Fast Electron-hole Recombination Research Articles

Stacking Engineering: A Boosting Strategy for 2D Photocatalysts.

Two-dimensional (2D) photocatalytic material is a vital project for modern solar energy conversion and storage. Despite a vast family of potential 2D photocatalysts that is demonstrated, their commercial applications are severely limited because of fast photogenerated electron-hole recombination. Here, based on first-principles, we propose a general paradigm to boost the separation of photoexcited charge carriers in 2D photocatalysts by stacking engineering. Taking the emerging water splitting photocatalyst MoSi2N4 as an example, we show that specific interlayer stacking-induced electric polarization plays a significant role in altering the electronic properties and thus the suppressed recombination rate of photoexcited carriers. Moreover, we find that the catalytic performance can be further controlled by vertical strain. These generalized findings not only highlight the importance of stacking-induced electric polarization but also offer new prospects for the design and application of 2D photocatalysts.

Silver decorated ZnO photocatalyst for effective removal of reactive red azo dye and ofloxacin antibiotic under solar light irradiation

It is well accepted that fast electron-hole recombination is the main drawback affecting low performance of the ZnO photocatalyst which is active only under UV light covering less than 5% of sunlight. To overcome this problem, the promising strategy based on decoration of noble metals on ZnO photocatalyst has been proposed. In the present study, incorporation of silver from 1 to 5 wt% was performed. The 5Ag-ZnO photocatalyst, containing 5 wt% silver, showed hexagonal phase with excellent visible-light-responsive performance and improved anti-photocorrosion property. The complete removal of reactive red dye and ofloxacin antibiotic was achieved after 25 and 80 min, respectively. The enhanced photoactivity is attributed to great electron-hole separation efficiency at the interface of the photocatalyst. Decoration of the metallic silver on ZnO photocatalyst leads to the creation of the Schottky barrier at the silver/ZnO interface resulting in enhancement of the quantum efficiency and improvement of the photocatalytic activity. In addition, incorporation of silver metal also leads to red shift in the adsorption band toward the visible region due to the local surface plasmon resonance (LSPR) effect of the metallic silver on the surface of ZnO. The photocatalyst shows structural stability after three cycles of use. The 5Ag-ZnO photocatalyst retains its great efficiency even after the third cycle suggesting its excellent reusability. The present research provides a novel route for fabrication of a promising silver decorated ZnO for detoxification of organic pollutants in wastewater.

TiO2-supported Au144 nanoclusters for enhanced sonocatalytic performance.

The production of reactive oxygen species (ROS), such as hydroxyl radicals, by ultrasonic activation of semiconductor nanoparticles (NPs), including TiO2, has excellent potential for use in sonodynamic therapy and for the sonocatalytic degradation of pollutants. However, TiO2 NPs have limitations including low yields of generated ROS that result from fast electron-hole recombination. In this study, we first investigated the sonocatalytic activity of TiO2-supported Au nanoclusters (NCs) (Au NCs/TiO2) by monitoring the production of hydroxyl radicals (•OH) under ultrasonication conditions. The deposition of Au144 NCs on TiO2 NPs was found to enhance sonocatalytic activity for •OH production by approximately a factor of 2. Electron-hole recombination in ultrasonically excited TiO2 NPs is suppressed by Au144 NCs acting as an electron trap; this charge separation resulted in enhanced •OH production. In contrast, the deposition of Au25 NCs on TiO2 NPs resulted in lower sonocatalytic activity due to less charge separation, which highlights the effectiveness of combining Au144 NCs with TiO2 NPs for enhancing sonocatalytic activity. The sonocatalytic action that forms electron-hole pairs on the Au144/TiO2 catalyst is due to both heat and sonoluminescence from the implosive collapse of cavitation bubbles. Consequently, the ultrasonically excited Au144 (3 wt.%)/TiO2 catalyst exhibited higher catalytic activity for the production of •OH because of less light shadowing effect, in contrast to the lower catalytic activity when irradiated with only external light.

