Ni-doped ZnCo₂O₄ atomic layers to boost the selectivity in solar-driven reduction of CO₂

Regulating the selectivity of CO₂ photoreduction is particularly challenging. Herein, we propose ideal models of atomic layers with/without element doping to investigate the effect of doping engineering to tune the selectivity of CO₂ photoreduction. Prototypical ZnCo₂O₄ atomic layers with/without Ni-doping were first synthesized. Density functional theory calculations reveal that introducing Ni atoms creates several new energy levels and increases the density-of-states at the conduction band minimum. Synchrotron radiation photoemission spectroscopy demonstrates that the band structures are suitable for CO₂ photoreduction, while the surface photovoltage spectra demonstrate that Ni doping increases the carrier separation efficiency. In situ diffuse reflectance Fourier transform infrared spectra disclose that the CO₂^·- radical is the main intermediate, while temperature-programed desorption curves reveal that the ZnCo₂O₄ atomic layers with/without Ni doping favor the respective CO and CH₄ desorption. The Ni-doped ZnCo₂O₄ atomic layers exhibit a 3.5-time higher CO selectivity than the ZnCo₂O₄ atomic layers. This work establishes a clear correlation between elemental doping and selectivity regulation for CO₂ photoreduction, opening new possibilities for tailoring solar-driven photocatalytic behaviors.