Natural Seawater Research Articles

Mapping tidal restrictions to support blue carbon restoration

Blue carbon ecosystems (BCEs), encompassing mangroves, saltmarshes, and seagrasses, are vital ecosystems that deliver valuable services such as carbon sequestration, biodiversity support, and coastal protection. However, these ecosystems are threatened by various anthropogenic factors, including tidal restrictions like levees, barriers, and embankments. These structures alter the natural seawater flow, often converting coastal ecosystems into freshwater environments. Identifying tidal restrictions and assessing their suitability for tidal restoration in areas amenable for coastal management is a crucial first step to successfully restore BCEs and the associated ecosystem services they provide, i.e., managed realignment. This study presents a novel approach for detecting tidal restrictions in the state of Victoria, Australia, using high-resolution LiDAR data, geospatial analysis techniques, and a multi-criteria scoring system. Our model successfully identified 90 % of known tidal restrictions from an existing dataset, while also detecting an additional 118 potential tidal restrictions, representing a 35 % increase. The model performance analysis revealed trade-offs between precision, recall, and noise ratio when using different noise reduction thresholds, highlighting the importance of selecting an appropriate threshold based on project objectives. The multi-criteria scoring system, which considered factors such as proximity to BCEs and current land use, enabled the selection of tidal restrictions based on their hydrological suitability for restoration. The results of this study have significant implications for BCE restoration efforts not only in Victoria, but more broadly across Australia and globally, providing a systematic approach to identifying and targeting areas with the greatest potential for successful restoration projects. While the approach is low-cost and user-friendly, it is dependent on the availability of LiDAR data for the study area. This can make it accessible to researchers and practitioners worldwide, allowing for its adaptation and application in diverse regions to support global efforts in restoring BCEs through tidal restoration.

Facile electrodeposited sandwich-like CuSx/MnSx electrocatalyst for efficient hydrogen evolution in seawater splitting

This study investigates a sandwich-like CuSx/MnSx electrode fabricated through electrodeposition technique on nickel foam (NF) substrate for hydrogen evolution reaction (HER) in seawater splitting. The synthesized electrode exhibits plenty of active sites, substantial specific surface area, and a distinctive morphology reminiscent of a tuberose-type nanostructure. Moreover, synergistic activity between the copper and manganese components enhances the rate of electron transfer process, thereby augmenting the electrocatalytic performance. Partial oxidation serves to increase active sites and control the morphology of the nanoparticles. The optimized electrode exhibits a minimal overpotential of 144 mV at 10 mA/cm2 for saline water splitting. The Tafel slope of 197 mV/dec and a transfer coefficient (α) of 0.3 indicate that the rate-determining step for the HER is likely the initial Volmer reaction. A higher electrochemical surface area (ECSA) of 2268 cm2, a solution resistance of 0.84 Ω, and a charge transfer resistance of 5.18 Ω suggest improved ion diffusion in the synthesized electrode. The electrocatalytic performance was also investigated by carrying out experiments with varying alkalinity in natural seawater electrolytes. The catalyst demonstrated robust stability for HER in natural seawater splitting with constant current density after 50 h of chronoamperometric analysis. The facile electrodeposited electrocatalyst exhibits energy-efficient and sustainable performance, effectively catalyzing reactions in a seawater-based electrolyte during the HER.

ANALISIS EFISIENSI BIAYA DALAM PENYEDIAAN AIR LAUT UNTUK OCEANARIUM KOTA: STUDI KASUS BXSea BINTARO

This research focuses on assessing how to procure seawater for the BXSea Bintaro Oceanarium, which is located far from natural seawater sources. The two main options analyzed were the purchase of seawater directly from the coast and the creation of artificial seawater. The research method used in this study was conducted through a qualitative, case study approach by combining literature study, field observation, and the researcher's experience as an oceanarium designer, to gain an in-depth understanding of the technical, economic, and environmental aspects associated with both ways of seawater procurement. The results show that the use of native seawater is more economical and environmentally friendly than artificial seawater. Analysis of the initial costs, long-term operational costs, and logistical and environmental implications of both methods showed the superiority of direct seawater procurement. This method is not only efficient in reducing logistical complexity and initial investment, but also has minimal environmental impact. The conclusions of this study confirm that natural seawater procurement is a cheaper option than the use of artificial seawater. Artificial seawater is significantly up to 5.58 times higher than natural seawater. This study makes an important contribution to the literature of seawater resource management in educational and recreational facilities, and underscores the importance of a sustainable approach in oceanarium development.

