Breathing-Mimicking Electrocatalysis for Oxygen Evolution and Reduction

Electrocatalytic oxygen evolution and reduction reactions play a central role in clean energy technologies. Despite recent efforts to achieve fast gas reactant delivery to the reaction interface, efficient gas product evolution from the catalyst/electrolyte interface remains challenging. Inspired by the mammalian breathing process, here we developed an efficient electrocatalytic system to enable ample gas-solid-liquid three-phase contact lines and bidirectional gas pathways for evolution and consumption. During the oxygen evolution reaction, the newly formed O2 molecules quickly diffuse to the gas phase, waiving the bubble formation energy in the electrolyte. A record low overpotential of 190 mV at 10 mA⋅cm−2 was achieved using Au/NiFeOx catalysts. During the oxygen reduction reaction, O2 gas can transport to the catalyst/electrolyte interface, overcoming low O2 solubility in water and leading to ∼25-fold higher current densities for Ag/Pt bilayer nanoparticle catalysts. This breathing-mimicking design demonstrates efficient three-phase catalysis with a minimal catalyst thickness. [Display omitted] •The electrode design mimics the essence of the mammalian two-way breathing pattern•Ample gas-liquid-solid three-phase contacts are achieved with a small catalyst loading•Newly formed O2 in OER can diffuse to gas phase without bubble formation energy•O2 gas reactant in ORR can be quickly delivered to the catalyst/electrolyte interface The critical crisis of fossil fuel usage and emission has been driving the development of clean energy technologies, such as hydrogen production from water splitting and fuel cells to produce electricity. The optimization of both technologies should rely not only on rational realization of electrocatalyst compositions and structures but also on the efficient gas delivery from and to the catalyst surface. In this work, to mimic the mammalian alveoli with two-way breathing process, we demonstrate a pouch-type catalytic system for (1) efficient gas product evolution from and (2) gas reactant delivery to the catalyst surface, corresponding to oxygen evolution and reduction reactions, respectively. This design enables outstanding electrocatalytic performances with ample gas-liquid-solid three-phase contact interfaces and a small sub-100-nm catalyst thickness. Inspired by the breathing process of mammalian alveoli, we developed a breathing-mimicking, pouch-type, nanoporous polyethylene (PE) structure for two-way efficient gas transport f