Underwater Contact Angle Research Articles

Cotton fiber coated with a novel lysozyme-polymer brush conjugates for efficient oil-water separation

In this work, for the first time, a conjugate was generated by grafting poly(oligo(ethylene glycol)methacrylate) (POEGMA) on lysozyme (Lyso). Followed by a phase transition of Lyso (PTL) in the presence of tris(2-carboxyethyl)phosphine (TCEP), the resulting new film (PTL-POEGMA) was coated on cotton fibers to give PTL-POEGMA@cotton fiber. PTL-POEGMA film improved hydrophilicity and underwater superoleophobicity (underwater contact angle greater than 150º) of cotton fiber, which has good separation effect on oil-water mixture (with a separation efficiency of more than 99 %). In addition, the PTL-POEGMA@cotton fiber also has efficient antimicrobial adhesion effect and anti-oil (dichloromethane as an example) adhesion effect. Modified cotton fibers are expected to be used in the oil-water separation process of wastewater treatment. This PTL-POEGMA film is expected to be a new and effective modified material for oil-water separation medium.

TiO2 modified basalt fiber cloth with superhydrophilicity and underwater superoleophobicity for oil-water separation

Titanium mesh, stainless steel mesh and other substrate materials for oil-water separation membranes have excellent acid and alkali resistance. However, the preparation process pollutes the environment and is costly. Therefore there is an urgent need for an economical and eco-friendly new material to replace them. Here, this research found that eco-friendly basalt fibers can replace them. In this work, superhydrophilic/underwater superoleophobic TiO2/basalt fiber cloths were prepared by solvothermal method. It has a contact angle of 0° for water in air and maximum 161° for n-hexadecane underwater. The oil-water separation efficiency was up to 99.75%, which indicated its efficient oil-water separation capability. The underwater n-hexadecane contact angle was 154° after immersing it in 6 mol of HCl and NaOH for 2 h respectively. This indicates that it has excellent acid and alkali resistance. And with titanium mesh, stainless steel mesh separation membrane acid and alkali resistance is not much different. However, the price is only one percent of titanium mesh. In addition, the softness of basalt fiber can be folded to enhance the pressure-bearing capacity. Therefore, this work provides a green, acid and alkali resistant, inexpensive new material for oil-water separation membranes, which has great potential in the field of oil-water separation.

PVDF-Halloysite-Ceria multifunctional membrane for one-step treatment to industrial effluent

Industrial wastewater, containing diverse pollutants like dyes and oils, poses detrimental environmental challenges. Membrane technology addresses this complexity well but requires tailored nanofiller modifications that enhance hydrophilicity, oleophobicity, and antifouling potential for efficient separation. In this context, our work focuses on the development of mixed matrix membranes (PV-H-C) – PVDF, halloysite nanotubes (HNTs), and ceria nanoparticles – for effective dye and oil-water emulsion separation, enabling high flux recovery. The tubular structure of HNTs, with a lumen, enables the encapsulation and controlled distribution of ceria nanoparticles, preventing their agglomeration and leading to more uniform dispersion within the membrane matrix. HNTs porous structure, high surface area, and numerous adsorption sites within its nanotubes excel in rapid dye adsorption and ceria’s inherent hydrophobic properties along with low surface energy, forms a barrier against oil adhesion and spreading. Optimal results were achieved by loading 2% HNT and 1% ceria in the PVDF matrix, ensuring improved membrane performance. HNTs enhanced hydrophilicity and achieved pure water permeate flux of 1698 L/m2.h.bar. Developed membranes are super-oleophobic with an underwater contact angle of 132° + 3° and show a 100% increase in dyes and oils separation efficiency as compared to the pristine PVDF membranes. This unique integration of ceria with halloysite nanotubes in PV-H-C membranes is pivotal, bestowing exceptional anti-fouling characteristics and reusability, while providing a one-step, comprehensive solution for the effective treatment of complex industrial wastewater that encompasses both oil and complex dyes.