Amidoxime‐based Star Polymer Adsorbent with Ultra‐High Uranyl Affinity for Extremely Fast Uranium Extraction from Natural Seawater

AbstractPolymer adsorbents functionalized with amidoxime groups are widely considered to have the most industrial potential for uranium extraction from seawater. However, the entanglement upon the collapse of polymer chain in seawater greatly reduces the utilization ratio of amidoxime ligands. Herein, a novel star‐shaped molecular brush adsorbent (β‐CD‐g‐PAO) is obtained by densely grafting polyamidoxime (PAO) chains from β‐cyclodextrin (β‐CD). Experimental and theoretical results reveal that, in contrast to conventional linear polymer adsorbents, the star polymer adsorbent with a high grafting density of PAO side chains enables strong steric repulsion between the polymer chains, leading to increased persistence length and disentanglement of side chains. As a result, the star polymer adsorbent shows higher accessibility of the adsorption ligands with lower adsorption energy, achieving an adsorption capacity of up to 944.75 mg g−1 in uranium‐spiked seawater, surpassing that of conventional linear PAO by 3.2 times. Remarkably, this star polymer adsorbent demonstrates an extraordinarily adsorption capacity of 10.9 mg−1 g−1 in only 1 day in natural seawater, coupled with excellent affinity for uranyl ions (K = 0.31 pM). The unique topological structure design provides a new approach to solving the problem of low utilization ratio of functional ligands in polymer adsorbents.

The effects of acute ammonia stress on liver antioxidant, immune and metabolic responses of juvenile yellowfin tuna (Thunnus albacares)

The impact of acute ammonia nitrogen (NH3−N) stress on the antioxidant, immune, and metabolic capabilities of the liver in juvenile yellowfin tuna (Thunnus albacares) is not yet fully understood. This study set NH3-N concentrations at 0 (natural seawater, control group), 5, and 10 mg/L, and sampled the liver at 6, 24, and 36 h for analysis. As time progresses, NH3-N exposure leads to an increase in malondialdehyde (MDA) concentrations. The activity of superoxide dismutase (SOD) and the relative expression levels of related genes, as well as the activity of immune enzymes and ATPase, decrease. The levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and interleukin-10 (IL-10) exhibit different fluctuation patterns. Low concentrations of NH3-N increase the activity of catalase (CAT) and glutathione peroxidase (GHS-PX) and the relative expression levels of the Na+K+-ATPase gene. The relative expression levels of the interleukin-6 receptor (IL-6r) gene show a decreasing trend. High concentrations of NH3-N decrease the activity of CAT, GSH-PX, and the relative expression levels of related genes. When the NH3-N concentration is below 5 mg/L, the stress duration should not exceed 36 h. When the NH3-N concentration is between 5 and 10 mg/L, the stress duration should not exceed 24 h, otherwise, it will have a negative impact on the liver of the juvenile yellowfin tuna. This study provides scientific data for the artificial breeding and recirculating aquaculture of juvenile yellowfin tuna.

Effects of Wind Speed on Size-Dependent Morphology and Composition of Sea Spray Aerosols.

