Template‐Free Synthesis of Porous Fe 3 O 4 /SiOC(H) Nanocomposites with Enhanced Catalytic Activity

Schuch

et al. 2019

J Am Ceram Soc

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The ternary Nowotny phase (NP), with a composition Mo3+2xSi3C0.6 (x = 0.9‐0.764), is found to be catalytically active in the field of electrochemical water splitting. The NP embedded in a porous SiC/C nanocomposite matrix is synthesized via a single‐source‐precursor approach which involves the reaction of allylhydridopolycarbosilane with MoO2(acac)2. Thermal treatment of the single‐source‐precursor up to 1400°C in a protective atmosphere results in the in situ formation of nanocrystalline Mo3+2xSi3C0.6 immobilized in a thermally and corrosion‐stable SiC/C matrix. The weight fractions of the observed crystalline phases Mo3+2xSi3C0.6 and SiC amount to ca. 28 (26) and 72 (74) wt%, respectively, when prepared at 1400°C (1350°C). The porosity of the formed nanocomposite is adjusted by the addition of polystyrene (PS) as a pore former to the single‐source‐precursor resulting in a specific surface area up to 206 m2/g. The electrocatalytic activity of the Mo3+2xSi3C0.6/C/SiC nanocomposite with respect to the hydrogen evolution reaction (HER) is characterized by low over potentials of 22 and 138 mV vs reversible hydrogen electrode (RHE) for applying 1 and 10 mA cm−2 of current density, respectively. The analyzed electrocatalytic performance exceeds that of most Mo‐based electrocatalysts and shows high stability (over 90%) during 35 hours.

Section: Resultssupporting

confidence: 78%

Nowotny phase Mo₃₊₂_xSi₃C_0.6 dispersed in a porous SiC/C matrix: A novel catalyst for hydrogen evolution reaction

Schuch

et al. 2019

J Am Ceram Soc

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“…After annealing of the reaction mixture at 170°C for 2 hours, the reaction between SMP-10 and MoO 2 (acac) 2 results in the formation of Si-O-Mo bonds (950 cm −1 ) by consuming Si-H groups (2136 cm −1 ) of SMP-10, which has been discussed in our previous studies. 49 Besides, as compared with pure SMP-10 and DVB, the characteristic peaks of C = C (1627 cm −1 ) in SM/Mo/PS/DVB 2-1-4-2 disappear ( Figure 1B and previous studies, 49,50 an idealized reaction scheme is shown in Figure 1C.…”

Section: Characterization Of the Synthesized Single-source Precursorsupporting

confidence: 50%

“…PS as the pore former without functional groups cannot be involved in the chemical reaction between SMP‐10, MoO 2 (acac) 2 , and DVB. Based on the FT‐IR results and previous studies, an idealized reaction scheme is shown in Figure C.…”

Section: Resultsmentioning

confidence: 99%

Enhanced hydrogen evolution reaction catalyzed by carbon‐rich Mo_4.8Si₃C_0.6/C/SiC nanocomposites via a PDC approach

Riedel

2019

J Am Ceram Soc

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In this study, mesoporous carbon‐rich Mo4.8Si3C0.6/C/SiC ceramic nanocomposites were successfully prepared via a single‐source precursor route, starting from allylhydridopolycarbosilane (AHPCS, SMP‐10), bis(acetylacetonato) dioxomolybdenum (VI) [MoO2(acac)2], and divinylbenzene (DVB). Besides, polystyrene (PS) was used as a pore former. The obtained carbon‐rich single‐source precursor/PS mixtures were pyrolyzed at 1100°C, and then annealed at 1350°C‐1600°C to fabricate a series of carbon‐rich Mo4.8Si3C0.6/C/SiC ceramics comprised of high carbon content above 50 wt%. In comparison to the carbon‐poor materials, the carbon‐rich samples retain the higher specific surface area up to 214.6‐304 m2/g at higher annealing temperatures (1350°C‐1600°C) due to the enhancement of carbothermal reaction. The carbon‐rich samples synthesized at 1500°C, denoted as SM/Mo/PS/DVB 2‐1‐4‐2 1500 exhibit enhanced electrocatalytic performance with ultra‐low overpotentials of 119 mV vs reversible hydrogen electrode at a current density of 10 mA cm−2 in acidic media, which is superior to that of the Mo4.8Si3C0.6/C/SiC ceramic (138 mV) with lower carbon content reported in our previous study. Therefore, our porous materials comprised of high carbon content and Nowotny phase (Mo4.8Si3C0.6, NP) are considered as promising catalysts for the hydrogen evolution reaction (HER).

“…Polymer-derived ceramic (PDC) approach started from the 1960s and is a versatile method used for the fabrication of mainly Si-based advanced ceramics [1,2]. During the past 60 years, due to their physical-micro/mesoporous ceramics as catalyst supports with high specific surface area (SSA) and outstanding corrosion stability [14,[19][20][21][22].…”

Section: Introduction mentioning

confidence: 99%

Single-source-precursor synthesis of porous W-containing SiC-based nanocomposites as hydrogen evolution reaction electrocatalysts

Mao

2021

J Adv Ceram

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In this paper, W-containing SiC-based ceramic nanocomposites were successfully prepared by a polymer-derived ceramic approach using allylhydridopolycarbosilane (AHPCS) as a SiC source, WCl6 as a tungsten source, polystyrene (PS) as a pore forming agent as well as divinyl benzene (DVB) as a carbon rich source. High-temperature phase behavior of the W-containing SiC-based ceramics after heat treatment was studied, showing that excessive DVB content in the feed will inhibit the crystallinity of W-containing nanoparticles in the final ceramic nanocomposites. The high specific surface area (SSA) of 169.4–276.9 m2/g can be maintained even at high temperature in the range of 1400–1500 °C, due to the carbothermal reaction which usually occurs between 1300 and 1400 °C. All prepared W-containing SiC-based nanocomposites reveal electrocatalytic activity for the hydrogen evolution reaction (HER). In detail, compared with reversible hydrogen electrode (RHE), the ceramic sample PWA-2-1300 after heat treatment at 1300 °C has the smallest overpotential of 286 mV when the current density is 10 mA·cm−2 in acid medium, indicating the promising perspective in the water splitting field.