Facile Chemical Etching Research Articles

Modulating single-atom sulfur-vacancy defect in MoS2-x catalysts to boost cathode redox kinetics for vanadium flow batteries

Vanadium flow batteries (VFBs) have great potential for application in energy storage systems. However, the sluggish cathode redox kinetics still greatly restricts their operation at high current densities. Herein, we boost cathode redox chemistry by modulating single-atom sulfur-vacancy (S-vacancy) defect of MoS2-x in-situ grown on carbon felts via a facile chemical etching method. Firstly, the optimized S-vacancy concentration is figured out via high throughput calculations based on d-band center theory. By precisely controlling etching duration, we achieve a tailored S-vacancy concentration, leading to highly dispersed S-vacancies, increased specific surface area, and improved hydrophilicity. Electrochemical characterizations demonstrate that optimized S-vacancy state can significantly facilitate the VO2+/VO2+ kinetics. Moreover, analysis of electron density difference and integrated crystal orbital Hamiltonian group further reveals that dispersed S-vacancy distribution also contribute to efficient surface electronic structure and enhanced adsorption process. Benefiting from enhanced VO2+/VO2+ kinetics, VFB single cell achieves a superior EE of 78.73 % at 300 mA cm−2 and is able to last for 500 cycles without decay. This work demonstrates the promising potential of single-atom S-vacancies catalysts in the fabrication of flow battery electrodes and more importantly sheds light on the fundamental modulation essence of d-band center in MoS2-x towards enhanced cathode redox kinetics.

Site-selective etching and conversion of bismuth-based Metal–Organic frameworks by oxyanions enables efficient and selective adsorption via robust coordination bonding

Anisotropic etching and conversion of MOF micro/nanostructures results in innovative structures and regulates properties. However, the anisotropic higher-order construction of MOFs remains a major challenge. Here, for the first time, we report the preparation of two unprecedented Bi-MOF (CAU-17) derivative structures via facile chemical etching and simultaneous conversion on solid CAU-17 microrods by reaction with Te- and Se-containing oxyanions. The TeOx2−-mediated hollow tubular structures are obtained via unique splitting, self-welding, and dissolution processes, a tube-forming mechanism never before seen in MOFs. In comparison, SeOx2− ions tend to etch CAU-17 into hierarchical sponge-like structures assembled from fine nanoparticles. DFT calculations, XANES modeling, and EXAFS fittings suggest that the site-selective coordination of oxyanions with Bi-O bonds in the Bi-MOF forms robust Bi-O-Te/Se bonds, which in turn leads to an anisotropic structural transition of CAU-17. More interestingly, benefiting from the coordination bond-dominated conversion, CAU-17 is shown to be a superior adsorbent for the selective and irreversible capture of highly radiotoxic oxyanions containing Te and Se from wastewater. These findings provide new insights into the anisotropic etching and conversion mechanism of MOFs by oxyanions and a fundamental understanding for designing advanced MOF-based guest oxyanion adsorbents.

Multi-Scale Engineered 2D Carbon Polyhedron Array with Enhanced Electrocatalytic Performance.

Electrocatalyst engineering from the atomic to macroscopic level of electrocatalysts is one of the most powerful routes to boost the performance of electrochemical devices. However, multi-scale structure engineering mainly focuses on the range of atomic-to-particle scale such as hierarchical porosity engineering, while catalyst engineering at the macroscopic level, such as the arrangement configuration of nanoparticles, is often overlooked. Here, a 2D carbon polyhedron array with a multi-scale engineered structure via facile chemical etching, ice-templating induced self-assembly, and high-temperature pyrolysis processes is reported. Controlled phytic acid etching of the carbon precursor introduces homogeneous atomic phosphorous and nitrogen doping, as well as a well-defined mesoporous structure. Subsequent ice-templated self-assembly triggers the formation of a 2D particle array superstructure. The atomic-level doping gives rise to high intrinsic activity, while the well-engineered porous structure and particle arrangement addresses the mass transport limitations at the microscopic particle level and macroscopic electrode level. As a result, the as-prepared electrocatalyst delivers outstanding performance toward oxygen reduction reaction in both acidic and alkaline media, which is better than recently reported state-of-the-art metal-free electrocatalysts. Molecular dynamics simulation together with extensive characterizations indicate that the performance enhancement originates from multi-scale structural synergy.

