Carbon Nitrides with Grafted Dual-Functional Ligands as Electron Acceptors and Active Sites for Ultra-stable Photocatalytic H₂O₂ Production

Abstract

Photocatalytic production of H2O2 from earth-abundant water and oxygen using low-cost metal-free carbon nitrides (CNs) through oxygen reduction is a prospective route toward a greener future. However, the H2O2 productivity is restricted by rapid electron–hole separation and the low oxygen reduction activity of CNs. Herein, we rationally designed a series of CNs with covalently bonded dual-functional ligands acting as electron acceptors and active sites to achieve high photocatalytic H2O2 production and superior stability. The best-performing carbon nitride displays a H2O2 production rate of 7.3 mmol/g h with an apparent quantum efficiency of 20.2% at 420 nm using formic acid as the electron donor. Moreover, the modified CNs show excellent stable H2O2 generation over 110 h without significant decline. Mechanistic studies reveal that H2O2 was produced through a 2e– oxygen reduction reaction route. Photoluminescence, photo-electrochemical, and Kelvin probe force microscopy results together with theoretical calculations have revealed that the excellent photocatalytic performance originates from the dual-functional ligand. It not only acts as an electron acceptor to promote photogenerated charge carrier separation by withdrawing electrons but also works as an active site to accelerate oxygen reduction by lowering the oxygen adsorption and activation energy. Moreover, this facial strategy of grafting ligands provides a universal approach to synthesize photocatalysts with enhanced reactivity under mild conditions by choosing the proper ligands for a specific reaction.

Three-Dimensional Multihierarchical Hexagonal/Cubic ZnIn2S4 S-Scheme Heterophase Junction for Superior Photocatalysis

“…The flat-band potentials (FB) of C-ZIS, H-C-ZIS-1, and H-ZIS are about −1.14, −1.03, and −0.92 V vs NHE, respectively. Considering that the conduction band potential of n-type semiconductors is generally more negative than the flat-band potential by about 0.20 eV, the conduction band potentials of C-ZIS, H-C-ZIS-1, and H-ZIS are −1.34, −1.23, and −1.12 V vs NHE, respectively, which are in good agreement with the above results calculated from the VB-XPS data.…”

Solar‐driven seawater production H2O2 catalyzed by hydroxyl functionalized crystalline K‐doped g‐C3N4 under ambient conditions

“…The peak at about 3422 cm −1 was ascribed to the O‐H stretching vibration, which has a slightly blue shift. The structural backbones of heptazine were clearly observed within the ranges of 1100–1700 cm −1 , 20,21 which were assigned the stretching vibration of the C–N and C=N respectively. The intensity of C–O bond at the position of 1143 cm −1 increases, demonstrating the abundant oxygen‐containing functional groups.…”

Sustainable photocatalytic synthesis of hydrogen peroxide from catechol-formaldehyde resin microspheres modulated by nitrogen-doped carbon dots

“…These results indicate that CFR/NCDS-220 reduced O 2 to H 2 O 2 through a two-electron path in visible light, but could not produce H 2 O 2 through 4e − water oxidation. 26,57…”