Variable wind speeds over the ocean can have a significant impact on the formation mechanism and physical-chemical properties of sea spray aerosols (SSA), which in turn influence their climate-relevant impacts. Herein, for the first time, we investigate the effects of wind speed on size-dependent morphology and composition of individual nascent SSA generated from wind-wave interactions of natural seawater within a wind-wave channel as a function of size and their particle-to-particle variability. Filter-based thermal optical analysis, atomic force microscopy (AFM), AFM infrared spectroscopy (AFM-IR), and scanning electron microscopy (SEM) were employed in this regard. This study focuses on SSA with sizes within 0.04-1.8 μm generated at two wind speeds: 10 m/s, representing a wind lull scenario over the ocean, and 19 m/s, indicative of the wind speeds encountered in stormy conditions. Filter-based measurements revealed a reduction of the organic mass fraction as the wind speed increases. AFM imaging at 20% relative humidity of individual SSA identified six main morphologies: prism-like, rounded, core-shell, rod, rod inclusion core-shell, and aggregates. At 10 m/s, most SSA were rounded, while at 19 m/s, core-shells became predominant. Based on AFM-IR, rounded SSA at both wind speeds had similar composition, mainly composed of aliphatic and oxygenated species, whereas the shells of core-shells displayed more oxygenated organics at 19 m/s and more aliphatic organics at 10 m/s. Collectively, our observations can be attributed to the disruption of the sea surface microlayer film structure at higher wind speeds. The findings reveal a significant impact of wind speed on morphology and composition of SSA, which should be accounted for accurate assessment of their climate effects.

3D Nickel–Manganese bimetallic electrocatalysts for an enhanced hydrogen evolution reaction performance in simulated seawater/alkaline natural seawater

In this paper, we report an inexpensive one-step synthesis of self-supported 3D nickel-manganese (NiMn) bimetallic coatings and their application for the hydrogen evolution reaction in simulated seawater (1 M KOH + 0.5 M NaCl) and alkaline natural seawater (1 M KOH + natural seawater). These binary coatings were electrodeposited on a titanium substrate using a facile electrochemical deposition method by a dynamic hydrogen bubble template technique. The as-deposited NiMn coatings with variable Mn amounts produce typical globular and unique porous architecture with abundant pores of different sizes. The activity of these fabricated catalysts towards the hydrogen evolution reaction was investigated by linear sweep voltammetry towards simulated seawater and alkaline natural seawater at different temperatures. The surface morphology and composition of the catalysts were also characterized by scanning electron microscopy and inductively coupled plasma optical emission spectroscopy. The as-prepared NiMn/Ti electrocatalyst, which was electrodeposited using a chemical bath containing Ni2+ and Mn2+ ions with a molar ratio of Ni2+:Mn2+ = 1:5, exhibits excellent hydrogen evolution activity in simulated seawater with an ultra-low overpotential of 64.2 mV to reach a current density of 10 mA cm−2. It is noteworthy that this NiMn/Ti electrocatalyst also achieves a current density of 10 mA cm−2 in alkaline natural seawater with a comparably low overpotential of 79.3 mV. The current densities increase by ca. 1.75–2.35 times with an increase in temperature from 25 °C to 75 °C for hydrogen evolution in both electrolytes. This bimetallic catalyst has shown excellent long-term stability at a constant potential of −0.23 V (vs. RHE) and a constant current density of 10 mA cm−2 for 10 h, which ensures higher durability and robustness for practical application of seawater splitting technology.

CrOx Modified Nickel Phosphides Electrocatalyst for Stable Hydrogen Evolution Reaction in Neutral Media

AbstractThe development of efficient and long‐term stable electrodes for hydrogen evolution reaction (HER) in seawater is highly desirable for hydrogen generation but remains challenging. In this work, a highly active CrOx@Ni2P‐Ni5P4/NF electrode is developed and investigated its dynamic reconstruction for HER in neutral electrolytes. The combination of in situ Raman spectra and electrochemical measurements revealed the dynamic surface reconstruction of the catalyst during HER. The CrOx modification not only effectively facilitates water dissociation but also stabilizes the structure post‐reconstruction, enabling rapid and stable hydrogen generation in neutral media. Remarkably, CrOx@Ni2P‐Ni5P4/NF exhibits overpotentials of 109 and 263 mV at current densities of 10 and 100 mA cm−2 in 1 m PBS, respectively. Concurrently, it exhibits stable operation for 500 h in 1 m PBS and 140 h in natural seawater at current densities of 50 and 100 mA cm−2, respectively. The proposed catalytic electrode and the mechanistic insights present a significant stride toward the realization of metal phosphides for direct seawater splitting.