Hollow NiMo-based nitride heterojunction with super-hydrophilic/aerophobic surface for efficient urea-assisted hydrogen production

Hydrogen evolution reaction (HER) and urea oxidation reaction (UOR) are key reactions of the water-cycling associated catalytic process/device. The design of catalysts with a super-hydrophilic/aerophobic structure and optimized electron distribution holds great promise. Here, we have designed a three-dimensional (3D) hollow Ni/NiMoN hierarchical structure with arrayed-sheet surface based on a one-pot hydrothermal route for efficient urea-assisted HER based on a simple hydrothermal process. The Ni/NiMoN catalyst exhibits super-hydrophilic/aerophobic properties with a small droplet contact angle of 6.07° and an underwater bubble contact angle of 155.7°, thus facilitating an escape of bubbles from the electrodes. Density functional theory calculations and X-ray photoelectron spectroscopy results indicate the optimized electronic structure at the interface of Ni and NiMoN, which can promote the adsorption/desorption of reactants and intermediates. The virtues combining with a large specific surface area endow Ni/NiMoN with efficient catalytic activity of low potentials of 25 mV for HER and 1.33 V for UOR at 10 mA cm−2. The coupled HER and UOR system demonstrates a low cell voltage of 1.42 V at 10 mA cm−2, which is approximately 209 mV lower than water electrolysis.

Robust underwater superoleophobic coatings based on zwitterionic P(CBMAE‐co‐TMSPMA)/SiO2 with anti‐adhesive behavior

AbstractThis study focuses on the surface modification of substrates using a poly(N,N‐dimethyl‐N‐(ethoxycarbonylmethyl)‐N‐[2′‐(methacryloyloxy) ethyl]‐ammonium chloride‐co‐3‐(trimethoxysilyl)propylmethacrylate) P(CBMAE‐co‐TMSPMA) and ethyl orthosilicate (TEOS). By covalently bonding the Si‐OH pendant of the copolymer with hydroxyl residues on the material's surface, a stable polymer coating is formed. The properties of P(CBMAE‐co‐TMSPMA) coatings were evaluated using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscope (SEM), and contact angle (CA) meter. The addition of TEOS allows for the regulation of surface roughness. With the increase of TEOS content, the contact angle of underwater oil first increased and then decreased. The water contact angles were 8°, the underwater superoleophobic contact angle reached 168°, and the number of adherent platelets and Escherichia coli were significantly reduced to 7.5% and 5% on the surface of the coating, respectively. After undergoing simultaneous hydrolysis, the superoleophobic contact angle of P(CBMAE‐co‐TMSPMA)/SiO2 coating further increased to 174°. These interesting and robust properties make them promising candidates for biomedical applications.Highlights The underwater superoleophobic coating (contact angles of 174°). The P(CBMAE‐co‐TMSPMA)/SiO2 coating with excellent resistance to oil adhesion. Solve the hydroxyl residue problem. The coating resistance to E. coli and platelet adhesion.

Designing effective underwater self-cleaning surfaces by investigating the oil dewetting ability of hydrophobic and underwater superoleophobic Poly(Diisobutyl Glycolide)-Silica composite surfaces

This study introduces composite thin films of amphiphilic structures to fabricate underwater superoleophobic surfaces. The hydrophobic part of the structure is created by poly(diisobutyl glycolide) thanks to a side chain of isobutyl groups, while the hydrophilic component is formed with hydrophilic silica nanoparticles. Poly(diisobutyl glycolide), having a 77° water contact angle, was obtained through ring-opening polymerization of l-diisobutyl glycolide in a bulk medium, resulting in excellent conversion (97.9 %) and narrow polydispersity (1.47), while maintaining the chiral center. The investigation revealed a notable increment in the underwater hexadecane contact angle from 110° to 160° In contrast, the water contact angle exhibited partial constancy in the air environment because of the augmenting silica content. At a silica content reached up to 30 %, the self-cleaning underwater oil-repellent surface was accomplished, attributable to the phenomenon of the underwater Cassie state, which effectively trapped air within the hierarchical rough structure. Moreover, the surface free energy (SFE) of the composite films was evaluated using both the van Oss-Chaudary-Good and Owens-Wendt methods. Notably, the contact angle of underwater hexadecane decreased with the increase of polar interactions as determined by both methods, owing to the influence of the underwater Cassie state of the hierarchical composite surface.

