Self-assembled sulphur doped carbon nitride for photocatalytic water reforming of methanol

The ability to effectively harness and store renewable solar energy in chemical forms, e.g., methanol has been widely recognised as a promising and sustainable strategy for H_{2} storage. Though traditional steam reforming of methanol enables effective H_{2} release from methanol and water, the harsh operating conditions result in high energy consumption and CO by-product. To minimize CO emission and maximise H2 production, photocatalytic liquid water reforming of methanol has been developed to produce H_{2} by sulphur doped graphitic carbon nitride (SCN) in this work. Consequently, both H_{2} and carbon dioxide (CO_{2}) can be evolved in an ideal ratio of 3:1 and H_{2} yield has been found to be dependent on pH and the reaction temperature. A stable and reproducible H_{2} evolution rate of 14.7 mmol g^{-1}h^{−1} from water/methanol over 95 h without CO evolution has been achieved, with an apparent quantum efficiency (AQE) of c.a. 30 % at 365 nm. The sulphur was found to exist as N-S-H and C-S-H bonds in the SCN photocatalysts, while the latter was found to be well correlated to the photocatalytic activity of H_{2} production. Such sulfur doping narrows the bandgap and offers enhanced charge separation, thus leading to enhanced photocatalytic activity

Hydrothermal assisted morphology designed MoS2 material as alternative cathode catalyst for PEM electrolyser application

In this work, we developed a simple and cost-effective hydrothermal route to regulate the formation of molybdenum disulfide (MoS2) in different morphologies, like, nano-sheet, nano-capsule and nano-flake structure by controlling the reaction temperature and sulphur precursor employed. Such a fine tuning of different morphologies yields a leverage to obtain novel shapes with high surface area to employ them as suitable candidates for hydrogen evolution catalysts. Moreover, we report here the first time observation of MoS2 nano-capsule formation via environmentally benign hydrothermal route and characterized them by X-ray diffraction (XRD), nitrogen adsorption and desorption by Brunaer–Emmett–Teller (BET) method, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray photo-electron spectroscopy (XPS) techniques. MoS2 nano-capsules exhibits superior activity towards hydrogen evolution reaction (HER) with a low over-potential of 120 mV (RHE), accompanied by large exchange current density and excellent stability in 0.5 M H2SO4 solution. MoS2 nano-capsule catalyst was coated on solid proton conducting membrane (Nafion) and IrO2 as anode catalyst. The performance of the catalyst was evaluated in MEA mode for 200 h at 2 V without any degradation of electrocatalytic activity

Facile one-step synthesis and enhanced photocatalytic activity of WC/ferroelectric nanocomposite

The development of noble-metal-free co-catalysts is seen as a viable strategy for improving the performance of semiconductor photocatalysts. Although the photocatalytic efficiency of ferroelectrics is typically low, it can be enhanced through incorporation of co-catalyst into nanocomposites. Here, we demonstrate the influence of ferroelectricity on the decolorization of Rhodamine B under simulated solar light using RbBi2Ti2NbO10 and compared the performance with nonferroelectric RbBi2Nb5O16. The decolorization rate for RbBi2Ti2NbO10 was 5 times greater than RbBi2Nb5O16. This behaviour can be explained in terms of ferroelectric polarization, which drives separation of the charge carriers. The photocatalytic activity of the RbBi2Ti2NbO10 was further enhanced to over 30 times upon preparing nanocomposite with tungsten carbide (WC) through high energy ball milling. This enhancement was not only attributed to the increased specific surface area, but also to the incorporated WC co-catalyst which also serves as source of plasmonic hot electrons and extends the photocatalytic activity into the visible light range. The WC/RbBi2Ti2NbO10 nanocomposite shows interesting water oxidation property and evolves O2 with a rate of 68.5 μmol h-1 g-1 and the quantum yield of 3% at 420 nm. This work demonstrates a simple route for preparing WC containing nano ferroelectric composites for solar energy conversion applications

Facile one-step synthesis and enhanced photocatalytic activity of a WC/ferroelectric nanocomposite

