Potassium-Derived Charge Channels in Boron-Doped g-C 3 N 4 Nanosheets for Photocatalytic NO Oxidation and Hydrogen Evolution.

The application of graphitic carbon nitride (g-C 3 N 4 ) in photocatalytic NO oxidation was limited due to severe recombination of photogenerated carriers and low concentration of oxidizing species. In this work, K and B were introduced into the interlayer and in-plane framework of g-C 3 N 4 to address this challenge through the thermal polymerization process. The synthesized K-doped B-g-C 3 N 4 nanosheets exhibited expanded light absorption and low charge recombination efficiency. In addition, the doping of K and B reduced the band gap of g-C 3 N 4 , which corresponded to enhanced light absorption. B was introduced into the in-plane structure by replacing C atoms, which adjusted the in-plane electron distribution. K was inserted into the interlayer by binding to the N and C atoms of adjacent layers. K-derived electron transfer channels were constructed, which increased electron delocalization and expanded the π-conjugate system. More electrons were transferred through the interlayer channels and were involved in the reaction process. The severe carrier recombination and weak transfer were improved due to the synergistic effect of K and B doping. K-doped B-g-C 3 N 4 nanosheets exhibited enhanced generation of superoxide radicals and hydroxyl radicals, which played a key role during NO oxidation. The photocatalytic NO oxidation efficiency of codoped g-C 3 N 4 nanosheets reached 61%, which was 2.1 and 1.2 times of that of pristine g-C 3 N 4 and B-doped g-C 3 N 4 , respectively. The codoped g-C 3 N 4 sample still exhibited stable photocatalytic NO oxidation efficiency after five cycles. This result provided a potential idea for improving the charge distribution and transfer of layered materials by codoping metallic and nonmetallic elements and for photocatalytic NO oxidation.