Synthesis, Characterization, and Photocatalytic Activities of Graphene Oxide/metal Oxides Nanocomposites: A Review

Innovative Graphene-Based Nanocomposites for Improvement of Electrochemical Sensors: Synthesis, Characterization, and Applications

Graphene, renowned for its exceptional physicochemical attributes, has emerged as a favored substrate for integrating a wide array of inorganic and organic materials in scientific endeavors and innovations. Electrochemical graphene-based nanocomposite sensors have been developed by incorporating diverse nanoparticles into graphene, effectively immobilized onto electrodes through various techniques. These graphene-based nanocomposite sensors have effectively detected and quantified various electroactive species in samples. This review delves into using graphene nanocomposites to fabricate electrochemical sensors, leveraging the exceptional electrical, mechanical, and thermal properties inherent to graphene derivatives. These nanocomposites showcase electrocatalytic activity, substantial surface area, superior electrical conductivity, adsorption capabilities, and notable porosity, which are highly advantageous for sensing applications. A myriad of characterization techniques, including Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), BET surface area analysis, and X-ray diffraction (XRD), have proven effective in exploring the properties of graphene nanocomposites and validating the adjustable formation of these nanomaterials with graphene. The applicability of these sensors across various matrices, encompassing environmental, food, and biological domains, has been evaluated through electrochemical measurements, such as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). This review provides a comprehensive overview of synthesis methods, characterization techniques, and sensor applications pertinent to graphene-based nanocomposites. Furthermore, it deliberates on the challenges and future prospects within this burgeoning field.

Photocatalytic Degradation of Organic Pollutants-Nile Blue, Methylene Blue, and Bentazon Herbicide-Using NiO-ZnO Nanocomposite

Water pollution poses a significant threat to both human health and ecosystem integrity. Chemical pollutants such as dyes and pesticides affect the water quality and endanger aquatic life. Among the methods for water purification from organic pollutants, photodegradation is certainly a valid technique to decrease such contaminants. In this work, pristine NiO, ZnO, and NiO-ZnO photocatalysts were synthesized by the homogeneous co-precipitation method. X-ray diffraction confirms the formation of a photocatalyst consisting of ZnO (Hexagonal) and NiO (Cubic) structures. The crystalline size was calculated by the Scherrer formula, which is 19 nm for the NiO-ZnO photocatalyst. The band gap measurements of the prepared samples were obtained using the Tauc Plot, equation which is 2.93 eV, 3.35 eV and 2.63 eV for NiO, ZnO, and NiO-ZnO photocatalysts, respectively. The photocatalytic performance of NiO-ZnO nanocomposite was evaluated through the degradation of Methylene Blue and Nile Blue dyes under sunlight, and Bentazon herbicide under a UV light. Photocatalyst degradation efficiency was 95% and 97% for Methylene Blue and Nile Blue in 220 min under sunlight while a degradation of 70% for Bentazon after 100 min under UV light source was found.

Synthesis of AZO-Coated ZnO Core-Shell Nanorods by Mist Chemical Vapor Deposition for Wastewater Treatment Applications

AZO-coated ZnO core-shell nanorods were successfully fabricated using the mist chemical vapor deposition method. The influence of coating time on the structural, optical, and photocatalytic properties of zinc oxide nanorods was investigated. It was observed that the surface area of AZO-coated ZnO core-shell nanorods increased with an increase in coating time. The growth orientation along the (0001) crystal plane of the AZO thin film coating was the same as that of zinc oxide nanorods. The crystallinity of AZO-coated ZnO core-shell nanorods was significantly improved as well. The optical transmittance of AZO-coated ZnO core-shell nanorods was greater than 55% in the visible region. The degradation efficiency for methyl red dye solution increased with an increase in coating time. The highest degradation efficiency was achieved by AZO-coated ZnO core-shell nanorods with a coating duration of 20 min, exhibiting a degradation rate of 0.0053 min-1. The photodegradation mechanism of AZO-coated ZnO core-shell nanorods under ultraviolet irradiation was revealed.

