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Photocatalytic H2O2 and NH3 production on Zn–Cu–In–S QDs coupled with BiOI MFs via a Z-scheme charge transfer dynamic.

Photon-assisted hydrogen evolution over a co-catalyst-free CIS–BOI composite abiding by the direct Z-scheme charge transfer mechanism.

To address the growing energy demand, remarkable progress has been made in transferring the fossil fuel-based economy to hydrogen-based environmentally friendly photocatalytic technology. However, the sluggish production rate due to the quick charge recombination and slow diffusion process needs careful engineering to achieve the benchmark photocatalytic efficiency. Piezoelectric photocatalysis has emerged as a promising field in recent years due to its improved catalytic performance facilitated by a built-in electric field that promotes the effective separation of excitons when subjected to mechanical stimuli. This review discusses the recent progress in piezo-photocatalytic hydrogen evolution while elaborating on the mechanistic pathway, effect of piezo-polarization and various strategies adopted to improve piezo-photocatalytic activity. Moreover, our review systematically emphasizes the fundamentals of piezoelectricity and piezo-phototronics along with the operational mechanism for designing efficient piezoelectric photocatalysts. Finally, the summary and outlooks provide insight into the existing challenges and outline the future prospects and roadmap for the development of next-generation piezo-photocatalysts towards hydrogen evolution.

Schematic representation of the photo-Fenton degradation of levofloxacin under solar-light illumination.

Efficacious H2 and O2 evolution over mediator free direct Z-scheme oriented 0D-2D CIS-BOI heterostructure photocatalyst.

Au loaded ZnCr-LDH/RGO ternary photocatalyst for H2 and H2O2 production under visible light illumination.

Promising 0D non-stoichiometric CuxIn1−xS quantum dots show robust photodegradation towards gemifloxacin under visible light.

The nitrogen reduction reaction is of great scientific significance as a hydrogen fuel carrier as well as a source of value-added products; in context to this, photoelectrochemical (PEC) nitrogen fixation emerges as an effective and environmentally benign strategy to meet the need. Hence, the current work reports an effective catalytic system containing a low-cost iron boride-based cocatalyst onto the CeO

Environmental protection and the necessity of green energy have become fundamental concerns for humankind. However, rapid recombination of photoexcitons in semiconductors often gets in the path of photocatalytic reactions and annoyingly suppresses the photocatalytic activity. In this study, a polypyrrole (PPY)-supported step-scheme (S-scheme) ZnFe2O4@WO3–X (PZFW15) ternary composite was fabricated by a multistep process: hydrothermal and calcination processes, followed by polymerization. During the formation of the heterojunction, the oxygen vacancy (OV) on WO3–X promotes effective separation and increases the redox power of the photogenerated excitons via the built-in internal electric field of S-scheme pathways between ZnF and WO3–X. The successful construction of the S-scheme heterojunction was substantiated through X-ray photoelectron spectroscopy, experimental calculations, radical trapping experiment, and liquid electron spin resonance (ESR) characterization, whereas the existence of OVs was well confirmed by EPR and Raman analyses. Meanwhile, the PPY served as a supporter, and the polaron and bipolaron species of PPY acted as electron and hole acceptors, respectively, which further enhances the charge-carrier transmission and separation in the ternary PZFW15 photocatalyst. The designed ternary nanohybrid (PZFW15) displays outstanding gemifloxacin detoxification (95%, 60 min) and hydrogen generation (657 μmol h–1), i.e., 1.5 and 2.2 times higher than the normal S-scheme ZFW15 heterostructure and pure ZnFe2O4 (ZnF), respectively, with an apparent conversion efficiency of 4.92%. The ESR and trapping experiments indicate that the generated •OH and •O2– radicals from the PZFW15 photocatalyst are responsible for gemifloxacin degradation. This unique PPY-supported S-scheme heterojunction is also beneficial for the enhanced electron-transfer rate and provides abundant active sites for photocatalytic reactions.

The generation of sustainable and eco-friendly energy is the lifeline of modern civilization. Electrocatalytic water splitting producing molecular hydrogen using inexpensive, non-noble metal, and eco-friendly materials is a promising and sustainable approach that can minimize the dependency on fossil fuels and the carbon footprint of society. However, there are some major obstacles such as complex/sluggish reaction pathway, high overpotential, low catalyst durability, limited faradic efficiency and pricey catalyst (Pt, Ir, and Ru) in the process of constructing commercial electrochemical HER systems, and hence, there is an immediate need for fabricating a cost-viable non-precious HER electrocatalyst. In addition to the widespread use of 2D metal chalcogenides, in particular MoS2, this layered electrocatalyst shows robust catalytic performance towards hydrogen evolution reactions under grating acidic conditions. However, its catalytic efficiency is still inferior to that of the standard catalyst (Pt). Thus, through this Mini review, we try to cover the fundamentals, underlying catalytic mechanism, activity evaluating parameters, future opportunities, and associated challenges with MoS2 electrocatalysts and adopted advanced strategies for subduing the shortcomings. Furthermore, different edge and basal plane modification strategies, various developed MoS2 preparation techniques, and characteristic advantages of MoS2 nanosheets towards HERs are also briefly discussed. Additionally, the review provides a comprehensive collection of the latest pioneering research outcomes on layered MoS2 for HER applications, particularly in acidic electrolytes. The included state-of-the-art MoS2 catalytic performance, synthesis procedure, and advanced modification methods will act as a guiding tool to tune other materials accordingly to achieve the benchmark activity and turn the dream of H2-fuel commercialization in an environmentally sustainable manner, i.e. by non-noble metal-based HER electrocatalysis.

