Alkaline Freshwater Research Articles

Self-Supported Porous Carbon Monoliths for Electrocatalytic Hydrogen Evolution in Alkaline Freshwater and Seawater.

Developing efficient catalysts for seawater electrolysis hydrogen evolution reaction (HER) is crucial for producing green hydrogen. Carbonized wood (CW), a porous carbon monolith, is a promising self-supporting electrocatalytic electrode owing to its environmentally friendly, sustainable, and hierarchically porous properties. However, the impact of different tree species on the hydrogen evolution performance remains unclear. In this study, various types of CWs, including carbonized poplar (PoCW), carbonized balsa (BaCW), carbonized fir (FiCW), and carbonized pine (PiCW), have been selected to investigate their electrocatalytic performance in hydrogen evolution. Among these, the PoCW exhibits superior electrocatalytic HER performance compared to the other CWs, attributed to its electrochemically active surface area, resistance, and the content of oxygen-containing functional groups. PoCW demonstrates a low overpotential of 284 mV and 356 mV at 10 mA cm-2 in alkaline freshwater and seawater, respectively. Moreover, PoCW shows long-term durability for 100 h in both alkaline freshwater and seawater. This work guides the selection of wood-based carbon monoliths and demonstrates that metal-free, CW-based self-supporting electrodes hold great potential for electrocatalytic hydrogen evolution in both freshwater and seawater.

Thermal strain engineering in cobalt-coordinated Mo2N for efficient ampere-level current density alkaline fresh/seawater hydrogen evolution electrocatalysis

Lattice-strain engineering has demonstrated its capability to influence the electronic structure and catalytic performance of electrocatalysts. Herein, we present a facile method for inducing thermal strain in cobalt/molybdenum nitride rod-shaped structures (denoted Co/Mo2N) via ammonia-assisted reduction, which effectively modulating the HER performance. The optimized Co/Mo2N-500, characterized by 3% tensile lattice strain, demonstrates exceptional HER activity with lower overpotentials of 140 mV and 184 mV at high current density of 1000 mA cm−2 in alkaline freshwater and seawater electrolytes, respectively. Co/Mo2N also exhibits excellent long-term durability even at a high current density of 300 mA cm−2, surpassing its counterparts and benchmark Pt/C catalyst. Density functional theory calculations validate that the tensile strain optimizes the d-band states, water dissociation, and hydrogen adsorption kinetics of the strained Mo2N in Co/Mo2N, thereby improving its catalytic efficacy. This work provides valuable insights into controlling lattice strain to develop highly efficient electrocatalysts towards advanced electrocatalytic applications.

Fe dimers incorporated within Ni(OH)2 nanosheets to enable rapid oxygen radical coupling and exceptional durability in oxygen evolution

Earth-abundant NiFe (oxy)hydroxides are promising substitutes for scarce noble-metal electrocatalysts in the oxygen evolution reaction (OER), yet their commercialization in alkaline water electrolyzers is hindered by poor durability. Here, we report that different Fe configurations can be deliberately incorporated into Ni(OH)2 nanosheets in FezNi1-zOxHy (z=0–0.4) via in-situ electrochemical delamination. The strongly synergistic catalysis between Fe dimers and low-valence host Ni(2-δ)+ is enhanced by the interactively roaming space-charge, which dynamically adapts to varying intermediates, mediating the oxide path mechanism, thereby accelerating deprotonation and oxygen radical coupling. Beyond high catalytic activity, the extended Ni-O shells surrounding Fe dimers create a locally flexible reaction microenvironment that prevents Fe dissolution at dynamic catalyst/electrolyte interfaces, ensuring ultralong-term stability at industrial OER current densities. This study highlights the great potential for commercial alkaline freshwater and seawater electrolysis, and offers new strategies for atomically manipulating metal species in (oxy)hydroxides to develop active and durable electrocatalysts.