Electrospun Polysulfone Hybrid Nanocomposite Fibers as Membrane for Separating Oil/Water Emulsion

Commercial polymer membranes are largely utilized to separate oil/water mixtures; however, membrane fouling, flux decline, and short lifetime often inhibit their high performance. In order to resolve these drawbacks of the commercial membranes, we introduce a surface modification strategy following the electrospinning method. Electrospun fibers of polysulfone (PSf)/iron oxide (FeO)/halloysite nanotubes (HNT) nanocomposite are applied to modify the polyether sulfone (PES) standard membrane support surface for developing highly efficient oil/water emulsion separating membranes. This facile and simple spinning process for shorter periods ensures nanocomposite coatings on the standard PES membranes and allows a better oil/water separation. We analyze the structural and morphological characteristics of the modified membrane surface using scanning electron microscopy, Fourier transformation infrared spectroscopy, and X-ray diffraction studies and hydrophilicity from contact angle studies. FeO nanoparticles of 2–5 nm and HNTs of < 50 nm size mixed in PSf produce fibers of 531 ± 162 nm average diameter at a relatively lower applied electrical voltage of 14.5 kV, compared to PSf. Underwater and under-oil contact angle values are used to prove the surface characteristics of the membranes and total organic content (TOC) values for the emulsion separation performance. From PES support to PSf and PSf/HNT-FeO, the TOC values respectively change from 67 to 75 and 79%. We find moderately hydrophilic membranes (PSf/HNT-FeO) resulting in a higher permeate flux (28,447 Lm−2·h−1) and quicker separation performance. We believe this study provides a notable solution to modify the surface of commercial membranes for better emulsion separation performance.

Nanomagnets doped antifouling membrane for fine emulsion separation

Reutilizing domestic and industrial wastewater can be the best solution to global water issues. However, the treatment of oily wastewater is a long-standing problem due to the complex fine emulsion produced by mixing the different types of oils and organic solvents. In this work, nanocomposite membranes were fabricated using phase inversion technique by loading polysulfone matrix with varying amounts of magnetic nanoparticles (MNPs). Developed nanocomposite membrane has shown hydrophilic and super-oleophobic properties with an underwater contact angle of 145 ± 3°. Incorporating MNPs into the Psf membranes enhanced the performance and permeability with the oil rejection efficiency as high as ∼99 %. Psf-MNP composite membranes exhibited remarkable antifouling properties, preventing oil deposition on the membrane surface with improved mechanical properties. Our studies suggest that the developed Psf-MNP nanocomposite membrane shows increased surface functionality, which leads to promising long-term performance and reusability of the membrane.

Cellulose acetate superhydrophobic coatings for efficient oil–water separation using a combination of electrostatic spraying and chemical vapor deposition

AbstractThe efficient and simple separation of oil–water mixtures has been a global challenge due to the growing problem of oily wastewater. To address this issue, various materials with special wetting properties and functionality have been developed in the past decades for oil–water separation. In this study, a superhydrophobic cellulose acetate (CA) functional coating was prepared by electrostatic spraying of CA and chemical vapor deposition of methyltrichlorosilane (MTCS) on a stainless steel mesh (SSM). Water contact angle in air (WCA) of the resulting coating is154° or more, and oil under water contact angle (UWOCA) is 0°. Simultaneously, the separation flux of the resulting coating for oil–water mixtures is as high as 23977.77 L·m−2·h−1, with separation efficiencies exceeding 99%. Due to its excellent water repellency, the CA functional coating can effectively separate oil and water, and can be easily dried for continuous use. Furthermore, the CA functional coating exhibits good stability in salt solutions and acidic environments, making it an ideal material for addressing oily wastewater challenges.Highlights The coating obtained by electrostatic spraying and CVD was superhydrophobic. The separation flux and separation efficiencies of coatings is 23977.77 L·m−2·h−1 and 99%. Coatings remain stable under polar environment conditions (pH = 2–12 and NaCl = 1–3 mol/L).

Novel Anionic-Nonionic Surfactant Based on Water-Solid Interfacial Wettability Control for Residual Oil Development.

Irreversible colloidal asphaltene adsorption layers are formed on formation rock surfaces due to long-term contact with crude oil, and large amounts of crude oil adhere to these oil-wet layers to form residual oil films. This oil film is difficult to peel off due to the strong oil-solid interface effect, which seriously restricts further improvement in oil recovery. In this paper, the novel anionic-nonionic surfactant sodium laurate ethanolamide sulfonate (HLDEA) exhibiting strong wetting control was synthesized by introducing sulfonic acid groups into the nonionic surfactant laurate diethanolamide (LDEA) molecule through the Williamson etherification reaction. The introduction of the sulfonic acid groups greatly improved the salt tolerance and the absolute value of the zeta potential of the sand particles. The experimental results showed that HLDEA altered the wettability of the rock surface from oleophilic to strongly hydrophilic, and the underwater contact angle increased substantially from 54.7 to 155.9°. In addition, compared with LDEA, HLDEA exhibited excellent salt tolerance and enhanced oil recovery performance (the oil recovery was improved by 19.24% at 2.6 × 104 mg/L salinity). Based on nanomechanical experimental results, HLDEA was efficiently adsorbed on the core surfaces and regulated microwetting. Moreover, HLDEA effectively reduced the adhesion force between the alkane chains and the core surface, which facilitated residual oil stripping and oil displacement. This new anionic-nonionic surfactant affording great oil-solid interface wetting control has practical significance for the efficient development of residual oil.

