Electronic structure regulation of an S-scheme CuBi2O4/Sr0.5NaTaO3 heterojunction with efficient carrier spatial transfer

The conduction/valence band (CB/VB) edge of perovskite-type ATaO3 largely straddles across the Fermi level, which endows it to be an attractive semiconductor with superior redox capacity. Nevertheless, the pristine ATaO3 suffers from the limited light responsive range and the low quantum efficiency. Herein, an S-scheme CuBi2O4/Sr0.5NaTaO3(CBSNT) heterostructure was firstly constructed, and being applied into the antibiotic water remediation. The kinetic constant for 40CBSNT composite (0.022 min−1) was 3.1 and 5.5 times higher than pristine SNTO (0.007 min−1) and CBO (0.004 min−1). h+ and ·O2– were proved as the dominant active radicals in CBSNT photocatalytic system. The reversible Cu+/Cu2+ redox pairs enables rapid hole extraction and efficient charge separation on the interface of CBSNT heterojunction. The synergistic effect of work function, Fermi energy level and the built-in electric field drive the electrons transfer from CBO to SNTO. The electrons flow trend on the heterojunction interface was jointly proved by XPS and DFT-calculated work function results. According to the DFT results, the photo-excited electrons was migrated from the Ta5d + O2p hybrid orbitals of SNTO's CB to recombine with the holes in the O2p orbital of CBO's VB in the S-type CBSNT heterostructure. The S-scheme pathway facilitated the carriers’ separation, and retained the strong redox capacity. Additionally, the AQE of the photodegradation system according to COD results was 0.15%. This work could layout some enlightenment for the efficient carrier spatial transfer implement in the heterojunction system design.