Alkali Cation Interactions with Superoxide Intermediates during the Oxygen Evolution Reaction on Ni_1–xFe_xOOH

Alkali-cation-dependent kinetics have been widely observed for the oxygen evolution reaction (OER); however, reported trends and the underlying mechanism lack consensus. Herein, the OER activity on Ni 1– x Fe x OOH was determined to follow the order Cs + > K +, Na + > Li + . Coupling operando surface-enhanced Raman spectroscopy (SERS) with X 2 O (X = H or D) and H 2 Y O ( Y = 16 or 18) isotope labeling revealed scavenging of superoxide (O–O – ) intermediates in the presence of Li + leading to the formation of Li 2 CO 3, resulting in a modified reaction path and subgrade activity. Ni 1– x Fe x OOH catalytic films revealed stable performance during 18 days of anodic polarization in 1 M XOH at 60 °C. Conversely, severe degradation was observed in 6 M XOH due to delamination of the catalytic coating as well as loss of active sites and formation of unwanted FeOOH and NiO x moieties, regardless of alkali metal cation type.