Imperative inquiries.


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age Misfortune Commitments - H2/Air
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Slide 1

“On the dry terrains there will spring up modern provinces without smoke and without smokestacks; woodlands of glass tubes will stretch out over the fields and glass structures will rise all over; within these will occur the photochemical procedures that until now have been the monitored mystery of the plants, yet that will have been aced by human industry which will know how to make them bear significantly more bottomless organic product than nature, for nature is not in a rush and humankind is.” Giacomo Ciamician Science 36, 385 (1912)

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Biomimetic methodologies and part of organic procedures as standards for sun powered to fuel LBNL Workshop “Solar to Fuel - Future Challenges and Solutions” 28-29 March 2005 Important inquiries Can bio-propelled develops assume a part in substantial scale sun oriented vitality change? Give models to the catch and change of sun based vitality? Then again, does the way of natural vitality transformation block it serving as a worldview vast scale vitality creation to address human issues?

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Global vitality stream Is natural vitality transformation adequately substantial scale to be significant? Pretty nearly 4 x10 21 J of substance vitality put away in photosynthetic biomass every year. Force speaks the truth 125 TW

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Solar vitality transformation emf pmf Non-natural Biological Photoinduced electron exchange response focuses (atomic level photovoltaics, emf) photovoltaics emf layer conveyance H + H + wire appropriation other electrical work Transducers for: union work mechanical work transport work driving complex non-straight procedures Halophilic Archaea, bacterioplankton

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Bio-enlivened impetuses for reasonable expansive scale vitality generation and change Photosynthetic living beings give bunch samples of catalysis including a few key redox ones that work with basically no overpotential. These include: 2H 2 O = 4H + 4e - + O 2 oxygen advancing complex H 2 = 2H + 2e - hydrogenase O 2 + 4H + 4e - + 4H + (pumped) = 2H 2 O + 4H + (pumped) complex 4 With these three compounds nature has given the essential ideal models to power module operation and recovery of hydrogen and oxygen.

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Questions with respect to counterfeit photosynthesis, water oxidation, oxygen lessening and hydrogen generation . Why doesn’t complex 4, cytochrome c oxygen oxido-reductase, work backward? O 2 + 4H + 4e - + 4H + (pumped) = 2H 2 O + 4H + (pumped) complex 4 Can the oxygen developing complex (oec) work backward? 2H 2 O = 4H + 4e - + O 2 oec Can the chemically dynamic locales of redox compounds be gathered in simulated develops and electrically coupled to terminals? Adequate thickness of reactant locales on cathodes to make genuine vitality fluxes conceivable? 1 amp/cm 2 See: Basic Research Needs for Hydrogen Production, Storage, and Use. The workshop report is accessible as a 3 MB pdf document on the BES website:â  http://www.sc.doe.gov/bes/hydrogen.pdf

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Characteristics of organic synergist action : slower, atomic acknowledgment close thermodynamic breaking point effectiveness profoundly particular, sub-atomic acknowledgment power through substitution/self repair Characteristics of present day human-built reactant movement : quicker give up proficiency for rate (overpotential) less particular strength innate (yet some effortlessly harmed) Evolution of bio-enlivened catalysis incorporates components from both sides

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But, maybe the most critical normal for natural impetuses is that

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Biological impetus don\'t come wired to anodes Nature does not utilize metallic channels and emf in either amalgamation or vitality yielding procedures (as in human do). An atom - metal interface must be made. Sub-atomic wire, redox transfer transport, leading polymer, redox hydrogel, or different method for electrically joining synergist site to anode.

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O 2 O 2 water Schematic of wiring chemical with hand-off or specifically to cathode M bull/M red E 0.82 V - E o M E o M O 2 water 0.82 V Perfect anode SHE ~ O.82 V E Low beta “molecular wire” at low inclination uniting E to terminal Electron burrowing 10 pA momentum

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Methods of wiring redox protein to cathode

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Wiring with a rotaxane atomic transport Katz et al., Angew. Chem. Int. Ed . 43 , 3292-3300 (2004)

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Amine oxidase wired to gold terminal Hess et al., J. Am. Chem. Soc . 125 , 7156-7157 (2003)

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Calculated ideal electron exchange rates log k et = 13 - (1.2 - 0.8 )(R - 3.6) Dutton and colleagues Nature, 402 , 47–52 (1999) Nature , 355 , 796–802 (1992)

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Parameters for bio-catalyzed O 2 lessening at power device cathode Catalytic site 4H + O 2 2H 2 O Molecule - metal interface. Atomic wire, redox transfer transport, directing polymer, redox hydrogel, or different method for electrically uniting synergist site to anode 4e - Cathode Metallic conveyor to R L , current no less than 1 A/cm 2 Current will rely on upon: Number of locales/cm 2 Turnover number/site Carrying limit of interface

