and UTP 220) was conducted at current densities from 2 up to 3500 mA cm−2 at varying temperatures (20–75 °C) in 30 wt% KOH. The coatings were conducted using two different approaches, which were compared with each other: spray coating and stencil coating. Using platinum group free catalysts, which are either available commercially or easy to synthesize (Raney Ni; FeNi LDH), we reached 3.5 A cm−2 at less than 2.3 or 2.5 V, for Zirfon UTP 220 and 500, respectively. The improvements compared to conventional Ni felt were linked to a reduction in the kinetic overpotential due to better catalytic properties and an increase in active surface area. The internal resistance corrected potential at 1 A cm−2 was as low as 1.75 V (at 75 °C), showing that high current operation for industrial alkaline water electrolysers is possible, when ohmic resistances are adequately addressed. The catalyst coated diaphragms were stable under room temperature for at least 60 h, however, showed degradation at 75 °C over the course of up to 240 h. The catalyst layers degraded by fracturing followed by delamination to the porous transport layer, where they showed elongated stability.

Regional relationship between total alkalinity and salinity in the surface waters of the western South Atlantic margin

Regional relationship between total alkalinity and salinity in the surface waters of the western South Atlantic margin

Chemodynamic covalent adaptable network-induced robust, self-healing, and degradable fluorescent elastomers for multicolor information encryption.

Elastomers are of great significance in developing smart materials for information encryption, and their unique self-healing and highly flexible properties provide innovative solutions to enhance security and anti-counterfeiting effectiveness. However, challenges remain in the multifunctional combination of mechanical properties, self-healing, degradability, and luminescence of these materials. Herein, a chemodynamic covalent adaptable network (CCAN)-induced robust, self-healing, and degradable fluorescent elastomer is proposed. Thanks to the CCANs, the resulting elastomer exhibits a tensile strength of 33.44 MPa (300 times higher than that of a linear elastomer) and an elongation at break of 1265%, and its mechanical properties can be restored to about 20 MPa after 72 h of healing at room temperature, and a self-healing efficiency of 94.67% can be realized for 24 h at 70 °C. Simultaneously, the dynamic chemical balance of keto and enol structural transitions of curcumin chain segments can be driven by CCANs, realizing multi-color (from yellow to violet) display and broad wavelength (300-500 nm) excitation, which in turn enables surface read-write and color rosette and QR code pattern printing. In addition, it can also achieve adaptive degradation under biological, alkaline, and hot water conditions. This work has guiding significance for developing the next generation of high-performance multifunctional elastomer materials, which have potential applications in the field of smart anti-counterfeiting materials and smart flexible optoelectronics.

Ostracod-based transfer function shifting to a broad prospect in palaeolimnology and palaeoclimate.

The ostracod-based transfer function is a common method in palaeolimnology and palaeoclimate research, serving as an interpreter from fossil record to palaeoenvironment history. However, migration application of the transfer function remains challenging, and it is characterized by the use of the threshold of the transfer function and restriction of the understanding of palaeolimnology and palaeoclimate. Here, we constructed transfer functions for water salinity, alkalinity, and Ca conditions employing ecological information about four key species in the Yamdrok-tso basin. The prediction power of the transfer functions and their migration application in the Pumoyum Co were evaluated. The results show that the prediction power of the transfer functions was maintained according to the statistical indices of the cross-validation (R2, root mean square error, Rjack2, and root mean square error of prediction). The palaeoenvironment records constructed for the Pumoyum Co using transfer functions are in good agreement with the lake depth, mean grain size, ostracod diversity, and stalagmite δ18O records, indicating the considerable applicability of the transfer function in different ecosystems. Our study provides fresh insights for the application of transfer functions to palaeoenvironment reconstruction, enhancing the comprehension of palaeolimnology and palaeoclimate.

Facile engineering of CoS/rGO heterostructures on carbon cloth for efficient all-pH hydrogen evolution reaction and alkaline water electrolysis

A three-dimensional CoS/rGO@CC electrocatalyst was developed via a two-step electrodeposition, demonstrating excellent bifunctional activity and stability, with notable HER performance across various pH levels.

Self-supported Ni/NiO heterostructures with a controlled reduction protocol for enhanced industrial alkaline hydrogen evolution.

Self-supported Ni/NiO heterostructures with controllable ratios used in industrial alkaline water electrolysis (AWE) systems lead to an ultralow voltage of 1.79 V at 400 mA cm-2 for 2 weeks, ascribed to the synergic combination of abundant active sites, rapid electron/mass transfer and optimal HER kinetics.

Interface engineering of highly stable CeO2/CoFe@C electrocatalysts for synergistically boosting overall alkaline water splitting performance

A scalable and facile solvent free synthesis approach is used to synthesize highly dispersed CeO2/CoFe nanoparticles encapsulated within 3D hierarchically porous carbon heterostructures for efficient overall water splitting with robust stability.

Boosting hydrogen production from alkaline water splitting via electrochemical active surface reconstruction of transition metal sulfide electrocatalysts

The degree of surface reconstruction reaction of sulfide catalyst is controlled, 20 s-NMSO could reach a current of 1 A cm−2 at an ultra-low overpotential of 231 mV, and the voltage only increased by 0.06% after 6 days of constant current testing.

Electrocatalytic properties of ultrathin FeSe2/Ni0·85Se heterostructure hollow nanobelts for oxygen evolution in alkaline water and simulated seawater

Research into cost-effective electrocatalysts for alkaline water and simulated seawater oxidation is paramount for advancing the conversion and storage of renewable energy. In this study, a FeSe2/Ni0·85Se catalyst with the hollow and ultrathin nanobelts structure is synthesized. The distinctive structure characteristics of FeSe2/Ni0·85Se heterojunction nanobelts confer exceptional oxygen evolution reaction (OER) properties in diverse electrolytes, including alkaline 1 M KOH and simulated seawater (1 M KOH + 0.5 M NaCl) solutions. The FeSe2/Ni0·85Se catalyst presents the low overpotentials of 259 and 267 mV at a current density of 10 mA cm−2, along with the Tafel slopes of 33.7 and 65.5 mV dec−1 in two solutions, respectively. Additionally, the FeSe2/Ni0·85Se catalyst also demonstrates good stability. This exploration introduces a promising strategy for the development of high-performance electrocatalysts in the realm of green energy, marking the significant progress towards sustainable energy solutions.

Platinum nanoparticles modulated metal-organic frameworks derivatives for substantially enhanced electrocatalytic alkaline water splitting performance

Platinum nanoparticles modulated metal-organic frameworks derivatives for substantially enhanced electrocatalytic alkaline water splitting performance

Upgrading hydrogen production rate and energy efficiency of alkaline water electrolysis under effect of magnetic field

Upgrading hydrogen production rate and energy efficiency of alkaline water electrolysis under effect of magnetic field

Identification of the reconstruction induced high-entropy spinel oxide nanosheets for boosting alkaline water oxygen evolution

Identification of the reconstruction induced high-entropy spinel oxide nanosheets for boosting alkaline water oxygen evolution

Novel high-safety composite separator: Achieving efficient alkaline water electrolysis by compositing microporous polysulfone membrane on one side of complete structure polyphenylene sulfide fabric

Novel high-safety composite separator: Achieving efficient alkaline water electrolysis by compositing microporous polysulfone membrane on one side of complete structure polyphenylene sulfide fabric