Effect of Preparation Solvent and Calcination Atmosphere on Ni@SiO 2 Catalyst for Simultaneous Production of Hydrogen and Carbon Nanotubes from Simulated Plastic Waste Syngas

SiO 2 core supports are prepared via the Stöber method with various synthesizing solvents. Then, a Ni shell is deposited on SiO 2 by a deposition–precipitation method. The results illustrate that using isopropanol as the solvent governs the catalyst particle size with a superior dispersion and a high catalytic activity. Thus, the calcination atmosphere of the catalyst directly affects both the chemical state and the catalytic performance of the active sites. The Ni@SiO 2 ‐I‐air (isopropanol) catalyst calcined by air with more Ni 2+ facilitates the highest H 2 production of 142.2 mmol g −1 h −1 but provides a carbon nanotube (CNT) yield of only 7.6%. Most importantly, the Ni@SiO 2 ‐I‐H 2 catalyst calcined by ambient H 2 is prone to form Ni 0 species, thus providing the best crystalline conversion and metal–support interaction, which benefits the production of CNTs to a maximum yield of 19.8% with a H 2 production of 122.8 mmol g −1 h −1 .