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

Abstract

The performance of titanium dioxide-supported copper hydroxide nitrate (TiO<inf>2</inf>-Cu<inf>2</inf>(OH)<inf>3</inf>NO<inf>3</inf>) as a light-free catalytic adsorbent is studied for the degradation of hydrogen sulfide (H<inf>2</inf>S). These composites are coded as TC-x, where T and C denote the TiO<inf>2</inf> support and Cu<inf>2</inf>(OH)<inf>3</inf>NO<inf>3</inf> active phase, respectively with x as the nominal copper weight percentage (1–10 %). The H<inf>2</inf>S removal efficiency (X<inf>H₂S</inf>) 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 H<inf>2</inf>S concentration and RH levels to record a maximum kinetic removal rate of 14.1 mmol g−1 h−1 (at X<inf>H₂S</inf> = 10 %) and a maximum capacity of 10.3 mg g−1, when tested against 20 H<inf>2</inf>S (80 % RH). A maximum clean air delivery rate of 46.4 L min−1 is also achieved at 5 ppm H<inf>2</inf>S (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 TiO<inf>2</inf> scaffold which stabilizes reactive intermediates. Furthermore, in situ DRIFTS analysis reveals that water vapor and oxygen work synergistically to enhance H<inf>2</inf>S removal.