Anti-buoyancy and Unidirectional Gas Evolution by Janus Electrodes with Asymmetric Wettability.

The bubbles electrochemically generated by gas evolution reactons are commonly driven off the electrode by buoyancy, a weak force used to overcome bubble adhesion barriers, leading to low gas transporting efficiency. Herein, a Janus electrode with asymmetric wettability has been prepared by modifying two sides of a porous stainless-steel mesh electrode, with superhydrophobic polytetrafluoroethylene (PTFE) and Pt/C (or Ir/C) catalyst with well-balanced hydrophobicity, respectively; affording unidirectional transportation of as-formed gaseous hydrogen and oxygen from the catalyst side to the gas-collecting side during water splitting. "Bubble-free" electrolysis was realized when "floating" the Janus electrode on the electrolyte. Anti-buoyancy through-mesh bubble transportation was observed when immersing the electrode with PTFE side downward. The wettability gradient within the electrode endowed sticky states of bubbles on the catalyst side, resulting in efficient "bubble-free" gas transportation with 15 folds higher current density than submerged states.