Generating highly active oxide-phosphide heterostructure through interfacial engineering to break the energy scaling relation toward urea-assisted natural seawater electrolysis

Urea-assisted natural seawater electrolysis is an emerging technology that is effective for grid-scale carbon–neutral hydrogen mass production yet challenging. Circumventing scaling relations is an effective strategy to break through the bottleneck of natural seawater splitting. Herein, by DFT calculation, we demonstrated that the interface boundaries between Ni2P and MoO2 play an essential role in the self-relaxation of the Ni–O interfacial bond, effectively modulating a coordination number of intermediates to control independently their adsorption-free energy, thus circumventing the adsorption-energy scaling relation. Following this conceptual model, a well-defined 3D F-doped Ni2P-MoO2 heterostructure microrod array was rationally designed via an interfacial engineering strategy toward urea-assisted natural seawater electrolysis. As a result, the F-Ni2P-MoO2 exhibits eminently active and durable bifunctional catalysts for both HER and OER in acid, alkaline, and alkaline seawater-based electrolytes. By in-situ analysis, we found that a thin amorphous layer of NiOOH, which is evolved from the Ni2P during anodic reaction, is real catalytic active sites for the OER and UOR processes. Remarkable, such electrode-assembled urea-assisted natural seawater electrolyzer requires low voltages of 1.29 and 1.75 V to drive 10 and 600 mA cm−2 and demonstrates superior durability by operating continuously for 100 h at 100 mA cm−2, beyond commercial Pt/C ‖ RuO2 and most previous reports.

Engineering shrinkage resistance of nano-structured hydrogels in seawater for fast uranium capture

Synthetic hydrogels, which are 3D networks composed of crosslinked hydrophilic polymer chains, have been created using various crosslinked ways for uranium capture due to full exposure of chelate functional groups. However, the conventional honeycomb-like hydrogels exhibit non-connected micropore structure, which locks abundant water molecules and hence is unfavorable for mass transfer. Herein, we demonstrate a simple synthesis of the nano-structured hydrogel with activated nanogels as nano-crosslinkers (denoted as PGP hydrogel), and probe into the relationship between hydrogel structural parameters and uranium adsorption kinetics. It is found that the PGP hydrogel with a low crosslinking density of ∼0.02 mol/m3 possesses interconnected micropores, thereby facilitating diffusion of uranyl ions (UO22+) in 3D polymeric networks. Furthermore, a freeze-assisted soaking strategy is proposed to endow PGP hydrogel (denoted as target hydrogel) with strong shrinkage resistance in natural seawater, resulting in a ∼40 % increase in water permeance to reach 369 Lm−2h−1MPa−1. Correspondingly, the adsorption equilibrium time is shortened to ∼11 days. Although the uranium uptake capacity of PGP hydrogels with and without freeze-assisted soaking treatment remain basically unchanged (∼9.73 mg-U/g-Ads), a high uranium adsorption rate of 0.88 mg/g/d for the target hydrogel surpasses most currently available polymer adsorbents. The presented strategy is generalizable to a broader range of applications involving the adsorption of economically valuable ions in seawater or brine lake.

Unveiling Mechanistic Insight into Accelerating Oxygen Molecule Activation by Oxygen Defects in Co3O4-x/g-C3N4 p-n Heterojunction for Efficient Photo-Assisted Uranium Extraction from Seawater.

Photo-assisted uranium extraction from seawater (UES) is regarded as an efficient technique for uranium resource recovery, yet it currently faces many challenges, such as issues like biofouling resistance, low charge separation efficiency, slow carrier transfer, and a lack of active sites. Based on addressing the above challenges, a novel oxygen-deficient Co3O4-x/g-C3N4 p-n heterojunction is developed for efficient photo-assisted uranium extraction from seawater. Relying on the defect-coupling heterojunction synergistic effect, the redistribution of molecular charge density formed the built-in electric field as revealed by DFT calculations, significantly enhancing the separation efficiency of carriers and accelerating their migration rate. Notably, oxygen vacancies served as capture sites for oxygen, effectively promoting the generation of reactive oxygen species (ROS), thereby significantly improving the photo-assisted uranium extraction performance and antibacterial activity. Thus, under simulated sunlight irradiation with no sacrificial reagent added, Co3O4-x/g-C3N4 extracted a high uranium extraction amount of 1.08mgg-1 from 25 L of natural seawater after 7 days, which is superior to most reported carbon nitride-based photocatalysts. This study elaborates on the important role of surface defects and inerface engineering strategies in enhancing photocatalytic performance, providing a new approach to the development and design of uranium extraction material from seawater.

