Electrocatalytic Conversion of Renewable Electricity-What Molecules are More Promising as Energy Storage Media?

An analysis is conducted with the intention to clarify which molecules are more promising as renewable electricity storage media, taking into consideration some basic parameters like theoretical and practical voltage, theoretical energy density, etc. The central aspect of analysis is to apply sufficiently simple, but relevant criterion, the minimum cost of electricity required to produce a specific quantity of chemical energy storage medium, in relation to the prevailing market prices of the produced chemicals. Therefore, the study analyzes the cost of electrical energy needed to selectively convert CO₂ into specific molecules such as, CO, CH₃OH, and CH₄, among others, water into hydrogen, and nitrogen into ammonia, by considering both idealized and more realistic operational conditions. The results show that in the case of energy carriers that are too expensive to be generated under idealized conditions, further detailed analysis of other production factors is inconsequential. The production of hydrogen, formic acid, and syngas (CO and H₂) as energy carriers is economically feasible under realistic operational conditions. It is also conceivable that further electricity-to-chemical conversion efficiency gains can be realized for these molecules thus underscoring the need for their prioritization.