Na2S Solution Research Articles

Facile Electrodeposition Method for Constructing Li2S as Artificial Solid Electrolyte Interphase for High-Performance Li Metal Anode.

Designing current collectors and constructing efficient artificial solid electrolyte interphase (SEI) layers are promising strategies for achieving dendrite-free Li deposition and practical applications in Li metal batteries (LMBs). Electrodeposition is advantageous for large-scale production and allows the direct formation of current collectors without binders, making them immediately usable as electrodes. In this study, an adherent Cu2S thin-layer on Cu foil is synthesized through anodic electrodeposition from a Na2S solution in a one-step process, followed by the generation of Li2S layers as artificial SEI layers via a conversion reaction (3DLi2S-Cu foil). The Li2S layers move from the 3D Cu surface to the deposited Li surface, facilitating uniform and dense Li deposition. The 3DLi2S-Cu foil structure demonstrates stable cycling performance over 350 cycles in an asymmetric cell, with a capacity of 1 mAh cm-2 at 1 mA cm-2. Moreover, symmetric cells with 5 mAh cm-2 of deposited Li exhibit a stable cycle life for over 1200 h. When paired with commercial LiFePO4 (LFP), the full cells show substantially enhanced cyclability, regardless of the amount of deposited Li. This study provides new insights into the construction of artificial SEIs for facilitating commercial applications.

Constructing Long and Stable Ag‐Al2O3 Core–Shell Nanowires for Humidity Sensing and Triboelectric Energy Generation

Silver nanowires (AgNWs) are a promising alternative material to indium tin oxide as flexible transparent electrodes owing to their excellent optoelectrical properties and mechanical performance. However, the main challenge is the poor stability under diverse environments, ranging from high humidity, chemical exposure, and dynamic mechanical deformation. Herein, ultralong AgNWs (≈100 μm) have been synthesized via controlling growth kinetics by a facile acetic acid‐assisted solvothermal method, further decorated with a thin Al2O3 layer by electrodeposition to form a core–shell architecture. The resultant films based on Ag‐Al2O3 core–shell nanowires (NWs) possess a higher conductivity while preserving the optical transparency due to the enhanced NWs contact. More importantly, the constructed films exhibit strong resistance to various conditions, such as exposure to high temperature/humidity and immersion in NaCl, HCl, and Na2S solutions. The laser‐etched interdigital electrodes based on the chemically stable AgNWs are further integrated with graphene oxide layer for humidity sensing and respiration monitoring. Furthermore, the developed NWs with superior mechanical stability are constructed as triboelectric nanogenerators for electricity generation, and reliable output performance has been demonstrated. This work provides a convenient, scalable, and cost‐effective solution that offers great potential for designing robust, transparent electrodes for next‐generation flexible electronics.

Electrochemical processes for simultaneous sulfur and energy recoveries from sulfide-containing wastewater

Hydrogen sulfide and dissolved sulfide are notorious and lethal contaminants. The electrochemical process adopting the two-electron sulfide anodic oxidation reaction is an attractive strategy, which can simultaneously recycle and convert the chemical energy and sulfur resources into valued products. Sulfide pollutants are promising electron donors to reduce the electrochemical production cost, which is demonstrated in a sulfide/air fuel cell and a sulfide depolarized electrolyser. Sulfide oxidation behaviors are investigated on the developed IrxRu1-xO2 catalyst. A sulfide/air fuel cell is applied to evaluate the self-driven abilities of sulfur recovery and electricity generation. The sulfide/air fuel cell exhibits a notable discharge current density of > 120 mA cm−2 for 1.0 mol/L Na2S solution and 42.43 ± 1.94 mA cm−2 for the sulfide spent caustic stream. The potentials of sulfide anodic depolarization for electrochemical cost reduction are evaluated in a sulfide depolarized electrolyser for hydrogen production. Its open cell voltage is −0.33 V. For sulfur recovery, the cell can achieve about 20 mA cm−2 at 1.0 V, where the average energy cost of hydrogen production is about 2.39 kWh Nm−3. The sulfide removal rate is 0.26 ± 0.04 kgS m-2h−1, with an average current efficiency of 152.47 ± 28.59 %. This work may shed light on the potential of the incorporation of sulfide contaminants abatement and electrochemical productions.