Promoting OH- Adsorption and Diffusion Enables Ultrahigh Capacity and Rate Capability of Nickel Sulfide Cathode for Aqueous Alkaline Zn-Based Batteries.

Aqueous alkaline Zn-based batteries (AAZBs) possess great promise for large-scale applications thanks to their higher discharging plateau and unique reaction mechanism. However, the capacity and rate capability of Ni-based cathodes are still unsatisfactory due to their insufficient OH- adsorption and diffusion ability. Herein, heterostructured Ni3 S2 /Ni(OH)2 nanosheets with outstanding electrochemical performance are synthesized via a facile chemical etching strategy. The heterostructured Ni3 S2 /Ni(OH)2 nanosheet cathode shows significantly increased capacity and rate capability due to its boosted OH- adsorption and diffusion ability compared to Ni3 S2 . Consequently, the assembled Zn//Ni3 S2 /Ni(OH)2 cell can deliver an ultrahigh capacity of 2.26mAhcm-2 , an excellent rate performance (0.91mAhcm-2 at 100mAcm-2 ) and a satisfying cycling stability (1.01mAhcm-2 at 20mAcm-2 after 500 cycles). Moreover, a prominent energy density of 3.86mWhcm-2 is obtained, which exceeds the majority of recently reported AAZBs. This work is expected to provide a new modification direction for developing high-performance nickel sulfide cathode for AAZBs.

A robust and facile colorimetric aptasensor for the detection of Salmonella Typhimurium based on the regulation of Fe3O4@Cu@PCPy yolk-shell nanozyme activity

Due to their superparamagnetism and enzyme-like activity, iron oxide (Fe3O4) nanozymes can be readily used for sample pretreatment and the generation of detection signals, and have, thus, attracted much attention in the field of bioanalysis and diagnosis. However, the low catalytic activity of Fe3O4 nanozymes does reduce the sensitivity of Fe3O4-based methods, limiting their application. In this study, Fe3O4@Cu@poly(pyrrole-2-carboxylic acid) yolk-shell nanozymes (Fe3O4@Cu@PCPy YSNs) were synthesized using a facile approach and selective chemical etching technology. Compared with Fe3O4 nanozymes, the Fe3O4@Cu@PCPy YSNs demonstrated a three-fold increase in the peroxidase-like activity, good dispersity and strong superparamagnetism. In addition, the flower-shaped structure of aptamer-complementary strand (Apt-CS) conjugates was designed on the surface of the Fe3O4@Cu@PCPy YSNs, which effectively inhibited their peroxidase-like activity by creating a physical barrier that hindered the access of substrates to the center of the Fe3O4@Cu@PCPy YSNs. Based on this principle, a robust and facile colorimetric aptasensor was developed for detecting Salmonella Typhimurium. The flower-shaped Apt-CS were dissociated in the presence of S. Typhimurium, promoting the recovery of Fe3O4@Cu@PCPy YSN catalytic activity. Under optimized conditions, this proposed aptasensor successfully detected S. Typhimurium in a linear range of 3 to 3 × 106 CFU/mL, achieving a detection limit of 1 CFU/mL. Finally, the feasibility of this novel aptasensor was further validated by three actual samples, with recoveries of between 84.3% and 102%, thereby demonstrating the huge potential of the proposed aptasensor for detecting S. Typhimurium in foods.

