Stability of a Pyrimidine-Based Dye-Sensitized TiO2 Photoanode in Sacrificial Electrolytes

Dye sensitization of semiconductor metal oxides aims to extend the light absorption range into the visible region, of particular interest for their use as photoanodes in photoelectrochemical (PEC) water splitting. Organic dyes, however, suffer from limited chemical stability when they are exposed to constant potential and irradiation in aqueous media. Thus, in this work, we evaluate a novel metal-free donor-x-acceptor (D-xA) dye (AT-Pyri), demonstrating significant sensitization of film photoanodes based on TiO2 nanoparticles. Among a series of tested sacrificial agents, the addition of triethanolamine (TEOA) to the sodium sulphate electrolyte prevents the degradation of AT-Pyri even after several hours of operation. Combining two sacrificial agents (methanol and TEOA) results in a synergetic improvement of the PEC water-splitting activity. Notably, the stabilization of the AT-Pyri photoanode is accompanied by a substantial increase in the photocurrent over the reference TiO2 photoanode, while the associated spikes in transient photocurrent measurements disappear.