A well-designed honeycomb CoO@CdS photocatalyst derived from cobalt foam for high-efficiency visible-light H evolution

Well-designed honeycomb Co 3 O 4 @CdS (H-Co 3 O 4 @CdS) was fabricated via a one-step strategy for efficient water splitting. During the decoration of CdS, honeycomb Co 3 O 4 (H-Co 3 O 4 ) with macropores was formed simultaneously. H-Co 3 O 4 could enhance CdS visible-light absorption capacity conspicuously and narrow its band gap from 2.08 to 1.03 eV. Therefore, H-Co 3 O 4 @CdS presented a remarkable H 2 production of up to ca. 16 320 μmol g −1 h −1 ( λ > 420 nm), nearly 7.3 times higher than that of pristine CdS, indicating the excellent synergistic effect between H-Co 3 O 4 and CdS. Through various photoelectricity tests ( e.g. , PL spectra, EPR, photoelectric responsiveness and impedance), it could be found that the distinguished H 2 evolution was attributed to the improved charge carrier separation and electron generation. What's more, the enhanced H 2 production of H-Co 3 O 4 @CdS is related to the improved specific surface area (83.49 m 2 g −1 ) and pore volume (0.247 cm 3 g −1 ) as well. Density Functional Theory (DFT) calculations confirmed that CdS has the function of diverting electrons, and the orbital energy level of absorbed H 2 O molecules showed obvious migration due to the accumulation of electrons. Besides, the d-band of Co could induce more electrons to traverse the Fermi level. Subsequently, more electrons could be transferred from Co 3 O 4 to CdS and break the O-H 1 bond. Compared to the H-Co 3 O 4 @CdS system, the d-band center of the Co atoms in H-Co 3 O 4 @CdS-H 2 O shifted from −5.83 to −2.58 eV, thereby demonstrating that Co 3 O 4 served as an electron reservoir for charge redistribution in the photocatalytic water splitting process. In the end, a practicable mechanism for H-Co 3 O 4 @CdS about H 2 O dissociation and H 2 desorption was proposed. A well-designed honeycomb Co 3 O 4 @CdS photocatalyst derived from cobalt foam was synthesized for high-efficiency visible-light H 2 evolution ( ca. 16 320 μmol h −1 g −1 ).