Wide pH photocatalytic nitrate reduction at adaptive microenvironment-dominated liquid–liquid-solid trilayer reaction interfaces

Abstract

Developing highly efficient photocatalysts with a wide pH application range is the key to achieving widespread practical application of photocatalytic denitrification. However, the current study neglects the limitations of diffusion and mass transfer efficiency in the reaction interfacial microenvironment on high activity and selectivity, resulting in the inability to achieve the ideal results. Herein, the photocatalytic NO3– reduction system with a microenvironment-dominated trilayer reaction interface of liquid (external liquid)-liquid (adaptive interfacial microenvironment)-solid (Br-Bi2WO6-x photocatalysts with different charge transfer mechanisms under acid/base conditions and hydrophilic surfaces) (LEL-LIM-S) was successfully constructed. The interfacial microenvironment in the system can self-adapt and adjust its ion composition according to the changes in the pH environment, which facilitates timely supplementation of NO3–/HCOO– required for the reaction from external liquid, thus maintaining the relative stability of the microenvironment and achieving an excellent NO3– removal rate of over 90 % in a wide pH range from 3 to 9. Meanwhile, the trilayer reaction interface of LEL-LIM-S collectively constitutes a unique carrier shuttle and molecular reaction channel from the catalyst interior to the surface contaminants. Highly selective NO3– to NH3 conversion (NH3 selectivity of 91.7 %, NH3 yield of 750 μmol g-1h−1) could be accomplished utilizing this channel.