H2PtCl6 Research Articles

Convergent Active Site Evolution in Platinum Single Atom Catalysts for Acetylene Hydrochlorination and Implications for Toxicity Minimization.

Platinum single atoms anchored onto activated carbon enable highly stable Hg-free synthesis of vinyl chloride (VCM) via acetylene hydrochlorination. Compared to gold-based alternatives, platinum catalysts are in initial phases of development. Most synthetic approaches rely on chloroplatinic acid, presenting opportunities to explore other precursors and their impact on catalyst structure, reactivity, and toxicity aspects. Here, we synthesize platinum single atom catalysts (Pt SACs, 0.2-0.8 wt % Pt) employing diverse Pt2+ and Pt4+ complexes with ammine, hydroxyl, nitrate, and chloride ligands, following a scalable impregnation protocol on activated carbon extrudates. X-ray absorption spectroscopy (XAS) reveals that Pt4+ species reduce to Pt2+ upon deposition onto the support. Despite similar oxidation states, the initial activity is precursor dependent, with tetraammine-derived Pt SACs displaying 2-fold higher VCM yield than chlorinated counterparts, linked to superior hydrogen chloride binding abilities by density functional theory (DFT) simulations. Their activity gradually converges due to dynamic active site restructuring, delivering remarkable precursor-independent stability over 150 h. Operando XAS and DFT studies uncover reaction-induced ligand exchange, generating common active and stable Pt-Cl x (x = 2-3) species. Convergent active site evolution enables flexibility in metal precursor selection and thus toxicity minimization through multiparameter assessment. This study advances safe-by-design catalysts for VCM synthesis, highlighting the importance of toxicity analyses in early-stage catalyst development programs.

Evolution of the Active Phase of Pt/Sn-Al2O3 Catalysts During Acidic Impregnation and Their Use in Propane Dehydrogenation.

Alumina-supported PtSn is an industrialized catalyst for propane dehydrogenation. During the catalyst impregnation, the acidic impregnation solution with chloroplatinic acid as a precursor inevitably leads to the partial dissolution of the surface of amphoteric alumina support and finally varies catalytic performance. Herein, the structure evolution of the active phase, induced by an impregnated acidic solution, was studied with special care. According to the diffused double layer theory, we proposed a model of microgels during impregnation. The microgels formed in the solution with suitable acidity on the surface of the catalysts evolved into a structure of Al2O3-coated oxidized Pt by reprecipitation during drying and calcination. The covered Pt species could be exposed by Ar+ sputtering or migrate to the surface during reduction to serve as active sites for propane dehydrogenation. Noticeably, the surface Sn0 species was generated when the pH of the impregnated solution was around 0.56, which is solid proof for the unique active phase with the PtSn alloy present on SnOx species existing on the surface of the Sn-Al2O3 support. The synthesized catalyst exhibited high propylene selectivity (99.4%) and superior stability (kd = 0.002 h-1). This study provides new insight for the precise preparation of Pt/Sn-Al2O3 catalysts.

Multifunctional nanoenzyme lateral flow immunoassay strip for rapid and ultrasensitive detection of carbofuran in vegetables

A lateral flow immunoassay strip (LFIAS) is one of the most frequently rapid test technologies for carbofuran (CAR). Nevertheless, the LFIAS has a poor quantitative capability and low sensitivity. And, it also requires often complex sample handling steps, making testing time longer. In this study, Fe3O4 nanoparticles were successively modified with MIL-100(Fe)-based metal-organic framework (MOF) and chloroplatinic acid hexahydrate to obtain a core-shell complex of Fe3O4-MOF-Pt. The complex had a peroxidase-mimicking activity catalytic function that enabled signal amplification and sensitivity enhancement. Upon coupling with carbofuran monoclonal antibody (CAR-mAb), the magnetic separation properties of the probe enabled target-specific enrichment. The LFIAS based on Fe3O4-MOF-Pt nanocomposites could detect CAR in the range of 0.25–50 ng mL−1 with a limit of detection (LOD) of 0.15 ng mL−1, enabling colorimetric and catalytic analysis. In addition, the method showed high specificity and stability for detecting CAR in various vegetables, and recovery rates of the spiked samples were 91.40%−102.40%. In conclusion, this study provided one-stop detection of “target enrichment-visual inspection”. While lowering the LOD, it reduced the detection time and improved the detection efficiency. The multifunctional Fe3O4-MOF-Pt nanocomposite provides an idea for the construction of novel multifunctional probes to improve the detection performance of conventional LFIAS.

