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One of the main problems with water pollution is dye contamination of rivers, industrial effluents, and water sources. It has endangered the world's sources of drinking water. Several remediation strategies have been carefully developed and tested to minimize this ominous picture. Due to their appealing practical and financial benefits, adsorption methods in particular are often listed as one of the most popular solutions to remediate dye-contaminated water. Biopolymer-based hydrogel nanocomposites are a cutting-edge class of materials with a wide range of applications that are effective in removing organic dyes from the environment. Since the incorporation of various materials into hydrogel matrices generated composite materials with distinct characteristics, these unique materials were often alluded to as ideal adsorbents. The fundamental emphasis of the conceptual and critical review of the literature in this research is the significant potential of hydrogel nanocomposites (HNCs) to remediate dye-contaminated water (especially for articles from the previous five years). The review also provides knowledge for the development of biopolymer-based HNCs, prospects, and opportunities for future research. It is also focused on optimum conditions for dye adsorption processes along with their adsorption kinetics and isotherm models. In summary, the information gained in this review research may contribute to a strengthened scientific rationale for the practical and efficient application of these novel adsorbent materials.
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Nanocompostos , Poluentes Químicos da Água , Purificação da Água , Águas Residuárias , Poluentes Químicos da Água/análise , Corantes , Polissacarídeos , Hidrogéis , Adsorção , Água , CinéticaRESUMO
This paper reports a simple method of designing and synthesizing magnetic iron oxide (IO) integrated locust bean gum-cl-polyacrylonitrile hydrogel nanocomposites (LBG-cl-PAN/IONP) by in situ mineralization of iron ions in a hydrogel matrix. A two-step gel crosslink method followed by co-precipitation method was used to prepare these novel hydrogels embedded with magnetic iron oxide nanoparticles. The LBG-cl-PAN/IONP hydrogel nanocomposite (HNC) were tested in batch adsorption experiments for their ability to remove a cationic dyes, methylene blue (MB) & Methyl violet (MV), from aqueous solution. In order to analyze the LBG-cl-PAN/IONP HNC, FTIR, XRD, XPS, VSM, TEM, and EDX techniques were applied. Numerous operating parameters were studied, including the amount of adsorbent, the contact time, pH, temperature, the dye concentration, and the coexisting ion concentration. According to the Langmuir isotherm model, MB and MV had maximum monolayer adsorptive capacities of 1250 and 1111 mg/g, respectively. LBG-cl-PAN/IONP HNC controlled IONP oxidation as well as sustained adsorptive removal over a wide pH range (7-10). The key mechanism of adsorption consisted of electrostatic interaction and ion exchange. For successful use in successive cycles after regeneration using HNO3 as eluent, the LBG-cl-PAN/IONP HNC can easily be reused. As a material, the LBG-cl-PAN/IONP HNC is a promising sorbent or composite material for removing toxic dyes from water, and therefore can be applied to enhance water and wastewater treatment technology. Additionally, we have briefly evaluated LBG-cl-PAN/IONP HNC for antibacterial and supercapacitor applications. According to our knowledge, this is the first report describing the use of LBG-cl-PAN/IONP HNC multifunctional efficacy as an excellent sorbent, antibacterial and electrochemical supercapacitor applications.
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Nanocompostos , Poluentes Químicos da Água , Adsorção , Antibacterianos , Corantes , Galactanos , Violeta Genciana , Hidrogéis , Concentração de Íons de Hidrogênio , Cinética , Nanopartículas Magnéticas de Óxido de Ferro , Mananas , Azul de Metileno , Gomas Vegetais , ÁguaRESUMO
Photocatalytic removal is more appropriate for the destruction of organic contaminants. The ternary Bi2MoO6-reduced graphene oxide (rGO)-TiO2 catalyst was synthesized using a simple hydrothermal method, and various surface analytical optical techniques were analyzed. The photocatalytic decomposition efficiency of the Bi2MoO6-rGO-TiO2 composite was 92.3% higher than those of pure and binary photocatalysts. The effects of operational parameters, such as catalyst ratio, catalyst variation, rGO ratio variation, and pH value variation were also analyzed. The as-prepared ternary photocatalyst exhibited low photoluminescence and high photocurrent density, which suppressed photon-induced electron and hole (h+) recombination and effective charge separation. The study demonstrated that rGO has excellent electron transfer performance and enhanced photocatalytic reaction stability. The perfect cycling stability of Bi2MoO6-rGO-TiO2 was retained even after five consecutive cycles on the photocatalytic degradation reaction performance. In this study, we propose a decomposition performance mechanism for ofloxacin degradation that underwent visible-light irradiation.
