Enhanced formaldehyde sensing performance of CdFe2O4 via surface sensitization with MoS2 or WS2 nanosheets

Despite the recognized potential of two-dimensional transition metal dichalcogenides (2D TMDs) as effective sensitizers for metal oxides, comparative insights into their specific sensitization effects on spinel ferrites remain lacking. Herein, MoS 2 -CdFe 2 O 4 and WS 2 -CdFe 2 O 4 composites were synthesized via an in-situ solvothermal-calcination strategy. Characterization results confirmed that the incorporation of TMDs effectively modulated the microstructure and surface properties of CdFe 2 O 4 . Specifically, the WS 2 -CdFe 2 O 4 (WDF-10) had a larger specific surface area (10.14 m 2 /g) and pore volume than the MoS 2 -CdFe 2 O 4 (MDF-10), exposing more active sites. XPS suggests an increased fraction of defect-related/adsorbed oxygen species in the composites. Gas-sensing tests revealed performance differences: the WDF-10 sensor exhibited a remarkable response to 100 ppm formaldehyde at 140°C, approximately 2.5 times higher than the MDF-10. Meanwhile, the MDF-10 sensor demonstrated reduced response/recovery times, enhanced quantitative precision, and remarkable long-term stability. The sensitization mechanism is attributed to the synergistic effect of increased specific surface area and the proposed formation of p-n heterojunctions. Energy band analysis suggests that WS 2 , with its unique band alignment, may induce a stronger depletion layer modulation on CdFe 2 O 4 , thereby enhancing the response. This work demonstrates that surface sensitization with MoS 2 or WS 2 is an effective strategy to enhance the gas-sensing performance of spinel ferrites.