Designing Defective Crystalline Carbon Nitride to Enable Selective CO₂ Photoreduction in the Gas Phase

Abstract

Polymeric carbon nitrides are promising photocatalysts for CO2 photoreduction, but still show lower activity and selectivity. Herein, the synthesis of an ordered crystalline carbon nitride is reported which is simultaneously rich in special defects, accomplished via the co‐condensation of guanidine hydrochloride and dicyandiamide under acetonitrile‐promoted solvothermal conditions. The high crystallinity boosts charge migration, and the structural terminations with cyano and carboxyl groups result in the improvement of optical absorption, the ability to store charges at the surface, and CO2 binding. The crystalline carbon nitride with surface defect design enables the effective gas‐phase CO2 photoreduction into hydrocarbon fuels while oxidizing water to oxygen, at a rate of 12.07 µmol h−1 g−1 and a selectivity of 91.5%, both values of which are remarkably higher than those of most previous carbon nitride photocatalysts. This study highlights the preparation of defective crystalline carbon nitride using a low‐temperature solvothermal synthesis, as well as a resultant good selectivity toward hydrocarbons in the application of gas‐phase CO2 photoreduction in the absence of any cocatalyst or sacrificial agent.

Atomic‐Level Reactive Sites for Semiconductor‐Based Photocatalytic CO2 Reduction

“…Xia et al developed crystalline carbon nitride with connecting cyano and carboxyl groups (CCN) on the surface using guanidine hydrochloride (GH) and dicyandiamide (DCD) as precursors in acetonitrile by solvothermal reactions. From XRD patterns, CCN samples have meaningfully different layer distances with ordinary g‐C 3 N 4 because of the interstitial functional groups, Figure 10 .…”

“…e) Fourier filtered Cs‐corrected HRTEM and f) AFM images of CCN. Reproduced with permission . Copyright 2019, Wiley‐VCH.…”

g‐C3N4/Cu3P/UiO‐66 Ternary Composites for Enhanced Visible Light Photocatalytic H2 Evolution

“…Figure A shows the XRD diffraction pattern of CNC, CNU and the standard card of Cu 3 P. The diffraction peaks of g‐C 3 N 4 in the sample coincide with the in‐plane stacking structure of the aromatic system. The characteristic diffraction peaks are located at 27.5°corresponding to (002) interface ,. This characteristic peak indicates that graphite carbonitridation, has been successfully synthesized.…”

“…It is widely used in formaldehyde decomposition, dye degradation, nitrogen oxide removal and carbon dioxide reduction . However, due to the low specific surface area, few reaction sites and the rapid recombination for photoelectrons and holes of pure g‐C 3 N 4 , the photocatalytic hydrogen production performance of pure g‐C 3 N 4 is weak . Researchers have explored a variety of modification strategies to improve the performance of this material, for example, g‐C 3 N 4 with TiO 2 , CdS, ZnWO 4 , BiPO 4 , precious metal (Pt, Pd) and other semiconductor coupling materials are compounded to improve the separation efficiency of photogenerated electron hole pairs, and thus improve photocatalytic activity…”

Optimizing electronic structure and charge transport of sulfur/potassium co‐doped graphitic carbon nitride with efficient photocatalytic hydrogen evolution performance

“…One of the promising technologies is photocatalytic technology because it can utilize the abundant energy of the sun. Many materials have been fabricated to produce hydrogen from water and degrade various organic pollutants as well as reduce CO 2 under sunlight irradiation. Recently, graphitic carbon nitride (CN) as a metal‐free photocatalyst has attracted wide interests due to its suitable bandgap energy and excellent thermal and chemical stability .…”