The construction of a wide-spectrum-responsive and high-activity photocatalyst, Bi25CoO40, via the creation of large external dipoles

Abstract

Currently, a major issue in the field of photocatalysis is the insufficient utilization of solar energy by photocatalysts. Thus, to overcome this problem, herein, a new sillenite photocatalyst, Bi₂₅CoO₄₀, was designed to exhibit a nearly full visible-light spectrum response (up to 750 nm) and high activity. In particular, its photocatalytic activity for the degradation of typical wastewater pollutants (e.g., MB and 4-CP) reached up to 3.402 h⁻¹ for MB under visible-light irradiation and 1.576 h⁻¹ for 4-CP under full spectrum irradiation. The degradation rates are ca. 2–4 times higher than those of well-studied photocatalysts such as P25-TiO₂, Bi₂WO₆, and g-C₃N₄, and are also the best for organic pollutant removal among reported photocatalysts absorbing above 700 nm. Results showed that the remarkable degradation on Bi₂₅CoO₄₀ is mainly due to the efficient charge separation resulting from the large external diploe moment between [Co^IIIO₄] and [Bi^VO₄] tetrahedrons. Results further illustrated that the VBM of new photocatalysts is composed of Co 3d–O 2p orbitals and exhibits a potential (ca. 2 eV) positive enough to produce oxidative species for the degradation of organic pollutants. The construction of a large external dipole moment without sacrificing the valence band edge potential may provide some design rules for the development of more efficient photocatalysts with a wide-spectrum response.