Particle shape optimization by changing from an isotropic to an anisotropic nanostructure: preparation of highly active and stable supported Pt catalysts in microemulsions

Catalytic Activity of Cellulose-Supported Platinum and Palladium Nanoparticles for Allylbenzene Hydrogenation

Platinum and palladium nanoparticles were successfully deposited on tunicate cellulose via the photodeposition or microemulsion deposition method. Evenly distributed, small and narrow-sized particles in the range of 2-3 nm were obtained for microemulsion-prepared cellulose catalysts. The photodeposition method led to larger particle sizes, broader size distribution, and occasional agglomerations. The catalysts were tested in the allylbenzene hydrogenation reaction at room temperature and the results were compared to commercially available catalysts. Because of smaller particles, both microemulsion-prepared catalysts and photodeposited ones show better activity than commercial catalysts. Even platinum and palladium nanoparticles were active for the hydrogenation, only cellulose-supported platinum nanoparticles showed good stability. For palladium nanoparticles, stronger leaching from the surface of cellulose was observed. Cellulose-supported catalysts were recycled, and reusability is comparable to commercial catalysts. Therefore, cellulose could be used as an alternative catalyst support.

Effect of design parameters in nanocatalyst synthesis on pyrolysis for producing diesel-like fuel from waste lubricating oil

Converting waste lubricating oil into diesel-like liquid fuels using pyrolysis presents a dual solution, addressing environmental pollution while offering a viable response to the fossil energy crisis. However, achieving high-quality fuel with a substantial yield necessitates the utilization of highly active and cost-effective catalysts. We report the development of Fe-Ni nanocatalysts, synthesized using a green approach and supported on TiO2, as a promising strategy for converting waste lubricating oil into premium-grade diesel-like fuel. To ensure efficient and effective pyrolysis processes, tailoring the synthesis parameters of these nanocatalysts is indispensable. In this study, we investigate the effect of design parameters on nanocatalyst synthesis, such as the concentrations of pre-catalysts and reducing agents, reducing time, and the amount of support material, and evaluate their impact on the quality and quantity of pyrolysis products. Through optimization of the synthesis process, a high quality diesel-like fuel with a product yield of about 54% at a mild reaction temperature of 400 °C was obtained. This study highlights the critical role of nanocatalysis in addressing persistent environmental and energy challenges while showcasing the potential of green nanocatalysts in sustainable waste-to-energy conversion processes.

Efficient preparation of nanocatalysts. Case study: green synthesis of supported Pt nanoparticles by using microemulsions and mangosteen peel extract

Greener nanocatalyst synthesis is growing in importance, especially when using scarce noble metals such as platinum (Pt) as the active metal. In the synthesis process presented herein, we utilized extract of mangosteen peel as a green reductant and found that it produces Pt nanoparticles (NPs) with high activity. The supported Pt NPs were synthesized via thermos-destabilization of a mangosteen extract microemulsion and subsequently tested with α-methyl styrene (AMS) hydrogenation at SATP. Additionally, we optimized the green synthesis of the supported Pt nanocatalyst (NPs) in terms of their synthesis yield and catalytic activity using the approaches of full factorial design (FFD), central composite design (CCD), and response surface methodology (RSM). In comparing the results of single and multiple optimization, it was found that for the single optimization, the synthesis yield of supported Pt NPs could be increased from their average value of 78.9% to 99.75%, and their activity from 2136 to 15 600 μmol s^-1 g_Pt ^-1. The results of multiple response optimization to the yield and activity are 81.71% and 8255 μmol s^-1 g_Pt ^-1, respectively. The optimization approach presented in this study is suitable for similar catalyst synthesis procedures where multivariate responses are sensitive to a number of experimental factors.

Insight into the Morphology-Dependent Catalytic Performance of CuO/CeO2 Produced by Tannic Acid for Efficient Hydrogenation of 4-Nitrophenol