Manipulating interfacial charge redistribution in Mott-Schottky electrocatalyst for high-performance water/seawater splitting

Interface engineering is an effective approach towards developing low-cost highly efficientelectrocatalystsforgreen hydrogen productionin alkaline water or seawater environments. Herein, we have successfully fabricatedan interface engineered Mott-Schottky heterostructure catalyst i.e.,Fe3O4@Ni3S2, in which, Ni3S2 nanosheets are evenly dispersed on the surface of Fe3O4 flower-like nanosheets, which are supported by a Ni foam substrate. Due to the synergistic effect between Ni3S2 and Fe3O4, theFe3O4@Ni3S2 heterostructure catalystdemonstrates remarkable catalytic activity under alkaline conditions whichis attributed to thehighlyexposed active sites, adjustment of the d-band center, and the built-in electric field at the interface. The catalyst Fe3O4@Ni3S2 has low overpotentials of 207 and 217 mV for the OER (oxygen evolution reaction) and 99 and 118 mV for the HER (hydrogen evolution reaction) in alkaline and seawater electrolytes, respectively, allowing it to yield a current density of 10 mA cm−2. Furthermore, the Fe3O4@Ni3S2||Fe3O4@Ni3S2 electrolyzer can achieve a current density of 10 mA cm−2 for alkaline fresh water and seawater (1 M KOH + seawater) electrolysis at low voltages of 1.57 V and 1.58 V, respectively. This study presents a novel approach for fabricating high-performance multi-interface 3D catalysts for overall water/seawater splitting.

MOF-derived NiCo2S4/FeS heterostructures with built-in electric field for enhanced electrooxidation in freshwater/ brine /ethanol/methanol

Oxygen evolution reaction (OER), as a half-reaction of water decomposition, has a high theoretical overpotential. Therefore, the development of electrocatalysts with high OER performance is favorable for electrolytic hydrogen production. In situ growth of nanomaterials on conductive substrates is an effective strategy for the preparation of electrocatalysts. In this work, we grew Ni/Co bimetallic metal-organic framework (MOF) on carbon cloth substrates and successfully constructed a robust NiCo2S4/FeS@CC electrocatalyst through a MOF derivatization strategy. This electrocatalyst can be used for efficient and robust OER performance. MOF-derived NiCo2S4/FeS has the advantage of a porous heterostructure and multicomponent with many active sites and faster charge transfer rate, while sulfur doping greatly improves the OER performance. The current density of this self-supported heterogeneous material in alkaline freshwater reaches up to 10 mA cm−2 with an overpotential of only 238 mV. NiCo2S4/FeS@CC exhibited good OER performance in alkaline brine with an overpotential of only 241 mV at 10 mA cm−2. We speculate that this is due to the generation of a negatively charged SO42− anionic layer on the catalyst surface during the electrooxidation process, which effectively avoids Cl− corrosion. And both conditions demonstrate excellent long time stability. Additionally, we succeeded in further reducing the onset potential and energy consumption by adding ethanol or methanol to the electrolyte. This work provides an effective method to improve the OER performance of MOF-derived transition metal electrocatalysts for hydrogen production from electrolytic water.

Unveiling Preliminary Study of the Holocene Sedimentary Environments and Biofacies in Western of Al-Hammar Marsh, Southern Part of Iraq

Biofacies and sedimentary environment analyses were conducted across three sites west of Al-Hammar Marsh. Excavations were undertaken at different depths for a comprehensive study. The initial site was probed at 9 m depth, followed by the second site at 5 m, and the third site at 9 m. Subsequent examination of these samples aimed to unveil insights into grain size, fossil contents, and their respective ecological settings. The grain size analysis revealed three distinct sediment types: silt, sandy silt, and muddy sand. Additionally, fossil assemblages hinted at three primary biofacies. The first facies represented a fresh marsh-fluvial environment identified across all three sites at different depths. Specifically, this biofacies manifested from the surface to about 200 cm in site one, 50-150 cm in site two, and 50-250 cm in site three. The second biofacies indicated a shallow marine environment at depths ranging from 250 to 550 cm in site one, 200-300 cm in site two, and 300-650 cm in site three. Lastly, the third biofacies denoted a lagoon or tidal flat environment observed at 600-900 cm depths in site one, 300-500 cm in site two, and 700-900 cm in site three. Notably, the third biofacies in site three exhibited signs of influence from alkaline freshwater, particularly in the third location at a depth of 700-800 cm. This influence was attributed to a mixture of marine and freshwater species, including; Quinqueloculina candeiana, Quinqueloculina angulta, Cubicula fluminalis, and Melanoides tuberculate. Abundant occurrences of these species were noted in the silty clay lithology of this layer.

