  The overall process of photosynthesis consists of two main phases, the
so-called light and dark eactions: light energy is absorbed by chlorophyll
molecules and transferred to regenerate NADH and ATP, then drive Calvin-Benson
cycle to synthesize sugar. In order to synthesize sugar through artificial
photosynthesis, one of the key is to regenerate ATP economically and improve
the efficiency of dark reactions. Here 9 kinds of dark reaction pathways are
proposed, which only NADH is regenearated from hydrogen or electricity for
driving, the efficiency of dark reactions is improved, combined with solar
photovoltaic or solar hydrogen technology, the total efficiency of artificial
photosynthesis can reach 30%, several ten times more than natural
photosynthesis. One of them, to use chemical synthesis of formaldehyde from CO2
and H2, no NADH and ATP is need, to synthesize sugar efficiently through 9
enzymes, so it will be easier to produce in large scale, and the sugar will be
a good energy carrier as the sugar can be efficiently converted to energy
carrier hydrogen through enzymes.