Surface defects and crystal facet engineering are the two important strategies which effectively enhance the efficiency of a photocatalyst by modulating its physiochemical properties. To date, surface defects and morphology dependent photoactivity have been explored by taking different nanostructured photocatalyst. Among them CeO2 based materials have recently received foremost interest, due to their easy tunable surface structure and low formation energy for surface defects. To covenant with these novel reasons, in this review we have comprehensively summarized the recent achievements and progress on the surface defect enriched low dimensional nanostructure CeO2 and CeO2 based heterostructure photocatalysts towards clean fuel generation reactions such as water splitting, CO2 reduction, N2 fixation and organic/inorganic environmental pollutant removal applications. The present review highlights the designing of CeO2 with particular crystal facet and morphology and positive impact of the crystal facets on the construction of different CeO2 based heterostructure materials (0D-2D, 0D-1D, 1D-2D, 2D-2D, 0D-3D etc.) with other photocatalysts of a dimensional architect. Next, the surface defects, crystal facets and heterojunctional interface responsible for improved photoactivity were briefly discussed with proper experimental evidence and the mechanism along with the theoretical concept. Further, this review sheds the light on the current challenges and different angle of future perspective in this research area.

Environmental pollutions are now regarded as a major catastrophe for society, so the scientific community in search of efficient technology which can tackle this issue. Photocatalysis has emerged as one of the cost effective, clean and eco-friendly approach, which efficiently deals the various type of environmental pollutants. In this contest, different semiconductor materials have gained much more popularity. In this regard, we have modified 2D-CeO2 with CdSQDs with a simple deposition precipitation technique. As CdSQDs posses high cross-sections for multiple photon absorption and large oscillator strengths as compared with their bulk CdS counterparts makes it a suitable candidate for hybrid material with CeO2 which extends the spectral range of the absorption from UV to UV-visible range. Further, the formation of type-II heterostructure in between CdSQDs and 2D-CeO2 efficiently enhances the interfacial charge transfer and chemical stability. Structural, optical and morphological characterization of the fabricated samples were carried out by XRD, UV, PL and TEM analysis. The photocatalytic activity of the fabricated samples was tested towards phenol degradation where the degradation efficiency of hybrid CeO2NS-CdSQDs was found to be 71% in 2 h.

The TiO2 semiconductor photocatalyst is in the limelight of sustainable energy research in recent years because of its beneficial properties. However, its wide band-gap and rapid exciton recombination rate makes it a lame horse, and reduces its photocatalytic efficiency. Recently, researchers have developed facile methods for lowering the band-gap, so that it captures a wide range of solar spectrum, but the efficiency is still way behind the target value. After the discovery of black titania (B-TiO2), the associated drawbacks of white TiO2 and its modified forms were addressed to a large extent because it not only absorbs photons in a broad spectral range (UV to IR region), but also modifies the structural and morphological features, along with the electronic properties of the material, significantly boosting the catalytic performance. Hence, B-TiO2 effectively converts solar energy into renewable chemical energy i.e. green fuel H2 that can ultimately satisfy the energy crisis and environmental pollution. However, the synthesis techniques involved are quite tedious and challenging. Hence, this review summarizes various preparation methods of B-TiO2 and the involved characterization techniques. It also discusses the different modification strategies adopted to improve the H2 evolution activity, and hopes that this review acts as a guiding tool for researchers working in this field.

Semiconductor based photocatalyst have attracted great interest in energy and environments. CoWO4@g-C3N4 nano-composites were fabricated by a reflux-calcination method in the ratio of 1:1, 1:2, and 1:3 respectively. The structural, morphological, auto electrical properties of the prepared samples are thoroughly characterised by PXRD, SEM, UV–Vis DRS, PL, measurements. This effective excition separation leading to enhanced photocatalytic activity due to synergistic contact between CoWO4 and g-C3N4. The prepared photocatalysts shows excellent activities towards the degradation of ciprofloxacin under visible light illumination. As compared to neat g-C3N4 and CoWO4, the photocatalytic activity (20 ppm ciprofloxacine degradation) of CoWO4@g-C3N4 (1:2) nanocomposite is higher i.e.88%. Hydroxyl radical (•OH) and (•O-2) were played crucial role in the photocatalytic degradation process, which is confirmed by trapping experiments.