A review on self-modification of zirconium dioxide nanocatalysts with enhanced visible-light-driven photodegradation of organic pollutants

Over the past few years, photocatalysis is one of the most promising approaches for removing organic pollutants. Zirconium dioxide (ZrO2) has been shown to be effective in the photodegradation of organic pollutants. However, low photoresponse and fast electron-hole recombination of ZrO2 affected the efficiency of catalytic performance. Modifying the photocatalyst itself (self-modification) is a prominent way to enhance the photoactivity of ZrO2. Moreover, as ZrO2-like photocatalysts have a large bandgap, improving the spectral response via self-modification could extend the visible light region and reduce the chance of recombination. Here, we review the self-modification of ZrO2 for enhanced the degradation of organic pollutants. The approaches of the ZrO2 self-modification, including the type of synthetic route and synthesis parameter variation, are discussed in the review. This will be followed by a brief section on the effect of ZrO2 self-modification in terms of morphology, crystal structure, and surface defects for enhanced photodegradation efficiency. It also covers the discussion on the photocatalytic mechanism of ZrO2 self-modification. Finally, some challenges with ZrO2 catalysts are also discussed to promote new ideas to improve photocatalytic performance.

Highly Efficient Degradation of Persistent Pollutants with 3D Nanocone TiO2-Based Photoelectrocatalysis.

Photoelectrocatalytic (PEC) degradation of organic pollutants into CO2 and H2O is a promising strategy for addressing ever-growing environmental problems. Titanium dioxide (TiO2) has been widely studied because of its good performance and environmental benignancy; however, the PEC activity of TiO2 catalyst is substantially limited due to its fast electron-hole recombination. Herein, we report a TiO2 nanocone-based photoelectrocatalyst with superior degradation performance and outstanding durability. The unique conical catalyst can boost the PEC degradation of 4-chlorophenol (4-CP) with 99% degradation efficiency and higher than 55% mineralization efficiency at a concentration of 20 ppm. The normalized apparent rate constant of a nanocone catalyst is 5.05 h-1 g-1 m2, which is 3 times that of a nanorod catalyst and 6 times that of an aggregated particle catalyst, respectively. Further characterizations reveal that the conical morphology of TiO2 can make photogenerated charges separate and transfer more efficiently, resulting in outstanding PEC activity. Moreover, computational fluid dynamics simulations indicate that a three-dimensional conical structure is beneficial for mass transfer. This work highlights that tuning the morphology of a photoelectrocatalyst at the nanometer scale not only promotes the charge transfer but also facilitates the mass transportation, which jointly enhance the PEC performance in the degradation of persistent pollutants.

Preparation of g-C3N4/TiO2 by template method and its photocatalytic performance

A method for preparing TiO2 supported on g-C3N4 by freeze-drying was proposed using NaCl as template as well as TiO2 dispersion and melamine as raw materials. This method solves the problems of low specific surface area and fast electron-hole recombination rate of traditional g-C3N4. During the calcination process, the generated g-C3N4 and TiO2 formed a heterojunction, which reduced the rate of electron-hole combination. After removing the template, a 3D porous g-C3N4 network supporting TiO2 was obtained. In this study, XRD, FT-IR, TG-DSC, XPS, TEM and SEM were used to explore the microstructure evolution of g-C3N4/ TiO2 at different stages. And then the band structures of different samples were analyzed by UV-Vis. Finally, the photocatalytic activity of different samples was studied by photolytic water experiment. The results showed that the TiO2 nanoparticles were successfully supported on the surface of the 3D porous g-C3N4 network, and the photocatalytic activity of g-C3N4 was significantly improved. When g-C3N4: TiO2 = 2.5: 1, the sample had the highest photocatalytic efficiency, and the hydrogen production rate reached 200.806 μmol/g/h.

S = 1/2 Chain in BiVO3F: Spin Dimers versus Photoanodic Properties.

BiVO3F was prepared, characterized, and identified as a unique example of bismuth vanadyl oxyhalide with paramagnetic V4+ centers. Its crystal structure shows 1D magnetic units with rare alternation of edge-sharing O-O and F-F μ2 bridges along the octahedral chains. Structural pairing across the O2 edges induces antiferromagnetic spin dimers (S = 0) with J/Kb ≈ 300 K, ∼15 times greater than the exchange across the F2 bridges, within a non-ordered magnetic ground state. Despite multiple compositional, structural, and electronic analogies with the BiVO4 scheelite compound, one of the most promising photoanodes for solar water splitting, the photoactivity of BiVO3F is relatively modest, partially due to this electronic pairing benefitting fast electron-hole recombination. Similar to monoclinic VO2, the V4+ spin dimerization deters the singlet → triplet electronic photoexcitation, but results in potential carrier lifetime benefits. The reduction of the bandgap from an Eg of ∼2.4 eV to ∼1.7 eV after incorporation of d1 cations in BiVO4 makes BiVO3F an inspiring compound for local modifications toward an enhanced photoactive material. The direct d → d transition provides a significant enhancement of the visible light capture range and opens a prospective route for the chemical design of performant photoanodes with a mixed anionic sublattice.

