A potentially clean, low-cost CO2 photo-hydrogenation by mimicking
photosynthesis via photocatalytic water splitting is one of
the best routes of obtaining renewable energy. Remarkable result
has been demonstrated. The efficiency of CO2 hydrogenation was
significantly enhanced (two-fold improvement) when a gaseous
mixture of CO/CO2 was used to yield CH3OH under artificial sunlight,
comparing with the one using only CO or CO2. In the presence of CO co-feed, the consumption or generation of methyl formate,
an intermediate product of CH3OH, was promoted, which inhibits
or enhances respectively the formation of CH3OH. Based on the
experimental result, we have proposed a possible mechanism of
CO2 photo-hydrogenation over Pt/CuAlGaO4 and Pt/SrTiO3:Rh
photocatalysts to explain the key trends as well as the species
involved during the photoreaction. Although the novel idea to
mimic natural photosynthesis via water splitting and hydrogenation
is promising, such concept still needs further improvement.