Modulating electronic by construction WS2/WN heterostructure coupled with N-doped carbon to boost alkaline seawater hydrogen production

The development of an efficient and durable non-precious electrocatalyst for alkaline seawater electrolysis is of great significance. Herein, two-dimensional (2D) lamellar heterostructure WS2/WN was dispersed on the carbon matrix (marked as WS2/WN@CM). The obtained WS2/WN@CM catalysts demonstrate exceptional performance in the hydrogen evolution reaction (HER) in alkaline freshwater (1.0 M KOH), alkaline simulated seawater (1.0 M KOH + 0.5 M NaCl) and alkaline natural seawater (1.0 M KOH + seawater), respectively, which achieved a low overpotential (92 mV, 95 mV and 113 mV) at 10 mA cm−2 and outstanding long-term durability at 200 mA cm−2 for 100 h. The catalyst benefits from the 3D carbon skeleton, which not only effectively prevents stacking of the 2D lamellar WS2/WN to fully utilize the active material, but also provides rapid electron transport. Moreover, stress effects at WS2/WN interfaces lead to distortions of torsion angles in the WS2 lattice, thereby increasing crystal surface defects accompanied by an enhancement of electrical conductivity. Density functional theory (DFT) calculations combined with XPS evidence confirm the electronic structure reorganization of WS2/WN at interfaces, which optimizes the adsorption energy of specific intermediates. Additionally, WN captures many electrons from WS2, so the WN region favors the reduction reaction and thus enhances the HER process.

Cr-doped tri-metallic nano prism catalyst for efficient alkaline and seawater splitting

Electrochemical water splitting is one of the most promising methods for sustainable production of green hydrogen. The oxygen evolution reaction (OER) is a crucial step in the process of water splitting. However, it exhibits sluggish kinetics and requires a significant overpotential for functioning at reasonable reactionrates. The efficiency of the reaction can be enhanced by reducing the overpotential, lowering the energy barrier, and using an effective electrocatalyst. Transition metal-basedcatalysts are well studied for this purpose. Specially, nickel–cobalt (Ni-Co) based catalysts have been regarded as the best OER electrocatalysts. Therefore, several studies have been carried out to enhance the electrocatalytic efficiency of Ni-Co catalysts. While mixing other transition metals with Ni-Co is a straightforward and reliable method to improve the OER activity of Ni-Co catalysts, there is still a need for a thorough examination of the design of Ni-Co catalysts with various additional elements. Seawater electrolysis, which utilizes abundant water resources that constitute over 97% of the world’s water, is highly appealing for sustainable energy production. To achieve commercial feasibility, scientists are striving to solve challenges, such as corrosion resistance, highoverpotential, and the need for efficient and durable electrocatalysts.In this study, we fabricated a transition metal-based trimetallic catalyst (CNF), consisting of cobalt (Co), nickel (Ni), and iron (Fe). Furthermore, CNF was doped with chromium (Cr-doped CNF) and tested for the OER in alkaline freshwater and alkaline seawater. Our Cr-doped trimetallic CNF catalyst demonstrates exceptional performance in both seawater and freshwater, with overpotential of 320 mV and 280 mV at 10 mA cm−2 current density, making it a promising candidate for large-scale, sustainable hydrogen production.

Advanced multi-component FeCoCuAlMo intermetallic electrocatalysts for efficient and sustainable hydrogen evolution in alkaline freshwater and seawater