Environmental pollution and energy scarcity is a major issue of the current scenario which forbear the progress of developing world. To overcome these problems towards a sustainable future, the utilization of sunlight by means of photocatalysis can be regarded as a best and suitable pathway. To validate this purpose, design and development of efficient heterogeneous photocatalyst for harvesting solar energy should be the major research concern for scientific community. In this regard herein, we have prepared a series of stable and efficient CoTiO3/UiO-66-NH2 p-n junction mediated heterogeneous photocatalyst by hydrothermal method. The functionalised linker of UiO-66-NH2 provided an intimate interfacial contact with CoTiO3 by Co/Ti O N ionic interaction, as proved by HRTEM and XPS analysis. Moreover the inverted V-shaped Mott-Schottky plot confirmed the junction formation in the optimised CoTiO3/UiO-66-NH2 material. In addition, EIS and PL analysis also provides sufficient evidence about the hindrance of active species recombination in composite as a result of p-n hetero junction. LC-MS characterization technique traces the assorted intermediate species produced in the course of photodegradation of Norfloxacin and confirms its complete degradation to corresponding CO2, H2O and NH4+ by the optimised CoTiO3/UiO-66-NH2. The highest photo-catalytic activity obtained towards Norfloxacin degradation is 90.13% and H2 production is 530.87 µmol in 1 h. The enhanced photo-catalytic reaction follows Type-II p-n hetero junction charge transfer mechanism and thus, paves a new way to design MOF based heterojunction photocatalyst for diverse photo catalytic performance.

Lethargic kinetics is the foremost bottleneck of the photocatalytic water oxidation reaction. Hence, in this respect, the CeO2 coral reef made up of nanosheets is studied focusing on the oxygen vac...

To surmount incompatibility provoked efficiency suppression of an anisotype heterojunction and to pursue an improved intrinsic photocatalytic activity by manipulating oriented transfer of photoindu...

For better exciton separation and high catalytic activity, the most trailblazing stratagem is to construct defect engineered low-dimensional p-n heterojunction framed photocatalytic systems. In this context, we have developed a rod-sheet (1D-2D) p-n heterojunction of MCeO2-BiFeO3 by a simple hydrothermal method and scrutinized its photocatalytic performance toward N2 fixation and phenol/Cr(VI) detoxification. The intimate contact between MCeO2 and BiFeO3 in the junction material is well established via X-ray diffraction (XRD), UV-vis diffuse reflectance spectrosopy (DRS), transmission electron microscopy (TEM), and photoelectrochemical studies. Further, scanning electron microscopy (SEM) and TEM pictures clearly support the decoration of MCeO2 nanorods over BiFeO3 sheets and also depict the junction boundary. Additionally, photoluminescence (PL), electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), and Raman measurements give solid evidence toward the presence of an oxygen vacancy. Moreover, the Mott-Schottky result indicates a feasible band edge potential favoring the p-n heterojunction with a built-in electric field between BiFeO3 and MCeO2 favoring a double charge dynamic. The MCeO2-BFO p-n junction displays a notable catalytic activity, i.e., 98.2% Cr(VI) reduction and 85% phenol photo-oxidation, and produces 117.77 μmol h-1 g-1 of ammonia under light irradiation. Electrochemical analysis suggests a four-electron/five proton-coupled N2 photoreduction pathway. The designed oxygen vacancy oriented p-n heterojunction suffering double charge migration shows significant catalytic performance due to effective electron-hole separation as justified via PL, electrochemical impedance spectra (EIS), and Bode phase analysis.

The present research reports the synthesis of two-dimensional (2D) sheet/flake-like nanostructures of crystalline carbon modified TiO2 (CT), B-TiO2 (B-CT), and S-TiO2 (S-CT) using a facile one-pot synthesis method. The crystallinity and phase purity (anatase) of the prepared nano-photocatalyst were characterised using X-ray diffraction, selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM) analysis. Furthermore, the morphological details and elemental content of the sample were studied via scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), respectively. Additionally, the optoelectronic features of all of the prepared specimens were measured via UV-vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL), impedance and Mott–Schottky studies. After successful characterisation, their photocatalytic performance was tested towards dinitrogen photo-fixation and tetracycline hydrochloride (TCH) degradation under visible light illumination. Moreover, the effective charge separation and greater availability of the active surface area led to the robust photocatalytic activity of the fabricated B-CT compared to the CT and S-CT samples, which correlates well with the PL, impedance and surface area analysis. B-CT displays the highest photocatalytic activity, i.e. 32.38 μmol L−1 (conversion efficiency = 0.076%) of ammonia production, and 95% tetracycline hydrochloride (10 ppm) degradation. Here, we have effectively designed a novel and productive pathway towards the enhancement of the photocatalytic performance of visible photon active TiO2-based materials for energy and environmental sustainability.