Improved Visible Light Activity of Copper Oxide/Carbon Nitride Photocatalysts Prepared by Photodeposition for Phenol Degradation

A series of copper(II) oxide deposited on carbon nitride (CuO/CN) as visible light-active photocatalyst was successfully prepared via a photodeposition method. The CuO modification was carried out to improve the photocatalytic activity of CN having fast electron-hole recombination. The CuO loading was varied from 0.05 to 0.5 wt% and the photodeposition was carried out at room temperature under UV light illumination. The CuO/CN samples were confirmed to have similar optical properties and functional groups to those of the unmodified CN. Meanwhile, the emission intensity of the CN decreased with the increase of the copper species loading, which could correspond to the suppression of charge recombination on the CN. After a 24-h reaction under visible light irradiation, the best photocatalyst, i.e. the CuO(0.1)/CN, gave 41.7% phenol degradation, which was almost two times higher than the unmodified CN (21.3%). However, the photocatalytic activity decreased when the added copper species was more than 0.1 wt%. Therefore, the optimum amount of copper species deposited on the CN surface would have a prominent contribution to improve the photocatalytic activity. It was also confirmed that holes, hydroxyl radicals, and superoxide radicals were important for the photocatalytic degradation of phenol on the CuO(0.1)/CN.

Construction of 1T-MoS2 quantum dots-interspersed (Bi1-x Fe x )VO4 heterostructures for electron transport and photocatalytic properties.

The present study reports trigonal phase molybdenum disulfide quantum dots (MoS2/QDs)-decorated (Bi1−xFex)VO4 composite heterostructures. Initially, (Bi1−xFex)VO4 heterostructure nanophotocatalysts were synthesized through the hydrothermal method decorated with 1T-MoS2via a sonication process. 1T-MoS2@(Bi1−xFex)VO4 heterostructures were characterized in detail for phase purity and crystallinity using XRD and Raman spectroscopy. The Raman mode evaluation indicated monoclinic, mixed monoclinic-tetragonal and tetragonal structure development with increasing Fe concentration. For physiochemical properties, SEM, EDX, XPS, PL, EPR, UV-visible and BET techniques were applied. The optical energy band gaps of 1T-MoS2@(Bi1−xFex)VO4 heterostructures were calculated using the Tauc plot method. It shows a blue shift initially within a monoclinic structure then a red shift with an increase of Fe concentration. 1T-MoS2@(Bi40Fe60)VO4 with 2 wt% of 1T-MoS2-QDs carrying a mixed phase exhibited higher photocatalytic activity. The enhanced photocatalytic activity is attributed to the higher electron transportation from (Bi1−xFex)VO4 surface onto 1T-MoS2 surface, consequently blocking the fast electron–hole recombination within (Bi1−xFex)VO4. 1T-MoS2 co-catalyst interaction with (Bi1−xFex)VO4 enhanced the light absorption in the visible region. The close contact of small 1T-MoS2-QDs with (Bi1−xFex)VO4 develops a high degree of crystallinity, with fewer defects showing mesoporous/nanoporous structures within the heterostructures which allows more active sites. Herein, the mechanism involved in the synthesis of heterostructures and optimum conditions for photocatalytic degradation of crystal violet dye are explored and discussed thoroughly.

Engineering Surface N‐Vacancy Defects of Ultrathin Mesoporous Carbon Nitride Nanosheets as Efficient Visible‐Light‐Driven Photocatalysts

Graphitic carbon nitride (GCN) has become an attractive photocatalyst for solar energy conversion, but the photocatalytic activity of GCN is still limited by the extremely fast electron–hole recombination. Herein, a defective ultrathin mesoporous graphitic carbon nitride (DUMCN) photocatalyst with high specific surface area and mesoporous structure is fabricated through a facile three‐step heat‐treatment strategy, which reduces the distance of bulk photogenerated carriers to the surface, resulting in efficient adsorption and diffusion of reactants and products, and exposing adequate surface active sites. Moreover, suitable N‐vacancy defects are formed via high‐temperature surface hydrogenation, which can extend light absorption and produce ultra‐high intrinsic carrier mobility, and further increase the active sites. The photocatalytic hydrogen production rate is up to 13.63 mmol h−1 g−1 under visible light in the triethanolamine solution and 33.5 μmol h−1 g−1 for overall water splitting, which is much higher than that of bulk graphitic carbon nitride (BCN) structures. Density functional theory (DFT) calculations further reveal the effect of surface defects on the band structure for promoting the spatial charge separation. This facile strategy may offer new insights into designing other ultrathin mesoporous semiconductor photocatalysts with high performance.

