Efficient Photoreduction of Diluted CO2 to Tunable Syngas by Ni-Co Dual Sites through d-band Center Manipulation

Photocatalytic conversion of CO2 into syngas is a promising way to address the energy and environmental challenges. Here we report the integration of Ni-Co dual sites on Ni doped Co3O4 ultrathin nanosheets assembled double-hollow nanotube (Ni-Co3O4 NSDHN) for efficient photoreduction of low-concentration CO2. Quasi in situ spectra and density functional theory calculations demonstrate that the declining of d-band center of Ni-Co dual sites enables the electrons accumulation in the d(xz)/d(yz)-2 pi* and d(z2)-5 sigma orbitals. As a result, the binding strength of *CO is weakened and the *H adsorption site is modulated from metal sites to an oxygen site. Remarkably, Ni-Co3O4 NSDHN exhibits superior diluted CO2 photoconversion activity and controllable selectivity under the irradiation of visible light or even natural sunlight. A syngas evolution rate of 170.0 mmol g(-1) h(-1) with an apparent quantum yield of 3.7 % and continuously adjustable CO/H-2 ratios from 1 : 10 to 10 : 1 are achieved.