ORALS

SESSION: ElectrochemistryWedPM1-R10	4th Intl. Symp. on Electrochemistry for Sustainable Development
Wed. 29 Nov. 2023 / Room: Boardroom
Session Chairs: Alexander Oleinick; Ali Seifitokaldani; Session Monitor: TBA

14:05: [ElectrochemistryWedPM105] OS Plenary
IMPORTANCE OF DIFFUSIONAL CONSTRAINTS IN QUANTITATIVE EVALUATION OF CALIBRATION CURVES OF ENZYMATIC MICRO- AND NANOELECTROCHEMICAL SENSORS
Reina Dannaoui¹ ; Xiao-Ke Yang² ; Wei-Hua Huang² ; Irina Svir³ ; Alexander Oleinick⁴ ; Christian Andre Amatore⁵ ; ¹CNRS, ENS - PSL University, Sorbonne University, Paris, France; ²Wuhan University, Wuhan, China; ³CNRS & PSL, Paris, France; ⁴CNRS, Paris, France; ⁵CNRS & PSL, French Academy of Sciences, Paris, France;
Paper Id: 174 [Abstract]

Electrochemical calibration curves recorded at enzyme-modified micro- or nanoelectrodes are often quantitatively analysed using graphical approaches directly inspired from the practice widely used in enzymatic analysis when enzymes as well as their substrate and cofactors are homogeneously distributed in the electrolytic solution [1-3]. We will introduce a concise and simple but highly representative model [4] that demonstrates that this practice yields incorrect interpretation of the experimental results even for simple Michaelis-Menten mechanisms. The present modelling makes it possible to establish the correct relationships linking calibration currents and bulk substrate concentrations by a simple method allowing to take into account the biases due to diffusional constraints when steady or quasi-steady state conditions are achieved as occurs experimentally during calibrations of micro- and nanoelectrochemical sensors.These correct relationships provide kinetic data characterizing a given sensor that ought to be considered whenever a calibrated enzymatic electrochemical sensor is aimed to be used under non-steady state condition, e.g., as for monitoring transient concentration releases of target analytes under in vivo or pseudo in vivo conditions.The authors would like to acknowledge support from joint sino-french CNRS IRP NanoBioCatEchem. CA thanks Xiamen University for his Distinguished Visiting Professor position.

References:
[1] Y. Wang, D. Mishra, J. Bergman, J.D. Keighron, K.P. Skibicka, A.-S. Cans. Ultra-fast glutamate biosensor recordings in brain slices reveal complex single exocytosis transients. ACS Chem.Neurosci. 10 (2019) 1744-1752
[2] X.K. Yang, F.L Zhang, W.T. Wu, Y. Tang, J. Yan, Y.L. Liu, C. Amatore, W.H. Huang. Quantitative Nano-Amperometric Measurement of Intravesicular Glutamate Content and of its Sub-Quantal Release by Living Neurons. Angew. Chem. Int. Ed. 60 (2021) 15803-15808.
[3] M.Yuan, S. Sahin, R. Cai, S. Abdellaoui, D.P. Hickey, S.D. Minteer, R.D. Milton. Creating a Low-Potential Redox Polymer for Efficient Electroenzymatic CO2 Reduction. Angew.Chem. Int. Ed. 57 (2018) 6582-6586.
[4] R. Dannaoui, X.-K. Yang, W.-H. Huang, I. Svir, C. Amatore, A. Oleinick, 2023, submitted.

