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A series of CoMo/graphene selective hydrodesulfurization (HDS) catalysts were prepared using the hexamethonium bromide-assisted hydrothermal method, and the influences of the hexamethonium bromide/Mo molar ratio and the CoMoS/MoS2 ratio on the HDS activity and selectivity were investigated. The results show that the kHDS value (2.76 × 10−7 mol g−1 s−1) of thiophene and the HDS selectivity factor (13.6) over the as-prepared catalysts were 1.3 times and 1.6 times greater than those over the CoMo/graphene prepared using the conventional impregnation method. The higher HDS activity and selectivity of the as-prepared catalysts result from the higher dispersion of Mo species and the higher CoMoS/MoS2 ratio compared to the CoMo/graphene prepared by impregnation. Among all the catalysts, the catalyst with a hexamethonium bromide/Mo molar ratio of 6.0 presents the highest HDS selectivity due to its highest ratio of edge to corner Co atoms in CoMoS with a superior CoMoS/MoS2 ratio. The present investigation provides a route for developing highly selective HDS catalysts using graphene as support by adjusting the hexamethonium bromide/Mo ratio to finely tune the morphology of the active phases.

Oriented transfer of electron-hole charge carriers is important during photocatalytic processes. In this study, one-dimensional (1D) tubular B-doped graphitic carbon nitride (g-C3N4) with an effective charge transfer and separation was designed. The doping sites, energy level structure, and photo-generated electron-hole pair separation were predicted using systematical density functional theory (DFT) simulations. The supramolecular precursor for tubular g-C3N4 synthesis, namely melamine·cyanuric acid (M·CA), was controllably synthesized from a single melamine source. Intermolecular hydrogen bonding led to the arrangement of supramolecular aggregate structures into a prismatic crystal architecture during the hydrothermal treatment. The morphology modulation of g-C3N4 from bulk to 1D tubular architecture was realized by calcining the prism-like precursor. B-doped tubular g-C3N4 exhibited a narrower band-gap, multiple reflections of incident light, and oriented transfer of electron-hole charge carriers, which led to a widened light-harvesting range and improved photo-induced electron-hole pair separation and transfer ability. These factors contributed to the photocatalytic activity enhancement towards gaseous NOx degradation under visible light. In this work, a valuable design-fabrication pattern for g-C3N4 modification and engineering via DFT simulations was designed. Moreover, a strategy was developed for the simultaneous foreign atom doping and architecture control of g-C3N4 via the self-assembly of supramolecular precursors.

Oxygen vacancies of metal oxides play critical roles in tunning activity and selectivity for many photocatalysis mediated reactions, yet the mechanism of NO oxidation on defect enriched photocatalyst surface is seldomly discussed. Herein, we provide detailed insight into the relationship between oxygen vacancy manipulation by extrinsic Fe3+ substitution in SrTiO3 host lattice and the photocatalytic performance of NO abatement. In particular, the hydrothermal synthesized SrFexTi1-xO3-δ nanocubes (denoted as SFTO-hyd sample) rather than the impregnated-post annealing sample, enabled oxygen vacancy formation, and promoted O2 adsorption and superoxide anion radicals ( O2−) formation. The SFTO-hyd (x = 5%) sample showed remarkably higher NO removal activity and selectivity under Xe lamp (λ > 420 nm), in comparison with the pristine SrTiO3, P25 and impregnation-doped SFTO sample, underlining the important roles played by coexisted Fe3+ sites and oxygen vacancies. The in situ diffuse reflectance IR spectroscopy (DRIFTS) mechanically revealed that SrTiO3 provided Lewis acidic sites for NO dark adsorption and photoreaction with nitrates as final products; the substitutional Fe3+ sites provided more active sites for NO adsorption and photoreaction with enhanced number of radicals. This study deepens the understanding of photocatalytic NO abatement on defective surface, and may also provide a simple and cost effective strategy for synthesizing efficient and selective photocatalysts for environmental remediation.