Electrolyzing seawater to produce hydrogen is a promising sustainable energy production technology. The current non-precious metal-based hydrogen evolution reaction (HER) electrocatalysts demonstrate inadequate catalytic activity and poor stability in seawater electrolyte. Therefore, developing stable and efficient non-precious metal-based HER electrocatalysts is a major challenge for achieving sustainable green energy development. This work reports a multi-component intermetallic catalyst FeCoCuAlMo prepared by arc melting and chemical dealloying methods. The electrocatalytic hydrogen evolution performance of catalysts with varying atomic ratios (FeCoCu)20(Al70Mo30)80, (FeCoCu)30(Al70Mo30)70, (FeCoCu)40(Al70Mo30)60, and (FeCoCu)50(Al70Mo30)50 in alkaline seawater and alkaline electrolyte was studied. The findings indicate that these catalysts primarily consist of AlMo3 and (Cu0.35Fe0.35Co0.3)Al, among which the dealloyed (FeCoCu)30(Al70Mo30)70 exhibits excellent catalytic activity with overpotentials of 137.54 and 116.91 mV at a current density of 100 mA/cm2 in alkaline seawater and alkaline electrolyte, respectively, outperforming most catalysts. Additionally, it demonstrated long-term stability in alkaline seawater and alkaline electrolyte for 250 and 400 h without significant decay at overpotentials of 236 mV and 276 mV, respectively. This improved performance can be attributed to the unique structure of the multi-component intermetallic compound, which provides good thermodynamic stability and synergistic effects among its constituents, thereby enhancing HER performance. Within this multi-component intermetallic compound, AlMo3 particles serve as the primary conductive medium to accelerate electron transfer, while (Cu0.35Fe0.35Co0.3)Al serves as the main active site, resulting in a stable structure that provides the catalyst with high catalytic activity and good stability. Thus, the (FeCoCu)30(Al70Mo30)70 electrocatalyst is a promising candidate for seawater electrolysis aimed at hydrogen production.

Bimetal Metaphosphate/Molybdenum Oxide Heterostructure Nanowires for Boosting Overall Freshwater/Seawater Splitting at High Current Densities.

Exploring excellent non-noble bifunctional electrocatalysts for freshwater/seawater splitting at high current densities has attracted extensive interest owing to strong anodic oxidation and severe chloride corrosion challenges. Herein, hierarchical bimetal Ni-Co metaphosphate/molybdenum oxide heterostructure nanowires (NiCoMoPO) are rationally designed and fabricated to efficiently boost oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline freshwater/seawater, where the favorable electronic structure from heterostructures, signified by X-ray absorption spectra, endows NiCoMoPO with the enhanced intrinsic activity, while its hierarchical nanowire structure and heterostructures provide abundant active sites. Additionally, the PO3 - improves the chloride-corrosion resistance and efficiently facilitates the OER kinetics verified by theoretical and experimental studies. Therefore, NiCoMoPO drives 1000mA cm-2 at low overpotentials of 467 and 442mV for OER and HER in alkaline freshwater respectively, as well as a small cell voltage of 2.135V for overall freshwater splitting with robust durability of 300h. Impressively, due to the strong corrosion resistance, at 500mA cm-2 of overall seawater splitting, NiCoMoPO maintains almost 2.096V for 1200h, indicating promising practical applications. This work sheds light on the rational design and fabrication of outstanding electrocatalysts at high current densities of seawater/freshwater splitting.

S-doped amorphous multi-metal borophosphates for efficient alkaline seawater oxidation with a high corrosion resistance

Direct seawater splitting is a promising strategy for the production of green hydrogen to address water shortage and environmental concerns. However, the primary obstacle in direct seawater splitting is directly related to the high selectivity and durability of oxygen evolution reaction (OER) electrocatalysts. In this study, we developed sulfur-doped multimetal (Ni, Fe, and Co) borophosphates (BPOs) as high-performance OER catalysts for alkalized seawater electrolytes. The incorporated sulfur atoms act as precursors to enhance the corrosion resistance, as they form negatively charged polyanionic surface layers that block the chloride ions. The best catalyst demonstrates an overpotential of 278 mV in alkaline freshwater and 292 mV in alkalized seawater electrolytes when subjected to a current density of 100 mA cm−2. The overpotential disparity between the two media was only 14 mV, suggesting that the material has substantial resistance to chloride corrosion. Furthermore, excellent electrochemical durability was attained for the sulfurized and amorphized multi-metal BPOs, highlighting their high potential as promising catalysts for seawater oxidation.