Visible-light overall water splitting on g-C3N4 decorated by subnanometer oxide clusters

Two-dimensional (2D) nitrogenated holey carbon materials are promising non-precious photocatalysts for clean energy production. However, their efficiency is limited by the fast electron-hole recombination and lack of active sites. To overcome these drawbacks, here for the first time, we show that loading subnanometer p-block metal oxide clusters on 2D porous carbon-based semiconductors can trigger peculiar synergistic effect and offer an effective route for manipulating the photocatalytic behavior at atomic precision. As a prototype system, g-C3N4 monolayer decorated by MgO tubular clusters for overall water splitting is explored by time-dependent ab initio nonadiabatic molecular dynamic simulations. Such novel (MgO)n/g-C3N4 heterostructures possess excellent stability in aqueous solution, high activity for water splitting, and superior photocarrier transport properties. The basic rules for optimally steering the relaxation pathway and lifetime of excited carriers and creating bifunctional reaction centers by controlling the concentration and size of oxide clusters are thoroughly unveiled. Our work provides a new strategy to modify 2D porous carbon materials for practical solar energy conversion and shines light on utilizing subnanometer p-block oxide clusters with earth-abundant and low-cost elements for precisely dictating the performance of hybrid photocatalysts.

Synergic effect of Cu2O/MoS2/rGO for the sonophotocatalytic degradation of tetracycline and ciprofloxacin antibiotics

A ternary Cu2O/MoS2/rGO (Cu2MG) composite, synthesized by cost-efficient and eco-friendly microwave method, is potentially used for the sonophotocatalytic (visible light and ultrasonic irradiation) degradation of antibiotics namely tetracycline and ciprofloxacin. SEM and TEM observations reveal that the spherical Cu2O nanoparticles are decorated with MoS2 and rGO layered sheets. Furthermore, the incorporation of MoS2/rGO binary composite to Cu2O nanoparticles results in the reduction in fast electron-hole recombination and improve charge carrier ability of Cu2MG composite as confirmed by PL analysis. The Cu2MG composite demonstrates the synergic sonophotocatalytic degradation of Tetracycline (20 mg/L) and Ciprofloxacin (10 mg/L) antibiotics with high efficiency of 100% and 94% within a short duration of 10 min and 75 min, respectively. The kinetics study indicates that the degradation process obeys a pseudo-first order reaction with a rate constant as Ksonophotocatalytic > Kphotocatalytic > Ksonocatalytic. The high synergic value of 3.83 and 1.71 has been achieved for the degradation of TC and CIP antibiotics, respectively. The synergic effect of degradation is owing to the spontaneous production of OH˙ and ˙O2− radicals favoring free electrons to actively participate in the degradation process. This research work proves that the as-fabricated ternary Cu2MG nanocomposite is an efficient candidate for the degradation of antibiotics for better environmental protection.

Atomic‐ and Molecular‐Level Functionalizations of Polymeric Carbon Nitride for Solar Fuel Production

Polymeric carbon nitride (PCN) is a metal‐free semiconductor that has received extensive research attention due to its unique advantages such as low cost, high stability, and visible‐light response. However, pristine PCN is not an ideal photocatalyst because of fast electron–hole recombination and its inert surface for molecular adsorption. Nevertheless, benefiting from the N‐linked tri‐s‐triazine structure, PCN can be readily functionalized through chemical modifications. As such, researchers have made enormous efforts to develop various strategies for modifying PCN to achieve enhanced photocatalytic activities. Herein, recent advances in PCN functionalizations with different atomic or molecular units, including metal and nonmetal elements, small functional groups, organic functional fragments, and metal complex motifs, are summarized. Moreover, the effect of different PCN functionalization strategies on the molecular structure, optical properties, electronic behaviors, and photocatalytic activities particularly for water splitting and CO2 reduction is discussed. In the end, the remaining challenges in the structural modification of PCN and future opportunities of functional PCN‐based photocatalysts for efficient solar fuel production are elaborated on.