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Ofloxacino , Óxidos , Bismuto , Grafite , Molibdênio , TitânioRESUMO
Methylene blue (MB) dye is the most common harmful, toxic, and non-biodegradable effluent produced by the textile industries. The present study investigates the effect of zinc oxide (ZnO) nanoparticles (NPs) and Ag-Ni doped ZnO NPs on the performance of photocatalytic degradation of MB dye. Pure ZnO and Ag-Ni doped ZnO NPs are synthesized using the co-precipitation method. The crystalline nature and surface morphology of the synthesized pure ZnO and Ag-Ni doped ZnO NPs was characterized by powder X-ray diffraction, scanning electron microscopy (SEM), and high resolution transmission electron microscopy (HRTEM) analysis. The presence of spherical-like morphologies was confirmed from SEM and HRTEM analysis. The presence of Ni-O and Zn-O bands in the synthesized materials was found by Fourier transform infrared (FTIR) spectroscopy analysis. The MB dye was degraded under UV-light exposure in various pH conditions. The Ag (0.02%)-Ni doped ZnO NPs exhibits highest photocatalytic activity of 77% under pH 4.
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Nanopartículas , Óxido de Zinco , Catálise , Azul de Metileno , Prata , Difração de Raios XRESUMO
The minerals have a somewhat slower than other transition metals at critical reduction rates in their ability to deliver oxygen. Thus, single minerals alone do not exhibit a higher oxygen transfer capacity than metal oxide oxygen carriers. In this study, we try to solve the problem of single mineral ilmenite (FeTiO3) by combining it with Fe-based red mud and Cu oxide. When the ilmenite was used without calcination, the CH4-CO/air redox cycle showed rapid decayed. However, when ilmenite was calcined, the CH4-CO/air redox cycle became stable, and the oxygen transfer rate increased to 4.2%. This is because the FeTiO3 structure was converted to the pseudobrookite (Fe2TiO5) structure through the calcination process. That is, the Fe2+ ion in the ilmenite structure was converted into an Fe3+ ion. When 30 wt.% of red mud was added to the Fe ion, it reacted with the rutile-type titania mixed with pseudobrookite-typed Fe2TiO5, producing an almost perfect pseudobrookite crystal. This resulted in a slight increase in the capacity of oxygen transfer to 4.9%. When 15 wt.% of Cu oxide was added, the oxygen transfer capacity increased to 6.0%. This performance was indicated by the cyclic voltammetry curve that remained constant even after 200 cycles. Here, we argue that if low-cost minerals as a base material are used in appropriate amounts, the production of a lowest-cost oxygen carrier can be achieved.
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The objective of this study is to introduce Cu into SnO2 sorbent for improving its COS adsorption capacity. Cu-doped SnO2 adsorbents were synthesized using a conventional sol-gel method with citric acid. X-ray diffraction studies revealed that up to 0.4 mol of Cu ions were well-inserted within the SnO2 framework. Scanning electron microscopy images confirmed that the addition of Cu ions reduced the particle size of the SnO2 sorbents. Additionally, it led to an increase in the Brunauer-Emmett-Teller surface area of the sorbents. The COS adsorption tests were carried out in the temperature range of 300-400 °C with a gas hourly space velocity of 8,500 h-1. It was found that Cu0.6SnO2 displayed higher COS adsorption capacity than the sorbents of other compositions, and the breakthrough time and COS adsorption capacity on it at 400 °;C were 170 min and 4.87 mg/g, respectively. X-ray photoelectron spectroscopy results indicated that the Cu2+ ions in the CuxSnO2 adsorbent converted into CuS by binding to the S2- ions in COS gas, while the remaining CO segments combined with the Sn atoms in SnO2 and then are adsorbed as SnCO. Overall, this study showed that the hard-soft acid-base rule is better followed in the Cu0.6SnO2 adsorbent than in the SnO2 adsorbent and that the adsorption is more stable.
