Enhanced chlorine evolution from dimensionally stable anode by heterojunction with Ti and Bi based mixed metal oxide layers prepared from nanoparticle slurry

[Display omitted] •TiO2 nanoparticle over-layer accelerate reactive chlorine generation from Ir7Ta3Oy.•Uniform doping of Bi on TiO2 further elevate current and energy efficiency.•Surface ·OH exclusively mediate the reactive chlorine generation.•Ratio of ·OH to higher oxide primarily determine the current efficiency. This study reports enhanced current (CERCS) and energy efficiency (EERCS) of reactive chlorine species (RCS) generation on Ir7Ta3Oy anode by Ti/Bi mixed metal oxide heterojunction layers despite reductions in pseudo-capacitance and film conductivity. In potentiostatic electrolysis of 50 mM NaCl solutions, dramatic improvement (0.61 mmol cm−2 hr−1 at 2.5 V NHE) was noted by simple coating of thin (~2 μm) TiO2 layer from ball-milled TiO2 nanoparticle (80–100 nm) suspension, even with moderate elevation in voltammetric wave. Decoration of Bi2O3 particles (1 – 2 μm) showed limited or adverse effects for RCS generation and stability. However, Bi-doped TiO2 layers prepared from polyol-mediated or co-precipitation methods marked the highest CERCS (~100%) and EERCS (8.16 mmol Wh−1 at 2.5 V NHE) by increased mixing level and effective shift in surface charge. Surface ·OH exclusively mediated the RCS generation whose further transformation to higher oxide could be restrained by the heterojunction layer.