CeO2-Supported TiO2-Pt Nanorod Composites as Efficient Catalysts for CO Oxidation

Supported Pt-based catalysts have been identified as highly selective catalysts for CO oxidation, but their potential for applications has been hampered by the high cost and scarcity of Pt metals as well as aggregation problems at relatively high temperatures. In this work, nanorod structured (TiO₂-Pt)/CeO₂ catalysts with the addition of 0.3 at% Pt and different atomic ratios of Ti were prepared through a combined dealloying and calcination method. XRD, XPS, SEM, TEM, and STEM measurements were used to confirm the phase composition, surface morphology, and structure of synthesized samples. After calcination treatment, Pt nanoparticles were semi-inlayed on the surface of the CeO₂ nanorod, and TiO₂ was highly dispersed into the catalyst system, resulting in the formation of (TiO₂-Pt)/CeO₂ with high specific surface area and large pore volume. The unique structure can provide more reaction path and active sites for catalytic CO oxidation, thus contributing to the generation of catalysts with high catalytic activity. The outstanding catalytic performance is ascribed to the stable structure and proper TiO₂ doping as well as the combined effect of Pt, TiO₂, and CeO₂. The research results are of importance for further development of high catalytic performance nanoporous catalytic materials.

Hybrid Nanostructure Catalyst with Low Loading of Pt for the High-Efficiency Catalytic Hydrogenation of Chloronitrobenzene

Fabrication of low-loading, noble-metal, stable, and high-performance metal catalysts remains a thorny issue. Herein, we demonstrate the successful formation of a hybrid nanostructure Pt/TiO₂/SBA-15 catalyst (denoted as HNSC-P/T/S; Pt, 0.09%; TiO₂, 10%) with satisfactory activity in the hydrogenation of para-chloronitrobenzene (p-CNB). The HNSC-P/T/S showed >99% conversion and a high selectivity of >98%, and the turnover frequency number (TOF) reached 66 766 h^-1, which was impossible to achieve with Pt/TiO₂ (denoted as P/T) or Pt/SBA-15 (denoted as P/S). The success of the catalytic activity of the HNSC-P/T/S mainly relies on its synergistic effect and special structure, which can fully develop the catalytic ability of Pt, thereby reducing the Pt loading in the noble-based catalyst. Furthermore, the HNSC-P/T/S could also achieve an excellent catalytic activity in the hydrogenation of other nitroarenes. Hence, this work proposes a direction to prepare a noble-based catalyst with a low loading of noble metals for diverse applications.

Recent Advances in the Applications of Mesoporous Silica in Heterogenous Catalysis

Mesoporous silica is a class of silica material with a large specific surface area, high specific pore volume and meso-sized pores. These properties make mesoporous silica a good choice of...

Defect engineering and spilt-over hydrogen in Pt/(WO3–TH2) for selective hydrogenation of CO bonds

The effect of defects in pre-treatment WOx on the catalytic performance of selective hydrogenation of cinnamaldehyde to cinnamyl alcohol has been revealed.

Conductive interface promoted bifunctional oxygen reduction/evolution activity in an ultra-low precious metal based hybrid catalyst

Ultra low PtPd alloy deposited on Ni12P5 nanostructures (PtPd/Ni12P5) exhibited enhanced ORR activity (onset: 1.003 V and E1/2:0.95 V) on par with commercial Pt/C and superior OER activity with 81% reduction of the precious metal compared to the commercial catalyst.

Ruling Factors in Cinnamaldehyde Hydrogenation: Activity and Selectivity of Pt-Mo Catalysts

To obtain selective hydrogenation catalysts with low noble metal content, two carbon-supported Mo-Pt bimetallic catalysts have been synthesized from two different molybdenum precursors, i.e., Na₂MoO₄ and (NH₄)₆Mo₇O₂₄. The results obtained by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) combined with the presence and strength of acid sites clarified the different catalytic behavior toward cinnamaldehyde hydrogenation. After impregnating the carbon support with Mo precursors, each sample was used either as is or treated at 400 °C in N₂ flow, as support for Pt nanoparticles (NPs). The heating treatment before Pt deposition had a positive effect on the catalytic performance. Indeed, TEM analyses showed very homogeneously dispersed Pt NPs only when they were deposited on the heat-treated Mo/C supports, and XPS analyses revealed an increase in both the exposure and reduction of Pt, which was probably tuned by different MoO₃/MoO₂ ratios. Moreover, the different acid properties of the catalysts resulted in different selectivity.

Platinum and cobalt intermetallic nanoparticles confined within MIL-101(Cr) for enhanced selective hydrogenation of the carbonyl bond in α,β-unsaturated aldehydes: synergistic effects of electronically modified Pt sites and Lewis acid sites

PtCo/MIL-101(Cr) with high uniform dispersion Pt–Co IMNs synthesized by a polyol reduction method show higher activity for selective catalytic hydrogenation of α,β-unsaturated aldehydes due to the synergistic effect of PtCo and MIL-101(Cr) support.