Photothermal-enabled metal-free polyfuran photocatalysts for efficient solar-to-hydrogen peroxide energy conversion from seawater

Solar-driven H2O2 photosynthesis from inexhaustible seawater is promising for alleviating increasingly-serious energy/environmental crises. Herein, a new metal-free photothermal-assisted photocatalyst containing strong π-stacked polyfuran D-A couples is synthesized by employing 5-hydroxymethylfurfural as precursor, which enables the highly-efficient H2O2 photosynthesis from seawater without any sacrificial agent. Its unique aromatic and quinoid furan alternating structure promotes the photogenerated charge transfer and the activation of oxygen molecules, thus remarkedly boosting H2O2 production rate. Furthermore, its localized photothermal and “electron bridge” effects can enhance the kinetic process of this reaction and accelerate the charge transfer, respectively, resulting in a high H2O2 yield of 1883.81 μmol g−1 h−1 with a high solar-to-chemical conversion efficiency of 0.48 % in seawater under simulated-sunlight irradiation. Impressively, it can achieve a high H2O2 concentration of 1867.81 μmol L−1 in natural seawater in one day under natural-sunlight irradiation, representing the first successful application of metal-free polyfuran photocatalysts for the photothermal-assisted H2O2 photosynthesis from natural seawater.

Non-Contact Acoustic Emission Monitoring of Corrosion in Mooring Chain Links

Mooring chains are key parts of floating energy production units, such as floating wind turbines, photovoltaic islands, and floating production-storage-offloading units (FPSOs). These structures are predominantly subject to corrosion and fatigue. Detailed integrity assessment of mooring chains can be challenging due to difficult access, complex geometry, surface conditions (often with the presence of corrosion pits), and weather conditions. Additionally, the presence of marine growth on the surface of the chain links often requires the need of surface cleaning to obtain a detailed assessment of the structural integrity. This paper highlights an experimental investigation of monitoring of corrosion-induced damage in mooring chain links by means of non-contact Acoustic Emission (AE) technique. Accelerated corrosion experiments were performed on a large-scale mooring chain sample recovered from the field. A dedicated experimental set-up was designed to apply accelerated corrosion on two chain links submerged in natural sea-water. An immersion tank, i.e. an instrumented 1000x1000x1200mm3 water tank, was used to submerge the chain links in natural sea-water. The corrosion process was accelerated by means of anodic polarization. Ultrasound signals were continuously measured using two arrays of underwater AE transducers (in the frequency range between 50-450 kHz) placed on two perpendicular planes at a fixed distance from the chain links. Corrosion-induced AE sources were localized on the 3D geometry of the tested links. The variation and evolution of AE parameters extracted from the measured signals were analyzed as a function of testing time. The results of the accelerated corrosion experiment suggest that corrosion-induced ultrasound signals can be detected and monitored by means of non-contact AE. The results of this study may be used for characterization of corrosion-induced AE signals in mooring chain links.

PA/APVC nanofiltration membrane from reactive positively charged substrate membrane

Efficient Li+ and Mg2+ from natural seawater and salt lakes using nanofiltration is essential for efficient extraction of lithium resources and to address the global energy shortage. The combination of size sieving and the Donnan effect is crucial for optimal selectivity. We proposed a positively charged reactive support layer to design dual positively charged layer to enhance the magnesium-lithium separation. The positively charged support layer was prepared by ammoniating the PVC membrane with PEI, and then reacted with TMC to successfully prepare a dual positively charged layer PA/APVC nanofiltration membrane with high Li+/Mg2+ selectivity. The reactive support layer not only established a covalent bond connection with the PA layer, which increased the stability of the active layer, but also showed a positive charge (23.59 mV at pH=7) after ammonization, which further enhanced the Mg2+ repulsion from 82.57 % to 98.56 %. Furthermore, the highest separation factor achieved was 23.34 when a mixed solution containing Mg2+ and Li+ in a mass ratio of 50:1 was utilized, which was 13.48 times that of commercial nanofiltration membranes. The utilization of a reactive substrate membrane in the fabrication process of the PA/APVC membrane offers innovative prospects for future investigations on magnesium-lithium separation, contributing to the advancement of nanofiltration membranes.

