Polydopamine-engineered design of Nafion-free powder electrode with superhydrophilicity/superaerophobicity and superior adhesive structure for efficient overall water splitting

Abstract

Absolute exploitation on the intrinsic catalytic property of powder electrocatalysts always faces the obstacles caused by the existing gas–liquid-solid three-phase interface problem and overwhelming dependence on Nafion usage. Herein, a general polydopamine (PDA)-engineering method is developed to construct Nafion-free powder electrode for efficient overall water splitting. The several nanometer scale PDA coating layers that are self-polymerized on catalyst surfaces, enable the superhydrophilicity/superaerophobicity for more exposed electroactive sites and smoother interfacial mass transfer, and meanwhile, render a superior structural stability inside working electrode with equivalent but more homogeneous adhesion compared with that of Nafion-used electrode. At 300 mA cm−2, the CoMoSxOy@PDA exhibits the low overpotential of 311 mV for OER and 343 mV for HER, and meanwhile demonstrates a cell voltage of only 1.89 V for over 200 h of stable operation and almost unaffected catalytic activity even under harsh ultrasonic working conditions. By theory calculations, the reduced reaction energy barrier for oxygen evolution and the optimized adsorption free energy for hydrogen evolution are revealed in depth.