Facile synthesis of a GO-g-C3N4/BaTiO3 ternary nanocomposites for visible-light-driven photocatalytic degradation of rhodamine B

Photogenerated charge carriers can undergo rapid recombination in conventional photocatalyst systems, reducing their photocatalytic efficiency. To address this bottleneck, a g-C3N4/BaTiO3 (CNB) heterojunction composite was decorated with different mass ratios of graphene oxide (GO) to form a novel visible-light responsive ternary GO-g-C3N4/BaTiO3 (GOCNB) nanocomposite using a facile fabrication method. The GOCNB photocatalyst exhibited significantly higher light absorption and greater charge transfer than CNB, g-C3N4, or BaTiO3. The photodegradation performance of GOCNB was optimized with a 2% mass loading of GO, and it achieved a degradation rate constant of 14.9 × 10-3 min-1 for rhodamine B with an efficiency of 94% within 180 min. The rate constant was 8-fold and 6-fold higher than that of bare BaTiO3 and CNB, respectively. The stronger photocatalytic activity was attributed to the synergistic effect of GO, g-C3N4, and BaTiO3, with g-C3N4 and BaTiO3 promoting charge transfer within a wider visible light range and GO promoting electron mobility and the photocatalyst's adsorption capacity. In particular, the proposed system maintained the spatial separation of photogenerated electron-hole pairs, which is vital for high photocatalytic activity. This study provides new insights into semiconductor-based photocatalytic systems and suggests a route for more environmentally sustainable technologies.

ZnO nanostructured matrix as nexus catalysts for the removal of emerging pollutants

Water pollution stands as a pressing global environmental concern, elevating the significance of innovative, dependable, and sustainable solutions. This study represents an extensive review of the use of photocatalytic zinc oxide nanoparticles (ZnO NPs) for the removal of emerging pollutants from water and wastewater. The study examines ZnO NPs' different preparation methods, including physical, chemical, and green synthesis, and emphasizes on advantages, disadvantages, preparation factors, and investigation methods for the structural and morphological properties. ZnO NPs demonstrate remarkable properties as photocatalysts; however, their small dimensions pose an issue, leading to potential post-use environmental losses. A strategy to overcome this challenge is scaling up ZnO NP matrices for enhanced stability and efficiency. The paper introduces novel ZnO NP composites, by incorporating supports like carbon and clay that serve as photocatalysts in the removal of emerging pollutants from water and wastewater. In essence, this research underscores the urgency of finding innovative, efficient, and eco-friendly solutions for the removal of emerging pollutants from wastewater and highlights the high removal efficiencies obtained when using ZnO NPs obtained from green synthesis as a photocatalyst. Future research should be developed on the cost-benefit analysis regarding the preparation methods, treatment processes, and value-added product regeneration efficiency.

V2O5-Fe3O4/rGO Ternary Nanocomposite with Dual Applications as a Dye Degradation Photocatalyst and OER Electrocatalyst

The design and synthesis of structured nanomaterials with dual properties have always been highly attractive in various fields, especially in the reduction of environmental pollution as well as the generation of renewable energy. In this study, the synthesized ternary V2O5-Fe3O4/rGO nanocomposite was investigated to evaluate both the photocatalytic and electrocatalytic activities for the removal of methylene blue (MB) dye under UV/visible light radiation and oxygen evolution reaction (OER), respectively. The magnetized V2O5-Fe3O4/rGO nanocomposite is characterized by TEM, FE-SEM (with coupling by elemental mapping), EDS, XRD, FTIR, Raman, PL, DRS, and UV-vis analyses. The obtained results show that the graphene oxide substrate is decorated very well using Fe3O4 and V2O5 nanoparticles and converted to reduced graphene oxide (rGO). Furthermore, the V2O5-Fe3O4/rGO nanocomposite is considered as an active catalyst material to modify the commercial glassy carbon electrode for OER using linear sweep voltammetry (LSV). The photocatalytic activity of this novel nanocomposite revealed 89.2% (kobs = 1.7 × 10-2 min-1) and 76% (kobs = 8.3 × 10-3 min-1) degradation efficiencies of MB dye under UV and visible light irradiation at room temperature, respectively, and the surface area of the V2O5-Fe3O4/rGO nanocomposite was examined to be 705.8 cm2/g by N2 adsorption-desorption isotherms. In addition, electrochemical measurements determined the best OER performance of the ternary nanocomposite with the lowest overpotential (458 mV) and Tafel slope (132 mV dec-1) compared to the rGO substrate, Fe3O4, V2O5 nanoparticles, and binary nanocomposites. This work shows much enhancements in both photocatalytic and electrocatalytic activities due to the synergistic effect of the decorated GO support with V2O5 and Fe3O4 nanoparticles.

