Photoreduction of carbon dioxide using sensitised Co and Cu trimer TiO2 in aqueous medium ; Fotorreducción de dióxido de carbono usando TiO2 sensibilizado con trímeros de Co y Cu en medio acuoso

Abstract

Summary In this investigation, the performance of two titanium dioxide photocatalysts, one sensitised with a copper trimer (Cu3 (dpa) 4Cl2) (dpa = 2,2 ´-dipyridilamine), was evaluated and the other with a cobalt trimer (Co3 (dpa) 4Cl2) specifically in the photoreduction of carbon dioxide in aqueous medium. In a first experimental step, the TiO2 sensitisation process, which occurs in two successive reactions, was studied using a microwave reactor: on the first, the TiO2 surface is operated with p-aminobenzoic acid (PABA) which acts as a binder molecule between TiO2 and the respective trimer; then, in the second reaction, the metal trimer is anchored. Three levels of temperature, power and reaction time were analysed for each of the two reactions; however, robust Taguchi statistical analysis showed that there is no significant difference between treatments for the selected conditions. As a result, it was established that for the sensitisation process of the photocatalysts it is possible to work under the following conditions without affecting the final composition of each catalyst: 70 °C, 100 W and 5 min at the PABA operation stage and 80 °C, 150 W and 5 min at the anchor of both dyes. In the second experimental stage, the photocatalysts synthesised for CO2 reduction in aqueous medium were evaluated using a medium pressure ultraviolet lamp and a photoreactor at atmospheric pressure and 25 °C. The catalyst with the best performance was sensitised to the cobalt trimer, as it showed increased production of methane and carbon monoxide; the copper sensitised catalyst did not produce quantifiable carbon monoxide generation and methane production was considerably lower. The production of hydrogen by both catalysts was particularly important for the catalyst sensitised with the copper trimer. No other CO2 reduction products were detected in the liquid phase. ; Resumen En la presente investigación, se evaluó el desempeño de dos fotocatalizadores de dióxido de titanio, uno sensibilizado con un trímero de cobre ...