Ankur Bordoloi

Mesoporous Nitrogen‐Rich Carbon Materials as Catalysts for the Oxygen Reduction Reaction in Alkaline Solution

ORR MNC, FTW! Mesoporous nitrogen-rich carbon (MNC) materials are synthesized by using polymer-loaded SBA-15 pyrolyzed at different temperatures. The activity and stability of the catalysts in the oxygen reduction reaction (ORR) are investigated by using cyclic voltammetry and rotating-disk electrode measurements. The MNC material pyrolyzed at 800 °C exhibits a high electrocatalytic activity towards the ORR in alkaline medium.

Enhanced electrocatalytic stability of platinum nanoparticles supported on a nitrogen-doped composite of carbon nanotubes and mesoporous titania under oxygen reduction conditions.

Cheers for titania: An N-doped composite of carbon nanotubes (CNTs) and mesoporous TiO(2) is used as support for Pt nanoparticles applied in the oxygen reduction reaction. The composite Pt/N-TiO(2) -CNT shows a higher stability than Pt particles on carbon black or N-doped CNTs, as indicated by accelerated stress tests of up to 2000 cycles. The enhanced stability is attributed to strong interactions between TiO(2) and Pt and a higher corrosion resistance of TiO(2) as well as CNTs.

Metal–support interactions in surface-modified Cu–Co catalysts applied in higher alcohol synthesis

Cu–Co-based model catalysts were prepared by a sophisticated alkali-free synthesis method and tested in the conversion of synthesis gas to higher alcohols. MoO3-coated alumina was used as the support, providing both high specific surface area and strongly interacting sites for the deposition of the active metals. A bulk Cu/Co ratio of ~2 was found to be most suitable in terms of activity and product distribution. Surface enrichment of Mo for all samples was observed by XPS, which significantly influenced the performance of the catalysts. Mo was found to be both a structural and a chemical promoter. Strong metal–support interactions were further achieved by modification of alumina with magnesia. With 12 wt% Mg incorporated, the catalysts showed 40% total oxygenate selectivity including 11% selectivity to ethanol.

Oxidative coupling of aniline and desulfurization over nitrogen rich mesoporous carbon

Tungsten loaded mesoporous nitrogen rich carbon (WOxMCNx) materials were synthesized using SBA-15 as a hard template. With these new multifunctional materials, we performed a one-pot oxidative coupling of aniline to azo-benzene followed by desulfurization of dibenzothiophene (DBT) to dibenzothiophene sulfone (DBTSO). It was observed that the nature of the support for the catalyst has a strong influence on the activity of the WOx nanoparticle. Whilst WOx on MCNx proved to be a very active and selective catalyst for the formation of azo-benzene via oxidation of aniline as well as dibenzothiophene sulfone from dibenzothiophene, WOx on activated carbon or SBA-15 did not show comparable activity. These multifunctional hybrid catalysts retain their structural framework even after the reaction, and they were recovered easily from the reaction mixture through filtration and reused several times without a significant degradation in activity. Moreover, there was no contribution from leached active species in the activity and conversion was possible only in the presence of the multifunctional catalyst.

Acid–Base Cooperative Catalysis over Mesoporous Nitrogen‐Rich Carbon

WOx nanoclusters (2–3 nm) embedded on a mesoporous nitrogen‐rich carbon material were synthesized by using novel methodology. This material was very effectively capitalized as a new carbon‐based acid–base cooperative catalyst for sequential acetal hydrolysis and Knoevenagel condensation reactions. The protocol was also explored for the nitroaldol condensation reaction.

Single-step synthesis of hierarchical BxCN: a metal-free catalyst for low-temperature oxidative dehydrogenation of propane

A boron- and nitrogen-co-doped mesoporous carbon (BxCN) material with a hierarchical pore structure has been synthesized from a new boron precursor via a nanocasting approach. The newly synthesized material was thoroughly characterized by different characterization techniques. It was observed that the BxCN material has an excellent specific surface area, versatile pore diameter and large pore volume. Moreover, the pore diameter can be tuned by varying the amount of the boron source. By using solid-state MAS NMR and XPS, we demonstrated the N–B–C-type structure of the material. The material presented here has excellent stability under an oxygen atmosphere and we also confirmed the catalytic proficiency of this newly developed material in C–H bond activation reactions. The mesoporous BxCN material displays promising catalytic activity for the oxidative dehydrogenation of propane (6.7%) with excellent selectivity for propylene (84.6%) without the presence of any metal.