In situ preparation of spindle calcium carbonate-chitosan/poly (vinyl alcohol) anti-biofouling hydrogels inspired by shellfish

Hydrogels have received intensive interest in the marine environment due to their excellent anti-biofouling properties. In this work, a series of spindle CaCO3-Chitosan/poly (vinyl alcohol) (SCC/PVA) hydrogels were in situ prepared inspired by the good mechanical self-cleaning and properties of seashell. The morphologies, structure and components of the prepared hydrogels were studied by SEM, FTIR spectra, XRD, TGA, and TEM. The anti-biofouling properties of the prepared hydrogels against protein, bacteria and algae were evaluated by ultrahigh-resolution fluorescence microscopy. Results indicated that chitosan can affect the growth process of CaCO3 leading to the formation of a hollow spindle structure of CaCO3. The prepared SCC/PVA hydrogels have excellent underwater superoleophobicity properties. SCC/PVA-3 hydrogel has the best superoleophobicity property with an underwater contact angle of 167.5°. The compressive strength of SCC/PVA-3 hydrogel is 25 MPa, which is attributed to the doping of SCC. Compared to PVA hydrogel, the settlement of the Navicula, Nitzschia Closterium on the surface of SCC/PVA-3 hydrogels sample decreased by approximately 94 % and 88 %, respectively. The SCC/PVA hydrogels have some antibacterial ability against E. coli. SCC/PVA-3 hydrogel can effectively inhibit the adhesion of elegans with a test time of 180 days in the South China Sea.

Kirkendall effect Strengthened-Superhydrophilic/superaerophobic Co-Ni3N/NF heterostructure as electrode catalyst for High-current hydrogen production

The development of efficient electrocatalysts for large-scale water electrolysis is crucial and challenging. Research efforts towards interface engineering and electronic structure modulation can be leveraged to enhance the electrochemical performance of the developed catalysts. In this work, a surface-engineered Co-Ni3N/NF heterostructure electrode was prepared based on Kirkendall effect for high-current water electrolysis. In the experiments, the textural feature and intrinsic activity of the Co-Ni3N/NF heterostructure were tuned through cobalt-doping and the creation of structural defects. As a result, the increased surface energy endowed Co-Ni3N/NF heterostructure with superhydrophilic and superaerophobic properties. Meanwhile, the contact area of the gas–liquid-solid three phases was optimized. With a large underwater bubble contact angle (CA) of 169°, the electrolyte solution can infiltrate the Co-Ni3N/NF electrode within 150 ms. Sequentially, the generated gas bubbles were able to detach at high frequency, which ensured the rapid mass exchange. The performance tests showed that the optimal Co-Ni3N/NF electrode sample reached current densities of 100 mA cm−2 and 500 mA cm−2 at the overpotentials of 98 mV and 123 mV, respectively. Benefiting from the reduction of hydrogen embrittlement, the HER performance of the prepared Co-Ni3N/NF electrode sample decreased slightly after 100 h durability test, but the overall structure remained well. Those results allowed us to conclude that the prepared Co-Ni3N/NF electrocatalyst holds the promises for large-scale water electrolysis in industries. More specifically, this work provided a new perspective that the efficiency of electrocatalysts for large-scale water electrolysis can be enhanced by constructing a heterostructure with good wettability and gas repellency.

Underwater superoleophobic poly(vinylidene fluoride)/poly(N-isopropylacrylamide) membranes for highly efficient oil-in-water emulsion separation

Superoleophobic and anti-oil adhesion behavior has been considered the central character of the materials for removing oil from wastewater. Herein, poly(vinylidene fluoride)/poly(N-isopropylacrylamide) (PVDF/PNIPAM) membranes were fabricated by vapor-induced phase separation (VIPS) and then further post-modified by deposition of sulfonated dopamine (SDA). The resulting membrane has a strong underwater superoleophobicity with an underwater toluene contact angle of 163 ± 2° and an ultralow adhesion force (1.9 ± 0.02 µN) between the surface and the oil. Therefore, it can efficiently remove emulsified toluene from water with a flux of 2211 ± 80 L m−2 h−1 bar−1 and an oil rejection of 99.5 ± 0.4%. This work offers a novel technique for the fabrication of porous membranes with excellent anti-oil fouling performance which will be practically used in the treatment of emulsified oils.