An expanding horizon: Recyclable dual-functional size-adjusted fluorinated mesh devices for large-scale oily wastewater remediation

The general lack of water resources makes the treatment of oily wastewater as an urgent concern, which causes catastrophic damage to ecosystems and environment. Construction of a universal oil/water separator is not an easy task, because the reported processes are relatively complex and it is difficult to achieve industrial large-scale production. To overcome this problem, herein, using the low-cost and frequently-used metal (stainless steel, etc.) meshes as raw materials, two kinds of oil/water separators with different moving models have firstly designed via a universal technique of a facile chemical etching and fluoridation coating process. The newly synthesized superhydrophobic/superoilphilic stainless steel or copper mesh with surface morphology, high purity and structure stability displayed an excellent anti-wetting property (high water contact angle of >157°) after a series of tests of immersion, droplet rolling-off, anti-impacting process, 30days exposure aging in open-air, etc. In addition, experimental results revealed that the fresh and aging separators can maintain excellent oily wastewater remediation efficiency up to ∼99% even after 25 separation cycles, making them economical and commercially viable. This study provides a novel perspective for advancement in designing oil/water separator with low cost, less energy consumption and high efficiency for universal application.

Controllable Water Penetration through a Smart Brass Mesh Modified by Mercaptobenzoic Acid and Naphthalenethiol

In this paper, a novel pH-responsive brass mesh modified by 3-mercaptobenzoic acid (MBA) and 2-naphthalenethiol (NPT) was demonstrated via a facile chemical etching method followed by surface modification. The smart wettability was dependent on the assembled MBA and NPT with suitable thiol proportions. The on–off control of water penetrating intelligently into the nanostructured brass mesh substrate was carried out by the pH change in the outside environment. The brass mesh modified with XNPT = 0.4 (mole fraction of NBT in the mixed solution) exhibited the strongest pH responsivity from superhydrophobicity to superhydrophilicity. Furthermore, the resulted Janus membrane (JM) fabricated by the integration of a smart brass mesh and hydrophobic Ni foam could be used as a water diode in air and liquid systems. Unidirectional penetration for the water droplet was realized by the resulting smart JM with a hydrophobic upper layer and a pH-responsive layer below.

A Free-Standing Polyaniline/Silicon Nanowire Forest as the Anode for Lithium-ion Batteries.

Despite its high theoretical capacity, silicon anode has limited intrinsic conductivity and experiences significant volume changes during charge-discharge. To overcome these issues, facile metal-assisted chemical etching and in-situ polymerization of aniline are employed to produce a dense 1D polyaniline/silicon nanowire forest without noticeable agglomeration as a free-standing anode for lithium-ion batteries. This hybrid electrode possesses high cycling performance, delivering a stable capacity capped at 2 mAh cm-2 for 346 cycles of charge-discharge. Maximum capacity of 2 mAh cm-2 is also achievable at high-rate cell testing of 2 mA cm-2 , which cannot be obtained by the anode with plain silicon wafer and silicon nanowire only. The introduction of polyaniline on the silicon nanowire is shown to reduce the solid electrolyte interface (SEI) resistance, stabilize the SEI layer, further alleviate the effect of volume changes, and boost the conductivity of the hybrid anode, resulting in the high electrochemical performance of the anode.

Fluorine-free superhydrophobic surface with micron-nanosized two-tiered structure for self-cleaning, anti-frosting, and anti-icing applications

Superhydrophobic surfaces with micron-nanosized two-tiered structures have huge potential in practical applications. However, the complex preparation process and low-stability of the versatile superhydrophobic surfaces restricted their wide application. Herein, a facile chemical etching process was applied to create a micron-sized rough structure on the 1060 aluminum alloy substrate, and the micron-sized rough structure surface (M-surface) was hydrophobic with a water contact angle of 113.50° ± 2.7°. Then, the M-surface was modified by hydrophobic SiO2 nanoparticles, and a superhydrophobic micron-nanosized two-tiered structure surface (MNSS-TMES/H-SiO2 coating) with a water contact angle of 161.20° ± 2.3° was constructed. The as-prepared MNSS-TMES/H-SiO2 coating can maintain superhydrophobicity after self-cleaning, sand impact, and anti-frosting tests. More importantly, the MNSS-TMES/H-SiO2 coating exhibited superior anti-icing performance and higher defrosting efficiency. The freezing delay time of a water droplet on the MNSS-TMES/H-SiO2 coating was prolonged to 4973.87 s at − 15 °C, and the frost layer on the resultant coating was melting speedily and turned into several isolated spherical water droplets in approximately 20 s. Therefore, the prepared durable fluorine-free superhydrophobic MNSS-TMES/H-SiO2 coating with self-cleaning performance, higher defrosting efficiency, and the ability to delay icing, which has great prospects in practical applications.