Designing promising photocatalytic systems with wide photon absorption and better exciton separation ability is a cutting-edge technology for enhanced solar-light-driven hydrogen production. In this context, non-stoichiometric Cu

The production of Hydrogen energy through the splitting of water is a promising pathway for clean environment and sustainability. Herein we have synthesized a series of ZnFe2O4 (ZFO)@Reduced Graphene Oxide (RGO) nanocomposites by hydrothermal followed by calcination method and studied its application towards hydrogen energy production and ciprofloxacin degradation. Powder X-ray diffraction (XRD) study and X-ray photoelectron spectroscopy (XPS) analysis indicate the good crystallinity and suitable chemical environment for the photocatalytic process. Among all the samples, ZFO@3%RGO showed 73.4% of CIP degradation under solar irradiation of 1 h, which is 1.67 times higher than that of pure ZFO nanoparticles. CIP degradation process follows first order kinetics with a good rate constant of 0.021 min−1 which is 2.3 times greater than ZFO. The photocatalyst ZFO@3%RGO illustrated maximum H2 energy production i.e. 410.32 μmol/h, which is 1.35 times more than that of neat ZFO nanoparticles. ZFO@3%RGO demonstrates the highest photocurrent density of 0.6 mA/cm2 under light illuminations, which is 250 times superior to that of the pristine photocatalyst. Bode phase analysis confirmed that ZFO@RGO shows 13 times higher charge separation efficiency in comparison to neat ZFO. The best photocatalytic activity of ZFO@3%RGO nanocomposite is due to its high light absorption capacity, low photogenerated exciton recombination, high electron-hole separation, and high photocurrent density.

Development of highly efficient robust catalyst for pollutant abetment still remains an ongoing scientific challenge in the field of visible light driven photocatalysis. In this work a series of ZnFe2O4 (ZFO)/carbon derivatives (ZFO@CNT, ZFO@GO, ZFO@Fullerene) nanocomposite were fabricated by one-pot hydrothermal method followed by calcination. The detail anatomical featured such as crystal geometry, morphology, elemental composition, light absorption performance, electron-hole recombination properties and photocurrent density were characterized by XRD, SEM, HRTEM, XPS, UV–Vis DRS, PL and electrochemical analysis respectively. The photocatalytic performances of ZFO@carbon nanocomposites were studied for the degradation of antibiotics (Norfloxacin) and hexavalent Chromium under open sun light illumination and the obtained results suggested that loading of carbon derivatives of ZFO nanoparticles enhance the visible light absorption capacity and excitation separation efficiency. Among the fabricated composites, ZFO@CNT exhibits the highest activity in comparison to other nanocomposites. The highest activity of ZFO@CNT is due to low photoexcited electron-hole recombination and high charge transfer properties of ZFO@CNT as confirmed via PL and impedance measurement. Further, the fabricated ZFO@CNT nanocomposite exhibited highest photocurrent density i.e. 2.25 mA/cm2 which was 225 times higher than that of neat ZFO. The optimal photocatalytic efficiency was shown by ZFO@CNT i.e. 91.36% degradation of 50 ppm norfloxacin and 82% reduction of 10 ppm Cr (VI) in 90 min and 60 min respectively under solar light irradiation.

The abolition of environmental pollutants and production of hydrogen (H2) from water using a heterogeneous photocatalyst is a demanding science of the current scenario to solve the increasing environmental pollution and worldwide energy catastrophe in modern life. To validate this purpose, the design of low-cost and durable semiconductor-based photocatalysts with great light absorption capacity becomes the most challenging issue for researchers. Regarding this, herein the phosphotungstic acid (HPW)-anchored Zr6O4(OH)4(BDC)6 (UiO-66) metal-organic framework (MOF), i.e., HPW@UiO-66, has been prepared by a hydrothermal method and is efficient, stable, and capable of harvesting solar energy toward the degradation of tetracycline hydrochloride (TCH) and H2 production in the presence of a sacrificial donor. The ionic interaction between HPW and UiO-66 plays a key role toward the photostability and charge-transfer mechanism of the composite and is well characterized with X-ray diffraction, UV diffuse-reflectance spectroscopy, Fourier transform infrared, and X-ray photoelectron spectroscopy. A total of 30 wt % HPW@UiO-66 shows a maximum degradation of about 87.24% of a 20 ppm TCH solution in 60 min of solar-light irradiation and about 353.89 μmol/h of H2 production. The conduction- and valence-band potentials are well characterized with Mott-Schottky measurement and a delay charge recombination process through electrochemical impedance spectroscopy. The proposed mediator-free Z-scheme-oriented electron-hole migration route is well supported by photoluminescence, and the scavenger test well explains the better charge-carrier separation and high catalytic performance of the prepared composite. This research will bestow an advantageous blueprint to fabricate novel and challenging photocatalysts toward the photocatalytic treatment of environmental pollutants and H2 evolution.

