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• Comparative study of catalytic activity of amorphous Co-B catalyst. • The bonding region between Co and B atoms is most favorable for catalytic activity. • Threefold site with two Co and one B atom is most active site. • Stoichiometry of catalyst affects the number of active sites. • Amorphous Co2B shows perfect balance of all studied catalytic properties. The structural, electronic and hydrogen adsorption properties of amorphous CoB, Co 2 B and Co 3 B structures were investigated using first principle calculations to evaluate their catalytic activity for HER. A total of eight different sites were considered for hydrogen adsorption, of which the threefold site with two Co and single B atom (TF-2Co-B) was found to be most active site for all the three amorphous Co-B structures. The B atom donates electronic charge to the Co-B bond, while, the presence of Co atom is responsible for achieving the optimal charge density necessary for favorable hydrogen adsorption. This interaction between the Co and B atoms makes bonding region between the Co and B atoms most favorable for hydrogen adsorption and not lone Co atom nor the B atom, thus, determining the active sites of Co-B catalyst. The best catalytic behavior of Co 2 B stoichiometry was credited to the perfect balance of magnetic properties, optimum hydrogen adsorption energies and considerable number of active sites it displayed. [ABSTRACT FROM AUTHOR]

The ablation of a target, composed of a homogeneous mixture of Fe & Co metal with H 3 BO 3 powder, produces core-shell type particles on the as-deposited coating surface. Annealing at 600 °C in air transforms the core-shell into urchin-like particles having nanowires of 10–30 nm in diameter and 0.5–1 μm in length, grown radially from the particle surface as a result of the stress created between core and shell. Microstructural and analytical characterization confirms that nanowires are composed of CoFe 2 O 4 and CoO phases forming a heterojunction, which showed outstanding performance as a photocatalyst, requiring half the time for an organic water pollutant degradation reaction in comparison to similarly nanostructured single-metal oxide counterparts (Co 3 O 4 and Fe 2 O 3). Degradation reactions conducted in controlled conditions demonstrate that the urchin-like mixed oxide coatings are highly efficient both in direct photocatalysis and in photo-Fenton reaction. This overall enhancement in activity is due to a synergistic effect created at the heterojunction of CoFe 2 O 4 /CoO that allows the formation of a Z -scheme mechanism to facilitate the spatial separation of photoinduced electron-hole pairs. Moreover, the hierarchical urchin-like nanostructures provide a large number of active sites for photocatalytic reactions, while the lower band gap of CoFe 2 O 4 permits better visible light absorption to effectively degrade organic pollutants even under visible light. Based on all the results, a plausible reaction mechanism is proposed related to Z -scheme heterojunction formed with CoFe 2 O 4 /CoO. Unlabelled Image • A coating of urchin-like nanostructured CoFe 2 O 4 /CoO heterojunction is synthesized by PLD. • Implementation of a Z-scheme design greatly improves charge separation. • Hierarchical nanostructuring provides large number of active sites for photocatalytic reactions. • The coating shows outstanding photocatalytic activity towards a model pollutant. [ABSTRACT FROM AUTHOR]

Hydrogen storage capacity of 2D MXene Cr 2 C has been studied using density functional theory. Possibility to adsorb H 2 molecule on Cr 2 C surface at various sites has been studied. Among the studied adsorption sites on Cr 2 C surface, few sites were found suitable for chemisorption and physisorption of H 2 molecules. Few of the studied sites are also found to be suitable for Kubas-type interaction, which is useful for reversible hydrogen storage at ambient conditions. Electronic structure calculations and charge transfer analysis have been done to understand the interactions of adsorbed hydrogen with the Cr 2 C layer. It has been found that the total hydrogen storage capacity of Cr 2 C is 7.6 wt.% in which 1.2 wt.% of H is due to the chemisorption, 3.2 wt.% is bonded with Kubas-interaction and remaining 3.2 wt.% is bonded through weak electrostatic interactions (with binding energy of 0.26 eV/H 2 and charge transfer of 0.09 e − to H atom from Cr atom). Thus the reversible hydrogen storage capacity at ambient conditions (controlled by hydrogen bonded with energies ranging from 0.1 to 0.4 eV/H 2 , in the present case through Kubas and weak electrostatic interactions) is 6.4 wt.% which is greater than the 2017 DoE recommended target value of 5.5 wt.%. [ABSTRACT FROM AUTHOR]

Nanoparticles assembled Co-B-O thin film catalysts were synthesized by pulsed laser deposition (PLD) technique for hydrolysis of Sodium Borohydride (SBH). Surface morphology of the deposited films was investigated using SEM and TEM, while compositional analysis was studied using XPS. Structural properties of Co-B-O films were examined using XRD and HRTEM. Laser process is able to produce well separated and immobilized Co-B-O NPs on the film surface which act as active centers leading to superior catalytic activity producing hydrogen at a significantly higher rate as compared to bulk powder. Co-B-O thin film catalyst produces hydrogen at a maximum rate of ∼4400 ml min −1 g −1 of catalyst, which is four times higher than powder catalyst. PLD parameters such as laser fluence and substrate-target distance were varied during deposition in order to understand the role of size and density of the immobilized Co-B-O NPs in the catalytic process. Films deposited at 3–5 cm substrate-target distance showed better performance than that deposited at 6 cm, mainly on account of the higher density of active Co-B-O NPs on the films surface. Features such as high particle density, polycrystalline nature of Co NPs and good stability against agglomeration mainly contribute towards the superior catalytic activity of Co-B-O films deposited by PLD. [ABSTRACT FROM AUTHOR]

[Display omitted] • gC 3 N 4 nanosheets was incorporated with O anions and Fe metallic nanoparticles by a facile method. • Hybridization between Fe, N and O leads to the formation of an intermediate band within the bandgap of gC 3 N 4. • Exfoliation strategy by mixed acid treatment increased the surface area by one order of magnitude than pristine gC 3 N 4. • Cointegration of these strategies led to ∼17 times improvement in the photocatalytic rate. • Combined experimental and theoretical approach provides concrete evidence for improvement in all intrinsic properties. With graphitic carbon nitride (gC 3 N 4) showing considerable potential for photocatalytic applications, the four significant limitations: surface area, light-harvesting capability, photogenerated charge separation, and charge transfer at the interface, need to be comprehensively addressed. The present work aims to exfoliate the gC 3 N 4 stacking layers and fragment the layers horizontally to form ultra-thin nanosheets (NS) by a facile mixed-acid treatment. The surface area of gC 3 N 4 increased by one order of magnitude (120 m2/g), due to the formation of nanosheets with planar size below ∼50 nm. Moreover, incorporating non-metal (oxygen) anion dopants and metal (iron) nanoparticles enhances the overall reactivity of gC 3 N 4 NS under light irradiation. Co-integration of these strategies led to ∼17 times improvement in the photocatalytic pollutants degradation rate compared to pristine gC 3 N 4. First-principles calculations and experimental evidence suggest the formation of an intermediate band within the bandgap of gC 3 N 4 , caused by the hybridization of N -Fe-O, which assists in harvesting a larger number of photons. Nanosheet morphology provides a shorter distance to photogenerated charges towards the surface, while the incorporation of Fe and O together offers the lowest charge transfer resistance at the interface to efficiently degrade the adsorbed pollutant molecules on the surface. With all these promoting features along with cost-effective and stable elements, Fe-O-gC 3 N 4 NS provides an ideal solution for tuning the intrinsic morphological and electronic structure of gC 3 N 4 for its effective application in various photocatalytic reactions. [ABSTRACT FROM AUTHOR]