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This study examined the effects of additives to improve the COS absorption capacity of Cu-Al-based sorbents for the integrated gasification fuel cell (IGFC) process. To absorb a small amount of COS, an Al-based precursor was added to the precursor solution for Cu-Al-based sorbents because a high surface area absorber was required. Various transition metals (Zn, Fe, Mn) were used as additives to improve the stability of the Cu-Al-based absorbent. The changes in surface properties and sulfur absorption capacity of the Cu-Al-based absorbent were investigated according to the composition of transition metals. As a result of the sulfur absorption test, the difference in the sulfur absorption capacity of the Cu-based sorbents was confirmed depending on the type of additive, and changes in their surface area. Moreover, the pore characteristics were observed by the nitrogen adsorption method. Sorbents with high surface areas generally have high sulfur capacity, but the additive component has a strong effect. These results can be explained by the transition metal additive binding to Cu to form a composite metal oxide. Furthermore, manganese was found to be suitable for improving the stability and surface area of the copper-based absorbent.
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In order to enhance the photoreduction of CO2 to CH4, a new type of photocatalyst, Sb1.5Sn8.5-xTixO19.0, with high conductivity and low bandgap was developed by partially incorporating Ti into the framework of Sb1.5Sn8.5O19.0 (antimony-doped tin oxide, ATO) using a controlled hydrothermal method. XRD and TEM analyses indicated that the Sb1.5Sn8.5-xTixO19.0 particles exhibited a tetragonal crystal structure and were approximately 20 nm in size. Furthermore, the bandgap and conductivity of these materials increased with increasing Ti content. A study of the photoreduction of CO2 with H2O revealed a remarkable increase in the generation of CH4 over the Sb1.5Sn8.5-xTixO19.0 catalysts. In particular, CH4 generation was the highest when Sb1.5Sn8.5Ti1.0O19.0 was used as the photocatalyst, and was three-fold higher than that achieved by using anatase TiO2. Photoluminescence studies showed that the enhanced photocatalytic activity of the Sb1.5Sn8.5-xTixO19.0 materials could be attributed to the interfacial transfer of photogenerated charges, which led to an effective charge separation and inhibition of the recombination of photogenerated electron-hole (e-/h+) pairs.
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The catalytic activity of a macro-mesoporous catalyst coated on a metal foam plate in the reforming of bio-ethanol to synthesis gas was investigated. The catalysts were prepared by coating a support with a noble metal and transition metal. The catalytic activity for the production of synthetic gas by the reforming of bio-ethanol was compared according to the support material, reaction temperature, and steam/carbon ratio. The catalysts coated on the metal foams were prepared using a template method, in which macro-pores and meso-pores were formed by mixing polymer beads. In particular, the thermodynamic equilibrium composition of bio-ethanol reforming with the reaction temperature and steam/carbon ratio to produce synthetic gas was examined using the HSC (Enthalpy-Entropy-Heat capacity) chemistry program in this study. The composition of hydrogen and carbon monoxide in the reformate gas produced by steam reforming over the Rh/Ni-Ce-Zr/Al2O3-based pellet type catalysts and metal foam catalysts that had been coated with the Rh/Al-Ce-Zr-based catalysts was investigated by experimental activity tests. The activity of the metal foam catalyst was higher than that of the pellet type catalyst.
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The purpose of this study was to use a spinel structure to improve the performance and stability of chemical looping combustion processes. The oxygen carrier employed was Fe2MnO4, in which Ni was substituted at the Fe sites. Fe2-xNixMnO4 spinel particles were successfully synthesized by a sol-gel method. The obtained particles were characterized by X-ray diffraction (XRD), scanning electron microscopy, and CH4-/CO-temperature programmed desorption experiments. The XRD analysis confirmed that all the synthesized particles presented spinel structure. The performance of the particles was evaluated in redox cycle experiments under H2/air and CH4/air at 850 °C using a thermogravimetric analyzer. The Ni-substituted particles exhibited a higher performance than Fe2Mn1, being Fe1Ni1Mn1 the sample with the highest oxygen transfer capacity (19.68 wt% in H2/air and 15.90 wt% in CH4/air).