Emerging developments in dye-sensitized metal oxide photocatalysis: exploring the design, mechanisms, and organic synthesis applications

In the present day, the incorporation of environmentally conscious practices in the realm of photocatalysis holds a prominent position within the domain of organic synthesis. The imperative to tackle environmental issues linked to catalysts that cannot be recycled, generation of waste, byproducts, and challenges in achieving reaction selectivity during organic synthesis are more crucial than ever. One potential solution involves the integration of recyclable nanomaterials with light as a catalyst, offering the possibility of achieving sustainable and atom-efficient transformations in organic synthesis. Metal oxide nanoparticles exhibit activation capabilities under UV light, constituting a small percentage (4-8%) of sunlight. However, this method lacks sufficient environmental friendliness, and the issue of electron-hole recombination poses a significant hurdle. To tackle these challenges, multiple approaches have been proposed. This comprehensive review article focuses on the efficacy of dyes in enhancing the capabilities of heterogeneous photocatalysts, offering a promising avenue to overcome the constraints associated with metal oxides in their role as photocatalysts. The article delves into the intricate design aspects of dye-sensitized photocatalysts and sheds light on their mechanisms in facilitating organic transformations.

Graphene oxide-coated Ag-TiO2 hybrid nanocomposites for superior photocatalytic activity

Graphene oxide (GO) has now emerged as one of the most promising materials in different areas such as photocatalysis, adsorption, and energy storage due to its high surface area, unique layered structure, etc. Among various types of precursors, anthracite coal has attracted a lot of attention nowadays as it affords GO a high concentration of sp2 carbons resulting in high conductivity and superior absorbance in the visible region. In this report, we have prepared GO-TiO2 nanocomposites as it is supposed to possess high photocatalytic activity owing to facile electron transmission from the conduction band of TiO2 to the GO surface resulting in a much lower degree of electron-hole pair recombination. To boost the photocatalytic activity further, TiO2 was coated with Ag nanoparticles as well. These hybrid structures were characterized by different analytical techniques, for example, XRD, HR-TEM, SEM, and Raman spectroscopy. The XRD pattern of these composites consists of characteristic peaks corresponding to GO, TiO2, and Ag. The HR-TEM studies confirm the presence of GO layers, cube-shaped TiO2, and spherical Ag nanoparticles. Phenol and 4-nitrophenol have been used as model pollutants to evaluate the photooxidation efficiencies under both UV and visible light irradiation. Under UV irradiation, the GO/Ag-TiO2 ternary nanocomposite shows better photooxidation efficiency (62%) compared to Ag-TiO2 (38%), GO-TiO2 (9%), GO (17%), and TiO2 (8%) toward phenol degradation. The GO/Ag-TiO2 is also having the highest photocatalytic activity toward the removal of phenol under visible light irradiation (34%). The ternary heterostructure (85%) also possesses superior photooxidation activity compared to Ag-TiO2 (44%) and GO-TiO2 (71%) toward the degradation of p-nitrophenol under UV light radiation for 60 min. The above observation reveals that the cooperative effect of Ag, TiO2, and GO is playing a crucial role to result in the high photooxidation activity of the GO/Ag-TiO2 hetero-nanocomposites.

A Review on the Use of Metal Oxide-Based Nanocomposites for the Remediation of Organics-Contaminated Water via Photocatalysis: Fundamentals, Bibliometric Study and Recent Advances

The improper disposal of toxic and carcinogenic organic substances resulting from the manufacture of dyes, drugs and pesticides can contaminate aquatic environments and potable water resources and cause serious damage to animal and human health and to the ecosystem. In this sense, heterogeneous photocatalysis stand out as one effective and cost-effective water depollution technique. The use of metal oxide nanocomposites (MON), from the mixture of two or more oxides or between these oxides and other functional semiconductor materials, have gained increasing attention from researchers and industrial developers as a potential alternative to produce efficient and environmentally friendly photocatalysts for the remediation of water contamination by organic compounds. Thus, this work presents an updated review of the main advances in the use of metal oxide nanocomposites-based photocatalysts for decontamination of water polluted by these substances. A bibliometric analysis allowed to show the evolution of the importance of this research topic in the literature over the last decade. The results of the study also showed that hierarchical and heterogeneous nanostructures of metal oxides, as well as conducting polymers and carbon materials, currently stand out as the main materials for the synthesis of MON, with better photocatalysis performance in the degradation of dyes, pharmaceuticals and pesticides.