The construction of a heterogeneous nanocatalyst with outstanding catalytic performance via an environmentally benign and cost-effective synthetic category has long been one of the challenges in nanotechnology. Herein, we synthesized highly efficient and low-cost mesoporous morphology-dependent CuO/CeO₂ -Rods and CuO/CeO₂ -Cubes catalysts by employing a green and multifunctional polyphenolic compound (tannic acid) as the stabilizer and chelating agent for 4-nitrophenol (4-NP) reduction reaction. The CuO/CeO₂ -Rods exhibited excellent performance, of which the activity was 3.2 times higher than that of CuO/CeO₂ -Cubes. This can be connected with the higher density of oxygen vacancy on CeO₂ -Rods (110) than CeO₂ -Cubes (100), the oxygen vacancy favors anchoring CuO species on the CeO₂ support, which promotes the strong interaction between finely dispersed CuO and CeO₂ -Rods at the interfacial positions and facilitates the electron transfer from BH₄ ^- to 4-NP. The synergistic catalytic mechanism illustrated that 4-NP molecules preferentially adsorbed on the CeO₂ , while H₂ from BH₄ ^- dissociated over CuO to form highly active H* species, contributing to achieving efficient hydrogenation of 4-NP. This study is expected to shed light on designing and synthesizing cost-effective and high-performance nanocatalysts through a greener synthetic method for the areas of catalysis, nanomaterial science and engineering, and chemical synthesis.

Highly Active TiO2 Photocatalysts for Hydrogen Production through a Combination of Commercial TiO2 Material Selection and Platinum Co-Catalyst Deposition Using a Colloidal Approach with Green Reductants

In this contribution, four different commercial TiO2 catalysts (P25, P90, PC105, and PC500) were screened for the photocatalytic production of hydrogen using ethanol as the sacrificial agent. The physico-chemical properties of the TiO2 powders were characterized by using different methods. The photocatalysts mainly vary in the ratio of anatase and rutile phases, and in the surface area. It was found that the photocatalytic activity is governed by the surface area of the photocatalyst. Pure TiO2,PC500 showed the best performance, and in comparison to P25, the activity was more than twenty times higher due to its high surface area of about 270 m2 g−1. For further improvement of the photocatalytic activity, platinum nanoparticles (PtNPs) were immobilized onto TiO2,PC500 using two methods: a colloidal approach and a photodeposition method. For the reduction of the platinum salt precursor in the colloidal approach, different green reducing agents were used in comparison to ascorbic acid. The obtained platinum nanoparticles using natural reductants showed a higher photocatalytic activity due to the formation of smaller nanoparticles, as proven by transmission electron microscopy (TEM). The highest activity was obtained when mangosteen was used as the green reducing agent. Compared to ascorbic acid as a classical reducing agent, the photocatalytic activity of the Pt@TiO2,PC500 prepared with mangosteen was about 2–3 times higher in comparison to other as-prepared photocatalysts. The Pt@TiO2,PC500 catalyst was further studied under different operating conditions, such as catalyst and sacrificial agent concentration.

Promoting Photocatalytic Hydrogen Evolution Activity of Graphitic Carbon Nitride with Hole-Transfer Agents

Visible light-driven photocatalytic reduction of protons to H2 is considered a promising way of solar-to-chemical energy conversion. Effective transfer of the photogenerated electrons and holes to the surface of the photocatalyst by minimizing their recombination is essential for achieving a high photocatalytic activity. In general, a sacrificial electron donor is used as a hole scavenger to remove photogenerated holes from the valence band for the continuation of the photocatalytic hydrogen (H2 ) evolution process. Here, for the first time, the hole-transfer dynamics from Pt-loaded sol-gel-prepared graphitic carbon nitride (Pt-sg-CN) photocatalyst were investigated using different adsorbed hole acceptors along with a sacrificial agent (ascorbic acid). A significant increment (4.84 times) in H2 production was achieved by employing phenothiazine (PTZ) as the hole acceptor with continuous H2 production for 3 days. A detailed charge-transfer dynamic of the photocatalytic process in the presence of the hole acceptors was examined by time-resolved photoluminescence and in situ electron paramagnetic resonance studies.

Mercaptosilane-assisted synthesis of sub-nanosized Pt particles within hierarchically porous ZSM-5/SBA-15 materials and their enhanced hydrogenation properties

A novel catalyst that consists of sub-nanosized Pt particles within hierarchically porous ZSM-5/SBA-15 materials was synthesized. This catalyst exhibited high stability and a hierarchically porous structure of a micro-mesoporous composite and possessed a high density of active sites by confinement of sub-nanosized Pt particles within small-pore zeolites, showing high catalytic properties for the hydrogenation of 1,3-butadiene and cyclooctadiene at room temperature.

Support effect in the preparation of supported metal catalysts via microemulsion

Illustration of the situation around the support material when metal NPs are deposited onto the support material.