The growth of photocatalysis has led to increased interest in photocatalysts due to their crucial role in environmental protection, therapeutic, energy generation, and industrial processes. Extensive research has been conducted to invent photocatalysts with outstanding properties and excellent photocatalytic performances to alleviate large-scale applications. Hybrid nanocomposites are capable of exhibiting extraordinary and expected characteristics, which are attributed due to the presence of nanostructured materials having novel properties. This article aims to accumulate the significant aspects, including fundamental mechanisms, suitable nanomaterials and multiple methods for synthesis, strategies to boost the performances, various types, and prospective applications of photocatalysts. More detailed explanations and relevant examples have been provided regarding the efficient techniques used to produce photocatalysts based on hybrid nanocomposites and the successful approaches employed to improve their photocatalytic performance. In addition, biomaterial-based environmentally benign nanophotocatalysts have been focused on here since the hazard and toxicity of nanotechnology products are of great concern nowadays. The discussion has been concluded by addressing the existing challenges with concluding remarks.

N-doped ordered mesoporous carbons (NCMK-3) were synthesized using urea and ammonia as nitrogen sources via an incipient wetness impregnation method. To quantify the amount of nitrogen doping and classify the nitrogen bond formations, the XPS technique was used in this study. It was found that urea can increase the nitrogen content up to 2.54% and can classify nitrogen on NCMK-3 into three types: pyridinic-N, pyrrolic-N, and graphitic-N. Subsequently, 15 wt% of Cu–ZnO and 15 wt% of Cu–CeO2 were loaded on NCMK-3 and tested for methanol production from the CO2 hydrogenation reaction. The catalysts’ performance was evaluated in a fixed-bed reactor using 0.25 g of catalyst and a CO2/H2 (1/3) mixture at GHSV of 2444 h−1. The results showed that 15 wt% of Cu–ZnO on the nitrogen-doped CMK-3 using urea as a nitrogen source (CZ/NCMK-3U) provided the highest space time yield (STY) of 512 mgMeOH gcat−1 h−1 at the reaction temperature and pressure of 250 °C and 1.5 MPa, respectively.

Boron-containing materials are efficient catalysts for the oxidative dehydrogenation of propane to propylene, proceeding via radical intermediates. The radical mechanism is initiated by the solid surface and propagated in the gas phase. It has been hypothesized that the propylene selectivity could be increased by enhancing the gas-phase contributions by favoring the formation of iso- over n-propyl radical intermediates. Indeed, whereas n-propyl radicals can be converted to both propylene and ethylene, iso-propyl radicals yield exclusively propylene. In this contribution, we explore 3D printing to structure the hexagonal boron nitride (hBN) heterogeneous catalyst with high void space. 3D-printed hBN monoliths were found to exhibit a higher olefin selectivity and a higher rpropylene/rethylene ratio as compared to traditional pack beds of hBN pellets. Our kinetic studies indicate the increase of reaction order in propane from 1.5 to 2.3, implying the promotion of gas-phase reaction. This work does not only shows that 3D-structured catalysts lead to higher propylene selectivity, it also confirms the hypothesized reaction mechanism and illustrates the power of molecular insights in selective oxidation chemistry to improve the performance.Graphical abstract

Typically, the conversion of methane to value-added hydrocarbon (C2+) via the oxidative coupling of methane is accomplished using high energy due to the temperature of the operation (more than 700 °C). The conversion of methane to C2+ was investigated using a hybrid catalyst consisting of 15 wt% of Ni on Al2O3 (15Ni/Al2O3) and 10–25 wt% of Co supported on Al2O3 (Co/Al2O3) packed as a prioritized layer in a reactor. The effects of operating conditions—different Co loading in Co/Al2O3, reactor pressure and temperature, percentage of O2 in the feed, total feed flow rate, and different weights of Co/Al2O3—on the performance of the hybrid catalyst were studied for the reaction. The highest performance (3.6% C2+ yield with 7.9% C2+ selectivity and 46.3% CH4 conversion) of the hybrid catalyst was achieved at 6 bar, 490 °C, 37.5% of O2 in the feed, a total flow rate of 50 ml/min, and using 0.25 g of 15Ni/Al2O3 and 0.1 g of 15 wt% of Co/Al2O3 (15Co/Al2O3). The prepared catalysts were characterized using X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, N2-sorption analysis, X-ray photoelectron spectroscopy, NH3- and CO2-temperature-programmed desorption, and thermogravimetric analysis to acquire the chemical and physical properties of the catalysts. A time-on-stream testing of the optimized hybrid catalyst for 24 h was performed to determine the stability of the catalyst and revealed that the formation of coke caused rapid deactivation of the catalyst.Graphical Abstract