Statistical investigation of the experimental variables in the hydrosilylation reaction of a trimethylsiloxy‐terminated poly (methylhydro‐dimethyl)siloxane copolymer and an unsaturated polyethylene glycol using response surface methodology

The hydrosilylation reaction is a suitable route to prepare efficient, transparent, and low‐viscose silicone surfactants with low surface tension. Initial materials, the catalyst used, and experimental conditions are highly effective variables to achieve the maximum efficiency of the reaction, reduce the consumption of the catalyst, and prevent side reactions. To draw a comprehensive conclusion on the effect of these variables, a series of trimethylsiloxy‐terminated poly (methylhydro‐dimethyl)siloxanes copolymer (abbreviated as RSiH with different preceding numbers) and two unsaturated polyethylene glycols (UPEG200 and UPEG400) were selected, and the reactions in the presence of two platinum‐based catalysts, namely, hexachloroplatinic acid and ammonium hexachloroplatinate, were statistically studied by Design of Experiment. After initial pre‐investigations, the amounts of reactant and catalyst were subjected to analysis of variance using response surface methodology (RSM). Based on the results, low‐viscose and low‐surface tension silicone surfactants were obtained using UPEG400, RSiH105, and (NH4)2PtCl6 as catalysts, at temperatures over 170 °C. The best results were obtained with a relatively low concentration of the catalyst between 2.57 × 10−6 and 2.72 × 10−6 equivalent catalyst per UPEG. The relative equivalent ratio of [UPEG]/[RSiH] at the optimum condition was 1.6, which provided a surface tension below 21 mN/m together with a minimum amount of unreacted RSiH (less than 3%). The silicone surfactant was characterized as a pure product by a series of spectroscopic methods, such as FT‐IR and 1H NMR spectroscopies, as well as bromine number index. These excellent properties make this compound a new alternative in various industries.

Synthesis of high-performance low-Pt (1 1 1)-loading catalysts for ORR by interaction between solution and nonthermal plasma

One important approach to address the cost issue of fuel cells is to maximize the utilization of Pt by reducing its loading and enhancing the performance for the oxygen reduction reaction (ORR) as well as durability of catalysts. In this work, a one-step synthesis of highly dispersed low-Pt (111) electrocatalysts (p-Pt/KBs) supported by Ketjenblack is conducted using interaction between solution and nonthermal plasma (SNP). The results show that the plasma-treated platinum precursor dispersion efficiently avoids particle agglomeration and increases more defects of the support surface, which are conducive to the trapping and anchoring of platinum nanoparticles (Pt NPs). The catalyst (p-Pt/KB-NaOH) with a platinum load of 10.8 wt% is obtained by adding sodium hydroxide to the platinum precursor dispersion solution, showing better ORR performance (E1/2 = 0.88 V) and stability compared to the commercial platinum on carbon (Pt/C) catalyst (20 wt%, E1/2 = 0.86 V). This improvement is attributed to the fact that neutralizing chloroplatinic acid slows down the reduction rate of the platinum precursor, effectively controlling the rapid nucleation and slow crystal growth of platinum. As the cathode catalyst for PEMFCs, p-Pt/KB-NaOH exhibits remarkable mass-transfer performance in the high-current density domain (HCD), with maximum power density (Pmax) of 1131 mW cm−2 at 2500 mA cm−2, which is 9.1 % higher than commercial Pt/C. Moreover, the single-cell operates stably for at least 100 h at 1000 mA cm−2 with a negligible decay (1.9 %) of the working voltage, ensuring long-term durability.

