Development of copper-based Layered Double Hydroxides and derived oxides as innovative materials for photoelectrochemical CO2 conversion

The rising levels of atmospheric CO2 demand urgent, sustainable solutions to mitigate climate change. Photoelectrochemical (PEC) CO2 conversion, inspired by artificial photosynthesis, harnesses solar energy to transform CO2 into valuable fuels and chemicals, reducing emissions while enabling the production of renewable, carbon-neutral energy carriers to meet increasing global energy needs. Willing to contribute to the advancement of photoelectrochemical CO2 conversion through the exploration of novel photoelectroactive materials and operational conditions, this work present the development of copper-based Layered Double Hydroxides (Cu-LDHs) and derived Oxides (Cu-LDOs) as photocathode’s material for simultaneous light-absorption and CO2 catalytic conversion. By exploiting the unique properties of this class of compounds, i.e. variability in composition and CO2 affinity, photoelectrochemical CO2 conversion into C1-3 oxygenated products have been successfully performed in a PEC system. Taking advantage of reproducible and scalable synthetic procedures to produce both powders and photoelectrodes with 1 cm2 active area, i.e. coprecipitation and screen-printing technique, two different compositions of LDH, namely Cu/Mg/Al and Cu/Mg/Fe were obtained. Furthermore, full characterization of structure/morphology, photoelectrochemical, and catalytic properties allowed a deep understanding of the role of trivalent metal element within LDH structure on photocathodes performances and PEC CO2RR outcome. Moreover, LDH materials have been exploited as precursors for Layered Double Oxides which resulted a fruitful strategy to couple light absorbing, active sites, and reactant concentrating functionalities with CuMgAl-LDO photoelectrocatalyst giving the highest amount of acetic acid (0.84 µmol h-1 cm-2) among the investigated catalysts in this work, with remarkable faradaic efficiency of 60%. Besides, efforts in the optimization of reaction system have been attempted exploiting a PEC flow electrolyzer with larger active area Cu-LDHs-based electrodes (i.e. 10 cm2) made by an alternative deposition technique (i.e. spray coating). Here catalyst’s loading and conductive support choice have been assessed to guarantee the best compromise between catalytic performances and (photo)electroactivity.