Efficient oil-water emulsion treatment via novel composite membranes fabricated by CaCO3-based biomineralization and TA-Ti(IV) coating strategy

Continuous increasing discharge of industrial oily wastewater and frequent occurrence of oil spill accidents have taken heavy tolls on global environment and human health. Organic-inorganic modifications can fabricate superhydrophilic/submerged superoleophobic membranes for efficient oil-water separation/treatment though they still suffer from complex operation, non-environmental friendliness, expensive cost or uneven distribution. Herein, a new strategy regarding tannic acid (TA)-Ti(IV) coating and CaCO3-based biomineralization through simple inkjet printing processes was proposed to modify polyvinylidene fluoride (PVDF) membrane, endowing the membrane with high hydrophilicity (water contact angle (WCA) decreased from 86.01° to 14.94°) and underwater superoleophobicity (underwater contact angle (UOCA) > 155°). The optimized TA-Ti(IV)-CaCO3 modified membrane possessed perfect water permeation to various oil/water emulsions (e.g., 355.7 L·m−2·h−1 for gasoline emulsion) under gravity with superior separation efficiency (>98.8 %), leading the way in oil/water emulsion separation performance of PVDF membranes modified with polyphenolic surfaces to our knowledge. Moreover, the modified membrane displayed rather high flux recovery after eight cycles of filtration while maintaining the original excellent separation efficiency. The modification process proposed in this study is almost independent of the nature of the substrate, and meets the demand for simple, inexpensive, rapid preparation of highly hydrophilic antifouling membranes, showing abroad application prospect for oil-water emulsion separation/treatment.

Fabrication and Characterization of Zwitterionic Coatings with Anti-oil and Anti-biofouling Activities

Underwater ultraoleophobic materials with superhydrophilic surfaces have great potential for several applications due to their anti-fouling, self-cleaning, oil/water separation, droplet manipulation, and drag reduction properties. In our research described here an underwater ultraoleophobic coating containing zwitterion carboxybetaine acrylamide (CBAA) was prepared using self-polymerization of dopamine (DA) and co-deposition of polydopamine (PDA) with zwitterionic poly(carboxybetaine acrylamide) (PCBAA) based on hydroxyl radical activation. The morphology of the coatings could be easily controlled by adjusting the initial ratio of dopamine/carboxybetaine acrylamide (DA/CBAA). The structures, surface morphologies and properties of the coatings so obtained were analyzed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM) and contact angle measurements. The polydopamine/poly(carboxybetaine acrylamide) (PDA/PCBAA) coatings exhibited excellent superhydrophilicity and underwater superoleophobicity with water contact angles (WCA) of 1.5° and underwater oleophobicity contact angles (OCA) of 160°. The anti-biofouling, oil-water separation, and mechanical stability properties for PDA/PCBAA co-deposited coating were comprehensively investigated. These interesting properties make the coatings promising candidates for numerous applications.

Porous and carboxyl functionalized titanium carbide MXene sheets for fast oil-in-water emulsion separation

Titanium carbide MXene as a novel two-dimensional nanomaterial receives more attention in membrane separation, but its low water permeability has limited its application in wastewater treatment. Hence, we developed a new type of “oxidation-etching” method to fabricate porous titanium carbide MXene sheets to optimize the water channel. Meanwhile, carboxyl functionalized surface modification endowed porous MXene sheets with more hydrophilic groups, which was good for the improvement of membranes’ wettability. The as-prepared membranes exhibited superior underwater wettability, concretely, underwater contact angle up to 159.2° and sliding angle as low as 1.0°. Most importantly, the membrane displayed a high permeance (8083 L m−2 h−1 bar−1) for separating the oil-in-water surfactant-stabilized emulsion and was superior to most of the MXene membranes reported so far. It also exhibited an excellent separation performance for those emulsions prepared from high viscosity oil phases. This study reports a new “oxidation-etching” method to fabricate porous MXene sheets and carboxyl functionalized ensures the membrane with excellent underwater wettability and emulsions separation performance.

