TY  - JOUR
AU  - Zhu, Xinwei
AU  - Huang, Jun
AU  - Eikerling, Michael
TI  - pH Effects in a Model Electrocatalytic Reaction Disentangled
JO  - JACS Au
VL  - 3
IS  - 4
SN  - 2691-3704
CY  - Washington, DC
PB  - ACS Publications
M1  - FZJ-2023-01478
SP  - 1052–1064
PY  - 2023
AB  - Varying the solution pH not only changes the reactant concentrations in bulk solution but also the local reaction environment (LRE) that is shaped furthermore by macroscopic mass transport and microscopic electric double layer (EDL) effects. Understanding ubiquitous pH effects in electrocatalysis requires disentangling these interwoven factors, which is a difficult, if not impossible, task without physical modeling. Herein, we demonstrate how a hierarchical model that integrates microkinetics, double-layer charging, and macroscopic mass transport can help understand pH effects of the formic acid oxidation reaction (FAOR). In terms of the relation between the peak activity and the solution pH, intrinsic pH effects without consideration of changes in the LRE would lead to a bell-shaped curve with a peak at pH = 6. Adding only macroscopic mass transport, we can already reproduce qualitatively the experimentally observed trapezoidal shape with a plateau between pH 5 and 10 in perchlorate and sulfate solutions. A quantitative agreement with experimental data requires consideration of EDL effects beyond Frumkin correlations. Specifically, the peculiar nonmonotonic surface charging relation affects the free energies of adsorbed intermediates. We further discuss pH effects of FAOR in phosphate and chloride-containing solutions, for which anion adsorption becomes important. This study underpins the importance of a full consideration of multiple interrelated factors for the interpretation of pH effects in electrocatalysis.
LB  - PUB:(DE-HGF)16
C6  - 37124300
UR  - <Go to ISI:>//WOS:000978886200001
DO  - DOI:10.1021/jacsau.2c00662
UR  - https://juser.fz-juelich.de/record/1005447
ER  -