The Pitfalls of Using Potentiodynamic Polarization Curves for Tafel Analysis in Electrocatalytic Water Splitting

Abstract

Scheme 1. Graphical Sketch Advocating against the Use of Dynamic LSV/CV Responses for Deriving Tafel Plots a a TS and j 0 denote Tafel slope and exchange current density, respectively.

Unraveling the Mechanisms of Electrocatalytic Oxygenation and Dehydrogenation of Organic Molecules to Value‐Added Chemicals Over a Ni–Fe Oxide Catalyst

“…Another evidence for the distinctness between the OER and MOR mechanisms is the striking difference between the Tafel slopes. [ 33,34 ] While the OER exhibits a Tafel slope of 190 mV dec −1 , [ 35,36 ] the MOR has a Tafel slope of only 39 mV dec −1 (Figure 2e). This difference indicates more facile kinetics for the MOR than for the OER and different rdss for the two processes.…”

Activating Both Basal Plane and Edge Sites of Layered Cobalt Oxides for Boosted Water Oxidation

“…In addition to the Tafel plots obtained from the LSV curves (Figure S4, Supporting Information), steady‐state Tafel measurements are also provided (Figure 3c and Figure S5, Supporting Information). [ 24 ] Different Tafel slopes imply varied rate‐determining steps (RDSs), and a smaller Tafel slope value indicates better OER kinetics. The LCF electrocatalyst possessed a Tafel slope of 70 mV dec −1 , which is much smaller than the 86 mV dec −1 of the initial LC electrocatalyst.…”

The Significance of Properly Reporting Turnover Frequency in Electrocatalysis Research

“…[11][12][13][14][15] Conventionally,i na ll electrocatalysis studies,aset of activity markers are used to benchmark the performance of ac atalyst or as et of catalysts.A mong them, the most frequently used activity markers are overpotential (h)a nd exchange current density (j 0 ). [16][17][18][19][20][21] Overpotential is the measure in volts that describes the additional electromotive force required by the catalyst to begin the reaction from its equilibrium potential (mathematically, h = EÀE 0 ). In the determination of overpotential, several practices have been followed, such as reporting the onset overpotential, half-wave potential, or ap otential at af ixed current density.…”

“…The j 0 introduced earlier is another activity marker which is simply the current that flows across the catalytic interface at the reversible or equilibrium potential of the reaction under study. [17,20,38] This is generally obtained from the extrapolation of the linear portion of the Tafel line.However,because of the limitations in using potentiodynamic polarization curves for Tafel analysis and the effect of uncompensated resistance (R u ) that exists in all electrical circuits,the precise calculation of j 0 has been an ongoing problem. [20] Despite all these ambiguities,t he overpotential determined with ac urrent response normalized using the geometrical area of the electrode and the j 0 determined from aT afel line,which is in turn extracted from potentiodynamic polarization curves,have been used as the primary markers without ab road understanding that these markers only reflect the apparent activity and not the intrinsic activity.…”