An Amiable Design of Cobalt Single Atoms as the Active Sites for Oxygen Evolution Reaction in Desalinated Seawater.

Green fuel from water splitting is hardcore for future generations, and the limited source of fresh water (<1%) is a bottleneck. Seawater cannot be used directly as a feedstock in current electrolyzer techniques. Until now single atom catalysts were reported by many synthetic strategies using notorious chemicals and harsh conditions. A cobalt single-atom (CoSA) intruding cobalt oxide ultrasmall nanoparticle (Co3 O4 USNP)-intercalated porous carbon (PC) (CoSA-Co3 O4 @PC) electrocatalyst was synthesized from the waste orange peel as a single feedstock (solvent/template). The extended X-ray absorption fine structure spectroscopy (EXAFS) and theoretical fitting reveal a clear picture of the coordination environment of the CoSA sites (CoSA-Co3 O4 and CoSA-N4 in PC). To impede the direct seawater corrosion and chlorine evolution the seawater has been desalinated (Dseawater) with minimal cost and the obtained PC is used as an adsorbent in this process. CoSA-Co3 O4 @PC shows high oxygen evolution reaction (OER) activity in transitional metal impurity-free (TMIF) 1 M KOH and alkaline Dseawater. CoSA-Co3 O4 @PC exhibits mass activity that is 15 times higher than the commercial RuO2 . Theoretical interpretations suggest that the optimized CoSA sites in Co3 O4 USNPs reduce the energy barrier for alkaline water dissociation and simultaneously trigger an excellent OER followed by an adsorbate evolution mechanism (AEM).

Photoinduced Puffing with Large Volume Expansion and Photomechanical Motions induced by Topochemical [4+4] Reactions in Molecular Crystal Solvates.

In this work, we report the first example of two crystal solvates of an anthracene-benzhydrazide based molecule (Ant) that display very distinct photo-responsive behaviour when 365 or 405 nm or visible light is illuminated. For the first time, the crystal hydrate that has water molecule in the lattice (hereafter named as Ant-H2O) display fascinating puffing behavior with large volume expansion upto 50 % accompanied with surface modulation when illuminated with 405 nm light, a phenomenon very much similar to the rice or popcorn puffing by thermal treatment. Utilizing the properties of photoconverted Ant-H2O crystals, we have demonstrated their application in photoinduced enhanced liquid absorption using various liquids/solutions. The other crystal solvate having DMF in the crystal lattice (hereafter named as Ant-DMF) responds to 405 nm light by bending, twisting, chopping, jumping or splitting etc. The chopping of Ant-DMF crystal was also observed under ambient/white light but at a slower rate compared to 405 nm light. Single crystal X-ray diffraction study reveals that the photoinduced puffing and photomechanical effects of these materials are rooted to the topochemical [4+4] cycloaddition reaction between the anthracene moieties that facilitate molecular packing change assisted by the reconfiguration of intermolecular non-covalent interactions involving lattice trapped solvent molecules.

A Green Synthesis of CoFe2O4 Decorated ZIF-8 Composite for Electrochemical Oxygen Evolution.

Low-cost, sustainable hydrogen production requires noble metal-free electrocatalysts for water splitting. In this study, we prepared zeolitic imidazolate frameworks (ZIF) decorated with CoFe2O4 spinel nanoparticles as active catalysts for oxygen evolution reaction (OER). The CoFe2O4 nanoparticles were synthesized by converting agricultural bio-waste (potato peel extract) into economically valuable electrode materials. The biogenic CoFe2O4 composite showed an overpotential of 370 mV at a current density of 10 mA cm-2 and a low Tafel slope of 283 mV dec-1, whereas the ZIF@CoFe2O4 composite prepared using an in situ hydrothermal method showed an overpotential of 105 mV at 10 mA cm-2 and a low Tafel slope of 43 mV dec-1 in a 1 M KOH medium. The results demonstrated an exciting prospect of high-performance noble metal-free electrocatalysts for low-cost, high-efficiency, and sustainable hydrogen production.

Phosphorus-decorated Mo-MXene/CQD hybrid: a 2D/0D architecture for bifunctional electrochemical water splitting.

