Electron transfer accelerated polymer-TiO2 coatings for enhanced photocatalytic activity in photocathodic protection

The concept of integrated design with TiO2 photoanode coating generally encounters the problem of sluggish carrier transport in the coating due to inactive additives. The theoretical calculation and the corresponding experiment results suggest that the incorporation of polyacrylic acid (PAA) binder into TiO2 nanoparticles can enhance electron transport capability by chemical bonding between TiO2 and PAA. To construct a three-dimensionally interconnected network in the TiO2 matrix, sodium carboxymethyl cellulose (CMC) is introduced into PAA. An integrated photoanode coating with multicomponent interlinking among TiO2-PAA-CMC is realized by spin-coating method followed by thermal treatment in a vacuum. The photoanode exhibits good mechanical stability and superior photoelectrochemical performance for photocathodic protection of 304 stainless steel with a high photo-induced current of 61.26 μA cm−2 and a low corrosion potential of −550 mV under simulated solar irradiation in 3.5% NaCl electrolyte. Fourier transform infrared spectroscopy and electron paramagnetic resonance attribute the supreme performance to the interfacial –COO– bond among TiO2-PAA-CMC and the enhanced conductivity of dehydrated nonconjugated radical polymer CMC for charge transfer and transport respectively. It paves the way to exploit stable and efficient TiO2-based coatings for photoelectrochemical applications.