2D/2D Nanoarchitectured Nb2C/Ti3C2 MXene Heterointerface for High-Energy Supercapacitors with Sustainable Life Cycle

Layered 2D/2D heterointerface composites experience interesting properties that greatly stimulate the recent surge in the attention as robust supercapacitor electrode materials, especially the MXene-based 2D/2D heterointerface for its robust energy storage compatibility. This report unveils a synergistically in situ prepared 2D/2D Nb2C/Ti3C2 MXene (NCTC) heterointerface nanoarchitecture by facile one-pot chemical etching. The methodology adopted enables the interconnected and simultaneous growth of MXenes exposing and retaining their active surfaces for enhanced ion diffusion pathways, charge storage dynamics, microstructural stability, and a noticeable potential window. Henceforth, the in situ developed NCTC heterointerface electrode delivered an excellent specific capacitance of 584 F/g at 2 A/g with a commendable energy density of 38.5 W h/kg in MXene supercapacitors owing to the augmented surface- and redox-based charge storage at the interface. Finally, the developed all-solid-state system demonstrated a superior cycling retention of 98% capacitance after 50,000 cycles. These superlative results encourage the exploration of such prospective 2D/2D heterointerfaces with intriguing charge storage and microstructural attributes for designing next-generation energy storage systems.

Oxygen-Assisted Anisotropic Chemical Etching of MoSe2 for Enhanced Phototransistors

The etching process can serve as an effective top-down approach that facilitates direct construction of tuned patterns, reversely studying growth mechanisms and further inducing unexpected physical properties. Currently, etching behaviors of monolayer transition-metal dichalcogenides (TMDs) have been rarely explored and the intrinsic etching mechanism still needs to be fully elucidated. Here, we demonstrate a facile and controllable oxygen-assisted anisotropic chemical etching of two-dimensional (2D) materials. Taking MoSe2 as an example, a series of well-defined etched patterns can be fabricated by precisely modulating the pretreatment time of oxygen plasma and the etching time. Atomic characterization exhibits that the edges of etched patterns are mainly zigzag-terminated. Density functional theory calculations highly agree with the experimental results, indicating an energy preference for zigzag edges. The as-produced MoSe2 flakes can be used as part of heterojunctions to display intriguing optoelectronic properties. The field-effect transistor based on as-etched MoSe2 flakes and the 2D poly(3-hexylthiophene-2,5-diyl) crystal shows a distinct enhanced ambipolar photoresponse. Our strategy offers a new direction for preparing patterned 2D TMDs with desirable characteristics, opening the door for facilitating the development of optoelectronics.

A comparative study of mechanical and chemical durability of non-wetting superhydrophobic and lubricant-infused surfaces

