Enabling Hypoxic Electroanalysis Using Dense Gases in a Fish Tank

For many years, traditional deoxygenation methods, including gloveboxes and inert gas purging systems, have been essential for air- and moisture-sensitive electroanalysis. These techniques have offered opportunities to make discoveries in systems that are not accessible under ambient conditions. However, these methods limit dexterity, require frequent maintenance, and introduce potential risks to the data quality. These challenges restrict the accessibility of hypoxic electroanalysis. One main practice electrochemists have come to depend on is blanketing the inside of their electrochemical cells with argon gas. Unfortunately, this practice enhances solution evaporation and may result in unwanted convection. Here, we propose a practical alternative to creating and maintaining a hypoxic environment using a dense gas blanket in a fish tank (or any other such tank). By filling the enclosure with dense gas, such as butane or argon, we form a barrier that suppresses dioxygen re-entry and moisture intrusion, providing a low-humidity, hypoxic, stable environment over extended periods. Through time-resolved cyclic voltammograms and continuous monitoring of dioxygen and humidity, we demonstrate that dense gases delay by hours the return of atmospheric dioxygen compared with traditional argon purging. Most importantly, the oxygen reduction reaction peak reappears after ∼ 20 h in butane and ∼ 10 h in argon, whereas it reappears within minutes under ambient conditions and after 5 h in a nitrogen-filled tank. The large volume and accessibility of the fish tank allow for the ease of manipulation of the system without compromising the hypoxic environment. Our results support the effective use of dense gases to prevent atmospheric dioxygen diffusion and moisture re-entry, conserving hypoxic conditions suitable for oxygen-sensitive electroanalysis that minimize limitations associated with conventional methods.