Seawater Electrolysis Research Articles

Construction of 3D hollow NiCo-layered double hydroxide nanostructures for high-performance industrial overall seawater electrolysis

Construction of 3D hollow NiCo-layered double hydroxide nanostructures for high-performance industrial overall seawater electrolysis

Evidence of dark oxygen production at the abyssal seafloor

Deep-seafloor organisms consume oxygen, which can be measured by in situ benthic chamber experiments. Here we report such experiments at the polymetallic nodule-covered abyssal seafloor in the Pacific Ocean in which oxygen increased over two days to more than three times the background concentration, which from ex situ incubations we attribute to the polymetallic nodules. Given high voltage potentials (up to 0.95 V) on nodule surfaces, we hypothesize that seawater electrolysis may contribute to this dark oxygen production.

Taking Advantage of Potential Coincidence Region: Insights into Gas Production Behavior in Advanced Self-Activated Hydrazine-Assisted Alkaline Seawater Electrolysis.

Water electrolysis assisted by hydrazine has emerged as a prospective energy conversion method for achieving efficient hydrogen generation. Due to the potential coincidence region (PCR) between the hydrogen evolution reaction (HER) and the electro-oxidation of hydrazine, the hydrazine oxidation reaction (HzOR) offers distinct advantages in terms of strategy amalgamation, device architecture, and the broadening of application horizons. Herein, we report a bifunctional electrocatalyst of interfacial heterogeneous Fe2P/Co2P microspheres supported on Ni foam (FeCoP/NF). Benefiting from the strong interfacial coupling effect between Fe2P and Co2P and the three-dimensional microsphere structure, FeCoP/NF exhibits outstanding bifunctional electrocatalytic performance, achieving 10 mA cm-2 with low overpotentials of 10 and 203 mV for HER and HzOR, respectively. Utilizing FeCoP/NF for both electrodes in HzOR-assisted water electrolysis results in significantly reduced potentials of 820 mV for 1 A cm-2 in contrast to the electro-oxidation of alternative chemical substrates. The presence of a potential coincidence region makes the application of self-activated seawater electrolysis realistic. The gas production behavior at different current densities in this interesting hydrogen production system is discussed, and some rules that are distinguished from conventional water electrolysis are summarized. Furthermore, a new self-powered hydrogen production system with a direct hydrazine fuel cell, rechargeable Zn-hydrazine battery, and hydrazine-assisted seawater electrolysis is proposed, emphasizing the distinct benefits of HzOR and its potential role in electrochemical energy conversion technologies powered by renewable sources.

Rational design of highly corrosion-resistant chromium hydroxide coupled amorphous-crystalline heterostructure to achieve efficient and stable seawater oxygen evolution

The pressing issues of global energy scarcity and water shortages can be substantially mitigated through the electrolysis of seawater. In this study, we synthesized a unique lamellar amorphous-crystalline heterostructure electrocatalyst by integrating the amorphous chromium hydroxide (Cr-OH) with the crystalline NiFe layered double hydroxides (NiFe LDH). The resulting Cr-OH/NiFeLDH@NF exhibited an exceptionally low oxygen evolution reaction (OER) overpotential and strong corrosion resistance. The development of the crystalline-amorphous heterointerface significantly influenced electronic coupling and enhanced electron transfer rates. Through the methanol response mechanism, it was demonstrated that the Cr-OH enhanced the catalyst’s corrosion resistance in chloride-rich environments and significantly extended its durability in seawater. Operative Raman spectroscopy confirmed that the high OER activity and corrosion resistance of Cr-OH/NiFeLDH@NF originated from the preferential oxidation of the outer Cr-OH layer, which promoted the electrochemical oxidation of Ni2+ to Ni4+, and the stable Cl− resistant environment formed by the in-situ generated and dissolved CrO42−.

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.

The cobalt-based metal organic frameworks array derived CoFeNi-layered double hydroxides anode and CoP/FeNi2P heterojunction cathode for ampere-level seawater overall splitting

The seawater electrolysis technology powered by renewable energy is recognized as the promising “green hydrogen” production method to solve serious energy and environmental problems. The lack of low-cost and ampere-level current OER (oxygen evolution reaction) and HER (hydrogen evolution reaction) catalysis limits their industrial application. In this work, a unique tri-metal (Co/Fe/Ni) layered double hydroxide hollow array anode catalyst (CFN-LDH/NF) and the CoP/FeNi2P heterojunction hollow array cathode are successfully prepared via one in-situ growth of Co-MOF on nickel foam (Co-MOF/NF) precursor, which exhibits excellent catalytic performance. The η1000 values of 352 and 392 mV are achieved for CFN-LDH/NF (OER catalyst) in 1.0 M KOH and alkaline seawater solution, respectively. The CFNP/NF with a low overpotential of 281 mV is required to reach 1000 mA cm−2 current density for HER in 1.0 M KOH solution, while the η1000 in alkaline seawater solution is 312 mV. The CFN-LDH/NF||CFNP/NF electrolyzer exhibits excellent long-term durability over 100 h, achieving current density of 500 mA cm−2 at 1.825 V in 1.0 M KOH solution. The construction of hollow tri-metal LDH and phosphides heterostructures may open a new and relatively unexplored path for fabricating high performance seawater splitting catalysis.

