(528d) Is Potential of Zero Charge a Causal Descriptor for Solvent Dynamics in the Reversible Hydrogen Electrode?
AIChE Annual Meeting
Wednesday, November 10, 2021 - 4:15pm to 4:30pm
Here, we investigate through single-crystal voltammetry the importance of the interfacial electric field strength on hydrogen reaction kinetics using three complementary approaches: (1) correlating the potential of zero free charge (pzfc) with reaction kinetics using caffeinated Pt as a model surface; (2) varying the electrolyte ionic strength at constant pH; and (3) probing solvent dynamics via kinetic isotope effects. Our results show that pzfc seems to correlate with HER/HOR kinetics, but kinetic isotope effects on caffeinated Pt also suggest that the effect more likely originates from activation barriers to the reaction elementary steps than from electric field effects on solvent dynamics.Although the importance of interfacial phenomena such as the electrodeâs pzfc and water reorganization energy are well established, the pzfc may not be a mechanistic descriptor of the alkaline hydrogen reaction kinetics. Surface additives such as caffeine may help elucidate the origin behind the slow alkaline HER/HOR kinetics and ways to manipulate it.