Shear Stress Triggers Ultrathin-Nanosheet Carbon Nitride Assembly for Photocatalytic H₂O₂ Production Coupled with Selective Alcohol Oxidation

Abstract

Coupled photocatalysis without cocatalysts can maximize the utilization of photons and atoms, which puts forward higher demands on photocatalysts. Polymeric carbon nitride (CN) has become the most promising photocatalyst, but still suffers from major drawbacks of insufficient catalytic sites and low quantum efficiency. Herein, we report a fluid shear stress-assisted molecular assembly to prepare ultrathin-nanosheet-assembled acanthospherelike CN (ASCN) with nitrogen vacancy (Nv) and carbonyl modification. Shear stress breaks the stacking interactions between layers and cuts the stacked structure into ultrathin layers, which are further reassembled into acanthosphere bundles driven by "centrifugal force". Benefitted greatly from the ultrathin nature that provides more exposed active sites and improves charge carrier separation, ASCN-3 exhibits a 20-fold higher activity than the bulk counterpart toward oxygen reduction to H 2 O 2 coupled with 4methoxybenzyl alcohol (4-MBA) oxidation to anisaldehyde (AA), with significantly increased turnover frequency (TOF) values (TOF: 1.69 h −1 for H 2 O 2 and 1.02 h −1 for AA). Significantly, ASCN-3 exhibits 95.8% conversion for 4-MBA oxidation with nearly 100% selectivity. High apparent quantum yields of 11.7% and 9.3% at 420 nm are achieved for H 2 O 2 photosynthesis and 4-MBA oxidation. Mechanism studies suggest that carbonyl induces holes concentrated at the neighboring melem unit to directly oxidize the C α −H bond of 4-MBA to produce carbon radicals, and Nv as oxygen adsorption active site traps electrons to form a superoxide radical that further combines with the shed protons into H 2 O 2 . This work presents a simple physical method to break the layered stack of CN for creating hierarchical assembly for coupled photocatalysis.

Z-Scheme Heterojunction α-Fe2O3/Tubular g-C3N4 with C Defects for Photocatalytic Degradation of Microcystin-LR in Water: Generation and Effect of Critical Species 1O2

“…The active species capture experiments investigated the active substances that play a major role in the photocatalytic system of 2% α-Fe 2 O 3 /TDCN. The different ROS generated in the reaction system can be characterized using a capture agent in principle . 10 mM of methanol (MeOH) and tert -butanol (TBA), 10 mM of furfuryl alcohol (FFA), 10 mM of l -ascorbic acid ( l -AA), and 10 mM of ethylenediaminetetraacetic acid disodium salt (EDTA·2Na) were used for capturing • OH, 1 O 2 , • O 2 – , and h + , respectively (Figure a). , It can be observed that the effects of adding two different • OH trapping agents (MeOH, TBA) on the reaction system were fragile, which represents a small role in removing • OH from the system.…”

“…The different ROS generated in the reaction system can be characterized using a capture agent in principle. 63 10 mM of methanol (MeOH) and tert-butanol (TBA), 10 mM of furfuryl alcohol (FFA), 10 mM of L-ascorbic acid (L-AA), and 10 mM of ethylenediaminetetraacetic acid disodium salt (EDTA•2Na) were used for capturing…”

Insights into Molten Salts Induced Structural Defects in Graphitic Carbon Nitrides for Piezo‐Photocatalysis with Multiple H2O2 Production Channels

“…[ 33,34 ] Figure S1h (Supporting Information) demonstrates the deconvoluted peaks of N 1s spectra, containing ‐C = N‐C, N─C 3 , C─N─H, and π‐ ‐ π * in the systems. [ 35,36 ] The peak from N 1s spectra without deconvolutions of FCN, CCN, and BCN exhibit the right shift to a lower binding energy region, proving the modified systems gain more free electrons than the pristine CN, improving catalytic outcomes. Besides, the calculated ratio of N‐C 3 and C‐N‐H area of modified samples from XPS in Figure S1i (Supporting Information) witness a decrease, recommending the large concentration of primary amine moieties anchored on g‐C 3 N 4 surfaces of the modified samples in contrast with the pristine CN.…”

Controlled synthesis of 2D–2D conductive metal–organic framework/g-C3N4 heterojunctions for efficient photocatalytic hydrogen evolution

“…In recent years, polymer carbon nitride (g-C 3 N 4 ) has the advantages of nontoxicity, no secondary pollution, visible light response, stability, and low cost; moreover it has been widely used in the photocatalytic conversion of solar energy, such as hydrogen and oxygen production from photocatalytic water-splitting, selective organic photosynthesis, and degradation of organic pollutants, thus attracting people's attention. 10–13 However, bulk g-C 3 N 4 suffers from poor charge separation, insufficient visible light absorption, and few catalytic sites, which significantly reduces the photocatalytic efficiency. 14–16 One of the prevailing approaches in photocatalytic studies involves the integration of g-C 3 N 4 nanosheets with other semiconductors to fabricate heterojunctions.…”