Preparation and Characterization of Functionzliaed Silicone Oil for High Temperature Mold Release Agent

Silicohydrogen addition method was utilized to prepare long-chain alkyl silicone oils using high hydrogen-containing silicone oil, α-methylstyrene, and 1-tetradecene as raw materials and chloroplatinic acid as catalyst. FTIR and 1H-NMR were used to characterize the structure of the products, and the effects of reaction temperature, reaction time, catalyst dosage, and n(Si-H): n(C=C) on the Si-H conversion were investigated experimentally to determine the optimal reaction process. The experimental results showed that the optimized process conditions were n(Si-H): n(C=C) =1:1.1, reaction time of 6 h, reaction temperature of 150 °C, catalyst dosage of 2 ppm, and the Si-H conversion of the product was 96.3%.

Electrochemical Polymerization of a Novel Thiophene-Derived Monomer and Its Use as Support Material for Methanol Oxidation

This research, conductive polymer supported modified electrode system which was prepared for usage in direct methanol fuel cells. To test the behavior of these electrode system for methanol oxidation, cyclic voltammetry (CV), chronoamperometry (CHR) and electrochemical impedance spectroscopy (EIS) methods were used as electrochemical methods. As the working electrode, pencil graphite electrode (PGE) was preferred because of its porous structure, good ion conductivity, practicality in application and ease of preparation and obtaining. Thiophene derivative 4,4')-2,2'-(diazen-1,2 diylbis(4,1 phenylene))bis(4 (thiophene-2-ylmethylene) oxazol-5(4H)-one), (DiAzBiPhBiTyOx) monomer was prepared and electrochemically polymerized by CV method in 0.01M TBAP and 0.05 HClO4 containing ACN solution on the surfaces of PGE. The spectroscopic characterization of the synthesized monomer was performed by NMR spectroscopy. Optimum polymerization conditions of monomer was determined according to scanning rate, potential range and acid density. The obtained modified electrode system (PGE/PDiAzBiPhBiTyOx) was doped with chloroplatinic acid hexahydrat-Pt2Cl6.6H2O (Pt) at different densities and the optimum catalyst density was determined as 3.25mM (PGE/3.25mMPt@PDiAzBiPhBiTyOx). The methanol oxidation performances of conductive polymer film, platinum and conductive polymer supported platinum catalyst systems were investigated separately. While the methanol oxidation responses of the conductive polymer film and platinum are almost similar, the methanol oxidation response of the platinum doped conductive polymer film catalyst system is higher. The modified electrode characterization was performed by CV, CHR and EIS methods. Furtheremore obtained modified electrode systems were characterized by FESEM/EDS, XRD to confirm the structures and morphologies. Also, the theoretical values such as electrochemical surface area (ECSA) and specific capacitance (Cs) were calculated in aqueous acidic solution with and without methanol. Cs values of the PGE/3.25mMPt@PDiAzBiPhBiTyOx electrode in aqueous acidic solution with and without methanol were 3.861 and 3x10-4Fg-1 respectively. Also, the electrochemical surface area values of the same electrode in aqueous acidic solution with and without methanol were 196.437 and 21.150m2g-1 respectively.

