Enhanced spatially coupling heterojunction assembled from CuCo2S4 yolk-shell hollow sphere capsulated by Bi-modified TiO2 for highly efficient CO2 photoreduction

The metal sulfides with highly negative reduction potential and long life-span of photocreated electrons are conducive to being exceptional candidates for CO2 photoreduction, whereas they suffer from self-photo-oxidation (or photocorrosion) that puts the greatest impediment to their practical application. Up to now, the Z-type strategy is stated as a favorable solution to overtake photocorrosion of metal sulfides, while the eligible choice for coupling with these materials is still challenging. TiO2 with more negative onset potential holds favorable inherent peculiarities over other materials, which produces overlapped potential with various ranges of metal sulfides. In this investigation, in mind that the CuCo2S4 (CCS) thiospinel is a novel photocatalyst that has not been used for the CO2 photoreduction, the hierarchical yolk-shell hollow structure of CCS was prepared through an affordable solvothermal route without any surfactant/template, which endowed with the multiple scattering/reflections for utilizing the incident photons. Additionally, the optimum Bi-modified TiO2 (3B-TiO2) were capsulated on CCS via a novel isoelectric point-assisted calcination method that made an intimate contact between CCS and 3B-TiO2 and prevented from randomly coupling, which in turn constructs the efficient Z-type system (CCS@3B-TiO2). Herein, the as-prepared photocatalysts were well-characterized, and the outcome results of CO2 photoreduction imply that the CCS@3B-TiO2 sample possesses the highest CH4 and CO productivities (42.2 and 25.5 mu mol/g, respectively), which was about 10 times greater than pure TiO2 for CH4 productivity. In the matter of long-term reusability of CCS@3B-TiO2, no noticeable sign of performance decay was found after six consecutive reaction cycles. The merits of peculiar design merge with unique electronic behavior obtained from efficient Z-type mechanism open up new insight into affordable and facile synthesized method for constructing highly efficient catalysts in various domains.

Automated summary

Metal sulfides have potential for CO2 photoreduction but suffer from self-photo-oxidation. The Z-type strategy is effective in preventing self-photo-oxidation. This study successfully prepared an efficient catalyst using a unique design and synthesis method.