Using pseudo-steady-state operation to redefine stability in CO2 electrolysis

Whereas chemical reactors can be run for years with limited maintenance, no reactor is inherently stable. Catalysts and components naturally degrade over time. If degradation is slow enough and understood, however, performance losses with time need not impede commercialization. For example, thermochemical reactions can be run at progressively increasing temperatures to compensate for degrading catalysts. In recent years, various electrochemical reactions have been investigated to support the renewable electrification of various sectors, with stability being a key necessity for future use. Unfortunately, in fields such as CO2 electrolysis, more efforts have been placed on achieving stability instead of characterizing degradation, which is a lost opportunity. This Perspective provides a critical reflection on stability—a flawed performance metric—and advocates for a switch in mindset toward characterizing pseudo-steady-state operation. A classification of transient versus pseudo-steady-state degradation mechanisms present in CO2 electrolysis is also provided, along with recommended characterization practices. Collectively, it is advocated that redefining stability is the best way to improve it. A critical necessity of electrochemical catalysts and reactions is that they demonstrate stable operation over time, but what defines something as stable or unstable? This Perspective discusses the complexities of stability in CO2 electrolysis, calling for a re-evaluation and redefinition of stability as a performance metric.