Enhanced Kinetics of Oxygen Reduction Reactions in Alkaline Solutions inside Mesoporous Electrodes

Oxygen reduction reactions (ORR) in alkaline solutions attract increasing attention for their use as the cathodic reaction in metal-air batteries and alkaline fuel cells. However, the commercialization of these systems is impeded by high activation and concentration overpotentials of ORR, which originate from the sluggish kinetics on the catalyst surface and oxygen transport in the electrolyte, respectively. Although the practical electrode enables a decrease of the overpotentials with the porous structure, the effect of inner pores has not been understood. Among various pore sizes, it is crucial to investigate an electrochemical behavior in mesopores with a size of a few nm since such confined structures possibly change the intrinsic catalytic kinetics.1 In this study, we evaluated the ORR activity in the mesopore using Pt model electrodes with arrays of cylindrical pores with uniform pore sizes (Fig. a). We investigated the activity dependence on the electrode thickness to separate activation and concentration overpotentials, and found that the activation overpotential inside the mesopore with a size of 1.8 nm is smaller than that measured with the planer electrode. Pt model electrodes were electrodeposited from platinum salt in a liquid crystalline phase of a surfactant.2 The liquid crystalline phase was obtained by mixing 29 wt% of H2O, 29 wt% of hexachloroplatinic acid, and 42 wt% of octaethylene glycol monododecyl ether. The three-electrode cell consisted of an Au disk (φ 4 mm) working electrode, a Pt wire counter electrode, and an Ag|AgCl|sat’d KClaq reference electrode. The deposition was conducted at –0.055 V and 25 °C, and the charge densities were adjusted to obtain the electrode thickness of ca. 45, 100, 380, and 900 nm. Transmission electron microscopy (TEM) was performed to observe the pore structure. Electrochemical surface area (ECSA) and ORR activities were evaluated by cyclic voltammetry in N2/O2-saturated 0.1 mol dm–3 KOH solutions with a rotating disk electrode system, consisting of the porous model or a polished planar Pt working electrode, a Pt wire counter electrode, and a Hg|HgO reference electrode. The scan rate and rotation speed were 20 mV s–1 and 2000 rpm, respectively. TEM image exhibits the honeycomb arrays of mesopores with a pore size of 1.8 nm and a pore distance of 4.9 nm (Fig. a). The model electrodes possessed polycrystalline facets, and ECSA was calculated from the hydrogen adsorption peak area in blank voltammetry (Fig. b). The ECSA matched closely with the geometrically calculated surface area, suggesting that the cylindrical pores are uniformly distributed on the electrodes with defined pore lengths (Fig. c). ORR activities were evaluated with the Tafel plots (Fig. d), with current densities corrected for ECSA and concentration overpotential outside the mesopores. Since the oxygen transport resistance or the concentration overpotential is higher in longer pores, the electrodes with longer pore lengths caused smaller ORR current densities. In contrast, the concentration overpotential was suppressed enough to extract the activation overpotential when the pore length was 45 nm and 100 nm, and these electrodes led to higher ORR current density than the planar electrode. The result indicates that the activation overpotential inside the mesopore with a size of 1.8 nm is smaller than that measured with the planer electrode. We will report the origin of the enhanced kinetics inside the mesopore from the viewpoint of the electronic structure change.

Flexible metalized polyimide nonwoven fabrics for efficient electromagnetic interference shielding

Designing and fabricating efficient electromagnetic interference shielding materials has become a significant and urgent concern. Hence, a novel lightweight and flexible metallized polyimide nonwoven fabric is successfully prepared by polydopamine roughening, palladium-free activation of chloroplatinic acid, electroless nickel plating, and octadecanethiol corrosion-resistant treatment. As a result, the efficient construction of metallized surface on polyimide fibers facilitates the formation of multiple scattering for incident electromagnetic waves, leading to an excellent electromagnetic interference performance. More importantly, the strong binding force between nickel plating and polyimide fiber substantially improves the high/low-temperature resistance, endowing the composite with excellent stability and durability in electromagnetic interference performance. Meanwhile, the self-assembly modification of octadecanethiol on the surfaces of nickel plating effectively achieves the inhibition of metal corrosion. Additionally, the high electrical conductivity of metallized polyimide nonwoven fabric endows it with a rapid-responsiveness Joule heating performance, which makes it promising to become an efficient electromagnetic interference shielding material with a distinct competitive advantage in the cold environment.

