The Influence of the Pyrolysis Temperature on the Material Properties of Cobalt and Nickel Containing Precursor Derived Ceramics and their Catalytic Use for CO2 Methanation and Fischer–Tropsch Synthesis

Abstract

Ni and Co containing precursor derived ceramics (ceramers) were prepared from a polysiloxane based preparation route. All catalysts were characterised by BET, XRD and TEM as well as water and heptane adsorption and tested for CO2-methanation and Fischer-Tropsch synthesis. Different pyrolysis temperature between 400 and 600 °C were used to get catalysts with different surface hydrophilicities. With increasing synthesis temperature less organic groups remain on the surface resulting in a more hydrophilic catalyst. For all Ni containing ceramers, well dispersed particles in the range of 3 nm were formed with comparable surface areas. The catalysts with the lowest tendency towards water adsorption showed the highest activity for CO2-methanation. From the cobalt containing synthesis route, different material properties were observed. In contrast to the Ni catalysts, the Co particle formation depends on the pyrolysis temperature. While no metallic particles were formed above 400 °C, smallest particles were obtained using a pyrolysis temperature of 500 °C with particle sizes in the range of ~5 nm. With increasing pyrolysis temperature to 600 °C, particle size increases to ~10 nm. Nevertheless, first tests for CO2-methantion and Fischer-Tropsch reaction were successful and the catalysts with less hydrophilic surface showed higher activity and a higher selectivity towards C5+-products.

Porous SiOC monoliths with catalytic activity by in situ formation of Ni nanoparticles in solution‐based freeze casting

“…Consequently, the decomposition of the methyl group in MK is shifted to lower temperatures as it was observed in previous TGA measurements. This behavior of polysiloxanes has been reported in literature for nickel as well as for other metals . Studies using similar precursors found comparable BET SSA.…”

“…Thus, a connection of the Ni ion to the polymeric chain can be assumed as it was reported previously. 11,13,35 This is not true for the sample NiA2TMEDA/600 where the complexing agent TMEDA has no cross-linking active groups. Consequently, binding of the complexed Ni ions to the polymeric chain is not possible.…”

Metal Silicide Nanosphere Decorated Carbon‐Rich Polymer‐Derived Ceramics: Bifunctional Electrocatalysts towards Oxygen and their Application in Anion Exchange Membrane Fuel Cells

“…The organosilane ((3‐Aminopropyl)triethoxysilane) play an influential role as complexing and cross‐linking agent in the synthesis of intermetallic nickel/cobalt silicide particles upon SiOC matrix. The metal ions are chemically attached to the functional groups of the APTES (amino group ‐NH 2 ).…”

“…[12] The essential modification can be implemented in the sequence of stride during the formation of PDC by utilizing suitable polymer precursor, active fillers, complexing agents and pyrolysis temperature to acquire required morphology and active sites. [12][13][14][15][16] Silicon-oxy-carbide (SiOC) structures synthesized from polysiloxane polymers suitably cross-linked and pyrolysed at elevated temperature are relevant PDC structure with unique two-phase structure such as (i) the amorphous phase where Si is tetrahedrally bonded with oxygen and carbon; (ii) disordered carbon phase holding excellent chemical, thermal and physical properties that can be employed as bifunctional catalyst. [13,[17][18][19][20] The addition of precursor for transition metal particles such as cobalt and nickel at the atomic level is crucial in enhancing the properties such as electrochemical activity and conductivity of the SiOC material.…”

“…Recently polymer‐derived ceramics (PDC) is reconsider as a suitable alternative bifunctional electrocatalyst due to the flexibility involved in the synthesis process to attain the required structure and property . The essential modification can be implemented in the sequence of stride during the formation of PDC by utilizing suitable polymer precursor, active fillers, complexing agents and pyrolysis temperature to acquire required morphology and active sites . Silicon‐oxy‐carbide (SiOC) structures synthesized from polysiloxane polymers suitably cross‐linked and pyrolysed at elevated temperature are relevant PDC structure with unique two‐phase structure such as (i) the amorphous phase where Si is tetrahedrally bonded with oxygen and carbon; (ii) disordered carbon phase holding excellent chemical, thermal and physical properties that can be employed as bifunctional catalyst .…”