Employing shielding effect of intercalated cinnamate anion in NiFe LDH for stable and efficient seawater oxidation

Seawater electrolysis is a valuable and promising method for clean hydrogen generation. The corrosion induced from active anions in seawater and the competition between oxygen evolution reaction (OER) and chloride evolution reaction (CER) limit the overall efficiency of seawater electrolysis. Herein, shielding strategy was introduced with cinnamate anion (CNA) intercalated in NiFe LDHs (NiFe LDHCNAs) for efficient alkaline seawater oxidation. It displays an outstanding OER performance with 247 mV and 258 mV to achieve the current density of 50 mA/cm2 in 1 M KOH electrolyte and alkaline seawater (1 M KOH + real seawater), respectively. Meanwhile, CNA-NiFe LDH presents excellent durability (over 72 h at 100 mA/cm2) in 1 M KOH electrolyte and alkaline seawater. The enhanced catalytic performance and durability can ascribe to the enlarged interlayer spacing by CNA intercalation and shielding effect of CNA against chlorine corrosion. This research offers a novel approach to the design of efficient electrocatalysts for hydrogen production from seawater electrolysis.

A Study of the EH36 Surface Sediment Layer under Joint Protection from Seawater Electrolysis Antifouling and Impressed Current Cathode Protection (ICCP) in a Marine Environment

A joint protection device for seawater electrolysis antifouling and ICCP was constructed, and comparative experiments were conducted to study the composition of the EH36 surface deposition layer under joint protection in a marine environment. Surface morphology analysis, energy-dispersive spectroscopy (EDS) imaging analysis, and X-ray diffraction (XRD) composition analysis were performed on the surface deposition layers of the experimental samples. The experimental results showed that under joint protection, a sedimentary layer was rapidly formed on the surface of EH36 to isolate the seawater medium, and this layer was mainly composed of Mg(OH)2 and a small amount of CaCO3. There was no corrosion on the surface of the EH36 substrate. When only ICCP was used, a relatively thin layer of calcium magnesium was deposited on the surface of EH36. Marine fouling organisms adhere to the surface of calcium and magnesium sedimentary layers and the EH36 substrate, and their attachment affects the formation of calcium and magnesium sedimentary layers. Moreover, marine fouling organisms cause corrosion on the surface of the EH36 substrate. The joint protection of seawater electrolysis antifouling and ICCP can simultaneously prevent electrochemical corrosion and marine biological fouling corrosion on the surface of EH36.

Electrocatalytic Acetylene Hydrogenation in Concentrated Seawater at Industrial Current Densities.

Electrocatalytic acetylene hydrogenation to ethylene (E-AHE) is a promising alternative for thermal-catalytic process, yet it suffers from low current densities and efficiency. Here, we achieved a 71.2 % Faradaic efficiency (FE) of E-AHE at a large partial current density of 1.0 A cm-2 using concentrated seawater as an electrolyte, which can be recycled from the brine waste (0.96 M NaCl) of alkaline seawater electrolysis (ASE). Mechanistic studies unveiled that cation of concentrated seawater dynamically prompted unsaturated interfacial water dissociation to provide protons for enhanced E-AHE. As a result, compared with freshwater, a twofold increase of FE of E-AHE was achieved on concentrated seawater-based electrolysis. We also demonstrated an integrated system of ASE and E-AHE for hydrogen and ethylene production, in which the obtained brine output from ASE was directly fed into E-AHE process without any further treatment for continuously cyclic operations. This innovative system delivered outstanding FE and selectivity of ethylene surpassed 97.0 % and 97.5 % across wide-industrial current density range (≤ 0.6 A cm-2), respectively. This work provides a significant advance of electrocatalytic ethylene production coupling with brine refining of seawater electrolysis.