An eco-friendly and bio-surfactant assisted room temperature synthesis has been proposed for preparation of Magnetic retrievable Fe3O4@rGO nanocomposite in Averrhoa carambola leaf extract towards 2-nitrophenol reduction and TCH degradation under visible light illumination. The role of bio-molecules that are present in leaf extract is quite crucial in the process of tuning the morphology and opto-electronic features of Fe3O4 nanoparticles. Additionally, the insitu conversion of GO to rGO and preparation of Fe3O4 from Fe+2 and Fe+3 metal precursors leads to formation Fe3O4@rGO nanocomposite. rGO sheets play the key role in successful transfer and separation of photoexcited charge carrier resulting in better catalytic activity compared to neat Fe3O4. Among the designed nanocomposites 3 wt% loaded rGO i.e. FG-3 shows the best result with 95.85% 20 ppm 2 Nitrophenol reductions and 94.09% 10 ppm TCH degradation under visible light irradiation for 30 and 60 mins respectively. The observed high photocatalytic performance of FG-3 is attributed to synergetic chemistry operating between rGO and Fe3O4 components that causes effective separation and channelization of excitons to active sites and also due to increase in surface area of composite material. The above stated separation efficiency and surface area expansion is well supported by PL/Impedance measurements and BET analysis respectively. Further the phase purity, uniform distribution of nanoparticles and reduction of GO to rGO is well characterised through XRD, FESEM/TEM and Raman/FTIR analysis respectively.

Achieving organic transformation reactions using green synthesis methods under mild conditions is always an aspiration of scientists. In the present findings, a Zn–Cr layered double hydroxide (LDH)/graphene oxide (GO) nanocomposite modified with Au–Ag noble metal nanoparticles (NPs) was synthesized via the in situ crystallization of a LDH over a GO surface followed by the simultaneous photo-deposition of a metal alloy and the reduction of GO to reduced graphene oxide (RGO) under UV light irradiation, resulting in AuAg@GO/LDH. All prepared samples were suitably analysed via various sophisticated techniques to explore their structural, morphological, optical and compositional behaviours. The characterization outcomes showed the uniform distribution of AuAg alloyed NPs with a typical diameter of around ∼3 nm on the facade of the GO/LDH nanocomposite. The conversion of GO to RGO is confirmed via Raman analysis. This bimetallic alloy-based nanocomposite provides a novel platform for artificial photocatalysis, and shows excellent catalytic activity for the performed tandem redox reactions. The combined effects of the plasmon active AuAg alloy, the visible photon-responsive ZnCr LDH and the electron trapping and transporting properties of GO illustrate the existence of an intensified green photochemical process, which can be extensively developed to be applied to tandem liquid phase photocatalytic organic reactions. Here the photogenerated electrons and holes can be directly utilized by nitrobenzene (NB) and benzyl alcohol (BA) to produce aniline (AL) and benzaldehyde (BAD) via GO, respectively. This selective photoredox reaction is a synergistic type of process that proceeds via producing and consuming protons. The effective separation of charge carriers is well supported by photoluminescence (PL) studies. Compared to the parent GO/LDH and Au and Ag singly-modified GO/LDH samples, AuAg@GO/LDH revealed proficient photocatalytic potential owing to the existence of combined surface plasmon resonance (SPR) effects, characterised through UV-visible diffuse reflectance spectroscopy (UV-vis DRS), generating hot electrons from both photoexcited Au and Ag atoms under visible light illumination. The AuAg@GO/LDH hybrid photocatalyst showed ∼2.5 times better performance than GO/LDH, without any indication of leached metal or metal alloy over five runs.

Visible light harvesting by heterogeneous photocatalysts and their applications in organic transformation reactions for the synthesis of target molecules are quite demanding science in the current scenario. In this regard, herein, a novel metal (Au/Pd)-functionalized metal organic framework (UiO-66-NH2) was synthesized to carry out the Suzuki–Miyaura coupling (SMC) reaction under visible light irradiation at ambient conditions. In order to justify the claim regarding the formation of alloys, crystallinity, morphology, particle size, proper separation of excitons, elemental content and their environment, various sensitive characterization techniques such as XRD, XPS, HRTEM, BET surface area and UV-vis analysis were employed. A mechanistic approach by means of experimental investigations revealed that the strong LSPR effect of Au facilitated the transfer of electrons to the Pd surface to make the surface negatively charged and suitable for the activation of aryl halides. The formed electropositive Au nanoparticles were converted to Au0 by accepting the photo-induced electrons from pristine UiO-66-NH2 and made available only holes at VB for the activation of phenylboronic acid. Among all the synthesized photocatalysts (1 : 2), Au/Pd@UiO-66-NH2 showed the highest activity (>99%) with TOF = 426 h−1 in an EtOH/H2O medium towards the SMC reaction, and the highest activity of this catalyst was supported by the electron gas model, LSPR effect (UV-vis) and active species separation (PL) analysis. The bimetallic noble nanoparticle-anchored UiO-66-NH2 not only expands the synthesis scope of C–C coupling by the SMC reaction under ambient conditions but will also inspire the further exploration of the activation of various reactants towards a wide range of organic transformation reactions.