A sulphide resistant Ag|AgCl reference electrode for long-term monitoring.

Reference electrodes which demonstrate long-term potential stability are essential for many continuous monitoring applications and are commonly based on Ag|AgCl electrodes; however, these electrodes are susceptible to poisoning from aqueous sulphide species which are commonly present in wastewater and natural groundwater. This work presents a sulphide resistant solid-state reference electrode (SSRE) based on a composite material using suspended KCl electrolyte and sacrificial AgCl in a cross-linked polyvinyl acetate polymer matrix. Sulphidation of the sacrificial AgCl produces a stable Ag2S precipitate and prevents further ingress of the poisoning sulphide species through the composite material. A novel SSRE using this material is compared to a control SSRE without suspended AgCl and a typical liquid filled reference electrode. These three reference electrodes are studied using electrochemical impedance spectroscopy (EIS), and their application is also studied in potentiometric pH sensing and cyclic voltammetry (CV). The long-term sulphide resistance of the two SSREs is also studied with potentiometry, and cross-sections of these electrodes were examined using micro X-ray fluorescence (μXRF). Both SSREs demonstrated higher impedance than the liquid reference electrode but were similar to other SSREs reported in the literature. This impedance did not result a meaningful difference in potentiometric pH sensing or CV experiments done using typical scan rates. The KCl/AgCl SSRE exhibited remarkable sulphide resistance, with all samples demonstrating a stable potential without maintenance after ca. 120 days of continuous immersion in 1 g L-1 Na2S solution, whereas KCl SSRE samples all demonstrated significant drift before this time. μXRF sulphur maps revealed that suspended AgCl prevented sulphide ingress, thus protecting the embedded Ag|AgCl electrode. This work presents a reference electrode that could enable long-term monitoring in challenging sulphide solutions, and also highlights a novel approach for preventing reference electrode poisoning which could be more widely explored.

Self-supporting trimetallic NiCoFe layered-double-hydroxide/amorphous sulfide heterostructure on nickel foam for efficient water splitting

For efficient overall water splitting, a ternary layered double hydroxide (LDH) and sulfide (NiCoFeLDH/NiCoFeS) composite on nickel foam (NF) has been developed as a bifunctional catalytic electrode. The growth of NiCoFeLDH/NiCoFeS–NF catalysts take place employing a three-step process that involves hydrothermal-sulfurization-hydrothermal reaction. Ultrafine nano-needle NiCo(OH)2 is deposited on the NF using a hydrothermal process, followed by immersion in Na2S solution, which ensures its mild conversion to NiCo sulfide. The Fe ions incorporated during the secondary hydrothermal process participate in the dissolution-recrystallization process of the lattice and modify the electronic structure, thereby significantly enhancing endogenous activity. The hetero-structured interface between NiCoFeLDH and NiCoFeS provides additional catalytic reaction sites, improves electronic interactions, and facilitates water dissociation kinetics. NiCoFeLDH/NiCoFeS–NF demonstates improved performance in both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The HER and OER overpotentials are measured to be only 191 and 241 mV at a current density of 100 mA cm−2 in 1 M KOH solution, respectively. Therefore, when NiCoFeLDH/NiCoFeS–NF has been employed as bifunctional electrodes for water splitting, 50 mA cm−2 is reached at only 1.63 V.

