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Schematic representation of the SCD process for the preparation of supported nanoparticles and films.
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Supercritical fluid-based technologies are increasingly being used to develop novel functional nanostructured materials or improve the properties of existing ones. Among these, supercritical deposition (SCD) is an emerging technique to incorporate metals on supports. It has been used to deposit a wide variety of single or multi-metallic morphologie...
Citations
... Thanks to its high diffusivity, low surface tension and modular solvent power, scCO 2 enables the synthesis of nano-structured powders with high specific areas. 24,[26][27][28][29] The use of scCO 2 as a solvent could thus allow for avoiding the energyintensive size-reduction step, implementing a bottom-up strategy for SOC manufacturing. 30 Moreover, a supercritical treatment also allows the lowering of the crystallization temperature, which helps to avoid high-temperature treatments that are usually required for sol-gel and precipitation processes. ...
Supercritical CO 2 solvent enables the synthesis of crystallized oxide particles with high specific surfaces. A route was developed to generate nano-structured YSZ powders which may be suitable for porous SOC electrodes or dense electrolytes.
... Supercritical CO 2 (scCO 2 ) has been used as a solvent in several industrial applications in the fields of extraction Frohlich et al. 2023;Laurintino et al. 2023;Marill an and Uquiche 2023;M€ ock et al. 2023;Pereira et al. 2023), foaming (Ushiki, Hayashi, et al. 2019;Ushiki, Yoshino, et al. 2020;Ushiki, Kawashima, et al. 2022;Ushiki, Ota, et al. 2023;Li et al. 2021Guo et al. 2022), preparation of porous materials (Shimizu et al. 2012(Shimizu et al. , 2015Ushiki, Miyajima, et al. 2023;Epifanov et al. 2020;Erkey and T€ urk 2021;Jiang et al. 2021;Gunes et al. 2022;Jiang et al. 2022;Qi et al. 2022;Azim et al. 2022aAzim et al. , 2022bGarc ıa-Casas et al. 2023), and electronic devices (Oztuna et al. 2017;Tomai et al. 2017; Barim et al. 2020;Pandiyarajan et al. 2021) owing to its attractive features such as mild critical coordinates (critical temperature T c ¼ 304.12 K (Poling et al. 2000)), low viscosity, and high diffusivity into the microstructure. ...
... These problems can be resolved by applying alternative processes that employ supercritical CO 2 to regenerate the spent adsorbents. Supercritical CO 2 is used extensively in industrial applications, including for foaming [9][10][11][12][13], preparation of porous materials [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27], electronic devices [28,29], and extraction [30,31], owing to its attractive features such as its mild critical coordinates (critical temperature (T c ) = 304.12 K [32]), making it ideal for application in thermally sensitive materials. ...
... The viability of using the DA model to represent the adsorption of VOCs in supercritical CO 2 has been successfully explored in our previous studies [44,54]; however, the applicability of the model to ketone VOCs remains to be evaluated. The following equations were used to apply the DA equation to systems including VOCs and supercritical CO 2 [27][28][29]32]: ...
... Supercritical fluid deposition (SCFD) using supercritical carbon dioxide (CO 2 ) is a versatile and promising technique for depositing a functional material onto a substrate in a highly precise, uniform, and sustainable manner. Supercritical CO 2 (as a solvent) offers several advantages over traditional solvent-based deposition methods, including high diffusivity, low interfacial tension, and green solvent properties (Takahashi et al. 2016;Ushiki et al. 2014aUshiki et al. ,2017aUshiki et al. , 2020bUshiki et al. , 2022b; consequently SCFD is an ideal technology for depositing materials onto complex structures (Blackburn et al. 2001;Ushiki et al. 2017bUshiki et al. , 2018bUshiki et al. , 2018c, including electronic devices (Barim et al. 2020;Pandiyarajan et al. 2021) and catalysts (Qi et al. 2022;Gunes et al. 2022;Jiang et al. 2022Jiang et al. , 2021Ushiki et al. 2017b;Shimizu et al. 2012Shimizu et al. , 2015, while also reducing the environmental impact and processing costs associated with traditional solvent-based methods. Moreover, supercritical CO 2 is easily removed from the deposited material via depressurization, thereby eliminating the need for solvent drying, which avoids damaging the substrate structure and reduces processing time and costs. ...
... Supercritical fluid deposition (SCFD) using supercritical CO 2 as a solvent has attracted considerable attention as a suitable technique for fabricating functional materials such as supported catalytic metal nanoparticles [1][2][3][4][5][6][7][8][9] and electronic devices [10][11][12][13]. Supercritical CO 2 dissolves metal complexes such as metal acetylacetonates (acac), and its high diffusivity and low interfacial tension facilitate a high degree of penetration into substrates that contain microstructures [14,15]. ...
... Co(acac) 3 : k ij = aT 2 + bT + c (11) Fe(acac) 3 : ...