Exploiting the advantageous science of layered architectures, herein graphene oxide (GO) and a ZnCr-layered double hydroxide (LDH) have been united together and further modified by Au–Pd noble metal nanoparticles (NPs) to design a highly efficient novel GO/LDH@AuPd hybrid photocatalyst. The synthesis of this hybrid composite was carried out via the in situ nucleation of the ZnCr LDH over the surface of GO sheets, subsequently followed by the photo-deposition of bimetallic alloyed NPs and the reduction of graphene oxide (GO) to reduced graphene oxide (RGO) under light illumination. The successful formation of a GO/LDH@AuPd hybrid material was evidenced via XRD, UV-vis spectroscopy, TEM and XPS analysis. Here XPS techniques were employed to assess the electronic contribution of LDH towards the electron density on the noble metal through the GO surface during the photoreduction process. TEM images confirmed that bimetallic NPs are well dispersed on the LDH as well as over the GO surface. Moreover, the significant quenching of the PL intensity and the smaller arc radius of EIS measurements of an active AuPd alloyed sample demonstrate effective charge separation leading to superb photocatalytic activity. Here, an energy saving and green synthesis method was adopted by utilizing (i) visible-light active Zn–Cr-LDH nanoplates, (ii) SPR-effective gold NPs, (iii) the channelling features of GO, (iv) the charge heterogeneity of the AuPd alloy and (v) the efficiency of palladium towards the C–C coupling reaction, which made the catalyst more powerful in terms of enhancing the photocatalytic Suzuki coupling reaction compared to various chemical agents at high temperatures. The existence of Au enhances the abilities of Pd synergistically together with GO/LDH in the presence of visible light, boosting Suzuki coupling reactions. The Suzuki coupling product yield, i.e., biphenyl, is around 99.5% over the GO/LDH@AuPd composite, which is about 1.9 times higher than a single metal loaded GO/LDH composite. The enhanced catalytic activity resulted from the electron transfer pathways of LDH → Au → Pd and LDH → RGO → Au → Pd in the hybrid nanoarchitecture. We believe that this novel approach can lead to stable heterogeneous photocatalysts for other reactions with high activities.

The Haber–Bosch process enables the industrial production of NH3 from N2 and H2, it represents a high energy consumption route and also releases a large amount of anthropogenic CO2. However, solar light mediated N2 photoreduction through a semiconductor photocatalyst is a green and sustainable route, which could help to suppress global warming and serve as an attractive hydrogen fuel storage medium. Herein, we have synthesized a phosphide protected FeS2–FeP–CeO2NS ternary nanohybrid through a simple hydrothermal method followed by a sulfidation–phosphidation technique. The physicochemical and morphological properties of the synthesized materials were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The optimum CPS3 nanohybrid exhibits a remarkable ammonia evolution rate of up to 5.6 mmol h−1 g−1 under mild reaction conditions and without using any precious noble metal or organic scavengers. The obtained results were superior to those obtained from recently reported hybrid materials. The main reason for the high photofixation may be because: (i) the Ov/Ce3+ and Fe–P act as active sites for nitrogen adsorption and activation; and (ii) the photoelectrons are well separated and transfer to the activated N2 and the overall kinetic study reveals the two electron proton coupled reduction reaction. This work gives some insightful and significant information about the construction and selection of earth abundant photocatalysts for use in the ideal solar driven nitrogen reduction reaction (NRR).

For better exciton separation and high catalytic activity, the most trailblazing stratagem is to construct defect engineered low-dimensional p-n heterojunction framed photocatalytic systems. In this context, we have developed a rod-sheet (1D-2D) p-n heterojunction of MCeO

The present research reports the synthesis of two-dimensional (2D) sheet/flake-like nanostructures of crystalline carbon modified TiO

Lethargic kinetics is the foremost bottleneck of the photocatalytic water oxidation reaction. Hence, in this respect, the CeO2 coral reef made up of nanosheets is studied focusing on the oxygen vacancy that affects the water oxidation reaction. First, CeO2 was prepared in an oyster shell/crucible with the presence/absence of urea by a simple calcination technique to tune the oxygen vacancy. More oxygen vacancy was detected in CeO2 prepared from urea and oyster shell, which is evidenced from Raman and PL analyses. Further, the oyster shell-treated sample was found to be of nanosheet type with numerous pores as observed via TEM analysis. The theoretical approach was adopted to expose the role of oxygen vacancies and the fate of scavenging agents in the water oxidation mechanism. It was observed that an oxygen vacancy plays a vital role in minimizing the activation energy hump and opposes the reverse reaction. The apparent conversion efficiency of 7.1% is calculated for the oxygen evolution reaction. Oxygen vacancy, quantum confinement effect, and charge separation efficiency are mainly responsible for the better photocatalyzed water oxidation reaction and hydroxyl radical production. This investigation will help in providing valuable information toward designing cost-effective oxygen vacancy-oriented nanosheet systems and the importance of vacancy in the water-splitting reaction.

