For the reduction of the human carbon dioxide footprint we propose to use solar (or other renewable) energy and convert atmospheric or technical carbon dioxide and water to methanol, a liquid fuel which is easy to store and transport using readily existing technology.

Lay summary
This use-inspired proposal consists of two parts:

1) Water electrolysis in the presence of CO2 at the cathode which is coated with a conventional metal oxide hydrogenation catalyst such as Cu/ZnO which is expected to give methanol with high selectivity and yield. This part is centred at University of Pretoria and may be expected to produce first results during the first 18 months of the project, preferably obtained with a demonstration device, and will be developed further and scaled up towards a full device in the final 18 months period.

2) Artificial synthesis of methanol from CO2 and water in a photo-electrochemical cell for diagnostic monitoring and possible application of bias voltages, centred at Empa. The planned light harvesting components (Cu2O-CuO photocathodes and hematite-based photoanode heterostructures) have suitable band gaps (2.0-2.2 eV and 1.3-1.6 eV, respectively) and high absorption coefficients over a considerable part of the solar spectrum. The anode may initially be simply a platinum foil, but in view of avoiding transport limitations the design of a setup with short transport distances in the electrolyte will be addressed. Ideally, the system may be developed to work as a pure photoreduction in the absence of electrochemical assistance, much as natural photosynthesis which is to be mimicked. Empa will carry out initial exploratory experiments which permit a selection of systems for deeper investigation.