Engineering interfacial sulfur migration in transition-metal sulfide enables low overpotential for durable hydrogen evolution in seawater

Hydrogen production from seawater remains challenging due to the deactivation of the hydrogen evolution reaction (HER) electrode under high current density. To overcome the activity-stability trade-offs in transition-metal sulfides, we propose a strategy to engineer sulfur migration by constructing a nickel-cobalt sulfides heterostructure with nitrogen-doped carbon shell encapsulation (CN@NiCoS) electrocatalyst. State-of-the-art ex situ/in situ characterizations and density functional theory calculations reveal the restructuring of the CN@NiCoS interface, clearly identifying dynamic sulfur migration. The NiCoS heterostructure stimulates sulfur migration by creating sulfur vacancies at the Ni3S2-Co9S8 heterointerface, while the migrated sulfur atoms are subsequently captured by the CN shell via strong C-S bond, preventing sulfide dissolution into alkaline electrolyte. Remarkably, the dynamically formed sulfur-doped CN shell and sulfur vacancies pairing sites significantly enhances HER activity by altering the d-band center near Fermi level, resulting in a low overpotential of 4.6 and 8 mV at 10 mA cm−2 in alkaline freshwater and seawater media, and long-term stability up to 1000 h. This work thus provides a guidance for the design of high-performance HER electrocatalyst by engineering interfacial atomic migration.

Dual Doping of B and Fe Activated Lattice Oxygen Participation for Enhanced Oxygen Evolution Reaction Activity in Alkaline Freshwater and Seawater

AbstractThe exploitation of highly activity oxygen evolution reaction (OER) electrocatalysts is critical for the application of electrocatalytic water splitting. Triggering the lattice oxygen mechanism (LOM) is expected to provide a promising pathway to overcome the sluggish OER kinetics, however, effectively enhancing the involvement of lattice oxygen remains challenging. In this study, the fabrication of B, Fe co‐doped CoP (B, Fe─CoP) nanofibers is reported, which serve as highly efficient OER electrocatalyst through phosphorization and boronation treatment of Fe‐doped Co3O4 nanofibers. Experimental results combined with theoretical calculations reveal that simultaneous incorporation of both B and Fe can more effectively trigger the participation of lattice oxygen in CoFe oxyhydroxides reconstructed from B, Fe─CoP nanofibers compared to incorporating only B or Fe. Therefore, the optimized B, Fe─CoP nanofibers exhibit superb OER activity with low overpotentials of 361 and 376 mV at 1000 mA cm−2 in alkaline freshwater and alkaline natural seawater, respectively. The present work provides significant guidelines and innovative design concepts for the development of OER electrocatalysts following the LOM pathway.

Superhydrophilic NiFe-LDH@Co9S8-Ni3S2/NF heterostructures for high-current-density freshwater/seawater oxidation electrocatalysts

Designing oxygen evolution reaction (OER) electrocatalysts with high efficiency and stability at large current densities is paramount for achieving hydrogen production through water splitting. In this study, a heterostructured NiFe-LDH coating Co9S8-Ni3S2 grown on nickel foam (NiFe-LDH@Co9S8-Ni3S2/NF) was successfully synthesized. The distinctive hierarchical structures featuring abundant heterointerfaces can effectively expose abundant active sites. The synergistic effect and strong electronic interaction between Co9S8-Ni3S2 and NiFe-LDH can enhance the intrinsic OER activity. Furthermore, the superhydrophilic characteristic of NiFe-LDH@Co9S8-Ni3S2/NF favors close contact between the electrode and electrolyte. Due to these advantages, NiFe-LDH@Co9S8-Ni3S2/NF can provide distinguished OER activity with low overpotentials of 274 mV in alkaline freshwater and 298 mV in alkaline seawater at 1000 mA cm−2, along with outstanding stability at high current density of 500 mA cm−2 over 200 h in both solutions. This study offers a valuable insight into fabricating high-performance OER electrocatalysts for seawater electrolysis in industrial applications.

