Momentum-resolved electronic structure of LaTiO2N photocatalysts by resonant Soft-X-ray ARPES

Oxynitrides are promising materials for visible light-driven water splitting. However, limited information regarding their electron-momentum resolved electronic structure exists. Here, with the advantage of the enhanced probing depth and chemical state specificity of soft-X-ray ARPES, we determine the electronic structure of the photocatalyst oxynitride LaTiO2N and monitor its evolution as a consequence of the oxygen evolution reaction. After the photoelectrochemical reactions, we observe a partial loss of Ti- and La-N 2p states, distortions surrounding the local environment of titanium atoms and, unexpectedly, an indication of an electron accumulation layer at or near the surface, which may be connected with either a large density of metallic surface states or downward band bending. The distortions and defects associated with the titanium 3d states lead to the trapping of electrons and charge recombination, which is a major limitation for the oxynitride LaTiO2N. The presence of an accumulation layer and its evolution suggests complex mechanisms of the photoelectrochemical reaction, especially in cases where co-catalysts or passivation layers are used. LaTiO2N is a promising photocatalyst for light-driven water splitting. Here, ARPES is used to study the momentum-resolved electronic structure of the sub-surface region of LaTiO2N and monitor its evolution during the oxygen evolution reaction.

Automated summary

This study investigates the electronic structure of the photocatalyst oxynitride LaTiO2N and its evolution during the oxygen evolution reaction using soft-X-ray ARPES. It is found that distortions and defects associated with titanium and lanthanum-nitrogen atoms lead to electron trapping and charge recombination, which limits the efficiency of LaTiO2N. The presence of an electron accumulation layer and its evolution suggests complex mechanisms of the photoelectrochemical reaction, especially in the presence of co-catalysts or passivation layers.