Heterogeneous photo-catalysis from the perspective of the adsorbed state. The photo-oxidation of propan-2-ol to propan-2-one on rutile titanium dioxide

•TiO2 exposed to propan-2-ol results in spontaneous surface reduction at 300 K.•ESR confirms the presence of paramagnetic Ti3+A centres (θ = 0.003).•Exposure to O2(g) destroys all Ti3+A and 2 new signals, O− and Ti3+B appear.•TPD shows that lattice oxygen loss is much greater than detected by ESR.•Spin-paired [Ti3+]2 centres exist in overwhelming numbers.