New Insights into Cations Effect in Oxygen Evolution Reaction

Abstract Cations effect has been proposed to impact electrochemical activity, but the exact role of cations underlying the enhanced current density remains debated. Here, by rational design of the electrochemical process, we were able to identify the crucial role of cations in determining the electrochemical activity of oxygen evolution reaction (OER). The intentional addition of Fe cations leads to an increase in current density as much as 49.1% at applied potential of 2.2 V (vs RHE), while a decrease of 6.9% were observed in the presence of Cu cations. By following the valence state of surface Ni, we present direct evidence that the enhanced electrochemical activity originating from the addition of cations is independent of oxidation potential of surface Ni. Further investigation suggests that the cations additions mainly affect the charge and electrically active species transfer on the interface of electrocatalysts and electrolyte, thus contributing the variation in reaction paths and the activation of the typical less accessible sites. With the assistant of the trace Fe cations (smaller than 4 × 10−5 mol/L), the similar OER activity can be achieved even using 50% concentration of original electrolyte. The present study provides insight into cations effect and can serve as guidance for advanced energy-related device design.