SESSION: EnergyTueAM-R11	8th Intl. Symp. on Sustainable Energy Production: Fossil; Renewables; Nuclear; Waste handling , processing, & storage for all energy production technologies; Energy conservation
Tue. 28 Nov. 2023 / Room: DiscoRoom
Session Chairs: Manfred Mauntz; Harold Dodds; Session Monitor: TBA

12:25: [EnergyTueAM03] OS Keynote
ATOMIC HYDROGEN CAN BE GENERATED ELECTROCHEMICALLY AND EFFICIENTLY STORED ON SINGLE LAYER GRAPHENE
Dongping Zhan¹ ; Alexander Oleinick² ; Irina Svir³ ; Zhongqun Tian⁴ ; Christian Andre Amatore⁵ ; ¹Department of Chemistry, Xiamen University, Xiamen, China; ²CNRS, Paris, France; ³CNRS & PSL, Paris, France; ⁴Department of Chemistry, Xiamen Uinversity, Xiamen, China; ⁵CNRS & PSL, French Academy of Sciences, Paris, France;
Paper Id: 175 [Abstract]

Provided that hydrogen can be safely stored and transported at high densities, hydrogen fuel cells would offer highly efficient and completely environmentally friendly solutions for vehicle propulsion. However, neither compressed gas nor liquid hydrogen seems safe enough for everyday use in mobile applications given the risk of accidents and their possible consequences in urban environments related to the high flammability of hydrogen. Therefore, approaches consisting in adsorbing hydrogen atoms (i.e., H rather than H2) appear to offer an excellent solution for its storage in order to propel light and heavy vehicles in urban environments and evidently in between cities. Moreover, compared to solutions based on electric batteries, the ecological and environmental advantage would be obvious.Among the possible materials for storing hydrogen, graphene (Gr) has been suggested to be one of the most promising materials provided that a significant H/Gr weight ratio (ww%) is achieved. Specifically, the US Department of Energy (DOE) has set a target of 5.5 ww% to be achieved by 2025 as a condition for becoming operational. This goal is however extremely far from what can be achieved presently by direct storage of hydrogen molecules (H2) even using single graphene monolayers (SLGr) by physical adsorption because this requires extreme temperatures and pressures given the too weak attractive van der Waals forces and the stability of H2 with respect to its two dissociated atoms (H) and the intrinsic stability of the graphene sp2-carbon resonant network.In this respect, if possible, a stable chemical adsorption of atomic hydrogen on SLGr appears as the Holy Grail with a theoretical maximum storage capacity of 7.7 ww% for Gr-H atomic adducts and optimal safety conditions and performance. However, generating compact Gr-H adducts from H2 again requires extreme temperatures and pressures.On the contrary, hydrogen atoms can easily be produced under mild conditions by electrochemical reduction of common aqueous acidic solutions at the surface of a platinum nanoelectrode placed in straight contact with a SLGr (see adjacent figure) and spread spontaneously on the graphene sheet by reversible adsorption and site to site hopping diffusion at room temperature and atmospheric pressure and without significantly distorting the graphene geometry suggesting a physisorption rather than a covalent bonding [1]. The amount of platinum needed is minimal because it only serves as a catalyst as we were able to demonstrate using dynamic electrochemistry and SERS isotopic Raman spectroscopy. In addition, the process significantly rapid kinetics and its storage capacity (6.6 ww%, viz., more than 85% of the theoretical maximum, being already higher than the target set by DOE [2]) are associated with a substantial stability of the Gr-H layers at room temperature and atmospheric pressure. Furthermore, one would not need to proceed through the intermediacy of hydrogen gas for Gr-H reservoir loading, nor for its unloading to feed fuel cells anodes, removing then two important steps. The authors would like to acknowledge support from joint sino-french CNRS IRP NanoBioCatEchem. CA thanks Xiamen University for his Distinguished Visiting Professor position.

References:
[1] Q. He, L. Zeng, L. Han, M.M. Sartin, J. Peng, J.F. Li, A. Oleinick, I. Svir, C. Amatore, Z.Q. Tian, D. Zhan. Electrochemical Storage of Atomic Hydrogen on Single Layer Graphene J. Am. Chem. Soc., 143, 2021, 18419–18425.
[2] Hydrogen and Fuel Cell Technologies Office. Target Explanation Document: Onboard Hydrogen Storage for Light-Duty Fuel Cell Vehicles. https://www.energy.gov/eere/fuelcells/downloads/target-explanation-document-onboard-hydrogen-storagelight-duty-fuel-cell.