... Here, a, b, and c are coefficients ( Table 8). The binary interaction parameter k ij between CO 2 and Co(acac) 3 is a quadratic function of temperature, as shown in Eq. (11). This indicates that the PC-SAFT parameters for the metal complex determined from the solubility in organic solvents do not completely account for such temperature dependence. ...
A methodology to model the solubilities of metal complexes in supercritical CO2 is indispensable for effectively designing the supercritical CO2-based deposition method. Herein, the solubility of two metal acetylacetonates (acac), Co(acac)3 and Fe(acac)3, in supercritical CO2 was modeled based on the perturbed-chain statistical associating fluid theory (PC-SAFT) and experimentally-determined solid–liquid equilibria in organic solvents. This modeling approach is more predictive than conventional cubic-type equations of state or semi-empirical correlation models. The pure-component parameters of PC-SAFT for metal acetylacetonates are obtained by fitting the obtained solubility data to four typical organic solvents (toluene, acetone, 2-butanone, and ethyl acetate). By applying these PC-SAFT parameters, the model satisfactorily reproduced the solubilities of the metal complexes in supercritical CO2, particularly under low-temperature conditions even with the kij (binary interaction parameter) set to 0 in the combining rule. The isobaric solubilities can also be described by PC-SAFT by generalizing the temperature dependence of kij.
... 34 The density of scCO 2 is similar to the liquid-like densities, and metal precursors could be dissolved in scCO 2 . 35 In addition, compared to other solvents in their liquid form, the mass transfer rates of solute molecules in scCO 2 are considerably faster because scCO 2 possesses a higher penetration rate into porous nanomaterials. Zhao et al. reported on the synthesis of well-dispersed wormlike Pd NPs on pristine graphene (PG) sheets under supercritical CO 2 conditions. ...
A green method for synthesizing Pd nanoparticles/graphene composites from a choline chloride-oxalic acid deep eutectic solvent (DES) without a reducing agent or a surfactant is reported. Deep eutectic solvents are usually composed of halide salts and hydrogen-bond donors, and many are biocompatible and biodegradable. The merits of deep eutectic solvents include that they serve as reducing agents and dispersants, and Pd nanoparticles are tightly anchored to graphene. The size and dispersion of Pd particles are improved when supercritical carbon dioxide (scCO2) is used because it has gaslike diffusivity and near-zero surface tension, which results in excellent wettability between the scCO2 and the carbon surface. The prepared sc-Pd NPs/GR/SPCE shows excellent activity toward glycerol oxidation compared to composites not fabricated by scCO2 processes. This study demonstrates the potential of using this scCO2-assisted protocol combined with deep eutectic solvents to further construct nanoparticles/graphene composites.
... Supercritical fluid deposition (SFD) outstands among the numerous synthesis techniques to obtain nanostructured materials for different applications [6][7][8]. It has demonstrated to be an efficient and environmentally friendly process for the synthesis of heterogeneous electrocatalysts for energy conversion and storage applications [9][10][11]. ...
This work has focused on the synthesis of Cu nanostructured electrocatalysts for CO2 electroreduction by supercritical fluid deposition (SFD) technique. Different synthesis strategies such as the suppression of cosolvent (methanol) and/or reducing agent (hydrogen) have been studied. Good copper deposition yields (around 85%) have been attained in the absence of hydrogen. This material (C-200Me) has been tested as catalyst in the electrochemical reduction of CO2 in gas phase and the results obtained have been compared with those achieved with a catalyst synthesised using H2 as reducing agent (C-200H2Me). CO and formic acid have been the main reduction products with both catalysts. CO2 conversion rate has been almost six times higher with C-200H2Me, what may be probably attributed to a higher proportion of Cu⁰/Cu⁺ species in this catalyst. These results indicate the higher catalytic activity of Cu⁰ (than that of Cu2O) in the electrocatalytic reduction of CO2 in gas phase.