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Cu particles at the dynamic site of phenoxazinone synthase, a multicopper oxidase Max foot shaped impression ~ 9 nm 2 (assume 3x3nm squares) ~1x10 13 destinations/cm 2 10 2 s - 1 turnover? (what limits turnover?) 1x10 15 turnovers/cm 2/s 4x10 15 electrons/s cm 2/s (4 e -/turnover) About 700 µA/cm 2 As water oxidizer Solar driver at AM1.5 ~ 20 mA/cm 2 =1.25x10 17 e -/cm 2 Turnover shows up rate constraining O 2 + 4e - + 4H +  2H 2 O 2H 2 O  4H + 4e - + O 2 ? ~ 1 nm ~2 nm Francisco and Allen, 2005

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Carrying limit of interface How much current can be pushed through a “molecular wire” In single particle directing AFM investigations of leading polymers and atoms with low Beta, streams of around 10 pA are seen at low predisposition. 10 pA relates to ~ 6x10 7 e - s - 1 This effectively surpasses by requests of size the turnover number of any chemicals under thought. Along these lines, k feline cutoff points current. J. Am. Chem. Soc . 127 ,11384-1385 (2005)

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Consider bio-enlivened impetuses for enhanced energy units

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Two power modules, same cathodic rxn Mitochondrion as a power module 2NADH + O 2  2NAD + 2H 2 O Conversion of electrochemical potential to biochemical work with high (> 90%?) proficiency Good cathode H 2/air energy component 2H 2 + O 2  2H 2 O Conversion of electrochemical potential to work addressing human needs with humble effectiveness (~ half). Not all that great cathode

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E misfortune at 1.5 A/cm 2 : 400 mV (68%) 70 mV (12%) 120 mV (20%)  real misfortunes because of poor cathode energy (ORR)  minor misfortunes by ohmic resistance (half R H+,membrane , half R contact )  noteworthy voltage/influence thickness through FF/DM improvement (mass-tx) Voltage Loss Contributions - H 2/Air (H 2/air (s=2/2) at 150kPa, 80C, and 100%RH - 0.4mg Pt-cathode/cm 2 ) Thanks to Frank DiSalvo Source: H. Gastieger, GM Fuel Cell Division

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Enzymatic lessening of O 2 to H 2 O And a few inquiries that surface 1) Current thickness 2) V misfortune to overpotential 3) Availability of protein 4) Assembly on cathode 5) Robustness S. C. Barton et al., J. Am. Chem. Soc ., 123 , 5802 (2001)

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Proposed instrument for O 2 diminishment by a multicopper oxidase There is a great deal of science going ahead here - no big surprise it is moderate S. C. Barton, et al., Chem. Rev ., 104 , 4867-4886 (2004)

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Schematic of the overpotential issue S. C. Barton, et al., Chem. Rev ., 104 , 4867-4886 (2004)

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Example of a little scale biofuel cell utilizing the mitochondrial cathodic response Examples of little (vitality) scale gadgets utilizing biocatalysis incorporate Adam Heller’s glucose sensor. Numerous samples in writing of working frameworks. Small scale - µW - power creation.

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An energy component anode without Pt? Less muddled science and Pt functions admirably, be that as it may, it there enough of it? Could the H 2/H + response be catalyzed by Fe?

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A manufactured dynamic site copy of iron-just hydrogenase - a bio-roused anode Active site of all-iron hydrogenase Synthetic simple Synthetic simple shows reactant H + lessening on vitreous carbon terminal Tard et al., (Pickett), Nature , 433 , 610 (2005); N&V 433 , 589 (2005)

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Structure of the engineered dynamic site copy of iron-just hydrogenase from DFT computations H + diminishment on a vitreous carbon cathode at 200 mV more positive than cathode alone. Tard et al., (Pickett), Nature , 433 , 610 (2005)

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Mimicking Hydrogenase Synthetic model of dynamic site of a Fe-just hydrogenase Thomas B. Rauchfuss, et al ., J. Am. Chem. Soc., 2001, 123, 9476

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Solar vitality transformation emf pmf Non-organic Biological Photoinduced electron exchange response focuses (sub-atomic level photovoltaics, emf) photovoltaics emf Separate charge film appropriation H + H + wire circulation other electrical work Transducers for: blend work mechanical work transport work driving complex non-direct procedures Halophilic Archaea, bacterioplankton

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Photosynthetic response focuses

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Energetics and electron transport pathways of PS N.B. On account of B Blankenship

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Artificial response focuses Basis is photoinduced electron exchange Minimum prerequisites Donor chromophore ( P ) Suitable electron acceptor ( An) Electronic coupling Useful frameworks require more many-sided quality - Secondary benefactor or acceptor h n P - A  1 P - A 1 P - A  P •+ - A •–

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