Fabrication of bioinspired non-wetting superhydrophobic surfaces (SHS) and lubricant-infused surfaces (LIS) has been studied extensively on a variety of materials. In contrast, durability of the surfaces exposed to harsh mechanical and chemical environments has been the subject of little attention. This study considers the mechanical and chemical durability of SHS and LIS copper surfaces fabricated via facile electrodeposition and chemical etching methods. The as-fabricated surfaces demonstrate excellent non-wetting characteristics with water contact angle of 160° and sliding angle below 5°. The surfaces are subject to mechanical wear through scratch test and water jet impingement at 15 psi and 20 psi as well as accelerated corrosion following the ASTM-E407 standard. The performance of the electrodeposited and etched non-wetting surfaces is systematically assessed in terms of contact and sliding angles and corrosion rate in a simulated marine environment. All surfaces are shown to be robust to mechanical wear after scratch test, with excellent stability of contact and sliding angles, and up to two orders of magnitude reduced corrosion rate compared to bare copper surface. SHS retained steadfast non-wetting characteristics under high-pressure water jet tests compared to the other surfaces while LIS, regardless of texturing method, showed one to two orders of magnitude reduced corrosion rate compared to bare copper surface throughout water jet impingement and chemical durability tests. The study presents for the first time a systematic comparison of durability of SHS and LIS through a common set of fabrication and testing protocol and helps identify appropriate non-wetting surfaces and fabrication methods based on the use environment.

Chemical etching manipulated local electronic structure upheaval of graphdiyne for efficient hydrogen evolution

Graphdiyne (GDY), featured with unique sp2, sp-hybridized form and inherent inhomogeneous electron distribution, retains great expectation to be developed into highly efficient electrocatalysts for hydrogen evolution reaction (HER). However, the state-of-the-art GDY-based electrocatalysts still suffer from weak catalytic activity and sluggish reaction kinetics originating from the severe scarcity of in-plane active sites and insufficient electrical conductivity. Targeted at this bottleneck issue, electronic structure regulation, recognized as an extremely precise technical route, is promising to improve HER performances of carbon-based electrocatalysts. Herein, a facile controllable chemical etching strategy is well leveraged to introduce sp2-hybridized carbon–oxygen bonds (Csp2–O) into GDY for precise manipulation both of its electronic and spatial structures. Experimental results and theoretical calculations coherently manifest that Csp2–O introduction into GDY can not only induce its electronic structure upheaval to strengthen surface electron transport capability, but also trigger intensive carbon–oxygen p–p orbital hybridization to enhance the catalytic activity of acetylenic bond sites. As a result, the optimal GDY sample after etching delivers excellent HER performance with an overpotential of only 101 mV at a current density of 10 mA cm−2 and a low Tafel slope of 54 mV dec−1, which surpasses most of reported metal-free based electrocatalysts. This work provides a universal route for precise modulation of inherent electronic structure in GDY, and can be further extended to boost the overall performances of other carbon-based catalysts.

Facile preparation of superamphiphobic aluminum alloy surfaces and their corrosion resistance

Aluminum alloys (Al alloys) are susceptible to corrosion due to their high chemical activity, particularly in complicated marine surroundings. Liquid-repelling Al alloy surfaces with enhanced corrosion resistance were prepared via a facile one-step chemical etching and modification with 1H,1H,2H,2H-Perfluorodecyltriethoxysilane. Results indicated that the fabricated sample with step-like micro/nanostructures exhibited excellent superamphiphobicity, which the static contact angles achieved 162°, 158°, and 152° for water, ethylene glycol, and hexadecane, respectively. Furthermore, electrochemical tests shed light on that the superamphiphobic surface fabricated greatly improved the anti-corrosion performance and durability of the substrate in 3.5 wt% NaCl aqueous solution . The whole process requires no special equipment, providing a facile and environment-friendly method to fabricate superamphiphobic surfaces. • Superamphiphobic aluminum alloy surface is fabricated by a simple method. • The prepared superamphiphobic surface exhibited excellent superamphiphobicity. • The superamphiphobic surface greatly improves the corrosion resistance of substrate.