Development of biohybrid Ag2CrO4/rGO based nanocomposites with stable flotation properties as enhanced Photocatalyst for sewage treatment and antibiotic-conjugated for antibacterial evaluation

The proposed research outlines a facile method to synthesize Silver Chromate/reduced graphene oxide nanocomposites (Ag₂CrO₄/rGO NCs) with a narrow dissemination size for the ecological treatment of hazardous organic dyes. The photodegradation performance toward the decontamination of model artificial methylene blue dye was assessed under solar light irradiation. The crystallinity, particle size, recombination of photogenerated charge carriers, energy gap and surface morphologies of synthesized nanocomposites were determined. The experiment objective is to use rGO nanocomposites to increase Ag₂CrO₄ photocatalytic efficiency in the solar spectrum. Tauc plots of ultraviolet-visible (UV-vis) spectrum were used to calculate the optical bandgap energy of the produced nanocomposites ~1.52 eV, which resulted in a good photodegradation percentage of ~92 % after 60 min irradiation of Solar light. At the same time, pure Ag₂CrO₄ and rGO nanomaterials showed ~46 % and ~ 30 %, respectively. The ideal circumstances were discovered by investigating the effects of several parameters, including catalyst loading and different pH levels, on the degradation of dyes. However, the final composites maintain their ability to degrade for up to five cycles. According to the investigations, Ag₂CrO₄/rGO NCs are an effective photocatalyst and can be used as the ideal material to prevent water pollution. Furthermore, antibacterial efficacy for the hydrothermally synthesized nanocomposite was tested against gram-positive (+ve) bacteria viz. Staphylococcus aureus and gram-negative (-ve) bacteria viz. Escherichia coli. The maximum zone of inhibition for S. aureus and E. coli were 18.5 and 17 mm, respectively.

Dynamics of reduced graphene oxide: synthesis and structural models

Technological advancements are leading to an upsurge in demand for functional materials that satisfy several of humankind's needs. In addition to this, the current global drive is to develop materials with high efficacy in intended applications whilst practising green chemistry principles to ensure sustainability. Carbon-based materials, such as reduced graphene oxide (RGO), in particular, can possibly meet this criterion because they can be derived from waste biomass (a renewable material), possibly synthesised at low temperatures without the use of hazardous chemicals, and are biodegradable (owing to their organic nature), among other characteristics. Additionally, RGO as a carbon-based material is gaining momentum in several applications due to its lightweight, nontoxicity, excellent flexibility, tuneable band gap (from reduction), higher electrical conductivity (relative to graphene oxide, GO), low cost (owing to the natural abundance of carbon), and potentially facile and scalable synthesis protocols. Despite these attributes, the possible structures of RGO are still numerous with notable critical variations and the synthesis procedures have been dynamic. Herein, we summarize the highlights from the historical breakthroughs in understanding the structure of RGO (from the perspective of GO) and the recent state-of-the-art synthesis protocols, covering the period from 2020 to 2023. These are key aspects in the realisation of the full potential of RGO materials through the tailoring of physicochemical properties and reproducibility. The reviewed work highlights the merits and prospects of the physicochemical properties of RGO toward achieving sustainable, environmentally friendly, low-cost, and high-performing materials at a large scale for use in functional devices/processes to pave the way for commercialisation. This can drive the sustainability and commercial viability aspects of RGO as a material.

Electrochemical Behavior of β-Cyclodextrin-Ni-MOF-74/Reduced Graphene Oxide Sensors for the Ultrasensitive Detection of Rutin

Rutin, as a biological flavonoid glycoside, has very important medicinal value. The accurate and rapid detection of rutin is of great significance. Herein, an ultrasensitive electrochemical rutin sensor based on β-cyclodextrin metal-organic framework/reduced graphene oxide (β-CD-Ni-MOF-74/rGO) was constructed. The obtained β-CD-Ni-MOF-74 was characterized by X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and nitrogen adsorption and desorption. The β-CD-Ni-MOF-74/rGO presented good electrochemical properties benefiting from the large specific surface area and good adsorption enrichment effect of β-CD-Ni-MOF-74 and the good conductivity of rGO. Under optimal conditions for the detection of rutin, the β-CD-Ni-MOF-74/rGO/GCE showed a wider linear range (0.06-1.0 μM) and lower detection limit (LOD, 0.68 nM, (S/N = 3)). Furthermore, the sensor shows good accuracy and stability for the detection of rutin in actual samples.