Electrocatalytic Acetylene Hydrogenation in Concentrated Seawater at Industrial Current Densities

AbstractElectrocatalytic acetylene hydrogenation to ethylene (E‐AHE) is a promising alternative for thermal‐catalytic process, yet it suffers from low current densities and efficiency. Here, we achieved a 71.2 % Faradaic efficiency (FE) of E‐AHE at a large partial current density of 1.0 A cm−2 using concentrated seawater as an electrolyte, which can be recycled from the brine waste (0.96 M NaCl) of alkaline seawater electrolysis (ASE). Mechanistic studies unveiled that cation of concentrated seawater dynamically prompted unsaturated interfacial water dissociation to provide protons for enhanced E‐AHE. As a result, compared with freshwater, a twofold increase of FE of E‐AHE was achieved on concentrated seawater‐based electrolysis. We also demonstrated an integrated system of ASE and E‐AHE for hydrogen and ethylene production, in which the obtained brine output from ASE was directly fed into E‐AHE process without any further treatment for continuously cyclic operations. This innovative system delivered outstanding FE and selectivity of ethylene surpassed 97.0 % and 97.5 % across wide‐industrial current density range (≤ 0.6 A cm−2), respectively. This work provides a significant advance of electrocatalytic ethylene production coupling with brine refining of seawater electrolysis.

Enabling direct seawater electrolysis by redox-inactive amphiphilic amines via chloride sequestration

Sustainable hydrogen production requires large amounts of treated freshwater and precious metals. Direct electrolysis of seawater without additional electrolytes can be a practical approach to address these limitations, however, it usually suffers from kinetically favored chlorine evolution reaction (CER), which is detrimental to an electrolysis system. We report that organocatalytic amphiphilic diamines play a crucial role in preventing the generation of chlorine gas. The feasibility of direct seawater electrolysis was demonstrated with pH-responsive organic amines, which can self-assemble under neutral and acidic conditions. Electrochemical analysis of our electrolysis in saline solutions revealed that (electro)chemical stability of amphiphilic diamines was responsible for preventing CER and hypochlorite formation. Our findings may have significant implications for the chemical industry and energy sectors as the world transitions towards renewable energy sources.

Hydrogen production from seawater electrolysis: Challenges, strategies and future

Hydrogen production from seawater electrolysis: Challenges, strategies and future

Directional surface reconstruction of C and S Co-Doped Co2VO4/CoP for the cooperative enhancement of hydrogen production via seawater electrolysis

The endeavor to architect bifunctional electrocatalysts that exhibit both exceptional activity and durability heralds an era of boundless potential for the comprehensive electrolysis of seawater, an aspiration that, nevertheless, poses a substantial challenge. Within this work, we describe the precise engineering of a three-dimensional interconnected nanoparticle system named SCdoped Co2VO4/CoP (SCCo2VO4), achieved through a meticulously arranged hydrothermal treatment sequence followed by gas-phase carbonization and phosphorization. The resulting SCCo2VO4 electrode exhibits outstanding bifunctional electrocatalytic stability, attributed to the strategic anionic doping and abundant heterogeneous interfaces. Doping not only adjusts the electronic structure, enhancing electron transfer efficiency but also optimizes the surface-active sites. This electrode prodigiously necessitated an extraordinarily minimal overpotential of merely 92 and 350 mV to attain current densities of 10 and 50 mA cm−2 for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, in 1 M KOH solution. Noteworthily, when integrated into an electrolyzer for the exhaustive splitting of seawater, the SCP-Co2VO4 manifested an exceptionally low cell voltage of 2.08 V@50 mA cm−2 and showcased a durability that eclipses that of most hitherto documented nickel-based bifunctional materials. Further elucidation through Density Functional Theory (DFT) analyses underscored that anion doping and the inherent heterostructure adeptly optimize the Gibbs free energy of intermediates comprising hydrogen, chlorine, and oxygen (manifested as OH, O, OOH) within the HER and OER paradigms, thus propelling the electrochemical kinetics of seawater splitting to unprecedented velocities. These revelations unfurl a pioneering design philosophy for the creation of cost-effective yet superior catalysts aimed at the holistic division of water molecules, charting a course towards the realization of efficient and sustainable hydrogen production methodologies.

Cu-mediated electron-rich Ru centers on metal carbides for highly efficient hydrogen production from seawater

Seawater splitting for hydrogen production provides a promising pathway for green energy systems. However, the sluggish kinetics, corrosive ions, and the calcareous deposit seriously impede the wide-scale application of seawater electrolysis. Here, we report a trace amount of Cu-mediated anchoring electron-rich Ru centers on metal carbides (Cu-Ru/WC@C) for efficient hydrogen evolution from corrosive seawater. Benefiting from the conductive, electron-loss, and protophilic capacities of Cu atoms, the created Cu-Ru/WC@C catalyst possesses an electron-rich, anti-corrosive, and low oxophilic microenvironments, which eventually delivers excellent hydrogen evolution activities and anti-corrosion properties in seawater electrolysis. It requires a low overpotential of 392 mV to reach 1 A cm−2 and good long-term stability in alkaline seawater. Notably, the membrane electrolyzer with Cu-Ru/WC@C cathode exhibits outstanding performances for continuous H2 production under 1.875 V with 250 mA cm−2. This approach provides essential insights into the seawater corrosion resistance for cathode materials that match the electrochemical hydrogen production industry.