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This study examined the effects of Mn on Cu-Mn-based mixed metal oxides used as oxygen transfer particles in the chemical looping combustion process. Chemical looping combustion of fuel is induced by the oxygen contained in the metal oxide. The oxidation reaction of the metal oxide particles reduced in the fuel reactor occurs in the air reactor. The metal oxide, which allows oxygen transfer, circulates between the fuel reactor to air reactor and supplies oxygen in the fuel reactor. Both reactors are operated at high temperatures (>850 °C) and the heat of reaction is recovered to produce electricity and heat. Oxygen carriers must have high thermal stability, high oxygen capacity, and rapid transfer rate, and should have a high attrition resistance because they are used in a circulating fluidized bed reactor. Cu exhibits high oxygen transfer rates, but it cannot be used for chemical looping combustion under high temperature conditions because of its low thermal stability. In this study, Mn was mixed to improve the thermal stability of the Cu component and the effect of these was investigated. This study examined copper metal oxide and the stability of Cu according to the temperature that the spinel structure had been synthesized. As a result, the spinel structure was well maintained in the oxidation-reduction cyclic-repeated tests and the migration of Cu was not severe. The spinel structure had high durability. Overall, Mn inhibits the migration of Cu because it forms a spinel structure with Cu.
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To improve the light harvesting efficiency in dye-sensitized solar cells (DSSC) the light scattering layer is important. In this Letter, we present ball/dumbbell-like structured micrometer-sized Sb2S3 particles for photon propagation in DSSCs and demonstrate their effective usage in photoelectrodes. The analysis of the photoelectrode by a UV-vis spectrophotometer indicates that the absorption wavelength of an electrode with scattering layer can be obviously promoted from ultraviolet to visible light. The synthesized Sb2S3 particle structures were also characterized by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The photovoltaic performance of the ball/dumbbell-like structured Sb2S3 based cell exhibits excellent power conversion efficiency.
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This study explores a strategy to mitigate capacity fading in secondary batteries, which is primarily attributed to side reactions caused by residual Li impurities (LiOH or Li2CO3) on the surface of Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) layered cathode materials. By applying a 1.5 wt% Co3(PO4)2 coating, we successfully formed a thin and stable LiF cathode-electrolyte interface (CEI) layer, which resulted in decreased battery resistance and enhanced diffusion of Li+ ions within the electrolyte. This coating significantly improved the interface stability of NCM811, leading to superior battery performance. Specifically, the discharge capacity of uncoated NCM811 was 190 mA h g-1 at a charge of 4.3 V and a rate of 0.1C, whereas the 1.5Co3(PO4)2/NCM811 exhibited an increased capacity of 213 mA h g-1. Furthermore, the Co3(PO4)2 coating effectively reduced the levels of LiOH and Li2CO3 on the NCM811 surface to only 0.1 %, thereby minimizing adverse side reactions with the electrolyte salt (LiPF6), cation mixing between Ni2+ and Li+, and defects at the NCM811 interface. As a result, battery lifespan was significantly extended. This study presents a robust approach for enhancing battery stability and performance by efficiently reducing residual Li+ ions on the surface of NCM811 through strategic Co3(PO4)2 coating.
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An effective and rational pathway to tune the electronic bandstructure and visible light absorption properties of low-cost organic graphitic carbon nitride (g-C3N4, GCN) photocatalysts is still very challenging. Here, an efficient strategy is validated to tailor the bandstructure of g-C3N4 and C-doping can be regulated by polymerizing melamine with malonic acid, which can greatly extend the photoresponse range to 900 nm. The optimized GCN exhibits an improved photocatalytic hydrogen production rate of 663.6 µmol g-1 h-1 under visible light irradiation and an apparent quantum yield of 11% at 420 nm, which is three times higher than that of traditional bulk g-C3N4. This superior performance is derived from the unique ordered and porous structure of GCN, which effectively improves its light absorption and provides a larger specific surface area. In addition, the introduction of malonic acid into melamine and the subsequent thermal polymerization reaction further optimize the band structure of GCN, extend its light absorption via C-doping, and improve the photoinduced charge separation, resulting in high photocatalytic performance. This strategy provides a novel platform to design highly efficient GCN-based photocatalysts with precisely tunable operation windows and enhanced charge separation.