Corrosion Behavior of Ni–Mo Coatings Prepared by Different Electrodeposition Methods in Na2S Solution

Corrosion Behavior of Ni–Mo Coatings Prepared by Different Electrodeposition Methods in Na2S Solution

Cobalt sulfide nanosheets synthesized by anion exchange method for efficient Hg0 removal from flue gas

Transition metal sulfide adsorption has been recognized as a potential method for Hg0 removal, and the physicochemical properties of the adsorbent can significantly affect the Hg0 removal efficiency. The nanosheet structure with abundant unsaturated surface atoms can result in lower mass transfer resistance and give more adsorption sites. Thus, in the present work, cobalt sulfide nanosheet adsorbents with different Co/S ratio were synthesized by anion exchange method. Characterization results show that CS-10 has the lowest crystallinity and the highest Co3+/Co2+ and S22−/S2− ratio. These results give CS-10 the best Hg0 removal efficiency of nearly 100 % at a high GHSV of 180 000 h−1 at 60 °C. In addition, CS-10 has a good resistance to SO2 whose Hg0 removal efficiency decrease after SO2 introduction but recover to original level after SO2 cutting off. After being impregnated in Na2S solution, the adsorption efficiency of the used CS-10 can be easily regenerated. XPS results show that HgS can resolve in Na2S solution via HgS(ad) + S2− → [HgS2]2−. Furthermore, Co3+ and S22− as the main active sites for Hg0 removal can be replenished during the impregnation in Na2S solution. Kinetic study points that Hg0 adsorption characteristics on CS-10 obey pseudo-first-order and pseudo-second-order kinetic models, suggesting that the Hg0 diffusion on the external surface and the reaction at the adsorption site can both influence the Hg0 removal process.

In-situ fabrication of bimetallic FeCo2O4-FeCo2S4 heterostructure for high-efficient alkaline freshwater/seawater electrolysis

Rational construction of bifunctional electrocatalysts with long-term stability and high electrocatalytic activity is of great importance, but it is challenging to obtain highly efficient non-precious metal-based catalysts for overall seawater electrolysis. Herein, a nickel foam (NF) self-supporting CoFe-layered double hydroxide (CoFe-LDH/NF) was directly converted into FeCo2O4-FeCo2S4 heterostructure via hydrothermal method in 50 mM Na2S solution, instead of FeCo2O4@FeCo2S4 core-shell structure. The FeCo2O4-FeCo2S4 heterojunction shows nanosheets structure with rough surface (the thickness of ∼ 198.9 nm), which provides rich oxide/sulfide interfaces, high electrochemical active area, a large number of active sites, as well as fast charge and mass transfer. In 1.0 M KOH solution, 1.0 M KOH + 0.5 M NaCl, and alkaline natural seawater, the FeCo2O4-FeCo2S4 heterojunction exhibits eminently electrocatalytic performance, with overpotentials of η-100 = 225 mV, η-100 = 233 mV, and η-100 = 238 mV for OER, as well as η-100 = 271 mV, η-100 = 273 mV, and η-100 = 277 mV for HER, respectively. Furthermore, self-supporting FeCo2O4-FeCo2S4 electrode (FeCo2O4-FeCo2S4/NF) as the cathode and anode of an electrolyzer exhibits a lower cell voltage of E-100 = 1.75 V in alkaline seawater than those of FeCo2S4/NF (1.77 V), CoFe-LDH/NF (1.87 V), and FeCo2O4/NF (1.91 V). Specifically, FeCo2O4-FeCo2S4 electrolyzer can stably produce hydrogen for over 48 h in alkaline freshwater/seawater electrolyte. These outstanding electrocatalytic performances and corrosion resistance to salty-water can be attributed to the surface reconstruction behavior of the FeCo2O4-FeCo2S4/NF catalyst during OER, which leads to the in-situ formation of metal oxyhydroxides. In particular, the FeCo2O4-FeCo2S4 heterojunction is also very competitive among most state-of-the-art non-noble metal-based catalysts, whether in KOH or alkaline salty-water electrolytes.

