Catalytic Activity of Ni1-xLi2xWO4 Particles for Carbon Dioxide Photoreduction

This study introduces NiWO4 as a main photocatalyst, where the Ni component promotes methanation to generate a WO3-based catalyst, as a new type of catalyst that promotes the photoreduction of carbon dioxide by slowing the recombination of electrons and holes. The bandgap of NiWO4 is 2.74 eV, which was expected to improve the initial activity for the photoreduction of carbon dioxide. However, fast recombination between the holes and electrons was also expected. To overcome this problem, attempts were made to induce structural defects by partially replacing the Ni2+ ions in NiWO4 with Li+. The resulting CO2 conversion reaction was greatly enhanced with the Ni1-xLi2xWO4 catalysts containing Li+, compared to that of the pure NiWO4 catalysts. Notably, the total amount of CO and CH4 produced with the Ni0.8Li0.4WO4 catalyst was 411.6 nmol g−1. It is believed that the insertion of Li+ ions into the NiWO4 skeleton results in lattice defects due to charge and structural imbalance, which play a role in the capture of CO2 gas or excited electrons, thereby inhibiting recombination between the electrons and holes in the Ni1-xLi2xWO4 particles.