Pd-based catalysts supported on high-surface-area carbon are widely used in formic acid fuel cells. The composition, structure, and support can be modified to maximize the capabilities of Pd-based catalysts in terms of catalytic activity, durability, and cost. Various studies have investigated tuning the properties of Pd-based catalysts by alloying Pd with other metals. In this study, Cr, Ni, Cu, and Zn were incorporated into Pd-based catalysts. First, the effects of mole ratios were studied between Pd and the metals. The PdnNi ratios on a reduced graphene oxide support (PdnNi/rGO) were prepared using the one-pot method without the use of any surfactants. All obtained rGO-supported PdnNi catalysts (n = 1, 2, 4, with diameter of 5 nm) were used for the electrocatalytic oxidation of formic acid. The electro-oxidation measurements revealed that the PdnNi/rGO samples had superior electrocatalytic performance both in current densities and stabilities for formic acid oxidation (FAO) compared to Pd/rGO. Furthermore, Pd4Ni/rGO had greater electrocatalytic activity than the other PdnNi/rGO samples. In addition, with the same mole ratio of metals, Pd4Cr/rGO had higher efficiency toward FAO than the other series in the order: Pd4Cr/rGO > Pd4Ni/rGO > Pd4Cu/rGO > Pd4Zn/rGO.

To advance meaningful guidelines in the design of electrocatalytically active catalysts, a knowledge of the nature of active sites is the starting point. However, multiple factors such as material composition, site coordination, electrolyte effects, the support material, surface strain, and others influence catalytic behavior. Therefore, the identification of active sites can be complex. A substantial contributor can be in-situ experiments, which are able to identify active centers in a specific system while the reaction takes place. An example of such a technique is electrochemical scanning tunneling microscopy (EC-STM), which relates locally confined noise features to local electrocatalytic activity. In this work, we spotlight recent achievements of this technique with respect to palladium (Pd) surfaces for the hydrogen reduction reaction, where strain due to hydride formation comes into play in addition to surface coordination. Secondly, we demonstrate the high resolution of the technique on graphite-based surfaces. Here, edge sites are particularly active. Thus, with the EC-STM technique, we take strain effects (like on Pd) or effects of coordination (like on carbon) into account. Therefore, we can determine active sites with great accuracy under reaction conditions.

Several supported liquid-phase (SLP) catalysts with immobilized Rh-biphephos complexes on monolithic supports were prepared and applied for continuous gas-phase hydroformylation (HyFo) of 1-butene. The support comprised macroporous monolithic silicon carbide (SiC) with deposited silica nanoparticles (NPs) in order to provide mesopores with enhanced capillary forces to retain the liquid-phase. Variable parameters were examined for the monolithic SiC supports, including size and loading of deposited silica NPs and intermediate calcination between silica deposition steps to obtain the most efficient support configuration for the SLP system. The SLP catalysts with larger deposited silica NPs gave higher catalytic activity (i.e. 1-butene conversion and turnover frequency) compared to the supports with smaller sized silica NPs. However, the selectivity towards the preferred linear aldehyde was higher in the SLP catalysts with supports containing less silica with small silica NPs. Importantly, the prepared SLP catalyst systems showed long-term stability in HyFo with negligible formation of high boiling aldol condensation products.