Recent Progress on Transition Metal Nitrides Nanoparticles as Heterogeneous Catalysts

This short review aims at providing an overview of the most recent literature regarding transition metal nitrides (TMN) applied in heterogeneous catalysis. These materials have received renewed attention in the last decade due to its potential to substitute noble metals mainly in biomass and energy transformations, the decomposition of ammonia being one of the most studied reactions. The reactions considered in this review are limited to thermal catalysis. However the potential of these materials spreads to other key applications as photo- and electrocatalysis in hydrogen and oxygen evolution reactions. Mono, binary and exceptionally ternary metal nitrides have been synthetized and evaluated as catalysts and, in some cases, promoters are added to the structure in an attempt to improve their catalytic performance. The objective of the latest research is finding new synthesis methods that allow to obtain smaller metal nanoparticles and increase the surface area to improve their activity, selectivity and stability under reaction conditions. After a brief introduction and description of the most employed synthetic methods, the review has been divided in the application of transition metal nitrides in the following reactions: hydrotreatment, oxidation and ammonia synthesis and decomposition.

PBA@POM Hybrids as Efficient Electrocatalysts for the Oxygen Evolution Reaction

To realize the effective conversion of renewable energy through water decomposition, efficient electrocatalysts for the oxygen evolution reaction (OER) are essential. In this article, PBA@POM was successfully prepared with a Prussian blue analogue (PBA) as the initial structure. A facile hydrothermal process is reported for obtaining PBA@POM by etching the cubic PBA with a strong Brønsted acid, H₃ PMo₁₂ O₄₀ (HPMo). The hollow cube structure not only exposes more active sites but also promotes electron transport, which results in excellent electrocatalytic activity for the OER. Compared with the PBA, which initially simply adhered to POM, the optimum PBA@POM hybrids display remarkably enhanced OER catalytic activity, with an almost constant overpotential of 440 mV at a current density of 10 mA cm^-2 and a small Tafel slope (23.45 mV dec^-1 ). The facilely prepared PBA@POM with good electrochemical activity and stability promises great potential for the OER.

Preparation and Catalytic Performance of Metal-Rich Pd Phosphides for the Solvent-Free Selective Hydrogenation of Chloronitrobenzene

A facile synthesis method of palladium phosphide supported on the activated carbon was developed. The effects of Pd precursors for phosphatization, phosphatization temperature, and the ratio of hypophosphite/Pd on the generation of palladium phosphide were investigated, and a generation mechanism of the Pd3P crystal structure is proposed. The results demonstrate that only PdO, rather than Pd or PdCl2, can transform into Pd phosphide without damage to the activated carbon. The penetration of P into the Pd particle can dramatically improve the dispersion of Pd species particles on the activated carbon. The generation of Pd phosphide greatly depends on the phosphatization temperature and the ratio of hypophosphite/Pd. An intact Pd3P crystal structure was obtained when the ratio of hypophosphite/Pd reached 32 and the phosphatization temperature was above 400 °C. The Pd3P supported on the activated carbon exhibited superior catalytic performance in terms of the hydrogenation of halonitrobenzenes to haloanilines because it had few L acids and B acids sites and could not generate deficient-electron active hydrogen atoms as electrophiles.

Confinement of Pt nanoparticles in cage-type mesoporous silica SBA-16 as efficient catalysts for toluene oxidation: the effect of carboxylic groups on the mesopore surface

In this work, 3D cage-type mesoporous SBA-16 materials functionalized with –COOH groups are used to support Pt metals and provide high catalytic activity for toluene oxidation.

Pt nanoparticles supported on YCoxFe1−xO3 perovskite oxides: highly efficient catalysts for liquid-phase hydrogenation of cinnamaldehyde

The Pt/YCo_0.3Fe_0.7O₃ catalyst furnished ca. 95% selectivity to cinnamyl alcohol at nearly full conversion for the selective hydrogenation of cinnamaldehyde.

Sn-doped Pt catalyst supported on hierarchical porous ZSM-5 for the liquid-phase hydrogenation of cinnamaldehyde

3Pt0.05Sn/HPZSM-5 serves as a much more active and recyclable catalyst for the liquid-phase selective hydrogenation of cinnamaldehyde to cinnamyl alcohol.

Ultra-small Mo2N on SBA-15 as a highly efficient promoter of low-loading Pd for catalytic hydrogenation

Decreasing Pd usage whilst maintaining a superior performance is promising, but remains a challenge in the catalytic field. Herein, we have demonstrated the highly efficient promotion of Mo₂N with a reduced amount of Pd for the liquid-phase hydrogenation reaction. The Mo₂N (2-3 nm) was uniformly anchored onto mesoporous SBA-15 by using PMo₁₂ as the Mo source. The small size and good dispersion of Mo₂N is favourable for allowing their effective contact with post-loading Pd. This good contact is conducive to developing a synergistic catalyst, which was verified by studying the liquid-phase hydrogenation of p-nitrophenol (PNP) to p-aminophenol (PAP) with NaBH₄ as the H source. The conversion ability of PNP to PAP on 1 wt% Pd-Mo₂N/SBA-15 was vastly superior to 1 wt% Pd/SBA-15 and even better than 20 wt% Pd/SBA-15. The low-Pd, highly efficient catalysis is ascribed to the transfer of the electrons from Mo₂N to Pd for the easy activation of H. The synergy can be affected by the type of support used. SBA-15 is superior to SiO₂ and the other supports, which could be related to the large surface area and the plentiful number of pores on SBA-15, which is favourable to the dispersion of Pd and Mo₂N, and the transfer/diffusion of the reactants. In particular, a highly efficient catalyst can be achieved at an even more reduced Pd loading (0.05 wt%). The current method describes the design of a highly efficient catalyst for the hydrogenation reaction using low amounts of noble metals.