Li sensitized CdS/TiO2 nanocomposite photoanode for solar water splitting, hydrogen generation and photoelectrochemical (PEC) performance

Li–CdS/TiO2 nanocomposite with different composition 10Li–CdS/TiO2, 20Li–CdS/TiO2, 30Li–CdS/TiO2, 40Li–CdS/TiO2, 50Li–CdS/TiO2 were coated on FTO surface by using doctor blade followed by successive ionic layer adsorption and reaction (SILAR) method. As synthesized Li–CdS/TiO2 photoanode is characterized with field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX), high resolution transmission electron microscopy (HR-TEM), diffuse reflectance spectroscopy (UV-DRS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL). FE-SEM analysis suggests that, Li–CdS/TiO2 film is 10.2 μm thick, porous, spongy and uniformly covered on FTO surface. The HR-TEM images reveal that the CdS nanoparticles are in intimate contact with the TiO2 nanocrystal shells with the CdS/TiO2 interfaces and the particle size of CdS and Li2S lies in the range of 20 nm–50 nm. UV-DRS analysis shows that, as the loading of Li in CdS/TiO2 films increases, there is decrease in band gap energy. The XPS analysis supports the presence of Li+ in Li–CdS/TiO2 nanocomposite. The PL spectra suggest that, with the increase in extend of Li+ ions into Li–CdS/TiO2, intensity of green emission band increases and it is shifted to higher wavelength. This reflects the low recombination rate of photo generated charge carrier in Li–CdS/TiO2 which is responsible for higher photocatalytic H2 production. The visible light photoanodic performance of Li–CdS/TiO2 was investigated for H2 evolution using aqueous Na2SO3 and Na2S solution under natural sunlight. Among the all-synthesized nanocomposite material, the highest amount of hydrogen produced over 20Li–CdS/TiO2 was found to be 38.61 ml/g/h in natural sunlight. Photoelectrochemical (PEC) performance of Li–CdS/TiO2 was examined. A possible mechanism for photocatalytic hydrogen generation is also discussed.

Synthesizing and optimizing of AgCuS-CNTs composite coatings on AgCu10 substrate prepared by in-situ sulfide method

In order to improve the current-carrying properties of AgCu10 alloy, AgCuS-carbon nanotubes (CNTs) composite coatings were synthesized on AgCu10 substrates using an in-situ sulfide method. During the process, an entangled CNTs layer was formed firstly on the AgCu10 substrate by dipping the substrate into a CNTs dispersant and dried at room temperature, then an AgCuS-CNTs coating was synthesized in-situ by immersing the substrate with the CNTs layer in a 0.1 M Na2S solution. The current-carrying friction performance of the composite coating was significantly improved. Compared with the AgCu10 substrate, the friction coefficient was decreased from ∼0.35 to ∼0.15, and the wear rate was reduced by 2 orders of magnitude. Furthermore, the electrical resistivity of the coatings was as low as 2.44 × 10−6 Ω·cm, which was almost the same as the AgCu10 substrate.

Dual action of a distinctive colloidal 3-(Benzimidazole-2-yl)-2-hydroxybenzaldehyde grafted chitosan support for the continual detection ability for Hg (II) in aqueous environ and inherent emission-induced live cell imaging

In this research work, an interesting sugar based fluorescent materials has been successfully developed to detect metal ions (Hg2+) in aqueous solution. The prepared colloid, 3-(benzimidazole-2-yl)-2-hydroxy benzaldehyde/chitosan (ChI) has significant characteristics as greener and eco-friendly material. ChI has found for switching of proton transfer between enol-imine and keto-enamine forms of ChI through excited-state intramolecular proton transfer (ESIPT) mechanism. The internal chemical-bonding and functionality of ChI are confirmed through FTIR, UV–Vis, fluorescence, SEM, TEM, DLS etc. ChI shows its fluorescence-quenching, selectivity, scavenging and chelating capabilities for Hg2+ ions in the presence of other cations in aqueous solution. Spectral and XRD analysis have established the remarkable continual and consistent detection of Hg2+ in aqueous system with a limit of detection of 0.204 nM. The strong chelating agent EDTA is used to regain of fluorescence of ChI in support of labile chelation ability of ChI and to show reversibility for continual detection of Hg2+ due to the strong EDTA/Hg2+ complexation. Scavenging ability is investigated using Na2S solution followed by the XRD analysis of precipitate appeared. Also, ChI shows its efficiency for the fluorescence cell imaging in live HADF cells with negligible cytotoxicity. Convincingly, ChI has processed as materials with very significant addition and advancement for its multimodal and eco-friendly behavior in current material development research.