Understanding how hydrotreating oxygen-containing compounds together with nitrogen-containing compounds affects the reactivity and selectivity is relevant for processing renewable feedstocks. In this work, competitive hydrodeoxygenation (HDO) and hydrodenitrogenation (HDN) reactions were studied by co-hydrotreating palmitic acid (C16 acid) and tetradecylamine (C14 amine) over a Pt/ZrO2 catalyst in a batch reactor. HDO proceeded faster than HDN in the studied system, and the deoxygenation reactions were found to have an inhibitory effect on HDN. Co-hydrotreating the C16 acid and the C14 amine expanded the reaction network from the individual HDO and HDN networks and changed the prevailing reaction pathways, initially in favor of oxygen removal. The formation of heavy secondary amides and amines through condensation reactions became increasingly favored as the share of C16 acid in the feed increased. For a given conversion level, the condensation product selectivity was observed to increase as the reaction temperature was decreased, whereas increasing the reaction temperature promoted the formation of the desired paraffins. This work described the ease of HDO compared to HDN, the role of condensation reactions in the co-hydrotreating reaction network, and the inhibitory effect on HDN thereof.

Access to secure water sources has become one of the biggest challenges for human sustainability. Climate change and associated droughts make it difficult to guarantee the usual water source and move to groundwater use or to the re-use of treated wastewater remains unviable due the lack on the capacity of monitoring water quality. Moreover, reusing treated wastewater from repositories near anthropogenic sources represents a risk of high concentrations of emerging contaminants. The strategies involve a higher risk of encountering toxic elements with a heavy burden on human and environmental health. New accessible and reliable tools are required to detect any hazard from the waterbodies in real time to ensure safe management and also to decrease mismanagement or ilegal water discharges. One of the available options is to look into enzyme-based biosensors that can detect toxic elements in the water. The proposed biosensors require sensible elements to be accessible and durable for their proper function. The present revision shows in first place, the actual need of real time monitoring due the different sources and effects of emergent pollutants. Secondly, describes how enzymes can be immobilized for its application in biosensors and the rol enzymes play as bioreceptor element in biosensing. Thirdly, describes the transduction methods that can be observed, and finally the actual application of enzyme biosensors for the detection of different toxic elements. According to the presented literature enzyme-based biosensors have been successfully applied for the detection of a wide number of pollutants reaching detection limits comparable to traditional methods such as up to 0.018 nM of mercury. Furthermore, laccase seems to be the more applied enzyme in literature, but positive results are not limited to this enzyme and other candidates have been explored showing good detection rate.Graphical Abstract

Nanoscaled-VPO (vanadium phosphate oxide) catalysts have been prepared on an alumina support with the objective of obtaining crystallites of the active phase with a high surface-to-volume ratio. Since the catalysed reaction occurs at the surface, these nanoscaled catalysts allows studying surface species transformations with a minimized signal from the bulk dominion. The chemical environment and oxidation state of these species has been determined by a combination of NMR, ESR and XANES spectroscopies. The results have allowed to optimize V + P coverage and V/P molar ratio to minimize the concentration of isolated vanadium oxide species and maximize V4+ concentration. The distribution of phosphorus islands ordered and significantly distorted of tetra- and penta-coordinated aluminium sites of the catalytic support, thus shaping the catalytic material to an optimal structure for the desired partial oxidation reaction.

Burning hydrocarbon fuels at ever-increasing rates and producing huge amounts of carbon dioxide emissions are the root causes of the global energy problem and climate change. The transformation of CO2 into other forms of energy, such as CO, CH4, and CH3OH, is one potential approach to the complex problems of environmental pollution, climate change, and global warming. Methanol is one of these goods that is one of the most significant and highly adaptable chemicals regularly used in industry and daily life. Methanol is one of the most important and widely used chemicals. Photocatalysis answers the present problems facing the environment and the energy sector. This article explores recent developments in the photocatalytic conversion of CO2 to CH3OH using catalysts based on plasmonic TiO2 and TiO2 nanomaterial. The process involves converting carbon dioxide into methanol.

