Au Nanoparticle–polypyrrole Composite Coatings with Enhanced Conductivity and Corrosion Resistance for Ti-Based Porous Transport Layer Anodes in Proton Exchange Membrane Water Electrolysis

Nowadays, Ti-based materials are used as the construction materials of anode porous transport layers (PTLs) in proton exchange membrane water electrolysis (PEM WE). The major limiting factors of Ti anodes include passivation and corrosion. Herein, the challenges are addressed by using selective pulsed electrodeposition (PE), preparing orientated Au nanoparticles (AuNPs) and a degradable polypyrrole (PPy) composite coating (PE-Au/PPy coating) on Ti-based PTLs. The PTL treatment consists of four steps: electropolymerizing of PPy, mechanical polishing of PPy outside the pores of Ti felts, acid etching, and final electrodepositing AuNPs. Testing results show that etched Ti enables AuNPs to be preferentially deposited on the active surface to make the PE-Au/PPy coating highly conductive, effectively inhibiting Ti passivation. PPy formed a conductivity difference with highly active acid-etched Ti, promoting the preferential deposition of AuNPs on the active Ti surface, which improves noble metal utilization. The PE-Au/PPy coating presents a low interfacial contact resistance (ICR) (ca. 0.9 mΩ cm2 at 140 N cm–2) and excellent corrosion resistance (0.17 μA cm–2) in the simulated PEM WE environments. Significantly, the PE-Au/PPy coating exhibits high electrochemical properties and ultralong lifespans of over 1000 h, still with a low ICR (1.5 mΩ cm2), further validating the usefulness of the protective layer. In addition, here the preferential deposition process of AuNPs on the Ti surface is analyzed using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR), clarifying the protective mechanisms in PE-Au/PPy coating. Overall, this work not only shows the great potential of PE-Au/PPy coating as PTL anode materials but also optimizes noble metal utilization.