Oxygen self-doped g-C₃N₄ with tunable electronic band structure for unprecedentedly enhanced photocatalytic performance

Abstract

As a fascinating conjugated polymer, graphitic carbon nitride (g-CN) has attracted much attention for solving the worldwide energy shortage and environmental pollution. In this work, for the first time we report oxygen self-doping of solvothermally synthesized g-CN nanospheres with tunable electronic band structure via ambient air exposure for unprecedentedly enhanced photocatalytic performance. Various measurements, such as XPS, Mott-Schottky plots, and density functional theory (DFT) calculations reveal that such oxygen doping can tune the intrinsic electronic state and band structure of g-CNvia the formation of C-O-C bond. Our results show that the oxygen doping content can be controlled by the copolymerization of the precursors. As a consequence, the oxygen doped g-CN shows excellent photocatalytic performance, with an RhB photodegradation rate of 0.249 min and a hydrogen evolution rate of 3174 μmol h g, >35 times and ∼4 times higher than that of conventional thermally made pure g-CN (0.007 min and 846 μmol h g, respectively) under visible light. Our work introduces a new route for the rational design and fabrication of doping modified g-CN photocatalyst for efficient degradation of organic pollutants and H production.

Oxygen‐Functionalized and Ni+x (x=2, 3)‐Coordinated Graphitic Carbon Nitride Nanosheets with Long‐Life Deep‐Trap States and their Direct Solar‐Light‐Driven Hydrogen Evolution Activity

“…The peak at 287.9 eV belongs to the aromatic ring N−C=N. The other three peaks at 286.81, 288.94 and 293.51 eV were attributed to C−O, C=O and C−NH 2 bonds, respectively . The presence of C−O and C=O bonds confirmed the initial assumption from the EDS spectra that g‐C 3 N 4 was oxygen functionalized .…”

“…The O 1s spectrum (Figure c) was deconvoluted into five peaks at 530.58, 531.59, 532.56, 533.53, and 535.6 eV. The peak at 530.58 eV was attributed to C−O/N−C−O bonds in g‐C 3 N 4 , clearly confirming the oxygen functionalization of the g‐C 3 N 4 matrix . The oxygen functionalization occurred owing to thermal condensation of melamine in an air atmosphere .…”

“…Importantly, the g‐C 3 N 4 was prepared by thermal condensation of melamine in an open‐air muffle furnace. The preparation of g‐C 3 N 4 in an open‐air muffle furnace has been previously reported for oxygen functionalization of g‐C 3 N 4 . Besides oxygen, uniform distribution of C (red), N (green), and Ni (sky blue) was observed in the EDS color mapping of GNi4 (Figure c, d, f) and C (red) and N(green) in the g‐C 3 N 4 samples (Figure S2 e, f).…”

Photovoltaic Counter Electrodes: An Alternative Approach to Extend Light Absorption Spectra and Enhance Performance of Dye‐Sensitized Solar Cells

“…These results suggest that Ag 2 Se can absorb light around 700 nm. The Mott‐Schottky plots of Ag 2 Se manifest positive slopes, which turns out that Ag 2 Se is a typical n type semiconductors (Figure S7) . The intersection on the x‐axis is −0.20 V, which illustrates the flatband potential ( E fb ) of Ag 2 Se is −0.20 V vs .…”

Fe1‐xCoxS2 Solid Solutions with Tunable Energy Structures to Enhance the Performance of Triiodide Reduction in Dye‐Sensitized Solar Cells

“…The x ‐axis intercept in the Mott‐Schottky plots illustrates that the flatband potential ( E fb ) of Fe 1‐x Co x S 2 (x=0, 0.1, 0.3 and 0.5) solid solutions are determined to be −0.18, −0.49, −0.51 and −0.65 V versus Ag/AgCl, which are equal to 0.02, −0.29, −0.31 and −0.45 V versus the normal hydrogen electrode (NHE), respectively. In general, E fb of many n‐type semiconductors is about 0.1 ‐ 0.3 eV more negative than their conduction band (CB) and it is usually estimated as −0.20 eV . Thereby, the E CB position of Fe 1‐x Co x S 2 (x=0, 0.1, 0.3 and 0.5) can be approximately estimated as −0.18, −0.49, −0.51 and −0.65 eV, and their valence band potential ( E VB ) are correspondingly calculated to be 1.78, 0.77, 0.72 and 0.50 eV, respectively.…”