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 Co₃ O₄ ultrathin nanosheets assembled double-hollow nanotube (Ni-Co₃ O₄ 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 -2π* and d_z2 -5σ 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-Co₃ O₄ 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/H₂ ratios from 1 : 10 to 10 : 1 are achieved.