PHOTOELECTROCHEMICAL REDUCTION OF CO-2
This research was set up to verify and extend previous observations on CO-2 reduction at semiconductor powders and electrodes upon irradiation with light from the solar spectrum, corresponding to band gap or larger energies. For our study we chose titanates (TiO-2 and strontium titanate SrTiO-3). Titanate powders in aqueous suspensions are simple, stable and rather cheap systems. They produce C-1 compounds. However, the solar to chemical conversion yields of these systems are consistently low. Moreover, it has become clear that oxidation of these organic materials rather than reduction is the favoured process. We reinvestigated the suitability of titanates for CO-2 reduction and we found that the previously concluded preference of CO-2 over H-2O reduction is due to an artefact: it is due to pH effects at the electrode surface. The large overpotential for CO-2 reduction may be solved by using transition metal complexes as electron mediators between the electrode and CO-2. We have tested four tetra-azamacrocyclic cobalt (II) and nickel (II) compounds: they can be advantageously used to lower the overvoltage for CO-2 reduction and to favour successfully CO-2 over H-2O reduction. A serious drawback of these systems is that one still needs a rather negative potential for reducing CO-2.
Bibliographic Reference: EUR 9529 EN (1984), MF, 105 P., BFR 240, BLOW-UP COPY BFR 525, EUROFFICE, LUXEMBOURG, POB 1003
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Record Number: 1989123076700 / Last updated on: 1987-01-01
Available languages: en