Enhanced Photocatalytic Reaction at Air–Liquid–Solid Joint Interfaces

Abstract

Semiconductor photocatalysis has long been considered as a promising approach for water pollution remediation. However, limited by the recombination of electrons and holes, low kinetics of photocatalysts and slow reaction rate impede large-scale applications. Herein, we addressed this limitation by developing a triphase photocatalytic system in which a photocatalytic reaction is carried out at air-liquid-solid joint interfaces. Such a triphase system allows the rapid delivery of oxygen, a natural electron scavenger, from air to the reaction interface. This enables the efficient removal of photogenerated electrons from the photocatalyst surface and minimization of electron-hole recombination even at high light intensities, thereby resulting in an approximate 10-fold enhancement in the photocatalytic reaction rate as compared to a conventional liquid/solid diphase system. The triphase system appears an enabling platform for understanding and maximizing photocatalyst kinetics, aiding in the application of semiconductor photocatalysis.

Janus Membranes: Creating Asymmetry for Energy Efficiency

“…Gas dissolution and diffusion to the enzyme or catalyst surfaces can be a major limitation to catalytic efficiency. One solution to this problem is to immobilize enzymes or photocatalysts at the solid–liquid–gas joint interface. However, enzymes immobilized on hydrophobic surfaces can become inactive due to conformational changes caused by hydrophobic interactions.…”

“…The diffusion coefficient from air (≈2.0 × 10 −1 cm −2 s −1 ) is nearly four orders of magnitude greater than that through a liquid (≈2.1 × 10 −5 cm −2 s −1 ). In recent research, Sheng et al presented a Janus membrane composed of a TiO 2 catalyst layer on a superhydrophobic carbon fiber film . Compared with the biphase system (solid–liquid), the triphase (solid–gas–liquid) system showed nearly 12 times higher degradation rates.…”

“…a) Diagram of biphase and triphase photocatalysis systems. Adapted with permission . Copyright 2017, ACS.…”

“…Redrawn from data in ref. . c) Diagram of mass and heat transfer in a Janus membrane during membrane distillation.…”

Superaerophilic Materials Are Surprising Catalysts: Wettability‐Induced Excellent Hydrogenation Activity under Ambient H2 Pressure

“…There were two typical adhesion behaviors of gas bubbles on the surface of materials: superaerophilic “bursting” state and superaerophobic “pinning” state . These two different gas adhesion behaviors can be used in promoting capture and directionally transport gas bubbles, hydrogen evolution reaction (HER), oxygen evolution reaction, and catalysis reactions involved gaseous products . For example, Sun and co‐workers demonstrated that by constructing catalytic electrode material with a superaerophobic surface, the adhesion of as‐formed H 2 gas bubbles on the electrode surface could be alleviated by one order, resulting in a rapid removal of small gas bubbles and much better electrocatalytic performance in HER .…”