Trace amount Pt anchored on nitrogen-doped carbon nanoparticle with hollow capsule structure for efficient electrocatalytic oxygen reduction

The utilization of sustainable green energies requires the energy conversion devices to enhance the convenience of use and storage. The oxygen reduction reaction (ORR), as one of the necessary steps in the operation of these devices, exhibits a slow reaction kinetic rate that seriously affects energy conversion and output efficiency. Due to the low abundance and poor stability of Pt, it is essential to develop high-performance oxygen reduction catalysts with low Pt loading. In this work, a composite precursor consisting of ZIF-8 coupled with ferrocene and chloroplatinic acid was prepared, and subsequently derived to obtain nitrogen-doped carbon nanoparticles with hollow capsule morphology on the surface. These hollow capsule structure formed with the assistance of Pt and Fe significantly enhances the performance of Pt/FC@ZIF-8-C nanoparticles as the ORR electrocatalyst, exhibiting superior catalytic activity and stability compared to Pt/C at a low Pt loading (0.7 wt%). This is very important for promoting the design and preparation of Pt-based catalysts, as well as the application of energy conversion and storage devices in the field of green energy sources.

Monitoring of Pore Orientation by in Operando Grazing Incidence Small-Angle X-ray Scattering during Templated Electrodeposition of Mesoporous Pt Films.

We have used in operando grazing incidence small-angle X-ray scattering (GISAXS) to monitor structural changes during templated electrodeposition of mesoporous platinum films on gold electrodes from a ternary lyotropic liquid crystalline mixture of aqueous hexachloroplatinic acid and the diblock copolymer surfactant Brij56. While the cylindrical micelles of the lyotropic liquid crystal (LLC) in the hexagonal phase have a center-to-center distance of 7.5 nm with a preferential alignment parallel to the electrode surface, the electrodeposited platinum films contain highly ordered mesopores arranged in a 2D hexagonal structure, with a center-to-center distance of about 8.5 nm and a preferential orientation perpendicular to the electrode surface. The progression of structural changes of the LLC template and the deposited mesoporous Pt could be monitored for the first time in operando by GISAXS: within the first 14 s of deposition, a nucleation burst of Pt coincides with a loss of preferential alignment of the LLC. Initially, the morphology of the 2-dimensionally nucleated Pt replicates the Au substrate. During the following 5 to 7 min, the growth morphology of the Pt film changes, and vertically aligned mesopores form. Our results indicate mutual interaction between the species involved in the electrodeposition and the LLC template, leading to a partial loss of horizontal orientation of the LLC during Pt nucleation before vertical rearrangement of the micelles to the electrode surface. The vertically aligned mesopores in the Pt and the possibility to produce freestanding films make these materials interesting in fields such as electrocatalysis, energy harvesting, and nanofluidics.

Platinum nanoparticle-decorated reduced graphene oxide nanosheets: A recyclable and highly efficient catalyst towards the reduction of para-nitrophenol and methylene blue

The present study focuses on the design and development of Pt nanoparticle (PtNPs) decorated reduced graphene oxide (RGO) nanohybrid as an efficient heterogeneous catalyst towards the reduction of p-nitrophenol (p-NP) and methylene blue (MB). The citrate reduction of chloroplatinic acid in the presence of amino-propyl trimethoxy silane (APTMS) modified graphene oxide (GO) produced RGO/PtNPs nanohybrid comprised of uniform and high-density distribution of smaller-sized PtNPs. The APTMS provide efficient nucleation points via their amino groups and thereby play a vital role in regulating the size as well as the distribution of the anchored PtNPs in the present approach. The morphological and structural characterization of RGO/PtNPs nanohybrid was done by using X-ray powder diffraction, scanning and transmission electron microscopy, Fourier transform infrared and Raman spectroscopic techniques. The homogeneous and high-density dispersion of smaller-sized PtNPs endows superior catalytic activity to RGO/PtNPs nanohybrid. The nanohybrid exhibited outstanding catalytic performance enabling rapid reduction of both p-NP and MB at ambient conditions. The estimated rate constants for p-NP and MB reduction were 15.9 × 10−3, and 187 × 10−3 s−1 respectively, which outperform the rate constants of several previously reported metal-based GO/RGO nanocatalysts. The recycling tests showed that the nanohybrid maintained good catalytic stability even after the fifth recycle run. The RGO/PtNPs nanohybrid can be exploited for sustainable and efficient catalytic reduction of other environmental pollutants also. Further, the strategy followed in the present study to achieve homogenous and high-density distribution of Pt nanoparticles could be adopted for the anchoring of other metal/metal oxide/semiconductor nanoparticles.

