Unseen but Avoidable: How Impurities Bias Electrocatalysis from Interface to Interpretation

Abstract Impurities exert profound effects on electrocatalytic measurements and interpretations. Trace levels of contaminants introduced through electrolytes, electrodes, gases, or cell materials routinely generate false activity signals, accelerate degradation, and alter product selectivity. This review categorizes impurity effects by functional impact, including misleading activity, compromised stability, and shifted selectivity, and offers strategies to recognize, isolate, and mitigate these influences. We argue that reliable and reproducible electrocatalytic data require an impurity-aware approach, integrating both experimental protocols and systems engineering. By intentional design, impurities can be transformed from hidden liabilities into controlled variables, ensuring that reported advances in electrocatalysis reflect intrinsic catalyst properties and translate into durable energy technologies.