Nickel−iron−based electrocatalysts have been studied for decades as highly active anodes for the oxygen evolution reaction (OER) in alkaline media. Despite this long history, reports on their dissolution stability remain inconsistent, ranging from substantial Fe dissolution to significant losses of both Ni and Fe, or even negligible metal dissolution. Resolving these discrepancies is essential for a reliable assessment of catalyst durability. Here, electrodeposited NiFe oxyhydroxides, a commercial NiFe layered double hydroxide, and reference FeOOH and NiOOH films were investigated to elucidate the dissolution behavior of Ni and Fe in NiFe-based OER catalysts. A scanning flow cell coupled to inductively coupled plasma mass spectrometry was employed, combining conventional online measurements with a quasi-online accumulation approach to probe dissolution processes below the detection limits of standard online techniques while avoiding artifacts associated with offline analyses. While Fe dissolution is readily detected for FeOOH in online measurements, it is strongly suppressed in NiFe-based catalysts and becomes apparent only when accumulation protocols are employed, particularly at higher electrolyte alkalinity. In contrast, nickel remains essentially stable toward ionic dissolution under all investigated conditions. Overall, this work helps set the record straight by showing that reported Ni losses are likely dominated by particle detachment rather than true dissolution, whereas the apparent absence of Fe dissolution in many studies can arise from insufficient detection sensitivity. Beyond alkaline OER, the accumulation strategy presented here has the potential to be applied to other electrochemical systems where dissolution processes occur below the sensitivity limits of conventional online techniques.
Silva et al. (Tue,) studied this question.
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