Few-layered MoS2 with S-vacancies anchored on N-doped carbon flower for high performance sodium storage

Molybdenum disulfide (MoS2) has been regarded as a promising anode material for sodium ion batteries (SIBs) due to its high theoretical capacity and graphene-like layered structure. However, the intrinsically low conductivity and large volume expansion during charge/discharge cycling have become two key challenges hindering the practical application of MoS2 electrodes. Here, few-layered MoS2 nanosheets with S-vacancies are anchored on a 3D flower-like N-doped carbon frameworks (NCF@V-MoS2) by facile hydrothermal method and chemical etching strategy. The introduction of S-vacancies onto MoS2 nanosheet surface not only adjusts the electronic structure and intrinsically improves the conductivity, but also enlarges the interlayer distance and accelerates Na+ diffusion. The density functional theory calculations reveal that the existence of S-vacancies strongly accelerates Na+ absorption ability. Benefiting the synergistic effect of the conductive NCF and V-MoS2, the as-synthesized NCF@V-MoS2 yields a high specific capacity with excellent rate performance and cycling stability. This novel design strategy holds great promise for the development and application of high-performance SIBs in the future.

Hierarchical CoFe LDH/MOF nanorods array with strong coupling effect grown on carbon cloth enables efficient oxidation of water and urea

Oxygen evolution reaction (OER) and urea oxidation reaction (UOR) play important roles in the fields of hydrogen energy production and pollution treatment. Herein, a facile one-step chemical etching strategy is provided for fabricating one-dimensional hierarchical nanorods array composed of CoFe layered double hydroxide (LDH)/metal-organic frameworks (MOFs) supported on carbon cloth as efficient and stable OER and UOR catalysts. By precisely controlling the etching rate, the ligands from Co-MOFs are partially removed, the corresponding metal centers then coordinate with hydroxyl ions to generate ultrathin amorphous CoFe LDH nanosheets. The resultant CoFe LDH/MOFs catalyst possesses large active surface area, enhanced conductivity and extended electron/mass transfer channels, which are beneficial for catalytic reactions. Additionally, the intimate contact between CoFe LDH and MOFs modulates the local electronic structure of the catalytic active site, leading to enhanced adsorption of oxygen-containing intermediates to facilitate fast electrocatalytic reaction. As a result, the optimized CoFe LDH/MOF-0.06 exhibits superior OER activity with a low overpotential of 276 at a current density of 10 mA cm−2 with long-term durability. Additionally, it merely requires a voltage of 1.45 V to obtain 10 mA cm−2 in 1 M KOH solution with 0.33 urea and is 56 mV lower than the one in pure KOH. The work presented here may hew out a brand-new route to construct multi-functional electrocatalysts for water splitting, CO2 reduction, nitrogen reduction reactions and so on.

Redox-etching induced porous carbon cloth with pseudocapacitive oxygenic groups for flexible symmetric supercapacitor

Constructing high-performance electrodes with both wide potential window (e.g. ≥ 2 V in aqueous electrolyte) and excellent mechanical flexibility represents a great challenge for supercapacitors. Because of the outstanding conductivity and flexibility, carbon cloth (CC) has shown unlimited prospects for constructing flexible electrodes, but is rarely used directly as electrode material due to its electrochemical inertness and small specific surface area. To tackle these two critical limitations, we design a novel redox-etching strategy to synthesize CC-based electrode with 3D interconnecting pore structure. The sponge-like highly porous CC was further activated by strong oxidant to form abundant oxygenic groups, which occupy the interior and surface of current collector to render substantial pseudocapacitance. The as-synthesized CC electrode yielded an impressive capacitance of 4035 mF cm−2 at 3 mA cm−2 and satisfying cycling durability in a wide potential range of −1 – 1 V vs. SCE, which surpass the majority of reported CC-based electrodes. A symmetric supercapacitor with stable voltage of 2 V is assembled and delivers remarkable energy density of 6.57 mWh cm−3. Significantly, the device demonstrates an unparalleled flexibility with no capacitive decay after 100 bending cycles. This facile chemical etching and post-treatment processes are designed for large-scale manufacturing of the CC electrodes by providing high surface area and abundant electrochemically active sites, promising for industry application. The innovative synthetic strategy opens up new opportunities for high-performance flexible energy storage.

