Preparation Of Janus Electrode And Its Application In Gas Involving Electrochemical Reactions

Gas involving electrochemical reactions are of much importance in new clean energy and environmental fields,such as hydrogen and oxygen evolution reactions in electrolysis water process;Hydrogen oxidation and oxygen reduction reactions of hydrogen fuel cell;Chlorination reactions in the chlor-alkali industry.However,the limited solubility and insufficient diffusion of gas species in electrolyte would lead to bubble adhesion in gas evolution reactions and insufficient gas supply in gas consumption reactions,so as to affect the working efficiency of electrode.Apart from developing the new materials with excellent catalytic properties,the gas-liquid-solid multiphase mass transfer process and bubble behavior at the electrode has also been demonstrated to be critical for the performance improvement.Janus material is a special kind of material with asymmetric structure,its excellent mass transfer properties make it a promising three-phase reaction substrate.In this study,we have designed and demonstrated the Janus electrode with asymmetric wettability,realizing bubble unidirectional transportation in electrocatalytic-water splitting processes.After the optimization of the Janus electrode,the working efficiency of the Janus electrode in hydrogen evolution and oxygen reduction devices were investigated respectively,demonstrate it a promising application.The specific research results are listed as follows:1.The electrochemically generated bubbles by gas evolution reactions 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 catalyst with well-balanced hydrophobicity,respectively;affording unidirectional transportation of as-formed gaseous hydrogen 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.2.The synthesis of hydrogen peroxide by electrochemical oxygen reduction reaction as a green alternative to anthraquinone method has attracted wide attention.However,the traditional oxygen reduction reactions need to pump oxygen or air into the electrolyte,due to low oxygen solubility and diffusion rate in the electrolyte,and thus leading to high diffusion resistance and severe efficiency loss.Herein we propose a Janus electrode with superaerophilic side to promote air diffusion to the active site,with superaerophobic carbon nanotubes as catalyst on the other side.In the oxygen reduction reaction,the Janus electrode was placing over the electrolyte with the aerophilic side facing the air and the aerophobic catalyst side facing the electrolyte.The air was effectively introduced to the catalyst side,thus overcoming the gas diffusion limitation.The optimized wettability on the electrode promoted higher H2O2 production rate(140 mg/L·h)and with 1.5 folds higher current efficiency than weak-aerophilic one.When the electrode applied into electro-Fenton experiment,the removal rate of rhodamine organic dyes in the solution reached 73%after 60 minutes.