“Photoelectrochemical hydrogen generation: the effects of redox poise on biocatalayst interfaces”.

MICHAEL HAMBOURGER, MIGUEL GERVALDO, PAUL A. LIDDELL, DRAZENKA SVEDRUZIC, PAUL W. KING, MARIA GHIRARDI, DEVENS GUST, ANA L. MOORE AND THOMAS A. MOORE.

Pacific Grove, California, USA.

Congreso; 16th Western Photosynthesis Conference; 2007

Western Photosynthesis Conference

A photoelectrosynthetic cell, based upon the photoanode architecture of a dye-sensitized solar cell, has been assembled. A porphyrin dye, 5-(4-carboxyphenyl)-10,15,20-tris(4-methylphenyl)- porphyrin, sensitizes a TiO2 semiconductor over the visible range to beyond 650 nm. Photoinduced charge separation at the semiconductor/dye interface results in electron migration through the TiO2 conduction band to a cathode, while the ground state porphyrin sensitizer is regenerated via hole transfer to soluble electron mediating cofactors. The resulting increase in the [Ox]/[Red] ratio of the anodic mediator pool drives the solution-based enzymatic oxidation of biofuel substrates. Electrons injected into the TiO2 conduction band are of sufficient energy to reduce protons to hydrogen gas. The effect of anodic redox poise upon the cell performance has been investigated for both the NAD+/NADH and p-benzoquinone/1,4-hydroquinone redox couples. The cell performance is largely insensitive to the presence of NAD+, but is dramatically decreased in the presence of p-benzoquinone. These results are explained in terms of the different electrochemical behavior of the two redox couples, and highlight the ability of the NAD+/NADH couple to interface a dehydrogenase biocatalyst with the photochemical reaction. Using NADH, enzymatic hydrogen production has been demonstrated in the photoelectrosynthetic cell, with an Fe-Fe hydrogenase as the catalyst for the cathodic reaction. Preliminary electrochemical and photoelectrochemical data will be presented, investigating the interaction of this enzyme with a carbon electrode. (This work is supported by grants from the U.S. Department of Energy.)2 semiconductor over the visible range to beyond 650 nm. Photoinduced charge separation at the semiconductor/dye interface results in electron migration through the TiO2 conduction band to a cathode, while the ground state porphyrin sensitizer is regenerated via hole transfer to soluble electron mediating cofactors. The resulting increase in the [Ox]/[Red] ratio of the anodic mediator pool drives the solution-based enzymatic oxidation of biofuel substrates. Electrons injected into the TiO2 conduction band are of sufficient energy to reduce protons to hydrogen gas. The effect of anodic redox poise upon the cell performance has been investigated for both the NAD+/NADH and p-benzoquinone/1,4-hydroquinone redox couples. The cell performance is largely insensitive to the presence of NAD+, but is dramatically decreased in the presence of p-benzoquinone. These results are explained in terms of the different electrochemical behavior of the two redox couples, and highlight the ability of the NAD+/NADH couple to interface a dehydrogenase biocatalyst with the photochemical reaction. Using NADH, enzymatic hydrogen production has been demonstrated in the photoelectrosynthetic cell, with an Fe-Fe hydrogenase as the catalyst for the cathodic reaction. Preliminary electrochemical and photoelectrochemical data will be presented, investigating the interaction of this enzyme with a carbon electrode. (This work is supported by grants from the U.S. Department of Energy.)2 conduction band to a cathode, while the ground state porphyrin sensitizer is regenerated via hole transfer to soluble electron mediating cofactors. The resulting increase in the [Ox]/[Red] ratio of the anodic mediator pool drives the solution-based enzymatic oxidation of biofuel substrates. Electrons injected into the TiO2 conduction band are of sufficient energy to reduce protons to hydrogen gas. The effect of anodic redox poise upon the cell performance has been investigated for both the NAD+/NADH and p-benzoquinone/1,4-hydroquinone redox couples. The cell performance is largely insensitive to the presence of NAD+, but is dramatically decreased in the presence of p-benzoquinone. These results are explained in terms of the different electrochemical behavior of the two redox couples, and highlight the ability of the NAD+/NADH couple to interface a dehydrogenase biocatalyst with the photochemical reaction. Using NADH, enzymatic hydrogen production has been demonstrated in the photoelectrosynthetic cell, with an Fe-Fe hydrogenase as the catalyst for the cathodic reaction. Preliminary electrochemical and photoelectrochemical data will be presented, investigating the interaction of this enzyme with a carbon electrode. (This work is supported by grants from the U.S. Department of Energy.)2 conduction band are of sufficient energy to reduce protons to hydrogen gas. The effect of anodic redox poise upon the cell performance has been investigated for both the NAD+/NADH and p-benzoquinone/1,4-hydroquinone redox couples. The cell performance is largely insensitive to the presence of NAD+, but is dramatically decreased in the presence of p-benzoquinone. These results are explained in terms of the different electrochemical behavior of the two redox couples, and highlight the ability of the NAD+/NADH couple to interface a dehydrogenase biocatalyst with the photochemical reaction. Using NADH, enzymatic hydrogen production has been demonstrated in the photoelectrosynthetic cell, with an Fe-Fe hydrogenase as the catalyst for the cathodic reaction. Preliminary electrochemical and photoelectrochemical data will be presented, investigating the interaction of this enzyme with a carbon electrode. (This work is supported by grants from the U.S. Department of Energy.)+/NADH and p-benzoquinone/1,4-hydroquinone redox couples. The cell performance is largely insensitive to the presence of NAD+, but is dramatically decreased in the presence of p-benzoquinone. These results are explained in terms of the different electrochemical behavior of the two redox couples, and highlight the ability of the NAD+/NADH couple to interface a dehydrogenase biocatalyst with the photochemical reaction. Using NADH, enzymatic hydrogen production has been demonstrated in the photoelectrosynthetic cell, with an Fe-Fe hydrogenase as the catalyst for the cathodic reaction. Preliminary electrochemical and photoelectrochemical data will be presented, investigating the interaction of this enzyme with a carbon electrode. (This work is supported by grants from the U.S. Department of Energy.)+, but is dramatically decreased in the presence of p-benzoquinone. These results are explained in terms of the different electrochemical behavior of the two redox couples, and highlight the ability of the NAD+/NADH couple to interface a dehydrogenase biocatalyst with the photochemical reaction. Using NADH, enzymatic hydrogen production has been demonstrated in the photoelectrosynthetic cell, with an Fe-Fe hydrogenase as the catalyst for the cathodic reaction. Preliminary electrochemical and photoelectrochemical data will be presented, investigating the interaction of this enzyme with a carbon electrode. (This work is supported by grants from the U.S. Department of Energy.)+/NADH couple to interface a dehydrogenase biocatalyst with the photochemical reaction. Using NADH, enzymatic hydrogen production has been demonstrated in the photoelectrosynthetic cell, with an Fe-Fe hydrogenase as the catalyst for the cathodic reaction. Preliminary electrochemical and photoelectrochemical data will be presented, investigating the interaction of this enzyme with a carbon electrode. (This work is supported by grants from the U.S. Department of Energy.)