Environmental pollution and energy scarcity is a major issue of the current scenario which forbear the progress of developing world. To overcome these problems towards a sustainable future, the utilization of sunlight by means of photocatalysis can be regarded as a best and suitable pathway. To validate this purpose, design and development of efficient heterogeneous photocatalyst for harvesting solar energy should be the major research concern for scientific community. In this regard herein, we have prepared a series of stable and efficient CoTiO

In the present study, a series of Ce2Zr2O7@rGO nanocomposites were synthesized using a simple solution combustion method followed by a photoreduction technique. The as-prepared samples were well characterised using various analytical techniques to determine the morphological, optical, structural, electrochemical and compositional properties. The presence of oxygen defects was observed from Raman and photoluminescence spectra. The photoreduction of GO to rGO was determined from Raman and Fourier-transform infrared (FTIR) spectroscopy results. The role of rGO proved to be quite significant for the enhanced photocatalytic activity of the nanocomposites. The synergistic communication between Ce2Zr2O7 and rGO accelerates the photoreduction of 4-nitrophenol along with the degradation of ciprofloxacin under visible light irradiation. Of the rGO nanocomposites, 3 wt% GO loaded Ce2Zr2O7 reduces 99% of 20 ppm of 4-nitrophenol to 4-aminophenol in 120 min and decomposes 10 ppm of ciprofloxacin by up to 89% in 60 min. The significant enhancement in the activity of the Ce2Zr2O7@rGO nanocomposite was ascribed to the effective charge separation of excitons through π-conjugation of graphene at the interface, which is well supported by the impedance, photoluminescence and photocatalytic results.

The designing of novel heterostructures for excellent photocatalytic activity has recently gathered intense attention and has exerted an enormous fascination. In this regard 2D nanoarchitectured CeO2–FeOOH/Fe2O3 heterostructures have been synthesized controllably through a hydrothermal process. The nanohybrids present an excellent performance towards photocatalytic (O2 evolution and Cr(VI) reduction) as well as photoelectrochemical activity. Our results show that oxygen vacancies are induced due to the incorporation of low-cost iron materials (FeOOH and Fe2O3) onto CeO2, later confirmed by XPS and TEM analysis, which enhances the charge separation through an n–n junction, leading to enhanced catalytic activity. Furthermore, the highlighted feature of our synthesized binary hybrid is the self-healing process under light irradiation, which repairs structural damage without any activator, that mimics the self-repairing effect of living organisms. This work represents the concept of integrating different functional materials into one nanoarchitectured material and provides useful information about structural regeneration, which may be useful for the development of a new generation of auto-healing nanoarchitectured materials.

Construction of a visible light driven Z-scheme-based photocatalytic system is a hot topic of research because of the potential to alleviate both energy and environmental issues. In the present study a series of surface vacancy mediated BiOI–CeO2 nanocomposites were prepared and their crystallographic, morphological, optical, and electrochemical behavior were characterized through XRD, TEM, FESEM, UV–vis DRS, PL, ESI, and Mott–Schottky techniques. From the XPS analysis, it could be said that a high amount of oxygen defects and metallic bismuth were present on the composite than neat CeO2 which was the major cause of enhancement in the photocatalytic activity. Further the photocatalytic efficiency of the as prepared samples was tested toward RhB decolorization/phenol oxidation as well as for O2 gas evolution. It was observed that 40 wt % BiOI–CeO2 nanocomposite exhibited highest photocatalytic activity among neat and other composites, i.e., 89% decolorization of 100 ppm RhB and produces 323 μmol/2h of O2 u...

Ammonia is the most necessitate and second largely produces chemical reagent worldwide to address the need of the fertilizer industry, as a precursor for many value-added chemicals and a competing source (17.6 wt% H2) for the blooming hydrogen economy. Although N2 constitutes 78.09 % of the earth's atmosphere, however, its conversion to ammonia is strenuous because of its non-polar and triple bond character. To address the burgeoning demand, ammonia is typically synthesized via the conventional energy and capital intensive Haber-Bosch technique utilizing natural gas and releasing tons of (CO2) to the environment. On this basis, cost-effective photon-driven dinitrogen reduction reaction (NRR) is aroused thriving attention as a sustainable and eco-friendly process for ammonia production under ambient conditions. Yet, the photocatalytic ammonia production is not up to the mark for industrial application due to low conversion rate, less catalytic selectivity, ambiguous mechanism, and limited faradic or solar-to-chemical efficiency. Further, the NRR activity of a catalyst essentially depends upon its electronic and surface texture; hence the fabrication of advanced materials is of paramount interest to enhance the performance. The present review covers the underlying mechanism of N2 photoreduction, prevailing theories, different catalytic engineering techniques, various detection methods, and critical challenges encountered in the theme of photofixation of dinitrogen to ammonia. Additionally, the overarching goal of this review is to bestow an outline of recent research articles in earmarking high-caliber photocatalytic systems and hence planting a strong foundation to ensure the succeeding improvement in this promising and hastily stretching field of dinitrogen photofixation research.