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The visible-light-driven photocatalytic degradation of pharmaceutical pollutants in aquatic environments is a promising strategy for addressing water pollution problems. This work highlights the use of bromine-ion-doped layered Aurivillius oxide, Bi2WO6, to synergistically optimize the morphology and increase the formation of active sites on the photocatalyst's surface. The layered Bi2WO6 nanoplates were synthesized by a facile hydrothermal reaction in which bromine (Br-) ions were introduced by adding cetyltrimethylammonium bromide (CTAB)/tetrabutylammonium bromide (TBAB)/potassium bromide (KBr). The as-synthesized Bi2WO6 nanoplates displayed higher photocatalytic tetracycline degradation activity (~83.5%) than the Bi2WO6 microspheres (~48.2%), which were obtained without the addition of Br precursors in the reaction medium. The presence of Br- was verified experimentally, and the newly formed Bi2WO6 developed as nanoplates where the adsorbed Br- ions restricted the multilayer stacking. Considering the significant morphology change, increased specific surface area, and enhanced photocatalytic performance, using a synthesis approach mediated by Br- ions to design layered photocatalysts is expected to be a promising system for advancing water remediation.
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A hydrothermal technique was employed to synthesize a Sr2Nb2O7-rGO-ZnO (SNRZ) ternary nanocatalyst, in which ZnO and Sr2Nb2O7 were deposited on reduced graphene oxide (rGO) sheets. The surface morphologies, optical properties, and chemical states, of the photocatalysts were characterized to understand their properties. The SNRZ ternary photocatalyst was superior over the reduction of Cr (VI) to harmless Cr (III) compared to the efficiencies obtained using bare, binary, and composite catalysts. The effects of various parameters, including the solution pH and weight ratio, on the photocatalytic reduction of Cr (VI) were investigated. The highest photocatalytic reduction performance (97.6%) was achieved at pH 4 and a reaction time of 70 min. Photoluminescence emission measurements were used to confirm efficient charge migration and separation across the SNRZ, which improved the reduction of Cr (VI). A feasible reduction mechanism for the SNRZ photocatalyst is proposed. This study presents an effective, inexpensive, non-toxic, and stable catalyst, for the reduction of Cr (VI) to Cr (III) using SNRZ ternary nanocatalysts.
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Grafite , Óxido de Zinco , Óxido de Zinco/química , Grafite/química , Zinco , Oxirredução , Cromo/química , Compostos OrgânicosRESUMO
This study focuses on the electrochemical properties of layered double hydroxide (LDH), which is a specific structure of NiCoCu LDH, and the active species therein, rather than the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) of ternary NiCoCu LDH materials. Six types of catalysts were synthesized using the reflux condenser method and coated onto a nickel foam support electrode. Compared to bare, binary, and ternary electrocatalysts, the NiCoCu LDH electrocatalyst exhibited higher stability. The double layer capacitance (Cdl) of the NiCoCu LDH (12.3 mF cm-2) is greater than that of the bare and binary electrocatalysts, indicating that the NiCoCu LDH electrocatalyst has a larger electrochemical active surface area. In addition, the NiCoCu LDH electrocatalyst has a lower overpotential of 87 mV and 224 mV for the HER and OER, respectively, indicating its excellent activity with the bare and binary electrocatalysts. Finally, it is demonstrated that the structural characteristics of the NiCoCu LDH contribute to its excellent stability in long-term HER and OER tests.
