Synergistic role of electron-trapped oxygen vacancy and exposed TiO2 [001] facets toward electrochemical p-nitrophenol reduction: Characterization, performance and mechanism

Despite the fact that electron-trapped oxygen vacancy and [001] facets fundamentally affect the reactivity of TiO2, their synergistic role in the electrochemical activity of TiO2 toward p-nitrophenol (p-NP) reduction is still unknown. In this study, defective and [001] facets engineered TiO2 cathode, i.e. Ti/TiO2-x-001, was prepared for p-NP reduction. In comparison to defective Ti/TiO2 cathode with [101] facets (Ti/TiO2-x-101), the combination of the electron-trapped oxygen vacancy and [001] facets exhibited a synergistic effect to improve the electrochemical reduction efficiency of TiO2. Density functional theory calculations verified that the introduction of [001] facets and electron-trapped oxygen vacancy on TiO2 was beneficial to facilitate electron transfer and improve the indirect reduction efficiency for p-NP electrochemical reduction. Moreover, the electron-trapped oxygen vacancy extent of Ti/TiO2-x-0 01 was modulated by adjusting reduction temperature (250-650 C). The maximum electron-trapped oxygen vacancy amount of Ti/TiO2-x-001 was attained at the reduction temperature of 350 degrees C, which resulted in the highest p-NP reduction efficiency of 99.3%, accompanying the p-AP selectivity of 89.5%. In this case, the abundant active and adsorption sites were provided on the surface of Ti/TiO2-x-001 prepared at 350 degrees C, in which p-NP adsorption coefficient and electrochemical surface area increased to 1.01 L mg(-1) and 25 cm(2), respectively. Generally, this work provides a paradigm for the design of efficient nonmetallic catalyst for nitroaromatic chemicals reduction.

Automated summary

The electron-trapped oxygen vacancy and [001] facets of TiO2 have a synergistic effect on the electrochemical activity towards p-nitrophenol (p-NP) reduction. The introduction of [001] facets and electron-trapped oxygen vacancy on TiO2 can improve electron transfer and indirect reduction efficiency for p-NP electrochemical reduction. Modulating the reduction temperature can affect the electron-trapped oxygen vacancy extent on TiO2, with the Ti/TiO2-x-001 cathode prepared at 350 degrees Celsius showing the highest p-NP reduction efficiency.