Construction of K+ ions gradient in crystalline carbon nitride to accelerate charge separation for efficient visible light H2 production

Abstract

Like most of the recent reported semiconductor photocatalysts, the sluggish dynamic charges transfer and separation caused by weak driving force still restricts the further improvement of photocatalytic performance in crystalline carbon nitride (CCN). Here, we successfully prepared a series of heptazine-based K+ implanted CCN (KCN) for the first time, where the K+ ions concentration was gradiently inserted through controlling its diffusion from the surface to bulk in carbon nitride (CN). As a powerful driving force, the built-in electric field (BIEF) induced by this concentration gradient, greatly accelerates the drift movement and the transport from bulk to the surface, as well as the separation of photogenerated carriers. Consequently, the KCN with optimized BIEF displays a ～34 times promotion than original CN for visible-light H2 evolution. Such a high activity enhancement factor is at a relatively good level in reported CCN. Our proposed strategy to induce BIEF production by constructing concentration gradients through thermodynamically feasible diffusion controlled solid-state reaction, can be adopted to build other efficient photocatalytic systems.

Roles of Catalyst Structure and Gas Surface Reaction in the Generation of Hydroxyl Radicals for Photocatalytic Oxidation

“…In further exploitation of solar energy, polymeric carbon nitride (PCN) is prevailingly used in visible-light-driven or solardriven photocatalysis. 4,5 Nevertheless, the diffusion-driven motion of the photogenerated charge carriers as well as the low oxidation capacity of photoexcited VB-h + restrict the reactivity of PCN in ROS generation due to the impeded surface reaction and quantum efficiency.…”