Highly effective hydrogen evolution reaction in alkaline conditions using a sputtered bimetal Ni-Mo system: Experimental and computational evidence

Electrocatalytic water splitting is a promising method for large-scale green hydrogen production. Nevertheless, the electrodes used remain costly and exhibit limited adherence. We should develop alternative techniques using cost-effective materials to achieve robust catalyst-substrate adherence. Herein, we systematically investigate the HER performance of the bimetal Ni-Mo system fabricated by scalelable magnetron sputtering. The formation of the bimetal Ni-Mo system not only significantly increased the HER activity, but it also accelerated the kinetic reaction. The optimal ratio Ni/Mo of 6 enables the achievement of ultra-low overpotentials of 39 and 172 mV at current densities of −10 and −100 mA/cm2, respectively, in alkaline conditions. The performance of the electrode is also evaluated using the single-stack electrolyzer and further assessed in natural seawater. The long-term stability test at 1.6 and 4 A for each 50 hours shows stable performance. The HER improvement mechanism is systematically investigated through experimental and computational calculations.

Elucidating the role of S-containing structure in carbon-based catalysts towards efficient H2O2 synthesis in seawater

The on-site sustainable electrochemical synthesis of hydrogen peroxide (H2O2) in natural seawater holds significant practical value in the fields of energy storage and environmental treatment. However, the poisoning of the active sites by ions such as Cl−, Ca2+, and Mg2+ in natural seawater significantly inhibits the ORR activity of the catalyst. Herein, the 2e− ORR performance of S, N co-doped carbon materials in natural seawater was investigated, focusing on the anti-Ca2+/Mg2+ poisoning mechanism of S-doped carbon structures. The data indicate a Faradaic efficiency of 94.2 % for H2O2 production, with a yield of 3.52 mol/(gcat h), and an approximate 100 % sterilization of bacteria and inactivation of chlorella within 10 min. S-doped carbon structures demonstrated enhanced H2O adsorption and dissociation properties during the ORR process, optimized the micro-environment of the catalytic interface, effectively inhibited Ca2+ and Mg2+ deposition. Moreover, S-doping altered the N coordination structure, further enhancing the 2e− ORR selectivity of the catalyst. This study demonstrates the high selectivity of 2e− ORR in natural seawater, offering guidance for designing catalysts using in the complex environment and advancing marine energy storage and environmental treatment technologies.

Symmetry‐breaking of Dibenzo[b,d]thiophene Sulfone Enhancing Polaron Generation for Boosted Photocatalytic Hydrogen Evolution

AbstractThe current bottleneck in the development of efficient photocatalysts for hydrogen evolution is the limited availability of high‐performance acceptor units. Over the past nine years, dibenzo[b,d]thiophene sulfone (DBS) has been the preferred choice for the acceptor unit. Despite extensive exploration of alternative structures as potential replacements for DBS, a superior substitute remains elusive. In this study, a symmetry‐breaking strategy was employed on DBS to develop a novel acceptor unit, BBTT‐1SO. The asymmetric structure of BBTT‐1SO proved beneficial for increasing multiple moment and polarizability. BBTT‐1SO‐containing polymers showed higher efficiencies for hydrogen evolution than their DBS‐containing counterparts by up to 166 %. PBBTT‐1SO exhibited an excellent hydrogen evolution rate (HER) of 222.03 mmol g−1 h−1 and an apparent quantum yield of 27.5 % at 500 nm. Transient spectroscopic studies indicated that the BBTT‐1SO‐based polymers facilitated electron polaron formation, which explains their superior HERs. PBBTT‐1SO also showed 14 % higher HER in natural seawater splitting than that in deionized water splitting. Molecular dynamics simulations highlighted the enhanced water‐PBBTT‐1SO polymer interactions in salt‐containing solutions. This study presents a pioneering example of a substitute acceptor unit for DBS in the construction of high‐performance photocatalysts for hydrogen evolution.

