Overall water splitting under visible light irradiation over Ir and La-codoped NaTaO3 photocatalysts†

Ir and La-codoped NaTaO₃ has been found to be a novel photocatalyst for overall water splitting into H₂ and O₂ under visible light irradiation through systematic investigation in terms of doping amounts. The band structure of the sample depends on the doping amounts. Overall water splitting under visible light irradiation proceeds over Ir and La-codoped NaTaO₃ with low doping levels (0.05 at% or 0.1 at% Ir to Ta) through electron transitions from the donor impurity levels formed by Ir³⁺ to the conduction band of NaTaO₃, responding to visible light up to 500 nm. In contrast, Ir and La-codoped NaTaO₃ with higher doping levels (0.5 at% or 1 at% Ir to Ta) shows photocatalytic activity not for overall water splitting but for sacrificial H₂ evolution, responding to visible light beyond 600 nm.