A photocatalyst that includes Ag.sub.3VO.sub.4 nanowires for photocatalytic reduction of carbon dioxide to solid fuels and a method for the fabrication of the photocatalyst. The Ag.sub.3VO.sub.4 nanowires have a hierarchical structure that includes primary nanorods having a mean diameter of 2.5 to 50 nm arranged into nanowire bundles having a mean diameter of 100 to 500 nm. The photocatalyst is used a method of photocatalytically reducing carbon dioxide to methane, for example, using solar spectrum irradiation.

An air purifier for use in refrigerators contains in the path for the flow of air through the purifier: a photocatalyst wherein a layer based on tungsten oxide (WO.sub.3) is applied on a ceramic foam support. The layer may also contain tin oxide and silver oxide, as well as platinum. The oxide layer may be applied by immersion without the application of a primer. A method for increasing the shelf life of fruits, in particular also of strawberries, salad and vegetables in a refrigerator and a related refrigerator are also described. The purifier is characterized by low energy consumption, thanks to the use of white light to activate the photocatalyst, as well as little toxic impact.