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Earth abundant metal based plasmonic photocatalysis is one of the most proficient approaches to degrade the emergent organic pollutants in contaminated water. Here, we report that using one-dimensional CdS/zero-dimensional Bi quantum dot (QD) heterostructures (1D/0D CdS/Bi HSs) were obtained via a simple solvothermal reaction. The results specified that the Bi QDs were grown onto CdS NRs through the reduction of Bi3+ ions. The Bi modified CdS HSs were employed as a photocatalyst for pharmaceutical pollutant tetracycline degradation and the optimized sample showed the maximum photocatalytic degradation activity of 90% under visible light radiation within 60 min, which is greater than the pure CdS (52%) under identical conditions. Based on the structural characterizations and degradation efficiency, the obtained CdS/Bi is a promising photocatalyst for the treatment of wastewater which contains emerging pollutants such as organic dyes and pharmaceutical antibiotics during the industrial processes. The boosted photocatalytic degradation efficiency is credited to the doped Bi3+ species; surface plasmon resonance effect that raised from metallic Bi QDs and proficient photoinduced charge carriers separation.
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Poluentes Ambientais , Pontos Quânticos , Antibacterianos , Bismuto/química , Catálise , Preparações Farmacêuticas , TetraciclinaRESUMO
In this work, we tailor facile hydrogels nanocomposite (HNC) based on sustainable karaya gum for water treatment. Karaya gum crosslink poly(acrylamide-co-acrylonitrile) @ silver nanoparticle (KG-cl-P(AAm-co-AN)@AgNPs) HNC were made by an aqueous free radical in situ crosslink copolymerization of acrylamide (AAm) and acrylic acid (AA) in aqueous solution of KG-stabilized AgNPs. FTIR, XRD, DTA-TGA, SEM, and TEM were used to characterize HNC. The hydrogels' swelling, diffusion, and network characteristics were investigated. The removal efficiency of HNC was found to be 99% at pH 8 for a crystal violet (CV), dose of 0.02 g after 1 h. Dye adsorption by these hydrogels was also investigated in terms of isotherms, and kinetics. The dye's exceptionally high adsorption capacity on HNC for CV removal is explained by H-bonding interactions, as well as dipole-dipole and electrostatic interactions between anionic adsorbent and cationic dye molecules (Qmax, 1000 mg/g). The HNC can be regenerated with 0.1 M HCl and reused at least 10 times maintaining over 68% dye removal. The loading of AgNPs into the polymeric matrix of KG-cl-P(AAm-co-AN) significantly increases the removal percentage of CV dye from its aqueous solution, according to this study.
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Acrilonitrila , Poluentes Ambientais , Nanopartículas Metálicas , Poluentes Químicos da Água , Acrilamidas/química , Adsorção , Violeta Genciana , Hidrogéis/química , Concentração de Íons de Hidrogênio , Goma de Karaya , Cinética , Prata , Poluentes Químicos da Água/químicaRESUMO
Ternary heterostructures play a crucial role in improving the separation of charge carriers and fast surface reaction kinetics, which in turn helps in understanding the effective photocatalytic water splitting performance. Herein, CuS/Ag2O nanoparticles were presented on a graphitic carbon nitride (g-C3N4) surface to obtain CuS/Ag2O/g-C3N4 material using facile hydrothermal and precipitation methods. Structural and morphological studies confirmed the presence of ternary nanostructures comprising CuS, Ag2O, and g-C3N4 with nanoparticle and nanosheet morphologies. The as-synthesized CuS/Ag2O/g-C3N4 exhibited a remarkable photocatalytic H2 production of 1752 µmol.h-1.g-1cat, which is considerably superior than those of CuS and g-C3N4. The improved H2 production performance which is due to the effective interfacial CuS/Ag2O/g-C3N4 heterojunction interface and superior hole (h+) trapping capability of the CuS at the CuS/Ag2O/g-C3N4 interface. This can efficiently enhance the lifetime of photoexcited charge carriers and enhance the electron density for the production of H2. The optimum CuS/Ag2O/g-C3N4 heterostructure remained stable after 8 successive experimental cycles, although with a slight change in the H2 production rate. Therefore, this study offers a novel approach to exploit the efficacy through the synergetic effect of integrating CuS as the photocatalyst and Ag2O as the visible sensitizer, thus proposing a viable strategy of using earth-abundant material to enhance the conversion of solar energy to fuel.