Solid catalysts with ionic liquid layers (SCILLs) are heterogeneous catalysts which benefit significantly in terms of selectivity from a thin coating of an ionic liquid (IL). In the present work, we study the interaction of CO with a Pd model SCILL consisting of a 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)-imide ([C4C1Pyr][NTf2]) film deposited on Pd(111). We investigate the CO permeability and stability of the IL film via pressure modulation experiments by infrared reflection absorption spectroscopy (IRAS) in ultrahigh vacuum (UHV) and at ambient pressure conditions by time-resolved, temperature-programmed, and polarization-modulated (PM) IRAS experiments. In addition, we performed molecular dynamics (MD) simulations to identify adsorption motifs, their abundance, and the influence of CO. We find a strongly bound IL wetting monolayer (ML) and a potentially dewetting multilayer. Molecular reorientation of the IL at the interface and multilayer dewetting allow for the accumulation of CO at the metal/IL interface. Our results confirm that co-adsorption of CO changes the molecular structure of the IL wetting layer which confirms the importance to study model SCILL systems under in situ conditions.Graphical abstract

Nano zero-valent iron (nZVI), bimetallic Nano zero-valent iron-copper (Fe0- Cu), and fava bean activated carbon-supported with bimetallic Nano zero-valent iron-copper (AC-F e0-Cu) were prepared and characterized by DLS, FT-IR, XRD, and SEM. The influence of the synthesized adsorbents on the adsorption and removal of soluble anionic methyl orange (M.O) dye was investigated using UV-V spectroscopy. The influence of numerous operational parameters was studied at varied pH (3–9), time intervals (15–180 min), and dye concentrations (25–1000 ppm) to establish the best removal conditions. The maximum removal efficiency of M.O. using the prepared adsorbent materials reached about 99%. The removal efficiency is modeled using response surface methodology (RSM). The Bimetallic \(F{e}^{0}\)-Cu, the best experimental and predicted removal efficiency is 96.8% RE. For the H2SO4 chemical AC-\(F{e}^{0}\)-Cu, the best experimental and removal efficiency is 96.25% RE. The commercial AC-Fe0–Cu, the best experimental and predicted removal efficiency is 94.93%RE. This study aims to produce low-cost adsorbents such as Bimetallic Fe0-Cu, and Fava Bean Activated Carbon-Supported Bimetallic AC-Fe0-Cu to treat the industrial wastewater from the anionic methyl orange (M.O) dye and illustrate its ability to compete H2SO4 chemical AC-Fe0-Cu, and commercial AC-Fe0-Cu.

The as-deposited zinc oxide films with different aluminum doping ratios by radio frequency magnetron sputtering served as seed layers for aluminum-doped zinc oxide films growth by the mist chemical vapor deposition method. It was confirmed that the growth orientation of aluminum doped zinc oxide in mist CVD process was depended on the crystallinity of as-deposited AZO thin film. The growth direction of the obtained AZO films followed the same growth tendency in (0001) crystal orientation as the underneath as-deposited AZO seed layer. It was revealed that the lower lattice mismatch between the AZO films and the seed layer contributed to the higher columnar structure growth. The increase of aluminum doping ratio in ZnO film could release the compressive stress, resulting in the crystallinity improvement of AZO film. The highest photocatalytic efficiency was achieved from the AZO film deposited on the AZO seed layer with a 5 wt% Al doping ratio. The efficient photocatalytic activity covered the wavelength from 340 nm to 700 nm, indicating that the photodegradation efficiency could be improved not only in the ultra-violet region but also in the visible region. The AZO film deposited on the AZO-5wt% had the highest photocatalytic degradation rate of 0.0043 min-1.