Fe-NiO/MoO2 and in-situ reconstructed Fe, Mo-NiOOH with enhanced negatively charges of oxygen atoms on the surface for salinity tolerance seawater splitting

Seawater electrolysis is a promising technique for H2 production on a large scale. However, the electrocatalytic activity and stability will be deteriorated as the increase of salt concentrations which happened in the seawater splitting. Herein, through the electrodeposition and rapid Joule heating method, the Fe-NiO/MoO2 heterostructure is designed as a highly active bifunctional electrocatalyst. During the OER possess, Fe-NiO/MoO2 is reconstructed to the Fe, Mo-NiOOH with Fe and Mo co-doping. Based on the theoretical analysis, more electrons were transferred to the O atoms on the surface of Fe, Mo-NiOOH, thereby forming a more negatively charged surface. Moreover, that surface is found to repel Cl− ions while enriching H2O molecules to form a thin water layer on Fe, Mo-NiOOH surface based on molecule dynamics (MD) simulation, thereby improving the anti-corrosion capacity of Fe, Mo-NiOOH. The reconstructed Fe, Mo-NiOOH achieved an overpotential of 399 mV at 1000 mA cm−2 in alkaline seawater, and the increase of overpotential for Fe, Mo-NiOOH was about 0.02 V at 500 mA cm−2 from 0 M to 3 M NaCl in 1 M KOH electrolyte. For the HER, Fe-NiO/MoO2 achieved an overpotential of 169 mV and 417 mV at 100 and 1000 mA cm−2 in alkaline seawater, respectively, and the increase of overpotential for Fe-NiO/MoO2 was about 0 mV at 500 mA cm−2 from 0 M to 3 M NaCl in 1 M KOH electrolyte. This work sheds fresh light into the development of efficient electrocatalysts for salinity tolerance seawater splitting.

Enthralling Anodic Protection by Molybdate on High-Entropy Alloy-Based Electrocatalyst for Sustainable Seawater Oxidation.

Efficient and sustainable seawater electrolysis is still limited due to the interference of chloride corrosion at the anode. The designing of suitable electrocatalysts is one of the crucial ways to boost electrocatalytic activity. However, the approach may fall short as achieving high current density often occurs in chlorine evolution reaction (CER)-dominating potential regions. Thereby, apart from developing an OER-active high-entropy alloy-based electrocatalyst, the present study also offers a unique way to protect anode surface under high current density or potential by using MoO4 2- as an effective inhibitor during seawater oxidation. The wide variation of d-band center of high-entropy alloy-based electrocatalyst allows great oxygen evolution reaction (OER) proficiency exhibiting an overpotential of 230mV at current density of 20mA cm-2. Besides, the electrocatalyst demonstrates impressive stability over 500h at high current density of 1 A cm-2 or at a high oxidation potential of 2.0V versus RHE in the presence of a molybdate inhibitor. Theoretical and experimental studies reveal MoO4 2- electrostatically accumulated at anode surface due to higher adsorption ability, thereby creating a protective layer against chlorides without affecting OER.

Routes to Avoiding Chlorine Evolution in Seawater Electrolysis: Recent Perspective and Future Directions

Routes to Avoiding Chlorine Evolution in Seawater Electrolysis: Recent Perspective and Future Directions

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.

In-situ direct seawater electrolysis using floating platform in ocean with uncontrollable wave motion

Direct hydrogen production from inexhaustible seawater using abundant offshore wind power offers a promising pathway for achieving a sustainable energy industry and fuel economy. Various direct seawater electrolysis methods have been demonstrated to be effective at the laboratory scale. However, larger-scale in situ demonstrations that are completely free of corrosion and side reactions in fluctuating oceans are lacking. Here, fluctuating conditions of the ocean were considered for the first time, and seawater electrolysis in wave motion environment was achieved. We present the successful scaling of a floating seawater electrolysis system that employed wind power in Xinghua Bay and the integration of a 1.2 Nm3 h−1-scale pilot system. Stable electrolysis operation was achieved for over 240 h with an electrolytic energy consumption of 5 kWh Nm−3 H2 and a high purity (>99.9%) of hydrogen under fluctuating ocean conditions (0~0.9 m wave height, 0~15 m s−1 wind speed), which is comparable to that during onshore water electrolysis. The concentration of impurity ions in the electrolyte was low and stable over a long period of time under complex and changing scenarios. We identified the technological challenges and performances of the key system components and examined the future outlook for this emerging technology.

Reconstructed anti-corrosive and active surface on hierarchically porous carbonized wood for efficient overall seawater electrolysis

Reconstructed anti-corrosive and active surface on hierarchically porous carbonized wood for efficient overall seawater electrolysis