Light-free degradation of hydrogen sulfide via a Cu⁺ /Cu²⁺ redox cycle on a titanium dioxide supported copper...

The performance of titanium dioxide-supported copper hydroxide nitrate (TiO₂-Cu₂(OH)₃NO₃) as a light-free catalytic adsorbent is studied for the degradation of hydrogen sulfide (H₂S). These composites are coded as TC-x, where T and C denote the TiO₂ support and Cu₂(OH)₃NO₃ active phase, respectively with x as the nominal copper weight percentage (1-10 %). The H₂S removal efficiency (X_H₂S) of the prototype air purifier, when evaluated using TC-1, -2, -5, and -10 systems (0 % relative humidity over 240 s) reaches 66 %, 96.5 %, 100 %, and 100 %, respectively, while that of the pure TiO₂ attains 3 %. Their performance generally hinges on both H₂S concentration and RH levels to record a maximum kinetic removal rate of 14.1 mmol g^-1 h^-1 (at X_H₂S = 10 %) and a maximum capacity of 10.3 mg g^-1, when tested against 20 H₂S (80 % RH). A maximum clean air delivery rate of 46.4 L min^-1 is also achieved at 5 ppm H₂S (50 % RH). The remarkable performance of TC-5 is primarily attributed to a highly efficient Cu⁺/Cu²⁺ redox cycle through the well-dispersed copper hydroxide nitrate on the high-surface-area TiO₂ scaffold which stabilizes reactive intermediates. Furthermore, in situ DRIFTS analysis reveals that water vapor and oxygen work synergistically to enhance H₂S removal.