Recent progress in semiconductor/graphene photocatalysts: synthesis, photocatalytic applications, and challenges

The presence of an increasing number of organic pollutants in water now poses serious risks to both human health and ecological systems. Many of these pollutants are persistent and non-biodegradable. The contamination of fresh water by harmful substances has compelled researchers to develop innovative, efficient, and cost-effective water remediation techniques and materials. Thus, photocatalysis has long been recognized as a promising approach to tackle both environmental remediation and the energy crisis. However, semiconductor photocatalysts frequently suffer from defects such as photo-generated charge carrier recombination, poor visible light response, and slow surface reaction kinetics, which can be remedied by modifications with appropriate co-catalysts. Therefore, graphene and its derivatives have widely been used as supports for semiconductors and photocatalysts due to their distinctive optical, physicochemical, and electrical features. This critical review addresses the current progress in the design and synthesis of graphene/semiconductor photocatalysts, as well as their use in photocatalytic degradation of organic pollutants and hydrogen production. Several influencing parameters are addressed, including pH, photocatalyst loading, initial pollutant concentration, light wavelength, and oxidizing species, all of which could have a significant impact on the rate of organic pollutant's degradation. Furthermore, the recyclability of the catalyst and its photocatalytic activity mechanisms are thoroughly discussed. Numerous case studies are systematically presented. Moreover, future prospects and major challenges are highlighted.

Novel BiVO4-nanosheet-supported MoS2-nanoflake-heterostructure with synergistic enhanced photocatalytic removal of tetracycline under visible light irradiation

This paper describes a simple in-situ hydrothermal technique for the production of BiVO₄/MoS₂ binary nanocomposites as visible-light-driven catalysts. The as-prepared samples were analyzed by structural, morphological, compositional, optical, surface area, and photocurrent analyses. The lattice fringe spaces at 0.304 nm and 0.612 nm were indexed to the (112) and (002) crystal planes of BiVO₄ and MoS₂, respectively. Antibacterial photocatalytic capabilities were assessed using tetracycline (TC). Consequently, it was observed that the BiVO₄/MoS₂ nanocomposite demonstrated improved antibacterial removal ability compared with the pristine samples. The BiVO₄/MoS₂ nanocomposite exhibited 97.46% removal of TC compared with the pure BiVO₄ (43.76%) and MoS₂ (35.28%) samples within 90 min. Thus, the photocatalytic performance was observed to follow the given order: BiVO₄/MoS₂ nanocomposite > BiVO₄ > MoS₂. The removal of TC after 90 min of irradiation was approximately 97.46%, 96.62%, 95.59%, and 94.45% after the 1st, 2nd, 3rd, and 4th cycles, respectively. Thus, the recycling tests revealed the stability of the photocatalyst, which exhibited a TC removal efficiency of 94.45% without distinct decay, even after the 4th cycle. According to the trapping results, hydroxyl radicals and holes were the key species and demonstrated a greater influence on the photocatalytic performance than superoxide radicals. The increased activity of the BiVO₄/MoS₂ nanocomposite may be attributed to its large surface area and tunable bandgap, which accelerate the charge-transport characteristics of the photocatalytic system. This insight and synergetic effects can provide a new approach for the development of novel heterostructure photocatalysts.

High selectivity of photocatalytic reduction of CO2 to CO based on terpyridine ligand supported CuI metal organic framework

In this work, a 4’-(4-cynaophenyl)-4,2’:6′,4-terpyridine supported CuI MOFs photocatalyst (CuIMOF) was applied to the photocatalytic CO2 reduction for the first time. The micro-structural and physicochemical properties of the CuIMOF were systematically studied by the powder X-ray diffraction (PXRD), Single crystal X-ray diffraction (SCXRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR), UV-Vis diffuse spectroscopy (UV-vis DRS), ns-level photoluminescence spectra (ns-level PL), Ultraviolet photoelectron spectroscopy (UPS), and N2 adsorption-desorption test (BET-BJH). Moreover, the in situ diffuse reflectance infrared fourier transform spectroscopy (in situ DRIFTS) was applied to investigate the adsorption and reaction intermediates of photocatalytic CO2 reduction. As a result, CuIMOF exhibited good performance and outstanding selectivity toward photocatalytic reduction of CO2 to CO under full-spectrum and visible light illumination. Notably, 100% selective photocatalytic conversion of CO2 to CO was achieved. Thus, the study presents the high selectivity and CO2 reduction efficiency of CuIMOF as a potential family of photocatalysts.