Design and fabrication of petal shape C3N4/PPy hybrids with enhanced electron transporting and light harvesting capability

Carbon nitride (C3N4) is an attractive materials with high potential in the application fields of energy store, energy conversion, and catalyzing photoelectrochemical reactions, yet its application is restricted due to fast electron-hole recombination and limited light harvesting capability (λ < 460 nm). In this work, we demonstrate an easy-to-handle strategy for synthesizing petal shape C3N4/PPy hybrids which “inherited” the merits of C3N4 and PPy. Charge transfer efficiency was enhanced 12.4 times due to effective hybridizing between C3N4 and PPy when compared with pristine C3N4. Besides, the petal shape C3N4/PPy hybrids exhibited wide light harvesting range from 400 nm to 650 nm, and displayed larger photo-current than pristine C3N4 when driven by visible light.

NIR Light‐Driven Bi2Se3‐Based Nanoreactor with “Three in One” Hemin‐Assisted Cascade Catalysis for Synergetic Cancer Therapy

AbstractPhotocatalytic semiconductor‐based nanoreactors, that convert nontoxic molecules into toxic ones for cancer therapy, have attracted great interest. However, its therapeutic efficiency is limited by the fast electron–hole recombination within a narrow bandgap, low oxidative damage of H2O2, and tumor hypoxia. Herein, aggregation‐limited hemin is introduced onto Bi2Se3 nanoparticles for successively solving these problems. The nanoreactor (Bi2Se3@hemin‐(G‐H)‐HA NPs) is obtained through adamantane modified hemin and β‐cyclodextrin modified hyaluronic acid complexing and wrapping on Bi2Se3 NPs via host–guest and electrostatic interaction. Once irradiated by NIR light, the hemin assists Bi2Se3 to separate electron–hole pairs and catalyze endogenous H2O to generate vast H2O2, resulting in a 3.9‐fold higher H2O2 generation than that of individual Bi2Se3. Subsequently, H2O2 is catalyzed by aggregation‐limited hemin to generate highly toxic •OH and •O2−, which improves the total reactive oxygen species generation of Bi2Se3@hemin‐(G‐H)‐HA by 10.8‐fold compared to that of Bi2Se3 NPs. Importantly, the cytotoxicity result exhibits a death rate of HepG2 cells of above 90%, even though in a simulated hypoxic environment. Additionally, the in vivo result indicates this nanoreactor realizes an synergetic anticancer effect with a tumor inhibition rate of 92.3%. Overall, such a nanoreactor with hemin‐assisted cascade catalysis is a promising candidate for improving therapeutic efficacy.

Synthesis of novel visible light assisted Pt doped zinc vanadate (Pt/Zn4V2O9) for enhanced photocatalytic properties

Abstract In this report, Platinum (Pt) doped Zinc Vanadate (Zn4V2O9) nanoparticles were prepared by sonication assisted hydrothermal method. The composition, crystallinity, and photo-absorption attributes were characterized by; XRD, SEM, EDX, FTIR, BET, and PL techniques. UV–Vis DRS reflectance spectroscopy was used to find the optical energy bandgap. Photocatalytic responses of the Pt/Zn4V2O9 heterostructures were checked against Methylene Blue (MB) dye under visible light. The results exhibited that photocatalytic response was significantly enhanced after the Pt loaded moieties on Zn4V2O9 as compared to pure Zn4V2O9 composite. The improved photocatalytic response has been ascribed to the higher electron transfer from the semiconductor to the metal surface and as a result, hinders the fast electron-hole recombination. Pt in cooperation with Zn4V2O9 enhanced the light absorption intensity range from UV to visible region of light. The small Pt co-catalysts particles close intact with Zn4V2O9 and generate a nanoporous structure which offering more active agent sites.