During cold start of vehicles with gasoline combustion engines, conversion of pollutants in the exhaust gas to inert products is very low due to low catalyst temperature. Only above the light-off temperature, significant conversion can be achieved. Previous strategies to reduce cold-start emissions have been focused on developing catalysts with a low light-off temperature. Electric catalyst heating systems have also been discussed repeatedly. A disadvantage of such systems is the required volume flow through the catalyst, which is necessary for heat transfer to the catalyst. In contrast, microwave-assisted heating allows direct introduction of thermal power into the catalyst due to dielectric losses of the catalyst materials. This work analyses simulation-based the influence of the material on the heatability by microwaves. The focus is on the substrate materials rather than the catalytically active coatings, since the substrate represents the part in the TWC where most of the dielectric losses occur. For this purpose, the temperature-dependent dielectric material properties of cordierite and silicon carbide (SiC) are investigated. The determined material properties are then transferred to a simulation model that calculates heat distribution and heat insertion based on the electromagnetic field distribution. The heat propagates better throughout the monolith due to the higher thermal conductivity of SiC compared to cordierite. In summary, SiC leads to a homogeneous heating of the entire catalyst material. The fact that dielectric losses of SiC decrease with temperature may help to self-limit the catalyst temperature.

Organoboron compounds are important building blocks in organic chemistry for a variety of key transformations in the production of compounds in the pharmaceutical and agricultural industries. Direct C–H borylation provides many advantages over more traditional transformation via halide groups that lead to stoichiometric waste. In the direct C(sp2)–H borylation of arenes, Ir-bipyridine systems have shown excellent performance. However, to make the formation of borylated products more benign and greener, transformations catalyzed by heterogeneous catalysts are appealing as they provide easier recovery and reuse of the catalyst. In this study, two different porous organic polymers (POPs) based on polystyrene-bearing bipyridine (bpy) ligands were synthesized. These POPs can, upon metal ligation in situ create an active catalyst that is capable of borylation twice per B2pin2 molecule. Our Ir systems were tested with different arenes, and a preliminary mechanistic investigation was performed. The system was recyclable for up to three consecutive recycles, albeit, the polymer backbone had indications of being borylated during the reaction.

Bifunctional catalysts consisting of metal and acid sites are generally used for transformation of bio-oil/bio-oil model compounds via hydrodeoxygenation (HDO). Active metal sites are important for hydrogenation and demethoxylation reactions, while the acid sites are required for dehydration and alkylation reactions during HDO. Platinum group metals have demonstrated high HDO activity owing to their excellent hydrogenation character. In the present work, the HDO activities of Pt, Pd and Ru-supported activated carbon (AC) are evaluated for HDO of isoeugenol and binary mixtures of isoeugenol with acetic acid and furfural. Pt/AC showed superior HDO activity compared to other catalysts owing to the presence of metallic Pt0 over AC, while Pd and Ru were observed in both metallic and oxide states (Pd+ 2 and Ru+ 4). The selectivity to propyl cyclohexane (PC) enhanced as temperature increased from 240 to 280 °C over all the three catalysts. Further, the HDO of isoeugenol was investigated over physically mixed Pt/AC and HZSM-5 catalysts. An improved selectivity towards PC was observed over the mixed catalyst (57.1%) as compared to that over Pt/AC (36.9%), due to the presence of acid sites offered by HZSM-5. Noticeably, superior HDO activity was observed at shorter reaction time over mixed catalysts (60 min) compared to Pt/AC (120 min). While the HDO of single model compounds has been studied extensively, the effect of multiple oxygenate groups on catalytic activity is scarcely explored in the literature. Therefore, the activities of Pt/AC and mixed catalysts were evaluated for the HDO of binary blends of isoeugenol with acetic acid and furfural. Both acetic acid and furfural inhibited the HDO of isoeugenol. The presence of furfural drastically reduced the deoxygenation activity of both the catalysts. The yield of PC decreased drastically from 25.5 to 0.6% when treated with furfural over Pt/AC, and from 35.5 to 1.2% over physically mixed catalysts. The use of mixed catalyst, however, reduced the inhibiting effect of acetic acid on the HDO of isoeugenol.

