Influence of the catalyst layer thickness on the determination of the OER activity of Fe3O4@CoFe2O4 core-shell nanoparticles

Core–shell Fe3O4@CoFe2O4 nanoparticles as high-performance anode catalysts for enhanced oxygen evolution reaction

“…The increase in the Tafel slope at higher potentials may be related to the ohmic resistance across the catalytic layer. 29 At the higher potential, the Tafel slope of the Co (1−x) Fe (2+x) O 4 particles exceeds the one for core-shell NPs, which is in agreement with the lower conductivity of the cobalt ferrite NPs. Finally, the mediumterm stability of core-shell CS-3 NPs was studied using chronoamperometry at 1.65 V vs. RHE.…”

“…With Tafel slopes being often used for mechanistic interpretations, one should note that they are often affected by ohmic losses in catalytic layers. 29 Indeed, Tafel slopes increase with the electrode potential (Fig. 3B), notably for the Co (1− x ) Fe (2+ x ) O 4 NPs.…”

“…33 Additionally, we also showed that the OER activity of such Fe 3 O 4 @CoFe 2 O 4 NPs is signicantly enhanced by a thicker CoFe 2 O 4 shell although the resistivity of the NP layer increases. 29 It seems that the insulating properties of Co ferrite are compensated for by a larger number of active sites on the NP surface. It is worth noting that the Co-weighted activity of the most active Fe 3 O 4 @CoFe 2 O 4 core-shell NPs (CS-3) greatly outperforms that of TMO catalysts, either with uniform or core-shell structures, which were reported in the literature (Table S4 †).…”

“…28) the NP loading was set between ∼1 and 4 μg cm −2 (for more details regarding the influence of the NP loading on the apparent activity the reader is referred to ref. 29). In order to compare our results with the literature, current–potential curves were normalized in three different ways: to the mass of metal oxide, to the mass of cobalt (Co being considered a ‘strategic’ element), and to the NP surface area (estimated from the TEM mean diameter), see Fig.…”