Adsorptive and photocatalytic remediation of hazardous organic chemical pollutants in aqueous medium: A review

The provision of clean water is still a major challenge in developing parts of the world, as emphasized by the United Nation Sustainable Development Goals (SDG 6), and has remained a subject of extensive research globally. Advancements in science and industry have resulted in a massive surge in the amount of industrial chemicals produced within the last few decades. Persistent and emerging organic pollutants are detected in aquatic environments, and conventional wastewater treatment plants have ineffectively handled these trace, bioaccumulative and toxic compounds. Therefore, we have conducted an extensive bibliometric analysis of different materials utilized to combat organic pollutants via adsorption and photocatalysis. The classes of pollutants, material synthesis, mechanisms of interaction, merits, and challenges were comprehensively discussed. The paper highlights the advantages of various materials used in the removal of hazardous pollutants from wastewater with activated carbon having the highest adsorption capacity. Dyes, pharmaceuticals, endocrine-disrupting chemicals, pesticides and other recalcitrant organic pollutants have been successfully removed at high degradation efficiencies through the photocatalytic process. The photocatalytic degradation and adsorption processes were compared by considering factors such as cost, efficiency, ease of application and reusability. This review will be good resource material for water treatment professionals/scientists, who may be interested in adsorptive and photocatalytic remediation of organic chemicals pollutants.

Structural and Electrical Characterization of Pure and Al-Doped ZnO Nanorods

Pure and Al-doped (3 at.%) ZnO nanorods were prepared by two-step synthesis. In the first step, ZnO thin films were deposited on silicon wafers by spin coating; then, ZnO nanorods (NR) and Al-doped ZnO NR were grown using a chemical bath method. The structural properties of zincite nanorods were determined by X-ray diffraction (XRD) and corroborated well with the morphologic properties obtained by field-emission gun scanning electron microscopy (FEG SEM) with energy-dispersive X-ray spectroscopy (EDS). Morphology results revealed a minute change in the nanorod geometry upon doping, which was also visible by Kelvin probe force microscopy (KPFM). KPFM also showed preliminary electrical properties. Detailed electrical characterization of pure and Al-doped ZnO NR was conducted by temperature-dependent current–voltage (I–V) measurements on Au/(Al)ZnO NR/n-Si junctions. It was shown that Al doping increases the conductivity of ZnO NR by an order of magnitude. The I–V characteristics of pure and Al-doped ZnO NR followed the ohmic regime for lower voltages, whereas, for the higher voltages, significant changes in electric conduction mechanisms were detected and ascribed to Al-doping. In conclusion, for future applications, one should consider the possible influence of the geometry change of (Al)ZnO NRs on their overall electric transport properties.

Sustainable Synthesis of Silver Nanoparticles Using Marine Algae for Catalytic Degradation of Methylene Blue

Herein, Sargassum coreanum (marine algae)-mediated silver nanoparticles (AgNPs) were successfully synthesized by a simple reduction method. The synthesized AgNPs were characterized using ultraviolet-visible spectroscopy, attenuated total reflection Fourier transformed infrared spectroscopy, X-ray diffractometry, field emission scanning electron microscopy (FESEM) with energy-dispersive X-ray (EDX) spectroscopy, and high-resolution transmission electron microscopy (HR-TEM) analysis. The acquired colloidal AgNPs were strongly absorbed around 420 nm and displayed brown color under visible light. The XRD pattern of AgNPs exposed their face-centered cubic geometry along with crystalline nature. The HRTEM images of synthesized AgNPs confirmed the mean particle size of 19 nm with a distorted spherical shape, and the calculated interlayer distance (d-spacing value) was about 0.24 nm. Further, the catalytic degradation of methylene blue using sodium borohydride and AgNPs was monitored using UV–vis spectroscopy. The result revealed that AgNPs performed as a superior catalyst, which completely degraded MB in 20 min. The rate constant for MB degradation was calculated to be 0.106 min−1, demonstrating that the marine algae-mediated AgNPs had outstanding catalytic activity. This approach is easy and environmentally benign, which can be applied for environmental-based applications such as dye degradation and pollutant detoxification.