Electrospun Active Media Based on Polyvinylidene Fluoride (PVDF)-Graphene-TiO2 Nanocomposite Materials for Methanol and Acetaldehyde Gas-Phase Abatement

The abatement of organic pollutants by TiO2 photocatalysis has been established as one of the benchmark applications of advanced oxidation processes for both liquid and gas phase purification. Such solution is particularly suitable for indoor air pollution where volatile organic compounds (VOCs) represent a class of chemicals of high concern for their adverse effects on both environment and human health. However, different shortcomings still affects TiO2 photocatalytic performance in terms of weak adsorptivity and fast electron-hole recombination, limiting its applicability. As a result, different strategies have been investigated over the last years in order to promote a higher TiO2 photo-efficiency. In this study we used electrospun (PVDF) nanofibers as a support for the photo catalytic system obtained by coupling graphene based materials and TiO2 during solvothermal synthesis. The resultant nanostructured membranes have been tested for acetaldehyde and methanol degradation under UV light showing an increase in the photocatalytic activity compared to bare TiO2. Such results may be ascribed to the decrease of band-gap energy and to increased electron mobility in the photocatalytic nanocomposite.

Influence of Thermal Activation of Titania on Photoreactivity of Pt/TiO2 in Hydrogen Production

A series of Pt/TiO2 photocatalysts was prepared by impregnation of fresh and thermal-activated titania (commercial Evonik Aeroxide P25 TiO2) with an aqueous solution of H2PtCl6 followed by reduction in an aqueous solution of NaBH4. The thermal activation was performed by annealing in air. The photocatalytic activity of the Pt/TiO2 catalysts was measured for the hydrogen production from a mixture of glycerol under UV radiation. It was found that the activation at 300–600 °C provides an increase in the photoreactivity of resulting Pt/TiO2 photocatalysts in the production of hydrogen while its structural and textural properties do not change. This effect is due to formation of cationic vacancies that limits fast electron–hole recombination.

Heterojunction Photocatalysts Based on 2D Materials: The Role of Configuration

AbstractSemiconductor photocatalysis is currently attracting tremendous attention as it holds great potential to address the issues of energy shortage and environmental pollution. 2D materials are excellent candidates for photocatalysis owing to their attractive structural and electronic properties. However, practical applications of 2D materials are still hindered due to limitations, such as fast electron–hole recombination and poor redox ability, both of which lead to low efficiency of photocatalytic reactions. Constructing a heterojunction is the most widely used strategy to solve these problems. In particular, heterojunctions composed of 2D materials interfaced with other semiconductors of different dimensionalities can integrate the respective advantages and mitigate the drawbacks of each component. Hence, this review focuses on the recent developments in the rational design of 2D material‐based heterojunction photocatalysts with different configurations. The synthetic strategies, physicochemical properties, component functions, photocatalytic mechanisms, and applications of these heterojunctions are systematically summarized. Emphasis is placed on correlations between photocatalytic performance and heterojunction configuration. Finally, the ongoing challenges and potential directions for future development of 2D material‐based heterojunction photocatalysts are also proposed.

Enhanced visible light photocatalytic performance of SnO2 nanoparticle co-doped with (Co, Nb) for organic dye degradation

Fast electron–hole recombination rate, lower free radical generation, unsuitable valence band maximum (VBM) and conduction band minimum (CBM) position of SnO2 nanoparticle are the shortfalls in achieving a superior photocatalytic performance of organic dye degradation under sunlight irradiation. To rise above these margins, for the first time, the co-doping approach was attempted by a simple co-precipitation technique in which both cobalt (Co) and niobium (Nb) were doped in SnO2 nanoparticle. In this regard, pure, mono-doped 5 M Co, 5 M Nb and different concentrations of (Co, Nb) co-doped SnO2 nanoparticles were prepared and characterized through XRD, UV–Vis, PL, XPS, SEM, and cyclic voltammetry analyses. Moreover, the influence of crystalline nature, bond order, bandgap, electron–hole recombination rate, and VBM and CBM potential to the efficient photocatalytic activity have been discussed. The observed UV–Vis, PL, and cyclic voltammetry measurements revealed that the (Co, Nb) co-doped SnO2 nanoparticles have suitable CBM to meet better reduction capacity, lower electron–hole recombination rates, and higher stability than pure and mono-doped system. XPS analysis confirmed the presence of both Co and Nb in the SnO2 matrix and O1s spectrum revealed the presence of hydroxyl radical on its surface. Also, the terephthalic (TA) acid test showed that, at higher concentration of cobalt co-doped SnO2 nanoparticles, it generated maximum hydroxyl (OH·) radicals than that of others. Consequently, those nanoparticles exhibited 99% efficiency of methylene blue (MB) dye degradation at 30 min under direct sunlight atmosphere. For better photocatalytic outsight, the photodegradation mechanism was also proposed.