Hydrogen, energy conversion

In oiological systems, the most frequent mechanism of oxidation is the remov of hydrogen, and conversely, the addition of hydrogen is the common method of reduc tion. Nicotinamide-adenine dinucleotide (NAD) and nicotinamide-adenine dinucleotide phosphate (NADP) are two coenzymes that assist in oxidation and reduction. These cofactors can shuttle between biochemical reac tions so that one drives another, or their oxidation can be coupled to the formation of ATP. However, stepwise release or consumption of energy requires driving forces and losses at each step such that overall efficiency suffers. 

Molecular photocatalytic systems for solar energy conversion catalysts for the evolution of hydrogen and oxygen from water. K. I. Zamaraev and V. N. Parman, Russ. Chem. Rev. (Engl. Transl.), 1983,52,817-836(114). 

Trigonal, metallic selenium has been investigated as photoelectrode for solar energy conversion, due to its semiconducting properties. The photoelectrochemistry of the element has been studied in some detail by Gissler [35], A photodecomposition reaction of Se into hydrogen selenide was observed in acidic solutions. Only redox couples with a relatively anodic standard potential could prevent dissolution of Se crystal. 

Keywords chemical energy conversion energy storage chemical heat pump separation hydrogen production reaction equilibrium... 

---