Photo-oxidative NOx removal often encountered with sluggish charge carrier separation kinetics and poor selectivity. Herein, Pd/ferroelectric Bi4Ti3O12 nanoflakes (Pd/BTO NF) were constructed to investigate the photo-excited charge separation, O2 activation and the generated reactive oxygen species (ROS) in dictating NO removal. Results showed that the depolarization field of ferroelectric BTO NF significantly promoted bulk charge separation, leading to boosted NO removal reaction kinetics (10 times higher) for Pd/BTO NF comparing with Pd/TiO2. Revealed by electronic paramagnetic resonance and radical scavenging tests, it is observed that the primary O2 activation species differed among Pd, Ag and Pt supported BTO NF photocatalysts, which resulted in different selectivity. The underlying mechanism of NO photo-oxidative conversion pathway was studied by in situ diffuse reflectance infrared Fourier transform spectroscopy. This work illustrate that metal/ferroelectric interfaces can be tuned to obtain differing O2 activation species, and notable selectivity changes in photocatalysis mediated environmental remediation reactions.

This article proposes a novel sodium dodecylbenzenesulfonate (SDBS)-assisted equilibrium adsorption method for preparing highly dispersed Ni/Al2O3 and Fe-promoted NiFe/Al2O3 thioetherification catalysts. The proposed strategy anchors nickel cations onto the electronegative surface of an Al2O3 support modified by negatively charged DBS− bilayers. As a result, this method achieves highly dispersed Ni nanoparticles without strengthening the metal-support interaction, promoting the reducibility and sulfurization of the supported Ni species. The as-prepared Ni-based catalysts have a smaller size, a higher dispersion of metal nanoparticles, and a greater amount of active metal sulfides than their counterparts prepared by the conventional impregnation method, endowing them with excellent catalytic performance for the highly selective removal of mercaptans. This method provides a new opportunity to prepare highly dispersed metal nanoparticles without a strong metal-support interaction.

This investigation offers new understanding regarding the nature of CoMoS and MoS2 active phases coexisting on sulfided CoMo/Al2O3 catalysts for the selective hydrodesulfurization (HDS) of gasoline. Two series of the CoMo/Al2O3 catalysts with different ethylenediaminetetraacetic acid (EDTA)/Co molar ratios and the EDTA-containing CoMo/Al2O3 catalysts with different cobalt contents were prepared, and the properties of their active metal phases were systematically correlated with their HDS selectivities. It was found that a high concentration of CoMoS phases improves the HDS activity of the sulfided CoMo/Al2O3 catalysts but that a high concentration of MoS2 phases enhances the olefin hydrogenation (OHYD) activity of these catalysts. From the perspective of microstructure, it was evident that the thiophene HDS reaction occurs primarily at the edge of CoMoS active phases and that the OHYD reaction occurs mainly at the corner of MoS2 active phases. These understandings shed light on the development of highly selective HDS catalysts.

This article proposes a novel gemini surfactant-assisted synthesis of Mo precursor for preparing NiMo/SiO2-Al2O3 ultra-deep hydrodesulfurization (HDS) catalysts. The proposed method transforms polymolybdate anions into gemini surfactant-linked Mo precursor (GSMP), which facilitates the formation of highly dispersed MoS2 phases with improved stacking and therefore produces a large number of accessible Ni-Mo-S phases after Ni incorporation. The GSMP-based NiMo/SiO2-Al2O3 catalyst presents higher catalytic activity for the HDS of 4,6-dimethyldibenzothiophene and fluid catalytic cracking (FCC) diesel than its counterparts prepared via impregnation and the cetyltrimethylammonium bromide-assisted hydrothermal method.

Although oxygen vacancies (OVs) commonly act as adsorption/active sites in catalytic oxidation of formaldehyde (HCHO), thereby strongly influencing catalyst activity, their control and translation into scale-up products for practical application remain challenging. Herein, δ-MnOx/activated carbon was synthesized via in situ reduction coupled with ammonia modification, and the developed method was found to allow easy OV control for large-scale production. OV concentration was effectively regulated through adjustment of Mn3+ content, and OV roles in the catalytic reaction were probed by several techniques. The optimized catalyst featured superior HCHO removal efficiency and CO2 selectivity at room temperature, mainly due to oxygen activation by abundant OVs to form reactive oxygen species. The intermediates and pathways of HCHO removal were investigated. Thus, this work provides insights into the enhancement of active site exposure through OV control for a single bulk catalyst and demonstrates its applicability for efficient and commercially viable room-temperature oxidation of HCHO.