The Significance of Properly Reporting Turnover Frequency in Electrocatalysis Research

Abstract

For decades, turnover frequency (TOF) has served as an accurate descriptor of the intrinsic activity of a catalyst, including those in electrocatalytic reactions involving both fuel generation and fuel consumption. Unfortunately, in most of the recent reports in this area, TOF is often not properly reported or not reported at all, in contrast to the overpotentials at a benchmarking current density. The current density is significant in determining the apparent activity, but it is affected by catalyst‐centric parasitic reactions, electrolyte‐centric competing reactions, and capacitance. Luckily, a properly calculated TOF can precisely give the intrinsic activity free from these phenomena in electrocatalysis. In this Viewpoint we ask: 1) What makes the commonly used activity markers unsuitable for intrinsic activity determination? 2) How can TOF reflect the intrinsic activity? 3) Why is TOF still underused in electrocatalysis? 4) What methods are used in TOF determination? and 5) What is essential in the more accurate calculation of TOF? Finally, the significance of normalizing TOF by Faradaic efficiency (FE) is stressed and we give our views on the development of universal analytical tools to determine the exact number of active sites and real surface area for all kinds of materials.

In situ grown oxygen-vacancy-rich copper oxide nanosheets on a copper foam electrode afford the selective oxidation of alcohols to value-added chemicals

“…TOF is another important intrinsic indicator that determines the efficiency of a catalyst for the target reaction. However, before reporting TOF, one must ensure accurate determination of TOF free from any misleading calculations see Supplementary Note 7 for further details 41 . The as-prepared CuO/CF exhibit an outstanding TOF acetate (5.8k s −1 ) and TOF formate (6k s −1 ) normalized by their respective FE at an applied potential of 1.82 V vs. RHE (Supplementary Fig.…”

Recent advances in non‐precious Ni‐based promising catalysts for water splitting application

“…However, the TOF data not only report catalytic performance but also offer catalyst activity results. In catalyst, current density is considered with other essential parameters like the magnitude of TOF, which is a function of overpotential 51 …”

“…It gives the amount of product produced per unit of time for the available catalyst. 51 The TOF is calculated using the following equation 48,52 :…”

“…In catalyst, current density is considered with other essential parameters like the magnitude of TOF, which is a function of overpotential. 51…”

“…It is simple and straight‐forward intrinsic activity that presents the efficiency of a catalyst in terms of reaction interest. It gives the amount of product produced per unit of time for the available catalyst 51 . The TOF is calculated using the following equation 48,52 : In this equation, , , , , and are respectively the current density, surface area of the electrocatalyst, number of electrons, Faraday's constant, and the number of moles (two for HER and four for OER).…”