The exploration of nonprecious metal-based 2D bifunctional electrocatalysts is of great significance for transforming to sustainable energies in terms of hydrogen. However, to achieve commendable electrocatalytic performance via rational design of surface-interface-engineered Mo-MXene hybrids remain challenging and highly demanding. Herein, we report large size exfoliated Mo-MXene sheets, which provide a flat flexible interface for decoration with carbon quantum dots (CQDs) and controlled surface phosphorization (denoted as Mo-MX/C/P hybrid). The resulting Mo-MX/C/P hybrid exhibited the lowest onset potentials of 14 and 58 mV at an applied current of 0.2 mA cm-2 for the HER and OER, respectively. Strikingly, the electronegative nature of phosphorous (P) and quick charge transfer between the CQDs and Mo2CTx matrix were responsible for its superior catalytic activities. Despite the superior performance, the Mo-MX/C/P hybrid can also be used for full-cell division of water with a cell voltage of 1.34 volts at 10 mA cm-2 and was found to be durable up to 12. This work provides a novel insight into the further development of surface-interface-engineered Mo-MXene hybrids for sustainable energy.

Well-Designed Au Nanorod-Doped Cu2O Core-Shell Nanocube-Embedded Reduced Graphene Oxide Composite for Efficient Removal of a Water Pollutant Dye.

To ensure environmental safety, the removal of organic pollutants has gained increasing attention globally. We have synthesized uniform Au nanorod (NR)-doped Cu2O core-shell nanocubes (CSNCs) via a seed-mediated route embedded on the surface of rGO sheets. The Au NRs@Cu2O/rGO nanocomposite was characterized using various techniques such as transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared (FT-IR) and Raman spectroscopies. The scanning TEM-energy-dispersive spectroscopy (STEM-EDS) elemental mapping of the AuNRs@Cu2O/rGO nanocomposite indicates that the Au NR (40 nm) is fully covered with the Cu2O particles (∼145 nm) as a shell. N2 gas sorption analysis shows that the specific surface area of the composite is 205.5 m2/g with a mesoporous character. Moreover, incorporation of Au NRs@Cu2O CSNCs increases the nanogaps around the nanoparticles and suppresses the stacking/bundling of rGO, which significantly influences the pore size and increase the surface area. A batch adsorption experiment was carried out under various parameters, such as the effect of pH, contact time, temperature, initial dye concentration, and adsorbent dosage, for the removal of methylene blue (MB) in aqueous solution. The high surface area and mesoporosity can cause the adsorption capacity to reach equilibrium within 20 min with a 99.8% removal efficiency. Both kinetic and isotherm data were obtained and fitted very well with the pseudo-second-order kinetic and Langmuir isotherm model. The Langmuir isotherm revealed an excellent dye sorption capacity of 243.9 mg/g at 298 K. Moreover, after five adsorption cycles, the dye removal efficiency decreased from 99 to 86%. This novel route paves a new path for heterogeneous adsorbent synthesis, which is useful for catalysis and electrochemical applications.

Bio-inspired self-propelled diatom micromotor by catalytic decomposition of H2O2 under low fuel concentration.

Recently, active bubble-propelled micromotors have attracted great attention for fuel applications. However, for generating bubble-propelled micromotors, additional catalysts, such as Pt, Ag, and Ru, are required. These catalysts are expensive, toxic, and highly unstable for broad applications. To overcome these issues, in this study, we present an innovative methodology for the preparation of self-propelled motor machines using naturally occurring diatom frustules. This natural diatom motor shows effective motion in the presence of a very low concentration (0.8%) of H2O2 as a fuel at pH 7. Due to the unique 3D anisotropic shape of the diatom, the self-propelled motor exhibited unidirectional motion with a speed of 50 µm s-1 and followed pseudo first-order kinetics. It was found that a trace amount of iron oxide (Fe2O3) in the diatom was converted into Fe3O4, which can act as a catalyst to achieve the facile decomposition of H2O2. Interestingly, "braking" of the unidirectional motion was observed upon treatment with EDTA, which blocked the catalytically active site. These results illustrate that diatom catalytic micromotors have opened a new era in the field of catalysis and bioengineering applications.

Catalyst free boron carbon bond cleavage and facile formation of five-membered PNBCC heterocycles.

The [3 + 2] cycloaddition reaction of phosphanyl aminoborane [N(2,6-iPr2C6H3)(PPh2)(BCy2)] (1) with activated alkynes led to boron and phosphorus containing five-membered heterocycles [(2,6-iPr2C6H3)NPPh2(CO2R)C-C(Cy)(CO2R)(BCy)] [R = Me (2), Et (3) and H (4)] with facile cleavage of the B-C bond and concomitant formation of a P-C bond with an ylidic character. DFT calculations indicate that 1 can be considered as a non-conjugated 1,3-dipole having two reaction centers viz., a nucleophilic P-center and an electrophilic B-center. The reaction of 1 with the alkynes proceeds through a stepwise dipolar addition mechanism, followed by the migration of the cyclohexyl group from the B-atom to the adjacent C-atom.