... ɉɨɫɥɟɞɧɢɟ, ɛɥɚɝɨɞɚɪɹ ɨɫɬɪɨɜɧɨɦɭ ɬɢɩɭ ɫɬɪɭɤɬɭɪɵ, ɦɨɝɭɬ ɩɪɨɹɜɥɹɬɶ ɡɚɦɟɬɧɭɸ ɥɟɬɭɱɟɫɬɶ ɢ ɩɨɷɬɨɦɭ ɢɫɩɨɥɶɡɨɜɚɬɶɫɹ ɞɥɹ ɩɨɥɭɱɟɧɢɹ ɮɭɧɤɰɢɨɧɚɥɶɧɵɯ ɦɚɬɟɪɢɚɥɨɜ ɩɨɫɪɟɞɫɬɜɨɦ ɝɚɡɨɮɚɡɧɨɝɨ ɨɫɚɠɞɟɧɢɹ [ 8,9 ]. Ʉɪɨɦɟ ɬɨɝɨ, ɪɚɫɬɜɨɪɢɦɨɫɬɶ ɨɫɬɪɨɜɧɵɯ ɫɨɟɞɢɧɟɧɢɣ ɜ ɧɟɩɨɥɹɪɧɵɯ ɪɚɫɬɜɨɪɢɬɟɥɹɯ ɪɚɫɲɢɪɹɟɬ ɜɨɡɦɨɠɧɨɫɬɢ ɢɯ ɩɪɢɦɟɧɟɧɢɹ ɜ ɞɪɭɝɢɯ ɫɮɟɪɚɯ, ɧɚɩɪɢɦɟɪ, ɜ ɫɜɟɪɯɤɪɢɬɢɱɟɫɤɨɦ ɨɫɚɠɞɟɧɢɢ [ 10,11 ]. ɋ ɮɭɧɞɚɦɟɧɬɚɥɶɧɨɣ ɬɨɱɤɢ ɡɪɟɧɢɹ ɨɫɬɪɨɜɧɵɟ ɫɬɪɭɤɬɭɪɵ ɢɧɬɟɪɟɫɧɵ ɞɥɹ ɤɪɢɫɬɚɥɥɨɯɢɦɢɱɟɫɤɨɝɨ ɚɧɚɥɢɡɚ [ 12,13 ], ɧɚɩɪɢɦɟɪ, ɜ ɚɫɩɟɤɬɟ ɢɡɭɱɟɧɢɹ ɜɡɚɢɦɨɫɜɹɡɢ ɥɟɬɭɱɟɫɬɢ ɢ ɤɪɢɫɬɚɥɥɢɱɟɫɤɨɣ ɫɬɪɭɤɬɭɪɵ. ...
... Metals and metal oxides can be dispersed as nanoparticles on both the external and the internal surface of support materials. Supercritical deposition has been attracting interest because of the peculiar properties of scCO2, such as solvent power adjustable with small variations in pressure and temperature, absence of liquid waste and solvent residue on the substrate, fast rates of deposition because of high mass transfer rates at supercritical conditions [58,59]. According to Watkins and McCarthy [60], it is possible to consider three subsequent steps ( Figure 1): ...
Conventional methods generally used to synthesize heterogeneous photocatalysts have
some drawbacks, mainly the difficult control/preservation of catalysts’ morphology, size or structure, which strongly affect the photocatalytic activity. Supercritical carbon dioxide (scCO2)-assisted techniques have recently been shown to be a promising approach to overcome these limitations, which are still a challenge. In addition, compared to traditional methods, these innovative techniques permit the synthesis of high-performance photocatalysts by reducing the use of toxic and
polluting solvents and, consequently, the environmental impact of long-term catalyst preparation. Specifically, the versatility of scCO2 allows to prepare catalysts with different structures (e.g., nanoparticles or metal-loaded supports) by several supercritical processes for the photocatalytic degradation of various compounds. This is the first updated review on the use of scCO2-assisted techniques for photocatalytic applications. We hope this review provides useful information on different approaches and future perspectives.
... Such materials have been the subject of intense research in the field of inorganic or organic-inorganic hybrid materials aiming to improve the physicochemical properties compared to existing materials. In addition, the materials' characteristics and novel application opportunities depend on the fabrication method, creating the need to design and optimize new synthetic approaches [9,10]. For these reasons, a variety of materials processing technologies are utilized in a wide range of applications areas, including microelectronic devices, optics, energy conversion/storage, chemistry, and catalysis. ...
... A SCF is a hybrid phase of both liquid and gas that is easily tunable with small variations in temperature or pressure. Under typical processing conditions, SCF are characterized by liquid-like density, gas-like viscosity, higher diffusivity than liquids, and zero surface tension [9][10][11][12][13][14][15][16][17][18][19][20]. ...
Ni-Pt alloy thin films have been successfully synthesized and characterized; the films were prepared by the supercritical fluid chemical deposition (SFCD) technique from Ni(hfac)2·3H2O and Pt(hfac)2 precursors by hydrogen reduction. The results indicated that the deposition rate of the Ni-Pt alloy thin films decreased with increasing Ni content and gradually increased as the precursor concentration was increased. The film peaks determined by X-ray diffraction shifted to lower diffraction angles with decreasing Ni content. The deposited films were single-phase polycrystalline Ni-Pt solid solution and it exhibited smooth, continuous, and uniform distribution on the substrate for all elemental compositions as determined by scanning electron microscopy and scanning transmission electron microscopy analyses. In the X-ray photoelectron spectroscopy (XPS) analysis, the intensity of the Pt 4f peaks of the films decreased as the Ni content increased, and vice versa for the Ni 2p peak intensities. Furthermore, based on the depth profiles determined by XPS, there was no evidence of atomic diffusion between Pt and Ni, which indicated alloy formation in the film. Therefore, Ni-Pt alloy films deposited by the SFCD technique can be used as a suitable model for catalytic reactions due to their high activity and good stability for various reactions.
