Solar photothermo-catalytic conversion of CO2 on phyllosilicates modified with Ni and CeO2

Abstract

One of the strategies to mitigate the greenhouse effect is converting the CO2 into high-added value products. In this work, a photothermo-catalytic approach, using peculiar Ni-phyllosilicates samples, was applied for the CO2 conversion into solar fuels. In particular, the Ni-phyllosilicates were modified with the introduction of the Ce ions in their structure and successively they were covered with the CeO2 semiconductor. The structural, morphological, textural, optical and reducibility properties as well as the interaction with CO2 were investigated. The Ni/Ce-phyllosilicate covered with CeO2 achieved a CO2 conversion of 87% after 5 hours of photothermo-catalytic test using simulated solar irradiation at 120°C, producing 15.8 μmol/gcat∙h of CO and 5.6 μmol/gcat∙h of CH4. The same sample was tested in an integrated approach where the CO2 was evolved by the catalytic oxidation of toluene and then was converted into CO and CH4, obtaining a CO2 conversion of 50% and 8.8 μmolCO/gcat∙h and 3.3 μmolCH4/gcat∙h. The presence of Ni in the phyllosilicates structure guaranteed a good catalytic stability whereas the deposition of CeO2 allowed to exploit the improved thermal (redox) properties of cerium oxide and favoured the CO2 adsorption on its basic sites and oxygen vacancies. Furthermore, the high surface area of the as-synthetized Ni-phyllosilicates permitted to efficiently expose the CeO2 surface-active sites to the solar radiation. The here investigated catalysts showed versatile properties ideal for hybrid catalytic approaches as the photothermo-catalysis, allowing to propose new solutions for the CO2 valorization.