Photocatalytic H2 Production by Visible Light on Cd0.5Zn0.5S Photocatalysts Modified with Ni(OH)2 by Impregnation Method.

Nowadays, the study of environmentally friendly ways of producing hydrogen as a green energy source is an increasingly important challenge. One of these potential processes is the heterogeneous photocatalytic splitting of water or other hydrogen sources such as H2S or its alkaline solution. The most common catalysts used for H2 production from Na2S solution are the CdS-ZnS type catalysts, whose efficiency can be further enhanced by Ni-modification. In this work, the surface of Cd0.5Zn0.5S composite was modified with Ni(II) compound for photocatalytic H2 generation. Besides two conventional methods, impregnation was also applied, which is a simple but unconventional modification technique for the CdS-type catalysts. Among the catalysts modified with 1% Ni(II), the impregnation method resulted in the highest activity, for which a quantum efficiency of 15.8% was achieved by using a 415 nm LED and Na2S-Na2SO3 sacrificial solution. This corresponded to an outstanding rate of 170 mmol H2/h/g under the given experimental conditions. The catalysts were characterized by DRS, XRD, TEM, STEM-EDS, and XPS analyses, which confirmed that Ni(II) is mainly present as Ni(OH)2 on the surface of the CdS-ZnS composite. The observations from the illumination experiments indicated that Ni(OH)2 was oxidized during the reaction, and that it therefore played a hole-trapping role.

Fabrication of MnCoS Thin Films Deposited by the SILAR Method with the Assistance of Surfactants and Supercapacitor Properties

Compact MnCoS thin films on a nickel foam (NF) substrate were prepared by successive ionic layer adsorption and a reaction (SILAR) method, and two surfactants (SDS and CTAB) were used to improve the wettability of the NF. The MnCoS thin films were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The supercapacitive properties were evaluated by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and impedance spectroscopy (EIS). The results show that while the NF was first dipped in surfactant solution, followed by a mixture of Mn2+ and Co2+ or a Na2S solution, the load and density of the MnCoS on the NF’s surface significantly increased and delivered a much higher specific capacitance than that of the MnCoS thin film formed without the assistance of surfactants, which were 2029.8 F g−1 (MnCoS-CTAB), 1500.3 F g−1 (MnCoS-SDS), and 950.4 F g−1 (MnCoS-H2O) at a current density of 1 A g−1 in 3 M KOH aqueous solution. When the current density increased to 10 A g−1, the MnCoS-CTAB with the highest specific capacitance exhibited a capacitance of 1371.9 F g−1, with a 71% capacity retention up to 1000 cycles, showing a good rate performance and cycle stability.

Highly efficient twinned MnxCd1-xS homojunction photocatalyst modified by noble metal-free Ni12P5 for H2 evolution under visible light

A series of twin-phase MnxCd1-xS solid solutions with zinc blende (ZB) and wurtzite (WZ) structures were prepared by an alkaline hydrothermal method in this work. When using 0.35 M Na2SO3/0.25 M Na2S solution as a sacrificial agent under visible light (λ ≥ 420 nm), the H2 production activity of T-Mn0.5Cd0.5S is 33.4 mmol h−1 g−1, significantly higher than that of ZB-Mn0.5Cd0.5S (15.4 mmol h−1 g−1) or WZ-Mn0.5Cd0.5S (18.2 mmol h−1 g−1). The photocatalytic activity of T-Mn0.5Cd0.5S is further enhanced by introducing Ni12P5 as a cocatalyst, in which the H2 evolution rate of 0.2% Ni12P5/T-Mn0.5Cd0.5S can reach 96.5 mmol h−1 g−1, 2.89 and 1.77 times than that of pure T-Mn0.5Cd0.5S and 0.5% Pt/T-Mn0.5Cd0.5S (54.6 mmol h−1 g−1), respectively. The crystalline phase, microstructure, elemental composition, optical and optoelectronic properties of the samples were characterized by XRD, SEM, TEM, HRTEM, XPS, UV–vis, PL and electrochemical workstation. The results show that the formation of a homojunction with interlaced energy band inhibits carrier recombination in the bulk phase of T-Mn0.5Cd0.5S. In addition, Ni12P5 can substitute for the noble metal as a cocatalyst to reduce the overpotential and improve the separation rate of electrons and holes to enhance H2 evolution. This work provides reference for building homojunction photocatalysts and loading inexpensive transition metal phosphides instead of noble metals.