With the advancement of promising multifaceted powdered photocatalytic systems, problems related to environmental pollution and energy requirements have been addressed to a significant extent. The major reason for this great achievement lies in the combined effect of both structure modification and integration of different functional materials. Here, we report a ternary hybrid containing wide band gap CeO2 nanosheets with CdSQDs and Au nanoparticles, incorporated between this type II heterostructure through simple chemical reduction methods. Structural and morphological characterization of the fabricated samples was carried out by XRD, XPS, and TEM analysis. From a series of optical and photoelectrochemical measurements, it was found that the incorporation of Au nanoparticles into the interfaces of CeO2 and CdSQDs was the major cause of the enhancement in the photocatalytic activity. Au nanoparticles play a dual character by acting as a mediator and also inject hot electrons through LSPR (light-induced su...

g-C3N4 has been widely used as a smart material for photocatalytic applications. Due to insufficient solar-light absorption and fast electron–hole recombination, the photocatalytic activity of g-C3N4 remains a challenge for industrial applications. In this study, we prepared an exfoliated g-C3N4 homojunction in a single-step biomediated route, thereby addressing the major issues of g-C3N4. With a well exfoliated and layered sheet structure, g-C3N4 exhibits exceptional physical properties such as ultrahigh intrinsic carrier mobility and pronounced changes in the energy band structure due to weak van der Waals forces between C3N4 layers. The formation of well exfoliated sheets of g-C3N4 was confirmed by XRD, FESEM, TEM and AFM results. More importantly XPS confirmed the synthetic process by the biomediated route, in which some electron acceptor (–CN) groups were easily introduced at the edge of g-C3N4, aiding the in situ p–n homo-junction formation. The g-C3N4 homojunction was confirmed by Mott–Schottky analysis. This homojunction structure was proven by EIS and TRPL analysis to be highly proficient in charge transfer and separation processes. The exfoliated g-C3N4 homojunction showed significantly enhanced photocatalytic activity, compared to that prepared through the conventional route, due to the unique structural advantages, electron transfer, light harvesting, lower recombination rate of charge carriers and the richly available reaction sites during the photocatalytic reaction. g-C3N4 prepared through the one step biomediated route was able to evolve 87 μmol h−1 of H2 and degrade 90.2% of 200 ppm RhB solution, which is significantly higher than bulk g-C3N4 prepared through the conventional route.

Herein, we disclosed the g-C3N4/LaFeO3 nanocomposite photocatatalyst, a mediator-free direct Z-scheme photocatalytic system, prepared using a mechanical mixing method with reliable interfacial interactions. The nanocomposite formation was determined by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The optical properties of the nanohybrids were also characterized using UV-vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectroscopy. The results clearly indicated that the g-C3N4/LaFeO3 nanocomposite was effectively fabricated, with reliable interfacial interactions and a good heterojunction interaction between g-C3N4 and LaFeO3, which can considerably enhance the photocatalytic activity as compared to pristine g-C3N4 and LaFeO3. The high HER (1152 μmol h−1 g−1) was also confirmed by the PL spectra, Mott–Schottky plot, electrochemical impedance spectroscopy (EIS), and solid–solid interfacial interactions.

Nanoceria and its derivatives are promising photocatalysts for environmental sustainability due to their strong redox ability, high oxygen storage/release capacity, eco-friendly nature, photostability and cost effectiveness. This study highlights the first time N/S co-doped ceria prepared using a simple hydrothermal method from a Ce(NO)3 and thiourea source. The spectrographic, crystallographic and macroscopic features of the as-synthesised photocatalysts were characterised by TEM, DRUV-vis, PL, TRPL, XRD, Raman and photoelectrochemical measurements. Under visible light illumination, doped ceria exhibits remarkable photocatalytic activity towards Cr(VI) reduction, in contrast to neat CeO2. The enhanced photoreduction ability of doped species, particularly 36 h treated samples (NCS-36), is due to more light absorption capacity, greater photocurrent generation and high concentration of photoexcited electrons, which were well supported by characterization techniques. The average lifetime decay of photoexcited electrons and the photocurrent density of NCS-36 were found to be 75.37 ps and 3.87 mA cm−2, which is nearly 3- and 12-times higher than that of neat ceria, respectively. These obtained results clearly explain the 93% photoreduction ability of NCS-36 towards a 50 ppm Cr(VI) solution within a time span of 120 min under visible light irradiation.