Enhancing oxygen evolution reaction by cationic surfactants

Abstract

Oxygen evolution reaction is critical for water splitting or metal-air batteries, but previous research mainly focuses on electrode material or structure optimization. Herein, we demonstrate that surfactant modification of a NiFe layered double hydroxide (LDH) array electrode, one of the best catalysts for oxygen evolution reaction (OER), could achieve superaerophobic surface with balanced surface charges, affording fast mass transfer, quick gas release, and boosted OER performance. The assembled surfactants on the electrode surface are responsible for lowering the bubble adhesive force (∼ 1.03 µN) and corresponding fast release of small bubbles generated during OER. In addition, the bipolar nature of the hexadecyl trimethyl ammonium bromide (CTAB) molecule lead to bilayer assembly of the surfactants with the polar ends facing the electrode surface and the electrolyte, resulting in neutralized charges on the electrode surface. As a result, OH− transfer was facilitated and OER performance was enhanced. With the modified superaerophobic surface and balanced surface charge, NiFe LDHs-CTAB nanostructured electrode showed ultrahigh current density increase (9.39 mA/(mV cm2)), 2.3 times higher than that for conventional NiFe LDH nanoarray electrode), dramatically fast gas release, and excellent durability. The introduction of surfactants to construct under-water superaerophobic electrode with in-time repelling ability to the as-formed gas bubbles may open up a new pathway for designing efficient electrodes for gas evolution systems with potentially practical application in the near future.