Improvement of stability of perovskite solar cells with PbS buffer layer formed by solution process

To commercialize perovskite solar cells (PSCs), it is essential to ensure their stability against heat and humidity. However, organometal halide perovskites, which are employed as light absorbing materials in PSCs, have the disadvantage of being easily decomposed by moisture. Moreover, iodine ions in the perovskite are highly mobile, reducing the stability of PSCs by reacting with metal electrodes after moving to other layers when exposed to heat or light. Introducing a firm buffer layer on the perovskite surface can be an effective solution to increase stability by preventing the perovskite from such degradation. In this work, using a solution process in which Na2S solution was spin-coated on a perovskite surface and then heat-treated, we formed a buffer layer with PbS. The PbS buffer layer prevented the perovskite from being in direct contact with moisture and suppressed ion migration from the perovskite. With the PbS buffer layer, the PSCs exhibited significantly improved long-term stability, without any encapsulation 1) under continuous illumination of AM1.5G – 1 SUN light in ambient air, 2) at high temperature of 85℃ in nitrogen, and 3) in high humidity of 36.4 ± 5 % RH at elevated temperature of 60℃. In addition, the PbS buffer layer enhanced the extraction of holes from the perovskite, thereby improving the power conversion efficiency.

Initiation of Sulfide Stress Cracking Using Potentiostatic Liquid-Phase Ion Gun

A liquid-phase ion gun (LPIG) was used to create a local H2S enriched environment near Cr-containing steel surface in Na2S solutions in attempt to induce sulfide stress cracking on the specimen surface. In a 1.5 mM Na2S solution, anodic polarization of LPIG Pt microelectrode at a potential of 1.90 V vs SHE resulted in that local solution was successfully acidified to below pH 4, a pseudo-sour environment. When Cr-containing steels were potentiostatically polarized under this pseudo-sour environment by LPIG, sulfides were formed on the specimen surface depending on Cr-concentration, specimen potential, and chloride ion in solution. When LPIG was operated on Cr-containing steels subjected to tensile stress using a four-point bending tester, cracks were formed on the steel surface.

Optical reflectance studies on the oxidation of chemisorbed sulfur at the Pt(111) electrode

The oxidation of chemisorbed sulfur on Pt(111) was studied in 0.1 M H2SO4 using combined electrochemical and in situ optical reflectance. The adsorbed sulfur adlayer, prepared by immersion of the Pt electrode in Na2S solution, was successively removed by potential cycling between 0.05 and 1.22 V vs. RHE. Correlation of the electrochemical data with the parallel measured changes in optical reflectance provides insight into the intermediate steps of the sulfur oxidation process. In addition to features related to sulfur oxidation and Pt oxide formation and reduction, two transient cathodic current peaks at rather negative potentials (0.19 and 0.41 V) are observed the first cycles, which can be assigned to intermediates of the sulfur oxidation process. The sulfur coverage oxidized in each cycle is initially large but then decreases rapidly, becoming negligibly small after about 10 cycles. Furthermore, a nonlinear change of the reflectance with decreasing sulfur coverage is observed, which suggests changes in the nature of the S-Pt bond with coverage.

