Kinetics and Mechanism of the Electrooxidation of Formic Acid—Spectroelectrochemical Studies in a Flow Cell

Abstract

Go with the flow: A novel spectroelectrochemical flow cell with well‐defined mass transport allows time‐resolved electrochemical and in situ FTIR spectroscopy measurements under continuous electrolyte flow (e.g. during electrolyte exchange). Its potential for mechanistic and kinetic studies was demonstrated in studies on the electrooxidation of formic acid.

Voltage Inversion Caused by Self-organized Oscillations in a Direct Formic Acid Fuel Cell

“…To better assess the dynamics of these oscillations, it was selected a current value where the system presents kinetic instability, 0.076 A cm -2 , and a chronopotentiometry was performed to evaluate how the voltage evolves over time, figure 1B. It can be seen that between about 0.13 and -0.05 V there is a slow poisoning of the anode electrode due to carbon monox-ide adsorbed (CO ad ) from the dehydration of weakly adsorbed formic acid [10]. Another stable intermediate that also contributes to the loss of electrode activity is the bridgedbonded formate (HCOO ad ) which, like CO ad , inhibits the direct oxidation pathway of formic acid [10] [11].…”

“…It can be seen that between about 0.13 and -0.05 V there is a slow poisoning of the anode electrode due to carbon monox-ide adsorbed (CO ad ) from the dehydration of weakly adsorbed formic acid [10]. Another stable intermediate that also contributes to the loss of electrode activity is the bridgedbonded formate (HCOO ad ) which, like CO ad , inhibits the direct oxidation pathway of formic acid [10] [11]. Eventually the electrode reaches a critical coverage of catalytic poisons and, in order to keep the current constant, the anode overpotential increases (therefore the cell voltage decreases) leading to the formation of oxygenated species on platinum.…”

On the activation energy of the formic acid oxidation reaction on platinum electrodes

“…On the other hand, the reaction route which gives directly CO 2 is called the direct oxidation route. For this route, the nature of the intermediate is still subject of discussion [4][5][6][7][8][9][10][11].…”

ATR-SEIRAS study of CO adsorption and oxidation on Rh modified Au(111-25 nm) film electrodes in 0.1 M H2SO4

“…This effect allows distinguishing the orientation of adsorbed molecules. Direct access to chemical information on structure and dynamics of the electrode/electrolyte interfaces can be provided by this in situ spectroscopic approach, which has been employed as a powerful tool in the investigations of catalytically-active solid/liquid interfaces [38][39][40][41]. However, the ATR-SEIRAS technique requires the use of thin film electrodes, which usually have a less ordered surface structure than bulk single crystal electrodes.…”