Near-infrared light-enhanced enzymatic activity of laccase-platinum nanoparticles as a biosensor for colorimetric and visible detection of ascorbic acid

Enzymes, as green catalysts with high activity and substrate specificity, have attracted extensive interest in contrast to chemical catalysts with non-selectivity. However, the enzymes' activities are sensitive to external environments. Therefore, highly efficient strategies are encouraged to modulate the enzymatic activity and stability at the molecular level. Compared with conventional magnetic field, temperature, and pH-responsive enzymatic activities, the near-infrared (NIR) light-controlled activities have noninvasive and convenient controllability advantages, which remains a significant challenge. Besides, NIR light also possesses intense penetration and low phototoxicity compared with UV and blue lights. Herein, the supersmall platinum nanoparticles (Pt-NPs) were for the first time deposited on the laccase body (labelled as laccase-Pt), with the reduction of chloroplatinic acid hexahydrate by sodium borohydride. Fortunately, the synergetic catalysis between laccase and Pt-NPs was demonstrated. Moreover, with and without NIR light irradiation, laccase-Pt activities are 2.439 and 2.258 times of free laccase, respectively. NIR laser could also manipulate the reversible enzyme activity of laccase-Pt. Notably, the laccase-Pt displays a significant advance in three-dimensional structure compared with conventional immobilized and encapsulated enzymes. Then, the high-performance laccase-Pt was used as a sensitive biosensor to detect ascorbic acid, with a detection limit of 3.7 μM obtained by colorimetric approach and smartphone. Briefly, this work provides a novel and feasible idea for manipulating laccase activity by NIR laser, inspiring more scholars to control other natural enzyme activities. Simultaneously, it also gives clear proof for a better understanding of the component-activity relationship of the enzymes-metal nano-bio hybrid catalysts.

Spontaneous decoration of Ultrasmall Pt Nanoparticles on size-separated MoS2 nanosheets.

Liquid exfoliation can be considered as a viable approach for scalable production of 2D materials due to its various benefits, although the polydispersity in the obtained nanosheet size hinders their straightforward incorporation. Size-separation can help alleviate these concerns, however a correlation between nanosheet size and property needs to be established to bring about size-specific applicability. Herein, size-selected aqueous nanosheet dispersions have been obtained via centrifugation-based protocols, and their chemical activity in the spontaneous reduction of chloroplatinic acid is investigated. Growth of ultrasmall Pt nanoparticles was achieved on nanosheet surfaces without a need for reducing agents, and stark differences in the nanoparticle coverage were observed as a function of nanosheet size. Defects in the nanosheets were probed via Raman spectroscopy, and correlated to the observed size-activity. Additionally, the effect of reaction temperature during synthesis was investigated. The electrochemical activity of the ultrasmall Pt nanoparticle decorated MoS2 nanosheets was evaluated for hydrogen evolution reaction, and enhancement in performance was observed with nanosheet size, and nanoparticle decoration density. These findings shine light on the significance of nanosheet size in controlling spontaneous reduction reactions, and provide a deeper insight to intrinsic properties of liquid exfoliated nanosheets.

