Effects of Electrochemical Conditioning on Nickel-based Oxygen Evolution Electrocatalysts

Abstract

Electrochemical conditioning via chronopotentiometry (CP) and cyclic voltammetry (CV) is essential for the activation of oxygen evolution reaction (OER) electrocatalysts. While many reports have activated OER electrocatalysts using either CP or CV, the inherent differences between these two electrochemical conditioning methods for the activation of OER electrocatalytic materials have yet to be explored. Here, we investigate the effects of CP and CV electrochemical conditioning on a Ni-based OER precatalyst and substrate in Fe-purified and Fe-unpurified KOH electrolytes by employing (ⅰ) Ni foil, (ⅱ) NiSe precatalyst films with different thicknesses on the fluorine-doped tin oxide glass substrate, and (ⅲ) NiSe precatalyst films on Ni foil substrates. It was found that CV electrochemical conditioning can result in a higher degree of in situ oxidation and Fe incorporation for Ni-based precatalysts and substrates compared to CP electrochemical conditioning. In turn, this brought about different material properties (e.g., in situ oxidized layer thickness, composition, crystallinity, and morphology) and electrochemical characteristics (e.g., active surface area, electron transport limitation, and intrinsic activity) of Ni-based electrocatalysts, thereby not only affecting their OER activity but also complicating the interpretation of the origin of OER activity. This study identifies the distinct effects of CP and CV electrochemical conditioning on Ni-based OER electrocatalysts and provides insight into the choice of the electrochemical conditioning method to better investigate OER electrocatalysts.

Elevated Water Oxidation by Cation Leaching Enabled Tunable Surface Reconstruction

“…Also note that the redox overpotential increases upon cycling for each catalyst, i.e., E p,a increases and E p,c decreases (Figure S18), which is also similar to the behaviour of other Ni-based OER catalysts. [11] This universal phenomenon can possibly be attributed to the sluggish redox kinetics resulting from the thickening reconstructed amor- [18] Ni 0.9 Fe 0.1 O x , [19a] NiFeMo. [19b] phous layer.…”

“…[10] Similarly, Mullins et al reported a significant performance elevation for multiple Ni-based catalysts after electrochemical conditioning, which leads to different degrees of surface reconstruction. [11] In addition to catalytic activity, the redox behaviour of NiFe-based catalysts was also probed. Boettcher et al found that the Ni redox peak position shifts to higher potential and peak intensity decreases with higher Fe content, indicating that Fe can suppress Ni redox processes, which may also influence the reconstruction degree.…”