Redox switching and oxygen evolution electrocatalysis in polymeric iron oxyhydroxide films

Area of Science:

• Electrochemistry
• Materials Science
• Surface Chemistry

Background:

• Iron oxyhydroxide films exhibit complex redox switching and electrocatalytic properties.
• Understanding the oxygen evolution reaction (OER) is crucial for energy conversion technologies.

Purpose of the Study:

• To examine the redox switching characteristics of multicycled iron oxyhydroxide films.
• To elucidate the kinetics and mechanism of the oxygen evolution reaction (OER) on these films.
• To quantify charge percolation through the hydrous layer.

Main Methods:

• Cyclic voltammetry to quantify charge transport diffusion coefficient (D(CT)).
• Steady-state Tafel plot analysis to study OER kinetics.
• Electrochemical impedance spectroscopy (EIS) for mechanistic insights.

Main Results:

• Charge transport diffusion coefficient (D(CT)) determined to be approximately 3 x 10(-10) cm2 s(-1).
• Dual Tafel slope behavior observed for OER (60 mV dec(-1) at low overpotentials, 120 mV dec(-1) at high overpotentials).
• Reaction order with respect to hydroxide ion activity shifts from 3/2 to 1 with increasing potential.

Conclusions:

• A kinetic model involving Temkin adsorption and a physisorbed hydrogen peroxide intermediate explains the OER mechanism.
• The potential-dependent surface coverage of intermediates accounts for the dual Tafel slope behavior.
• Findings provide a deeper understanding of iron oxyhydroxide electrocatalysis for OER.