S-scheme heterojunction-mediated hydrogen production over the graphitic carbon nitride-anchored nickel stannate perovskite

A novel heterojunction between Sn-based perovskite and graphitic carbon nitride (gCN) is synthesized to achieve an enhanced spatial charge separation. The interfacial coupling between cube-shaped nickel tin oxide (NSO) and gCN is achieved through the surface sites in NSO. An improved hydrogen production rate of 646 µmol g−1 h−1 is measured in the composite (NSO-gCN), which is twice that in gCN, using triethanolamine (TEOA) and chloroplatinic acid (1% w/w) as holes scavenger and the precursor for the Pt cocatalyst, respectively. Such significant improvement in H2 production performance of the composite is benefited by the high reductive electrons generated via an S-scheme charge transfer pathway, as evidenced by radical trapping experiments and XPS elemental analysis. The composite shows good stability in hydrogen evolution, with marginal (3%) decrease measured in the materials activity after 5 cycles. This study provides an opportunity to develop an S-scheme heterojunction with the Sn-based perovskite anchored in gCN, as an alternative to Ti-based perovskite for various photocatalytic reactions.

Preparation of Ternary Core-Shell Structure for Room Temperature 1-Butylamine Sensing Application

In this work, platinum (Pt) loaded indium oxide (In2O3)/zinc sulfide (ZnS) nanocomposites were synthesized through simple and environmentally friendly methods. The platinum loading with optimal sensing performance was determined by changing the amount of chloroplatinic acid hexahydrate. These materials can detect volatile organic compounds near room temperature (50°C). When these sample sensors were exposed to 1-butylamine (100 ppm), the optimum operating temperature was 50°C for Pt/In2O3/ZnS nanocomposites and 130°C for Pt/In2O3 nanocomposites. The 5% Pt/In2O3/ZnS sensor exhibits the highest response among them. This study shows that the Pt-loaded In2O3/ZnS nanocomposites are promising 1-butylamine sensor materials at room temperature.

Ultrasound-Driven Defect Engineering in TiO2-x Nanotubes─Toward Highly Efficient Platinum Single Atom-Enhanced Photocatalytic Water Splitting.

Single-atom catalysts (SACs) have demonstrated superior catalytic activity and selectivity compared to nanoparticle catalysts due to their high reactivity and atom efficiency. However, stabilizing SACs within hosting substrates and their controllable loading preventing single atom clustering remain the key challenges in this field. Moreover, the direct comparison of (co-) catalytic effect of single atoms vs nanoparticles is still highly challenging. Here, we present a novel ultrasound-driven strategy for stabilizing Pt single-atomic sites over highly ordered TiO2 nanotubes. This controllable low-temperature defect engineering enables entrapment of platinum single atoms and controlling their content through the reaction time of consequent chemical impregnation. The novel methodology enables achieving nearly 50 times higher normalized hydrogen evolution compared to pristine titania nanotubes. Moreover, the developed procedure allows the decoration of titania also with ultrasmall nanoparticles through a longer impregnation time of the substrate in a very dilute hexachloroplatinic acid solution. The comparison shows a 10 times higher normalized hydrogen production of platinum single atoms compared to nanoparticles. The mechanistic study shows that the novel approach creates homogeneously distributed defects, such as oxygen vacancies and Ti3+ species, which effectively trap and stabilize Pt2+ and Pt4+ single atoms. The optimized platinum single-atom photocatalyst shows excellent performance of photocatalytic water splitting and hydrogen evolution under one sun solar-simulated light, with TOF values being one order of magnitude higher compared to those of traditional thermal reduction-based methods. The single-atom engineering based on the creation of ultrasound-triggered chemical traps provides a pathway for controllable assembling stable and highly active single-atomic site catalysts on metal oxide support layers.

Enhanced Acetone-Sensing Properties of Pt-Decorated In2O3 Hollow Microspheres Derived from Pt-Embedded Template.

