Following Electroenzymatic Hydrogen Production by Rotating Ring–Disk Electrochemistry and Mass Spectrometry**

Abstract

File list (3) download file view on ChemRxiv 170121 MS file.pdf (1.13 MiB) download file view on ChemRxiv 170121 Supporting information.pdf (1.82 MiB)

Facile Functionalization of Carbon Electrodes for Efficient Electroenzymatic Hydrogen Production

“…Using double-layer capacitance, we determined the surface area enhancement offered by the use of nanoITO to be 19 on glassy carbon electrodes (Figure S5; note that this is an estimate due to differences in specific capacitances of nanoITO and the underlying GC electrode); accounting for this enhancement yields a corrected electrocatalytic current density that remains >38× the current densities typically obtained on GC electrodes (>6× those typically obtained on PGEs) (Figure S6), reflecting the importance of ITO for efficient [FeFe]-hydrogenase (CpI) immobilization and orientation (improved H 2 production is not only due to increased electrode surface area). Control experiments on O 2 -deactivated hydrogenase from Figure S7 show >80% current loss at −0.8 V vs. SHE, further confirming that the electrocatalytic current originates from hydrogenase and not the nanoITO electrode, consistent with previous O 2 -deactivation experiments . The bioelectrode performance was also investigated under H 2 to understand if nanoITO could influence the reversibility of CpI.…”

“…Control experiments on O 2 -deactivated hydrogenase from Figure S7 show >80% current loss at −0.8 V vs. SHE, further confirming that the electrocatalytic current originates from hydrogenase and not the nanoITO electrode, consistent with previous O 2 -deactivation experiments. 36 The bioelectrode performance was also investigated under H 2 to understand if nanoITO could influence the reversibility of CpI.…”

Solvent Deuterium Isotope Effects of Substrate Reduction by Nitrogenase from Azotobacter vinelandii

“…From the relative distribution of isotopologue products of acetylene, proton, and cyanide reduction assays, the isotope effects of hydrogen/deuterium addition were determined for these processes. Under conditions when a process involves two proton/deuteron transfer steps, each with the same isotope effect, the mole fraction of each of the isotopologue products can be expressed in terms of the isotope effect and the deuterium enrichment of the solvent by the following equations (see Supporting Information for derivation) 40,41…”

“…From the relative distribution of isotopologue products of acetylene, proton, and cyanide reduction assays, the isotope effects of hydrogen/deuterium addition were determined for these processes. Under conditions when a process involves two proton/deuteron transfer steps, each with the same isotope effect, the mole fraction of each of the isotopologue products can be expressed in terms of the isotope effect and the deuterium enrichment of the solvent by the following equations (see Supporting Information for derivation) , X 2 normalH : 0 normalD = I E 2 f normalH 2 false( I E f normalH + f normalD false) 2 X 1 normalH : 1 normalD = 2 I E f normalD f normalH false( I E f normalH + f normalD false) 2 X 0 normalH : 2 normalD = f normalD 2 false( I E f normalH + f normalD false) 2 where X 2H:0D , X 1H:1D , a...…”

“…From the relative distribution of isotopologue products of acetylene, proton, and cyanide reduction assays, the isotope effects of hydrogen/deuterium addition were determined for these processes. Under conditions when a process involves two proton/deuteron transfer steps, each with the same isotope effect, the mole fraction of each of the isotopologue products can be expressed in terms of the isotope effect and the deuterium enrichment of the solvent by the following equations (see Supporting Information for derivation) 40 , 41 where X 2H:0D , X 1H:1D , and X 0H:2D are the mole fractions of the isotopologue product with 2 Hs (C 2 H 4 or H 2 ), 1 H and 1D (C 2 H 3 D or HD), or 2Ds (C 2 H 2 D 2 or D 2 ) incorporated, respectively. IE is the isotope effect of H/D addition ( k H / k D ), and f H and f D are the mole fractions of hydrogen and deuterium in the solvent, respectively.…”