Earth-abundant ZnS/ZnO/CuFeSk films for air purification and solar fuels production

Heterogeneous photocatalysis is one of the most viable solutions for environmental remediation, and it helps to overcome energy crisis by solar fuel generation with an environmentally friendly approach. Hence, the search for efficient, stable, and inexpensive photocatalysts is one of the most significant challenges that scientists currently face for the implementation of this technology on a larger scale. One alternative is to use naturally occurring semiconductor materials as photocatalysts because they are obtained at low cost and have great potential in environmental remediation and solar fuel generation. Therefore, in this study, an earth-abundant chalcogenide mineral (ZnS), which is obtained directly from nature, was used as raw material to fabricate thick films over glass substrates by the doctor-blade technique. Both materials (pristine and thick films) were evaluated as photocatalysts to remove CH2O a commonly volatile organic compound (VOC) gas pollutant found in indoor spaces from the air, and for solar fuel generation (H2, CH3OH, and HCOOH) from CO2 reduction under simulated visible light. Pristine mineral contained ZnS and traces of CuFeS2 as crystal phases of micrometer-sized particles with visible-light response. When the earth-abundant mineral was immobilized on glass substrates as a thick film, it exhibited ZnS/ZnO/CuFeS2 as crystalline phases with a hierarchical morphology formed by stacking several plate-like particles. The thickness of the film was 2.5 mu m and it was rough. These properties favored high efficiencies for air purification because more than 55% of gas pollutant was removed after 90 min. In addition, the films exhibited photocatalytic activity toward CO2 reduction to produce solar fuels such as H2 (615 mu mol/g), CH3OH (150 mu mol/g), and HCOOH (1693 mu mol/g) at 25 degrees C. The good photocatalytic performance of earthabundant films was related to an efficient charge transfer among the components (ZnS/ZnO/CuFeS2) and an enhanced light absorption owing to hierarchical morphology. The stability of samples was confirmed after three consecutive cycles.

Automated summary

Heterogeneous photocatalysis is an effective solution for environmental remediation, and using naturally occurring semiconductor materials as photocatalysts has shown promising results in air purification and solar fuel generation.