Nanoneedles like FeP engineered on Ni-Foam as an effective catalyst towards overall alkaline freshwater, urea, and seawater splitting

The slow kinetics of electrochemical urea and water oxidation processes at electrode surfaces, which can be recognised as promising resources for pollution-free hydrogen energy production, motivate the scientific community to design and fabricate low-cost, high-efficiency electrocatalysts. Because the performance of electrocatalysts is dependent on their structural, morphological, and electronic properties, herein, the tuning of these properties of Fe3O4@Ni-Foam via phosphorylation and sulfurization, yielding iron phosphide (FeP@Ni-Foam) and iron sulphide (FeS@Ni-Foam), with nanoneedles (along with microstructures) and nanoflower-like morphologies, respectively, is investigated. Among all the prepared samples, FeP is found to be the most effective electrocatalyst for the oxygen evolution process (OER), the urea oxidation reaction (UOR), and seawater electrolysis. The overpotentials observed for OER, UOR, and seawater splitting are significantly reduced when using FeP as compared to other materials, with values of 207 mV, 133 mV, and 287.1 mV, respectively, at a current density of 10 mA/cm2. The enhanced catalytic activity of FeP over FeS and Fe3O4 is attributed to morphological changes, improved electronic conductivity, and exceptional endurance. The theoretical studies reveal that FeP has a better density of states over the fermi level than FeS and Fe3O4, lowering the energy barriers for the OER and UOR processes and demonstrating significant catalytic activity towards these processes. This work demonstrates that phosphorylation and sulfurization treatments can alter morphologies and electrical characteristics, hence improving the catalytic activity of the materials.

Tuning d–p Orbital Hybridization of NiMoO4@Mo15Se19/NiSe2 Core‐Shell Nanomaterials via Asymmetric Coordination Interaction Enables the Water Oxidation Process

AbstractThe electrocatalytic performance of MoNi‐based nanomaterials undergo selenization has garnered significant interest due to their modified electronic structure, while still posses certain challenges for obtained bimetallic selenides. Here, a novel MoNi‐based electrocatalyst of NiMoO4@Mo15Se19/NiSe2 core‐shell nanomaterials is constructed to promote the desorption of OOH* which can facilitate the water oxidation process. NiMoO4@Mo15Se19/NiSe2 core‐shell nanoarrays show that the “cores” are mainly NiMoO4 nanorods while the “shells” are the bimetallic selenides nanoflakes, which are super architectures that can expand more active sites and accelerate the electron transfer. Moreover, the hybridization interaction between Ni 3d, Mo 4d, and Se 4p orbitals leads to an asymmetric distribution of electric clouds, which decreases the adsorption energy and transformation of oxygen‐containing species. Electrochemical data displays that the overpotentials of NiMoO4@Mo15Se19/NiSe2 core‐shell nanomaterials are only 195 mV, 220 mV, and 224 mV for oxygen evolution reaction (OER) in alkaline freshwater, alkaline simulated seawater, and alkaline natural seawater. The current density decay is negligible after 100 h stability at about 1.46 V with a three‐electrode system in alkaline natural seawater. The low cost and the unique MoNi‐based bimetallic selenides in this work provide a more constructive solution for designing efficient and stable OER catalysts in the future.

Moderately Reconstructed Ternary Metal Nitride Nanoparticles for Highly Efficient and Robust Freshwater and Seawater Oxidation under Industrial Current Density

Transition metal nitrides (TMNs) electrocatalysts experience rapid performance degradation during oxygen evolution reaction (OER) due to severe and irreversible electrochemical reconstruction, impeding their practical application in electrochemical water splitting. To address this issue, ternary metal (Ni, Fe, Cr) nitride nanoparticles on spongy nitrogen‐doped disordered carbon skeleton electrocatalyst (NFCN/C) is synthesized using a novel one‐pot pyrolysis of eutectic mixture method. The ionomer‐free NFCN/C electrode, which undergoes moderate electrochemical reconstruction, demonstrates high OER performance in both alkaline freshwater and seawater solutions, achieving a current density of 250 mA cm−2 with low overpotentials of 349 and 364 mV, respectively. The NFCN/C anode with Pt/C cathode delivers 10 mA cm−2 at a low cell voltage of 1.49 V and exhibits long‐term durability of 450 h at 500 mA cm−2. In situ Raman spectroscopy and ultraviolet photoelectron spectroscopy (UPS), along with pre‐ and post‐characterizations, elucidate that both high electrocatalytic activity and robustness of NFCN/C for OER stem from the proposed intrinsic strategy integrating physical and electronic structures. This work paves the way for designing highly efficient and robust TMNs electrocatalysts with moderate electrochemical reconstruction for industrial freshwater and seawater electrolysis.