Construction of carbon quantum dots embed α‐Co/Ni(OH)2 hollow nanocages with enhanced supercapacitor performance

AbstractThe etching strategy of metal‐organic frameworks is an effective process to prepare hollow electrode materials for enhanced electrochemical performance. But the relatively low conductivity of these electrode materials limits their further application. In this work, a series of carbon quantum dots (CQDs) embedded ZIF‐67 precursors (ZIF‐67@CQDs‐X, X = 1.25, 2.50, 5.00, 7.50) are synthesized firstly. Then, by a facile and controllable chemical etching process, the CQDs doped α‐Co/Ni(OH)2 hollow nanocages (α‐Co/Ni(OH)2@CQDs‐X, X = 1.25, 2.50, 5.00, 7.50) are successfully constructed. The optimized α‐Co/Ni(OH)2@CQDs‐2.50 electrode delivers a high specific surface area (277.99 m2 g−1) and dramatically enhanced conductivity. Therefore, α‐Co/Ni(OH)2@CQDs‐2.50 electrode presents a high specific capacitance (700 C g−1, 1 A g−1), superior rate performance (550 C g−1, 10 A g−1) and excellent cycling lifespan (retaining 79.93% of initial capacitance after 10 000 cycles). Coupled with the high‐performance PPD/rGO as a negative electrode, the fabricated Co/Ni(OH)2@CQDs‐2.50//PPD/rGO device exhibits an outstanding energy density of 57.29 Wh kg−1 at the power density of 0.375 kW kg−1. It is proved that the CQDs embedding and chemical etching strategy are an effective way for constructing hollow materials with enhanced energy storage performance.

Fabrication of micro–nano-roughened surface with superhydrophobic character on an aluminium alloy surface by a facile chemical etching process

In the present work, we have fabricated a superhydrophobic surface on aluminium alloy 2024 through a simple immersion chemical etching method in hydrochloric acid followed by a functionalization step in stearic acid solution. The impact of etching time on water contact angle was investigated and a contact angle of $$\sim $$ 167 $$^{{\circ }}$$ was reached on the superhydrophobic surface, which was etched for 4 min. Morphology of the surface was evaluated by scanning electron microscopy and the surface chemical analysis was performed by energy-dispersive X-ray spectroscopy and Raman spectroscopy. We show that the fabricated superhydrophobic samples can besides water, also repel other liquids. We also demonstrate the self-cleaning properties of the fabricated samples using graphite particles as contaminants. Ultimately, we assessed the corrosion resistance properties of the fabricated surfaces by the potentiodynamic polarization method. The superhydrophobic surface exhibited increased corrosion potential and polarization resistance along with reduced corrosion current density, all of which are indicative of a significant improvement in corrosion performance of the superhydrophobic surface in comparison with typical aluminium 2024. The cheap and facile superhydrophobic surface fabrication method presented in this study can be applied to large scale samples with no need for electricity or expensive raw materials.

Morphology control of c-Si via facile copper-assisted chemical etching: Managements on etch end-points

Abstract Micro-/nano-structures enable crystalline silicon (c-Si) to be prominent in many fields. In this work, an elaborate study on texturing c-Si via copper-assisted chemical etching (Cu-ACE) is reported. Various large-area craters arrays including gyro-like craters arrays, standard inverted pyramids arrays and deformed inverted pyramids arrays, together with mesoporous surfaces and polished-like surfaces are synthesized on Si wafers with Cu-ACE. An electrokinetic “H2O2 consumption” model and an energy band model are proposed to explain the synergetic effects between isotropic and anisotropic etching on preparing Si micro-/nano-structures during etching. It is demonstrated that the etched morphology is determined by the temporal H2O2 relative concentration at etch end-points, which is accurately controlled by etching conditions. A “curved sidewalls” model is put forward, for the first time, to illustrate the nuances among etched craters arrays. Based on this model, the local H2O2 relative concentration determines local curvatures of sidewalls. Textured Si wafers with inverted pyramids arrays exhibit excellent anti-reflection abilities and are promising for solar cells, photodiodes or other optoelectronic applications. Notably, our work provides a facile and controllable approach to produce various Si micro-/nano-structures which are of practical values in many domains.