Evolution of conformation and thermal properties of bovine hides collagen in the sodium sulphide solution

Conformations of secondary and super secondary structure from bovine hides collagen are very important for constructing collagen molecular space structure, and directly related to its properties. In this work, the evolutional mechanism of the collagen conformation in the environment of sodium sulphide (Na2S) solution is periodically studied by FT-IR spectroscopy, the Gaussian peak fitting of secondary derivative, and auxiliary methods such as SDS-PAGE, SEM and TG. As a result, the three polypeptide chains structure of bovine hide collagen was hardly affected by the ions of OH−, HS− and S2−. The conformation of collagen molecules such as β-turn, triple helix and β-strand were gradually evolved into unordered structure and α-helix with the sequential addition of OH−, HS− and S2−, which is because the hydrogen bond inside collagen molecular is extended or opened with the increase of the synergistic effect of pH and reducibility of HS− and S2− in the solution. The bound water content and thermal properties of the treated collagen molecules are decreased. Finally, the order of the hydrolysis ability to collagen is NaOH < NaHS < Na2S at the same condition, which was confirmed by measuring the content of hydroxyproline from their solutions after treating the collagen. This work provides very important information for understanding the evolutional mechanism of bovine hide collagen conformation in the Na2S solution, developing the alternatives of sulfide, extraction of collagen, tanning, and application of collagen in biological and material science.

Enhanced photoelectrochemical performance of P-doped g‑C3N4/Zn0.5Cd0.5S heterojunction photocathode for water splitting

Photoelectrochemical (PEC) hydrogen evolution reaction at semiconductor photocathode in the presence of visible light is a promising way to harvest renewable energy. Graphitic carbon nitride (g-C3N4) has intriguing properties, making it highly favorable for photoelectrode engineering. This work demonstrated P-doped g-C3N4 nanosheets (PCN-Nss) and Zn0.5Cd0.5S heterojunction (PCN-Nss/ZCS-40) for PEC hydrogen evolution reaction using simulated sunlight. A facile and simple two-step strategy developed PCN-Nss/ZCS-40 photocathode; including co-precipitation of ZnCdS in the highly dispersed suspension of PCN-Nss and then drop-casting it on the surface of a conductive substrate. The intimate contact between PCN-Nss and ZnCdS at the molecular level due to the formation of heterojunction efficiently triggers charge separation, suppressing electron-hole pair recombination and easing the movement of photo-generated holes towards the conductive substrate. PCN-Nss/ZCS-40 (40% P-C3N4 by weight) showed substantially improved photocurrent response (−12 µA cm−2) at −0.6 V vs Ag/AgCl reference electrode in 0.2 M Na2S solution, which is almost 40 times greater than simple P-C3N4 nanosheets under the same conditions. This work will expose new applications for P-doped graphitic carbon nitride-based heterostructures for PEC water splitting.

Selective Recovery of Cadmium, Cobalt, and Nickel from Spent Ni–Cd Batteries Using Adogen® 464 and Mesoporous Silica Derivatives

Spent Ni–Cd batteries are now considered an important source for many valuable metals. The recovery of cadmium, cobalt, and nickel from spent Ni–Cd Batteries has been performed in this study. The optimum leaching process was achieved using 20% H2SO4, solid/liquid (S/L) 1/5 at 80 °C for 6 h. The leaching efficiency of Fe, Cd, and Co was nearly 100%, whereas the leaching efficiency of Ni was 95%. The recovery of the concerned elements was attained using successive different separation techniques. Cd(II) ions were extracted by a solvent, namely, Adogen® 464, and precipitated as CdS with 0.5% Na2S solution at pH of 1.25 and room temperature. The extraction process corresponded to pseudo-2nd-order. The prepared PTU-MS silica was applied for adsorption of Co(II) ions from aqueous solution, while the desorption process was performed using 0.3 M H2SO4. Cobalt was precipitated at pH 9.0 as Co(OH)2 using NH4OH. The kinetic and thermodynamic parameters were also investigated. Nickel was directly precipitated at pH 8.25 using a 10% NaOH solution at ambient temperature. FTIR, SEM, and EDX confirm the structure of the products.