When the Experiment Starts Before You Think: Vapor-Induced Pre-Poisoning of Electrodes in Alcohol Electrooxidation

For decades, electrochemists have struggled with the same problem: Alcohol oxidation on Pt tends to show run-to-run variability. Peaks appear, disappear, or shift unpredictably, leaving mechanistic studies plagued by irreproducibility. Here it is uncovered why. Pt electrodes, it turns out, begin reacting before any potential is applied. Vapors from volatile alcohol reactants silently adsorb and decompose on the metal surface at open circuit, before the working electrode is connected and immersed into the electrolyte, forming strongly bound intermediates that poison the electrode within seconds. The result: the catalyst enters the experiment already altered, and the first voltammetric cycle no longer reflects a clean state. This vapor-induced pre-poisoning explains long-standing inconsistencies across laboratories and experiments. Strikingly, this phenomenon reaches far beyond alcohol oxidation. In reality, any system involving volatile reactants or reactive intermediates can silently initiate chemistry at open circuit, altering the catalyst before the experiment even starts. This realization forces a paradigm shift: electrocatalytic reactions may already be underway before we think they have begun—calling into question how we prepare, interpret, and ultimately trust electrochemical data. Fortunately, in most cases, there is a simple way to restore the pristine response, which will be described together with other strategies for an accurate analysis of the reaction reactivity and mechanism.