Ev nova problem with cheap reactor5/7/2023 The accuracy of the model was then confirmed by predicting the current density outcome of each experiment. Independently, a FEM was developed from basic physical principles and enzyme-activity dependence studies for pH, buffer concentration, and substrate concentration. The pH-activity solution assays for H 2ase and FDH had previously been undertaken, showing an optimum pH of 6 and 7.1, respectively ( SI Appendix, Fig. For this purpose, DvH H 2ase and DvH W-FDH were chosen as enzymes with high activity for their respective reduction reactions and low product inhibition ( SI Appendix, Fig. First, for the HER and then for the CO 2RR, the change in local pH on mesoporous electrodes was studied bioelectrochemically by the current density obtained in solutions with buffers of different pK a. Here, the local chemical environment of enzymatic HER and CO 2RR systems was studied by bioelectrochemistry and computational methods using a finite element model (FEM). Porous electrodes enable higher enzyme loading, and hence higher current densities, improving the overall performance by increasing the consumption or production of desired chemicals ( 10– 15). Bioelectrochemistry on thin-film electrodes has long provided mechanistic and analytical insight into enzyme function as well as established bioelectrolysis as a potential method of product synthesis ( 1, 3, 9). Formate dehydrogenases (FDHs) have similarly garnered attention due to their ability to reversibly reduce CO 2 to formate, with high selectivity when immobilized on an electrode ( 5– 8). Hydrogenases (H 2ases) combine protons and electrons to reversibly produce H 2 at the thermodynamic potential using Fe or NiFe active sites and have therefore been extensively studied as a model system for reversible electrocatalysis ( 3, 4). These considerations and insights can be directly applied to both bio(photo)electrochemical fuel and chemical synthesis, as well as enzymatic fuel cells, to significantly improve the fundamental understanding of the enzyme–electrode interface as well as device performance.Įnzymatic electrochemistry has rapidly expanded into research fields that encompass applications across disciplines from fundamental understanding of enzymology to biosensors, biofuel cells, and semiartificial photosynthesis ( 1, 2). This research emphasizes the critical importance of understanding the confined enzymatic chemical environment, thus expanding the known capabilities of enzyme bioelectrocatalysis. When applied to macroporous inverse opal electrodes, the benefits of higher loading and increased mass transport were employed, and, consequently, the electrolyte adjusted to reach −8.0 mA ⋅ cm −2 for the H 2 evolution reaction and −3.6 mA ⋅ cm −2 for the CO 2 reduction reaction (CO 2RR), demonstrating an 18-fold improvement on previously reported enzymatic CO 2RR systems. This improved understanding of the local environment enabled simple manipulation of the electrolyte solution by adjusting the bulk pH and buffer pK a to achieve an optimum local pH for maximal activity of the immobilized enzyme. Here, we apply electrochemical and computational techniques to explore the local environment of fuel-producing oxidoreductases within porous electrode architectures. While the local chemical environment has been studied in small-molecule and heterogenous electrocatalysis, conditions in enzyme electrochemistry are still commonly established based on bulk solution assays, without appropriate consideration of the nonequilibrium conditions of the confined electrode space. Bioelectrochemistry employs an array of high-surface-area meso- and macroporous electrode architectures to increase protein loading and the electrochemical current response.
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