The development of noble-metal-free co-catalysts is seen as a viable strategy for improving the performance of semiconductor photocatalysts. Although the photocatalytic efficiency of ferroelectrics is typically low, it can be enhanced through the incorporation of a co-catalyst into nanocomposites. Here, we demonstrate the influence of ferroelectricity on the decolorization of rhodamine B under simulated solar light using RbBi2Ti2NbO10 and compared the performance with that of non-ferroelectric RbBi2Nb5O16. The decolorization rate for RbBi2Ti2NbO10 was 5 times greater than that of RbBi2Nb5O16. This behaviour can be explained in terms of ferroelectric polarization, which drives the separation of charge carriers. The photocatalytic activity of RbBi2Ti2NbO10 was further enhanced to over 30 times upon preparing a nanocomposite with tungsten carbide (WC) through high energy ball milling. This enhancement was attributed not only to the increased specific surface area, but also to the incorporated WC co-catalyst, which also serves as a source of plasmonic hot electrons and extends the photocatalytic activity into the visible light range. The WC/RbBi2Ti2NbO10 nanocomposite shows interesting water oxidation properties and evolves O2 with a rate of 68.5 μmol h−1 g−1 and a quantum yield of 3% at 420 nm. This work demonstrates a simple route for preparing WC containing nano-ferroelectric composites for solar energy conversion applications

Energy Platform for Directed Charge Transfer in the Cascade Z-Scheme Heterojunction: CO2 Photoreduction without a Cocatalyst

A universal strategy is developed to construct a cascade Z-scheme system, in which an effective energy platform is a core to direct charge transfer and separation, blocking the unexpected type-II charge transfer pathway. The dimension-matched (001)TiO 2 -g-C 3 N 4 /BiVO 4 nanosheet heterojunction (T-CN/BVNS) is the first such model. The optimized cascade Z-scheme exhibits ~19-fold photoactivity improvement for CO 2 reduction to CO in the absence of cocatalysts and costly sacrificial agents under visible-light irradiation, compared with BVNS, which is also superior to other reported Z-scheme systems even with noble metals as mediators. The experimental results and DFT calculations based on Van der Waals structural models on the ultrafast timescale reveal the introduced T as the platform could not only prolong the lifetimes of spatially separated electrons and holes but also did not compromise their reduction and oxidation potentials

Single-atom Cu anchored catalysts for photocatalytic renewable H2 production with a quantum efficiency of 56

Single-atom catalysts anchoring offers a desirable pathway for efficiency maximization and cost-saving for photocatalytic hydrogen evolution. However, the single-atoms loading amount is always within 0.5% in most of the reported due to the agglomeration at higher loading concentrations. In this work, the highly dispersed and large loading amount (>1 wt%) of copper single-atoms were achieved on TiO2, exhibiting the H2 evolution rate of 101.7 mmol g-1 h-1 under simulated solar light irradiation, which is higher than other photocatalysts reported, in addition to the excellent stability as proved after storing 380 days. More importantly, it exhibits an apparent quantum efficiency of 56% at 365 nm, a significant breakthrough in this field. The highly dispersed and large amount of Cu single-atoms incorporation on TiO2 enables the efficient electron transfer via Cu2+-Cu+ process. The present approach paves the way to design advanced materials for remarkable photocatalytic activity and durability

Label-Free Electrochemical Immunoassay for C-Reactive Protein

C-reactive protein (CRP) is one of the most expressed proteins in blood during acute phase inflammation, and its minute level increase has also been recognized for the clinical diagnosis of cardio vascular diseases. Unfortunately, the available commercial immunoassays are labour intensive, require large sample volumes, and have practical limitations, such as low stability and high production costs. Hence, we have developed a simple, cost effective, and label-free electrochemical immunoassay for the measurement of CRP in a drop of serum sample using an immunosensor strip made up of a screen printed carbon electrode (SPE) modified with anti-CRP functionalized gold nanoparticles (AuNPs). The measurement relies on the decrease of the oxidation current of the redox indicator Fe3+/Fe2+, resulting from the immunoreaction between CRP and anti-CRP. Under optimal conditions, the present immunoassay measures CRP in a linear range from 0.4–200 nM (0.047–23.6 µg mL−1), with a detection limit of 0.15 nM (17 ng mL−1, S/N = 3) and sensitivity of 90.7 nA nM−1, in addition to a good reproducibility and storage stability. The analytical applicability of the presented immunoassay is verified by CRP measurements in human blood serum samples. This work provides the basis for a low-priced, safe, and easy-to-use point-of-care immunosensor assay to measure CRP at clinically relevant concentrations