Geopolymers are a type of inorganic polymer that typically have a monochromatic appearance. This study investigates the formation of artificial chrysocolla by immersing these materials in Cu(II) ion solutions. The resulting synthetic chrysocolla possesses magnetic properties and characteristic silicate bands in its structure, indicating geopolymerization and a similarity to natural chrysocolla. Furthermore, the inclusion of copper and zinc ferrites in the nano-modified geopolymer matrix enhances its properties and potential antiviral properties. The antiviral test results show that synthetic chrysocolla based on nano-modified geopolymers has a mild antimicrobial effect. However, more testing is needed to determine its effectiveness against bacteriophage, as bacterial growth was observed in the area where the nano-modified geopolymer bacteriophage blend was applied. In addition to its potential antiviral properties, synthetic chrysocolla's porous structure allows it to act as an adsorbent, making it useful in the development of antiviral filters. Artificial chrysocolla can be obtained through a geopolymeric matrix by immersing it in a solution of Cu(II) ions, which can occur by ion exchange of the ions present in the aluminosilicate structure with Cu(II). Neutralization of the geopolymer matrix by washing with distilled water is required prior to immersion to ensure proper formation of chrysocolla and not copper(II) hydroxide on the geopolymer surface. Overall, this study provides evidence for the successful preparation of nano-modified synthetic chrysocolla from geopolymers and ferrites, with properties and chemical composition similar to those of natural chrysocolla. The presence of copper ions in its composition and the incorporation of copper and zinc ferrites can contribute to its use as a resource to combat viral pathogens.

In this study, we synthesized xZnO–ZrO2 (x = 14–40 at%) by flame spray pyrolysis under a lean-fuel condition. The optimal ZnO content was investigated to obtain a ZnO–ZrO2 solid solution with high specific surface area for CO2-to-methanol hydrogenation. The Zn species in ZnO–ZrO2 were highly dispersed and hexagonal ZnO was not detected by X-ray diffraction (XRD). After heating the particles in Ar at 400 °C for 3 h, hexagonal ZnO particles were observed at x = 40 at%, while below x = 28 at%, the Zn species remained high dispersion state. A fraction of the Zn species was substituted into the bulk of the ZrO2 particles, as evidenced by the shift of the ZrO2 (101) peak in the XRD patterns. The elemental mapping of Zn and Zr in 28 at% ZnO–ZrO2 showed that the Zn species on the surface were uniformly distributed. The presence of partially reduced Zrδ+ state (δ < 4) was confirmed by X-ray photoelectron spectroscopy. The Zrδ+ state in the ZnO–ZrO2 particles was prominent when ZnO content was below 28 at%. The catalytic activity of 28 at% ZnO–ZrO2 for CO2-to-methanol hydrogenation was higher than that of 40 at% ZnO–ZrO2. At 300 °C and 1.0 MPa, the CO2 conversion and the selectivity to methanol over 28 at% ZnO–ZrO2 were 9 and 48%, respectively, resulting in the high yield of methanol (4.3%).Graphical abstract

A development of effective, low cost, and easily prepared catalyst has been a challenge to the viability of glycerol carbonate (GC) production via transesterification of glycerol (GLY) with dimethyl carbonate (DMC). This work proposes a facile method to prepare such catalyst from wasted pineapple peels (PP). The catalysts were simply prepared by calcination of dried PP powders in air under atmospheric condition using calcination time of 3 h and calcination temperatures between 300–800 °C. Several techniques were used to study the catalyst properties including, TGA, N2 physisorption, SEM, XRD, FT-IR, Hammett indicators and acid–base titration method. It was found that the PP calcined at 600 ºC (PP-600), showed the highest basicity and was the most active catalyst. With this catalyst, the highest GLY conversion of 92.85% and GC yield of 90.29% could be achieved under the optimal condition at a reaction temperature of 80 ºC, reaction time of 90 min, DMC:GLY molar ratio of 3:1 and amount of catalyst of 12 wt.%. At this condition, the catalyst could be used repeatedly up to 5 cycles while giving the conversion and yield on the fifth cycle of 64.81 and 61.13%, respectively.