Calcium oxide-modified mesoporous silica loaded onto ferriferrous oxide core: Magnetically responsive mesoporous solid strong base

The design of new type of solid strong base with ideal activity, stability, and reusability is strongly urged by the growing demand of green chemistry and sustainable development. In this study, a new type of mesoporous solid strong base, denoted as CaO/mSiO₂/Fe₃O₄, is successfully fabricated by successively coating SiO₂ onto Fe₃O₄ magnetic nanoparticles and loading CaO into the mesoporous SiO₂. Compared with a series of other typical solid bases, the CaO/mSiO₂/Fe₃O₄ exhibits higher activity towards the synthesis of dimethyl carbonate by the transesterification of ethylene carbonate and methanol. The activity of the CaO/mSiO₂/Fe₃O₄ is not observed to decrease obviously even after sextic catalyst recirculation, and in particular, the recovery of the catalyst without quality loss is very convenient due to the good magnetic responsiveness of the Fe₃O₄ cores.

Ni2P Entwined by Graphite Layers as a Low-Pt Electrocatalyst in Acidic Media for Oxygen Reduction

A simple and feasible strategy was reported to construct Ni₂P nanostructures entwined by graphite layers (Ni₂P/GC). In this process, a commercial amino phosphonic acid chelating resin was adopted as both the phosphorus and carbon resources. Then, Ni²⁺ was introduced into the resin framework via ionic exchange and chelation to form a resin-Ni²⁺ precursor. After carbonization, the highly dispersed Ni₂P particles, coupled with thin graphite layers, were simultaneously synthesized in situ. A ternary 7.5% Pt-Ni₂P/GC catalyst was further obtained by loading 7.5 wt % Pt on Ni₂P/GC. For the oxygen reduction reaction in acidic media, the 7.5% Pt-Ni₂P/GC catalyst exhibited even more positive onset (1.03 V) and half-wave (0.93 V) potentials, as well as a rather higher mass activity of 565.3 mA mg_Pt^-1 and a better long-term stability than those of the commercial 20% Pt/C (JM) electrocatalyst. The improved reaction kinetics is mainly attributed to the synergistic effect between Pt and Ni₂P/GC. This work not only provides a method for the synthesis of phosphides but also gives insight into the synergy between Pt and Ni₂P, which is helpful for the development of more low-Pt catalysts in acidic media.

An Effective Pt-Cu/SiO2 Catalyst for the Selective Hydrogenation of Cinnamaldehyde

The bimetal catalyst Pt-Cu/SiO2 was prepared by the impregnation method. Its catalytic performance was investigated by the selective hydrogenation of cinnamaldehyde. Pt-Cu/SiO2 exhibited much higher selectivity (64.1%) to cinnamyl alcohol than Pt/SiO2 (3.7%), while they showed similar conversion of cinnamaldehyde. This enhancement was attributed to the increase in the amount of the Pt0 species on the Pt-Cu/SiO2 surface, which is derived from the interaction between Pt and Cu revealed by XRD and XPS.

Potassium-incorporated mesoporous carbons: strong solid bases with enhanced catalytic activity and stability

Through chemical activation combined with the hard-templating strategy, potassium-incorporated mesoporous carbons were fabricated which showed strong basicity and enhanced catalytic performance.

A novel strategy for constructing mesoporous solid superbase catalysts: bimetallic Al–La oxides supported on SBA-15 modified with KF

Bimetallic Al–La oxides were conjointly precoated on SBA-15 prior to the introduction of potassium fluoride to achieve solid superbases at low temperature by a modified wetness impregnation method.

Effect of Carbon Supported Pt Catalysts on Selective Hydrogenation of Cinnamaldehyde

Selective hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL) is of both fundamental and industrial interest. It is of great significance to evaluate the possible differences between different supports arising from metal dispersion and electronic effects, in terms of activity and selectivity. Herein, Pt catalysts on different carbon supports including carbon nanotubes (CNTs) and reduced graphene oxides (RGO) were developed by a simple wet impregnation method. The resultant catalysts were well characterized by XRD, Raman, N2physisorption, TEM, and XPS analysis. Applied in the hydrogenation of cinnamaldehyde, 3.5 wt% Pt/CNT shows much higher selectivity towards cinnamyl alcohol (62%) than 3.5 wt% Pt/RGO@SiO2(48%). The enhanced activity can be ascribed to the high graphitization degree of CNTs and high density of dispersed Pt electron cloud.