Electrochemical Sensor for Bilirubin Detection Using Screen Printed Electrodes Functionalized with Carbon Nanotubes and Graphene

Practice oriented point-of-care diagnostics require easy-to-handle, miniaturized, and low-cost analytical tools. In a novel approach, screen printed carbon electrodes (SPEs), which were functionalized with nanomaterials, are employed for selective measurements of bilirubin, which is an important biomarker for jaundice. Multi-walled carbon nanotubes (MWCNT) and graphene separately deposited on SPEs provide the core of an electrochemical sensor for bilirubin. The electrocatalytic activity towards bilirubin oxidation (bilirubin to biliverdin) was observed at +0.25 V. In addition, a further peak corresponding to the electrochemical conversion of biliverdin into purpurin appeared at +0.48 V. When compared to MWCNT, the graphene type shows a 3-fold lower detection limit (0.3 ± 0.022 nM and 0.1 ± 0.018 nM, respectively), moreover, the graphene type exhibits a larger linear range (0.1–600 µM) than MWCNT (0.5–500 µM) with a two-fold better sensitivity, i.e., 30 nA µM−1 cm−2, and 15 nA µM−1 cm−2, respectively. The viability is validated through measurements of bilirubin in blood serum samples and the selectivity is ensured by inhibiting common interfering biological substrates using an ionic nafion membrane. The presented approach enables the design and implementation of low cost and miniaturized electrochemical sensors

Facile fabrication of dye-sensitized solar cells utilizing carbon nanotubes grown over 2D hexagonal bimetallic ordered mesoporous materials

High-surface area and well-ordered mesoporous Fe incorporated SBA-15 (Fe-SBA-15), FeeCr incorporated SBA-15 (FeeCr-SBA-15) and Cr incorporated SBA-15 (Cr-SBA-15) catalysts are synthesized following a controlled post synthesis grafting process. The activities of all the catalysts are tested systematically and quantitatively towards the production of carbon nanotubes (CNTs) by chemical vapour deposition. In order to obtain CNTs with high quality and quantity, the parameters like temperature, reaction time and gas flow rate are optimized. Under optimum conditions, the FeeCr-SBA- 15 catalyst is produced with high yield and uniform diameter of CNTs. The transmission electron microscopy result reveals high purity and well-graphitized structure of CNTs. The synthesized CNTs are used as counter electrode material for dye-sensitized solar cells (DSSCs). The CNTs based counter electrode shows good chemical stability, lower charge-transfer resistance and higher electrocatalytic activity towards I3 �/I� redox reaction than that of platinum (Pt) counter electrode. The energy conversion efficiency of the CNTs counter electrode based DSSCs reaches 8.86% under irradiation with a simulated solar light intensity of 100mWcm�2. The results prove that CNTs are one of the suitable candidates for Pt free counter electrode for DSSC

Fabrication of catalytically active nanocrystalline samarium (Sm)-doped cerium oxide (CeO2) thin films using electron beam evaporation

Samarium(Sm)-doped ceriumoxide (CeO2) thin films were fabricated using electron beam evaporation technique. The synthesized films were deposited either on glass or ITO substrates and studied their nature by annealing at different temperatures. The optical properties and other morphological studies were done by UV–Vis,XRD,XPS, SEM, EDS, and FT-IR analysis. XRD and XPS analysis clearly confirm the presence of Sm in the ceria site. From the SEM study, it was found that after annealing at high temperature (*300 or 500 �C), the particles sizewas reduced due to breakdown of large aggregates of particles which is also confirmed from UV–Vis, XPS, andXRDanalyses. The FT-IR study proves the presence of –COO–, –OH, or ammonium group on the particles surface. The deposition of Smdoped CeO2 nanomaterials was found more feasible on ITO substrate compared to that of glass substrate in terms of stability and depth of film thickness. The Sm-doped CeO2 nanomaterial acts as a re-usable catalyst for the reduction of organic dye molecules in the presence of NaBH4. The catalysis rate was compared by considering the electron transfer process during the reduction. The synthesized Sm-doped CeO2 thin films might find wide variety of applications in various emerging fields like solid oxide fuel cells (SOFCs), oxygen sensor or as catalyst in different types of organic and inorganic catalytic reactions. The fabrication process is very simple, straightforward, less time consuming, and cost effectiv