Symmetry-breaking of Dibenzo[b,d]thiophene Sulfone Enhancing Polaron Generation for Boosted Photocatalytic Hydrogen Evolution.

The current bottleneck in the development of efficient photocatalysts for hydrogen evolution is the limited availability of high-performance acceptor units. Over the past nine years, dibenzo[b,d]thiophene sulfone (DBS) has been the preferred choice for the acceptor unit. Despite extensive exploration of alternative structures as potential replacements for DBS, a superior substitute remains elusive. In this study, a symmetry-breaking strategy was employed on DBS to develop a novel acceptor unit, BBTT-1SO. The asymmetric structure of BBTT-1SO proved beneficial for increasing multiple moment and polarizability. BBTT-1SO-containing polymers showed higher efficiencies for hydrogen evolution than their DBS-containing counterparts by up to 166 %. PBBTT-1SO exhibited an excellent hydrogen evolution rate (HER) of 222.03 mmol g-1 h-1 and an apparent quantum yield of 27.5 % at 500 nm. Transient spectroscopic studies indicated that the BBTT-1SO-based polymers facilitated electron polaron formation, which explains their superior HERs. PBBTT-1SO also showed 14 % higher HER in natural seawater splitting than that in deionized water splitting. Molecular dynamics simulations highlighted the enhanced water-PBBTT-1SO polymer interactions in salt-containing solutions. This study presents a pioneering example of a substitute acceptor unit for DBS in the construction of high-performance photocatalysts for hydrogen evolution.

Vanadium boosted high-entropy amorphous FeCoNiMoV oxide for ampere-level seawater oxidation

A series of multi-principal elements composites (FeCoNiMoVOx-n) were synthesized on Ni foam (FeCoNiMoVOx-n/NF) to investigate the role vanadium (V) plays in improvingtheir electrocatalytic activity for oxygen evolution reaction (OER). Surprisingly, it was discovered that the addition of V not only changed the morphology of the catalysts from microsphere to three dimensional (3D) microflower shape, but also optimized the proportion of high-valent metal species that enhance the formation of active metal oxy(hydroxide) intermediates. The as-synthesized high-entropy amorphous FeCoNiMoVOx-1.5 coated Ni foam electrode (FeCoNiMoVOx-1.5/NF) with a 3D microflower structure exhibited higher OER activity than its counterparts. It exhibited extremely low over-potentials of 216 and 236 mV which are required at 10 mA cm−2in alkaline water and natural seawater, respectively. Particularly, this high-entropy amorphous catalyst showed long-time stability for a continuous 100-h high-performance OER at an ampere-level current density of 1 A cm−2in alkaline natural seawater. This shows that it can beapplied for large-scale seawater electrolysis.

Hydrogel polyamidoxime shell layer constructed on cyclized polyacrylonitrile nanofibrous mats for efficient uranium extraction from seawater

Extracting uranium from seawater, which contains hundreds of times more than terrestrial ores, furnishes a sustainable energy resource while curbing carbon emissions. Nanofibrous-based amidoxime is the most reliable uranium adsorbent due to its abundant chelating sites and large surface area. However, the amidoximation (AO) of polyacrylonitrile nanofiber (PAN NFs) produces brittle and shrunk AO-PAN NFs, and the spinning of pre-amidoximed PAN produces sub-micro stiff poly amidoxime (PAO) NFs, restricting their applicability. Herein, pre-cyclization (210 °C) and optimized amidoximation are applied to construct a hydrogel shell layer from PAO on cyclized electrospun PAN NFs. Among different amidoximation ratios, AO10-CPAN mats (10 g/L) with a thin hydrogel PAO shell layer exhibit excellent mechanical strength, high uranium adsorption capacity reached 380 mg/g at pH 8, and maintained their structure and 89 % of their initial adsorption capacity after six adsorption-desorption cycles. Furthermore, a 20.6 mg/g uranium adsorption capacity is reached after 15 days of circulating spiked (300 ppb uranium) natural seawater through the AO10-CPAN mats, proving their excellent selectivity and the open-chain amidoxime is the main compound of PAO shell. The surface amidoximed cyclized PAN (AO10-CPAN) mats satisfy the mechanical and physiochemical requirements for effectively extracting uranium from seawater.