Enhanced activity for the oxygen reduction reaction in microporous water

Electrocatalysis of small gas molecules driven by renewable energy sources offers a promising route to carbon-neutral fuels and chemicals. Such small-molecule conversion reactions rely on water as a source of protons and electrons, however, thus limiting energy and power densities owing to the low solubility of gas molecules in water. The oxygen reduction reaction (ORR) is an exemplar of such limitations. Here we demonstrate that the high O-2-carrying capacity of aqueous solutions endowed with porosity arising from microporous nanocrystals with hydrophobic internal surfaces and hydrophilic external surfaces-termed microporous water-enhances ORR electrocatalysis in water. Use of silicalite-1 nanocrystals to form an O-2-concentrating microporous electrolyte solution increases the ORR current so much that the activity of Pt, typically thought to be an ideal ORR catalyst, is partially limiting, thus allowing the intrinsic catalytic ORR activity of Pt to be measured directly.

Automated summary

Electrocatalysis of small gas molecules using renewable energy sources offers a promising pathway for carbon-neutral fuels and chemicals. However, the low solubility of gas molecules in water limits the energy and power densities of these reactions that rely on water as a source of protons and electrons. In this study, we show that the use of microporous water with hydrophilic external surfaces and hydrophobic internal surfaces significantly enhances the oxygen reduction reaction (ORR) electrocatalysis in water. The use of silicalite-1 nanocrystals as an O-2-concentrating microporous electrolyte solution greatly increases the ORR current, partially limiting the activity of Pt as an ORR catalyst and allowing direct measurement of Pt's intrinsic catalytic ORR activity.