Periodic Reporting for period 1 - PHOTOBIOCATH-CO2 (Photocathode engineering for efficient photobioelectrochemical CO2 reduction to formate)
Reporting period: 2021-09-01 to 2023-08-31
There is great concern in that greenhouse gases such as carbon dioxide (CO2) are probably the cause of global warming. Due to gradual increase in CO2 concentration, the recycling or transformation of CO2 into value-added fuels is considered as an interesting option to tackle the global warming and energy requirement without hindering development and urbanization. Among the several ways for CO2 conversion photoelectrochemistry (PEC) is recognized as the ideal method to convert CO2 into added value compounds. Therefore, the implementation of the project has allowed an advance on this field of technology,also called artificial photosynthesis due to its mimicking of nature’s energy cycle.
The overall objectives of the project have been:
-1. The design and synthesis of efficient and stable binary (two-component) and ternary (three-component) nanocomposite oxides for formate generation via CO2 reduction.
- 2. The design and fabrication of efficient and stable hybrid inorganic/biological photocathodes for photoelectrochemical CO2 reduction reaction (PEC-CO2RR).
- 3. The design and construction of an efficient and stable photoelectrochemical CO2 reduction cathode.
The main conclusion of the project was that inorganic composites based on p-type metallic oxide semiconductors of Fe, Cu and Bi and be combined to with the enzyme formate dehydrogenase anchored on a highly conductive carbon-based nanomaterial (COOH-MWCNT) film as photocathodes of formate reduction. The utilized carbon nanomaterial support provided fast charge transfer from the semiconductor to the biocatalyst, without altering the FDH catalytic center. Thus, the CNT/FDH interface was probably responsible for increasing charge accumulation and suppressing recombination phenomena.
The overall objectives of the project have been:
-1. The design and synthesis of efficient and stable binary (two-component) and ternary (three-component) nanocomposite oxides for formate generation via CO2 reduction.
- 2. The design and fabrication of efficient and stable hybrid inorganic/biological photocathodes for photoelectrochemical CO2 reduction reaction (PEC-CO2RR).
- 3. The design and construction of an efficient and stable photoelectrochemical CO2 reduction cathode.
The main conclusion of the project was that inorganic composites based on p-type metallic oxide semiconductors of Fe, Cu and Bi and be combined to with the enzyme formate dehydrogenase anchored on a highly conductive carbon-based nanomaterial (COOH-MWCNT) film as photocathodes of formate reduction. The utilized carbon nanomaterial support provided fast charge transfer from the semiconductor to the biocatalyst, without altering the FDH catalytic center. Thus, the CNT/FDH interface was probably responsible for increasing charge accumulation and suppressing recombination phenomena.
Four p-type semiconductors including Fe, Cu and Bi-based oxides were synthesized : Cu2O, CuFeO2, CaFe2O4 and CuBi2O4 . The synthesized compounds were characterized using different analysis methods, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and N2 physical adsorption analysis (BET). Binary (two-component), ternary (three-component) and cuaternary (4-component) nanocomposites have been prepared by combinig this four pure semiconductors and characterized for the photoelectrochemical reduction (PEC) of CO2. The effect of composite synthesis method on the PEC efficiency by h two different methods (hydrothermal and solid state dispersion) was studied. Films deposition of the synthesized samples (including semiconductors and composites) on fluorine doped tin oxide (FTO) was studied by two different methods: dip-coating and spin-coating. The number of semiconductor layers deposited and their amount was studied for optimization. Best results were obtained by spin coating 4 layers on the electrodes surface. Incorporation of carbon nanotubes fibers or multiwalled carbon nanotubes functionalized with carboxylic groups onto the FTO electrodes modified with semiconductors was studied to increase the charge transfer upon visible light irradiation. Only the strategy using the functionalized multiwalled carbon nanotubes worked out. The last step studied was the Immobilization of Formate Dehydrogenase (FDH) on the FTO electrodes modified with semiconductor films and MWCNTs, with or without redox polymer (cobaltocene). The best results wer obtained by physical adsorption of the enzyme in absence of the redox polymer and adding on top polyethylene imine as protection polymer. The highest photocurrents of CO2 reduction were obtained with the composite that contained the 4 synthesized semiconductor oxides.
An article reporting these scientific results is in preparation.
An article reporting these scientific results is in preparation.
In this project organic (CNTf or RGO), and inorganic (p-type semiconductors or their composites) nanohybrids were systematically synthesized and combined to fabricate novel hybrid-structured p-type semiconductor-based (in the form of pure or nanocomposites) photocathodes for studying their efficiency in a photoelectrochemical (PEC) for CO2 reduction.The achievement of these hybrid materials (which are designed for the first time) in PEC CO2 reduction was promising for the cuaternary composite formed from the four pure metallic oxides synthesized. There is no report of fabricating semiconductor-based composite heterostructures as proper catalysts for PEC CO2 reduction in the literature. This study provides alternatives to improve the performance of photocathodes for the CO2 reduction reaction to formate based on choosing a proper p-type semiconductor-based material combined with the specific catalytic activity of a redox metalloenzyme to tune structural, electronic, and catalytic properties of the produced photoelectrodes. This is anotable advance for obtaining efficent and sustainable photoelectrocatalysts for carbon dioxide reduction, which is one of the main global problems due to the increasing levels of this greenhouse effect gas in the atmosphere and its probable incidence on global warming.