Eco-friendly Dopamine-Modified Silica Nanoparticles for Oil-Repellent Coatings: Implications for Underwater Self-Cleaning and Antifogging Applications

Solid materials ubiquitously suffer from oil fouling in engineering applications. In this work, a facile and economical method was proposed to prepare a substrate-independent self-cleaning coating with remarkable oil repellency, which were realized by dints of the surface of nanocomposite structures with polar groups introduced by silica nanoparticles and polydopamine. The dip coating preparation process can be carried out in an ambient atmosphere without the use of hazardous reagents or complex equipment. The coating displays self-cleaning performance to detach the adhered oil after being immersed into water. The underwater contact angles were measured over 150° to various oils, further retaining stability in corrosive aqueous environments. Moreover, the coated glass shows resistance to water condensation, which can remain transparent after steaming or frosting, due to its hydrophilicity. The special wettability also endows the coated fabric with permselectivity to water and oil. Modified filter cotton was utilized to separate five kinds of oil/water mixtures. This study proposed a tried-and-true approach to realize oil repellency. It is anticipated that it could set a precedent for the design of self-cleaning or antifouling coatings.

Multiphase media superwettability regulated by coexisting prewetting phase

Understanding the wetting behaviors of a given superwetting surface in multiphase media is important for elaborately tailoring superwettability. Here the surface chemistry of two types of superhydrophobic surfaces was programmed to reveal crucial effect of a coexisting prewetting phase rather than the prewetting process on their wetting states in water and oil–water separation application. After prewetting with ethanol to remove the air layer, underwater contact angles of superhydrophobic surfaces for oil droplet and bubble gradually decreased from over 150° along with the reduced surface energy. When the superhydrophobic surfaces were directly immersed in water or prewetted with oil, a stable air layer or infused oil as the prewetting phase enabled oil droplet and bubble to rapidly spread out. Moreover, air-prewetting superhydrophobic/underwater superoleophobic fabric can selectively adsorb oils from water, whereas it showed an excellent antifouling property without the air layer. For the separation of oil-in-water emulsions using superhydrophobic/underwater superoleophilic sponge, the stable air layer obstructed emulsions into three-dimensional porous structures. After removing the air layer, emulsion separation can be efficiently realized. This discovery provides a feasible approach for the regulation and development of unusual superwettability in multiphase media.

In Situ Coupled Electrochemical‐Goniometry as a Tool to Reveal Conformational Changes of Charged Peptides

AbstractThe opportunity to manipulate cell functions by regulating bioactive surfaces is a potentially promising approach for organic bioelectronics. Here, the tuning of the orientation of charged peptides by means of an electrical input observed via optical tensiometry is reported. A stimuli‐responsive self‐assembled monolayer (SAM) with specially designed charged peptides is used as a model system to switch between two separate hydrophilic states. The underwater contact angle (UCA) technique is used to measure changes in the wetting property of a dichloromethane droplet under electrical stimuli. The observed changes in the UCA of the bio‐interface can be understood in terms of a change in the surface energy between the ON and OFF states. Molecular dynamics simulations in an electric field have been performed to verify the hypothesis of the orientational change of the charged peptides upon electrical stimulation. In addition, X‐ray photoelectron spectroscopy (XPS) is performed to clarify the stability of the functionalized electrodes. Finally, the possibility of using such a novel switching system as a tool to characterize bioactive surfaces is discussed.

Superhydrophilic/underwater superaerophobic self-supporting CuS/Cu foam electrode for efficient oxygen evolution reaction

Hydrogen production by electrochemical overall water splitting is an economic and green approach to resolve the looming energy and environmental crisis. However, the electrocatalytic oxygen evolution reaction (OER) generally occurs at low rate due to the delayed reaction kinetics of four-electron transfer. Herein, a kind of crater-like micro-nano structure CuS three-dimensional electrode that was supported on a Cu foam was prepared and used as an electrode anode for overall water splitting. The superhydrophilic/underwater superaerophobic structure can significantly reduce the bubble adhesion on the electrode surface and improve the OER performance. The CuS/CF electrode showed good wettability and superaerophobicity with an underwater contact angle of 153.5°. The CuS/CF (CuS/Cu foam) electrode has been proved to have excellent electrocatalytic activity for water decomposition. In 1.0 M KOH solution, the OER overpotential is 350 mV at 10 mA cm−2 and the Tafel slope is 83 mV dec−1. In acidic medium of 0.5 M H2SO4 solution, the overpotential of hydrogen evolution (HER) is 134 mV at 10 mA cm−2 and the Tafel slope is 114 mV dec−1. The underwater superaerophobic electrode still has strong stability after 10 h test. This work provides a new potential electrochemical catalyzed approach to water decomposition by constructing a super-infiltration electrode.