Ni nanocluster on modified CeO2–ZrO2 nanoporous composite for tri-reforming of methane

Modified CeO2–ZrO2 nanoporous composites have been synthesized by using a very facile solvothermal approach and Ni nanoclusters were deposited on this newly developed support by using urea deposition precipitation method. The physico-chemical properties of the prepared catalysts were thoroughly characterized by using X-ray diffraction (XRD), nitrogen physisorption (BET), temperature programmed reduction (TPR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The prepared materials have been well explored for methane activation with a well-balanced composition of H2O, CO2 and O2. The catalysts exhibit promising activity for tri-reforming (H2O, CO2 and O2) of methane with high selectivity towards synthesis gas (a mixture of hydrogen and carbon monoxide). Moreover, reaction parameters also been optimized in detail in terms of temperature, gas hourly space velocity (GHSV) and time on stream (TOS). The study demonstrates that the well synchronised catalyst system is highly stable for more than 100 h with almost a constant syngas ratio of 2.1 and over 95% methane conversion at 800 °C.

Highly selective transfer hydrogenation of α,β-unsaturated carbonyl compounds using Cu-based nanocatalysts

Simultaneous dehydrogenation of cyclohexanol to cyclohexanone and hydrogenation of α,β-unsaturated carbonyl compounds to corresponding α,β-unsaturated alcohols was carried out in a single pot reaction without addition of any external hydrogen donor. Cu nanoclusters supported on nanocrystalline MgO were found to be the active catalyst for the chemoselective transfer hydrogenation of unsaturated carbonyl compounds to produce the corresponding alcohols with very high yields. Transfer hydrogenation of cyclohexanol and cinnamaldehyde produced cyclohexanone and cinnamyl alcohol with 100% selectivity. This Cu/MgO catalyst can be easily recovered and recycled up to more than five times without any significant loss of activity, which confirmed the true heterogeneous nature of this catalyst. Several α,β-unsaturated compounds were also tested for this reaction and it was found that for all the cases the yield is >95%. The ease of handling without requiring high pressure H2 or a hazardous hydrogen source makes this transfer hydrogenation more practical and useful.

Reaction and Mechanistic Studies of Heterogeneous Hydroamination over Support‐Stabilized Gold Nanoparticles

Highly stable gold nanoparticles (GNPs) around 5–6 nm have been prepared by in situ reduction of chloroauric acid on the surface of nitrogen‐rich mesoporous carbon (MCN) without adding any extra stabilizing agent. The synthesized materials have been efficiently utilized as a catalyst for the truly heterogeneous hydroamination of phenylacetylene with aniline. Large turnover numbers (42×106) were achieved by suitably adjusting the gold/support (w/w) ratio, time, temperature, and solvent, leading to 98 % selectivity towards the Markovnikov product. Density functional theory (DFT) studies have been performed to predict the mechanistic pathway of hydroamination with Au0 in GNP@MCN. To understand the structure–activity relationship, the catalyst was characterized by using different techniques such as X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen physisorption studies (BET), X‐ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy.

Facile route for the regioselective synthesis of 1,4-disubstituted 1,2,3-triazole using copper nanoparticles supported on nanocellulose as recyclable heterogeneous catalyst

In this work, a green and efficient methodology has been developed for the synthesis of 1,2,3-triazoles by ‘copper nanoparticles supported on nanocellulose (CuNPs/NC)-catalyzed azide-alkyne cycloaddition reaction in glycerol, an environmentally benign solvent, with excellent yields. The present catalyst was characterized by TEM, XRD, SEM-EDX and FT-IR spectroscopy. The reusability of the prepared nanocatalyst was examined up to five times without significant loss of catalytic activity.Graphical Abstract:SYNOPSIS: A catalyst of copper nanoparticle supported on highly crystalline nanocellulose was prepared and was effectively used for the important regioselective synthesis of 1,4-disubstituted 1,2,3-triazole from the 1,3-dipolar cycloaddition of various azides and alkynes.