Pt-decorated In2O3 hollow microspheres were prepared using a template and reflux method. The size of the prepared carbon templates was adjusted from 200 nm to 1.3 μm by introducing chloroplatinic acid during the hydrothermal process. At the same time, Pt nanoparticles inside the carbon layer were protected from oxidation and agglomeration. Also, the folds created on the surface of the hollow sphere during shrinkage led to a substantial increase in specific surface area. The response of the In2O3-based sensor toward acetone was significantly enhanced by the addition of Pt decoration. This improvement can be attributed to the increased availability of active sites for the target gas and the consequential alteration of the energy band structure. In addition, high response sensitivity, rapid dynamic processes, long-term reliability, and selectivity have all been achieved. The detectable limit is less than 1 ppm, which might satisfy the 1.8 ppm threshold value in the exhaled breath of patients with diabetes. Consequently, the proposed sensor has great sensitivity and can detect low-concentration of acetone, making it an ideal choice for applications such as monitoring daily dietary intake, managing diabetes, and inspecting industrial production processes.

Synthesis of Platinum Nanoparticles Supported on Fused Nanosized Carbon Spheres Derived from Sustainable Source for Application in a Hydrogen Generation Reaction

The dwindling supply of fossil fuels has prompted the search for an alternative energy source that could effectively replace them. Potential renewable energy sources such as solar, wind, tidal, and geothermal are all promising but each has its own drawbacks. Hydrogen gas on the other hand can be combusted to produce energy with only water as a byproduct and can be steadily generated via the aqueous media hydrolysis reaction of Sodium Borohydride (NaBH4). This study successfully synthesized fused carbon spheres derived from sugar and decorated them with platinum nanoparticles to form a novel composite material (PtFCS) for catalyzing this reaction. The platinum nanoparticles were produced by reducing chloroplatinic acid in a solution with sodium borohydride and using sodium citrate as a capping agent for the nanoparticles. Transmission electron microscopy (TEM), Energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) were used to characterize and determine the size and shape of the Pt nanoparticles (PtNPs) and fused carbon spheres. TEM was able to determine the average size of the fused carbon spheres to be 200 nm and the average size for the PtNPs to be 2–3 nm. The PtFCS composite was tested for its ability to catalyze the hydrolysis of NaBH4 under various reaction conditions including various solution pH, various temperatures, and various dosages of sodium borohydride. The catalyst was found to perform the best under acidic solution conditions (pH 6), producing hydrogen at a rate of 0.0438 mL/mgcat·min. The catalyst was determined to have an activation energy of 53.0 kJ/mol and could be used multiple times in succession with no loss in the volume of hydrogen produced. This sugar-derived composite catalyst shows promise and could be implemented as a sustainable catalyst for the generation of hydrogen fuel.

Reactive Deposition Versus Strong Electrostatic Adsorption (SEA): A Key to Highly Active Single Atom Co-Catalysts in Photocatalytic H2 Generation.

In recent years, the use of single atoms (SAs) has become of a rapidly increasing significance in photocatalytic H2 generation; here SAnoble metals (mainly Pt SAs) can act as highly effective co-catalysts. The classic strategy to decorate oxide semiconductor surfaces with maximally dispersed SAs relies on "strong electrostatic adsorption" (SEA) of suitable noble metal complexes. In the case of TiO2 - the classic benchmark photocatalyst - SEA calls for adsorption of cationic Pt complexes such as [(NH3 )4 Pt]2+ which then are thermally reacted to surface-bound SAs. While SEA is widely used in literature, in the present work it is shown by a direct comparison that reactive attachment based on the reductive anchoring of SAs, e.g., from hexachloroplatinic(IV) acid (H2 PtCl6 )leads directly to SAs in a configuration with a significantly higher specific activity than SAs deposited with SEA - and this at a significantly lower Pt loading and without any thermal post-deposition treatments. Overall, the work demonstrates that the reactive deposition strategy is superior to the classic SEA concept as it provides a direct electronically well-connected SA-anchoring and thus leads to highly active single-atom sites in photocatalysis.