Enhancing the activity of oxygen-evolution and chlorine-evolution electrocatalysts by atomic layer deposition of TiO₂

We report that TiO₂ coatings formed via atomic layer deposition (ALD) may tune the activity of IrO₂, RuO₂, and FTO for the oxygen-evolution and chlorine-evolution reactions (OER and CER). Electrocatalysts exposed to ~3-30 ALD cycles of TiO₂ exhibited overpotentials at 10 mA cm^-2 of geometric current density that were several hundred millivolts lower than uncoated catalysts, with correspondingly higher specific activities. For example, the deposition of TiO₂ onto IrO₂ yielded a 9-fold increase in the OER-specific activity in 1.0 M H₂SO₄ (0.1 to 0.9 mA cm_ECSA ^-2 at 350 mV overpotential). The oxidation state of titanium and the potential of zero charge were also a function of the number of ALD cycles, indicating a correlation between oxidation state, potential of zero charge, and activity of the tuned electrocatalysts.