Enhanced Charge Separation in NiO and Pd Co-Modified TiO₂ Photocatalysts for Efficient and Selective Photoreduction of CO₂

Photocatalytic reduction of CO2 has been a challenge for some time because this complex reaction produces multiple products, some of which require a high electron density around the active sites to drive the multi-electron reduction. Herein, a Pd-NiO/TiO2 catalyst was prepared by hydrothermal production of anatase TiO2 nanosheets, followed by chemical deposition of NiO and photoreduction of Pd. The introduction of NiO to TiO2 formed a p–n junction, whose internal electric field drives the migration of holes to NiO. Meanwhile, the introduction of Pd to TiO2 formed a Schottky junction, which facilitated the photo-generated electron transfer from TiO2 to Pd. The directional migration of electrons and holes significantly enhanced the charge separation and generated high electron density on Pd, which efficiently and selectively reduced CO2 to CH4.