Anionic phosphorous and sulfur regulate self-supported Ni-Fe-based electrocatalyst for water-splitting under large current density

Nickel-iron based (Ni-Fe) catalysts are widely used in the electrolysis of water due to their high activity and low cost. However, the development of highly active non-precious metal catalysts is still a great challenge. Herein, self-supported nickel–iron phosphide is fabricated through a sulfurization/phosphorization approach (Ni-Fe-P-S-1/Ni-Fe-P-S-2). The prepared catalysts show excellent catalytic performance and stability. The HER performance of Ni-Fe-P-S-1 reaches 500 mA cm−2 with small overpotentials of 289 mV in alkaline freshwater. Meanwhile, the Ni-Fe-P-S-2 requires 312 and 375 mV to reach 500 mA cm−2 in alkaline freshwater and alkaline seawater for OER. Remarkably, at the current density of 500 mA cm−2, the Ni-Fe-P-S-1||Ni-Fe-P-S-2 electrolyzer requires only 1.85 V in alkaline. Interestingly, sustainable energies can power the electrolyzer effectively. The work provides methods for potentially promising and cost-effective electrocatalysts.

Unique CoP Microflower Decorated with Phosphorous‐Enriched PtP2 onto Nickel Foam with Interfacial Electronic Interactions to Boost Alkaline Water‐Splitting

AbstractThe development of stable and efficient electrocatalysts for overall freshwater/seawater water‐splitting has received significant attention. In this study, the fabrication and electrocatalytic properties of phosphorus‐enriched PtP2 dispersed on CoP (PtP2/CoP) for HER and OER in both alkaline fresh/seawater media are described. Physical characterization and density functional theory calculations reveal that strong electronic interfacial interactions between PtP2 and CoP optimized the reaction kinetics by regulating the adsorption/desorption of intermediates and the cleavage of reactants. Additionally, operando electrochemical impedance spectroscopy reveals that PtP2/CoP significantly decreased phase angle with increasing applied potential compared with CoP, demonstrating that the construction of heterostructure provides a faster charge transfer on the surface and in the inner layer. Notably, the catalyst only requires overpotentials of 101 and 298 mV to achieve a benchmark of 100 mA cm−2 in alkaline freshwater for HER and OER. Moreover, the prepared catalyst featured overpotentials of 108 and 330 mV in an alkaline seawater electrolyte. Furthermore, a stable and high‐efficiency water electrolysis operation can be achieved using PtP2/CoP as both the anode and cathode (1.63 V@100 mA cm−2) coupled with satisfactory durability. This finding provides a deeper comprehension of the interaction of Pt‐less compounds and matrix in electrocatalysis for bifunctional electrocatalysts.

Triphasic Ni2P-Ni12P5-Ru with Amorphous Interface Engineering Promoted by Co Nano-Surface for Efficient Water Splitting.

This research designs a triphasic Ni2P-Ni12P5-Ru heterostructure with amorphous interface engineering strongly coupled by a cobalt nano-surface (Co@NimPn-Ru) to form a hierarchical 3D interconnected architecture. The Co@NimPn-Ru material promotes unique reactivities toward hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media. The material delivers an overpotential of 30mV for HER at 10mAcm-2 and 320mV for OER at 50 mAcm-2 in freshwater. The electrolyzer cell derived from Co@NimPn-Ru(+,-) requires a small cell voltage of only 1.43V in alkaline freshwater or 1.44V in natural seawater to produce 10mA cm-2 at a working temperature of 80°C, along with high performance retention after 76h. The solar energy-powered electrolyzer system also shows a prospective solar-to-hydrogen conversion efficiency and sufficient durability, confirming its good potential for economic and sustainable hydrogen production. The results are ascribed to the synergistic effects by an exclusive combination of multi-phasic crystalline Ni2P, Ni12P5, and Ru clusters in presence of amorphous phosphate interface attached onto cobalt nano-surface, thereby producing rich exposed active sites with optimized free energy and multi open channels for rapid charge transfer and ion diffusion to promote the reaction kinetics.