Selective Etching of N‐Doped Graphene Meshes as Metal‐Free Catalyst with Tunable Kinetics, High Activity and the Origin of New Catalytic Behaviors

Abstract

New N‐doped reduced graphene oxide (N‐RGO) meshes are facile fabricated by selective etching of 3–5 nm nanopores, with controllable doping of N dopants at an ultrahigh N/C ratio up to 15.6 at%, from pristine graphene oxide sheets in one‐pot hydrothermal reaction. The N‐RGO meshes are illustrated to be an efficient metal‐free catalyst toward hydrogenation of 4‐nitrophenol, with new catalytic behaviors emerging in following three aspects: (i) tunable kinetics following pseudofirst order from commonly observed pseudozero order; (ii) strikingly improved activity with 26‐fold increased rate constant (1.0 s−1 g−1 L); (iii) no induction time required prior to reaction due to depressed back conversion, and dramatically decreased apparent activation energy (Ea) (17 kJ mol−1). The origin of these new catalytic properties can be assigned to the synergetic effects between graphitic N doping and structural defects arising from nanopores. Deeper understanding unveils that the concentration of graphitic N is inverse proportion to Ea, while the pyrrolic N has no impact on this reaction, and oxygenate groups hampers it. The porous nature allows the N‐RGO meshes to conduct catalyze reactions in continuous flow fashion.

Surface Engineering of Defective Hematite Nanostructures Coupled by Graphene Sheets with Enhanced Photoelectrochemical Performance

“…1 These attributes are favorable for effective charge transfer. 35 The Raman spectra in Figure 6A further confirmed the successful coupling of RGO sheets and Fe 2 O 3 nanostruc-tures. The Raman shifts located at 200−800 cm −1 are ascribed to Fe 2 O 3 , while the shifts at 1000−1800 cm −1 are characteristic peaks for carbon materials.…”

“…In this process, the GO can be reduced to RGO, owing to effective removal of oxygen-containing groups and the restored sp 2 structure of graphene . These attributes are favorable for effective charge transfer . The Raman spectra in Figure A further confirmed the successful coupling of RGO sheets and Fe 2 O 3 nanostructures.…”

Recent advances in metal-free heteroatom-doped carbon heterogonous catalysts

“…Dai and colleagues 194 developed a hydrothermal strategy for the fabrication of N-doped reduced graphene oxide meshes from pristine GO sheets in the presence of NH 4 OH as a nitrogen source at elevated temperature ( Fig. 7 ).…”

A Metal-Free Carbon-Based Catalyst: An Overview and Directions for Future Research

“…The authors proposed that the unpaired electrons of GO were major contributors in determining the catalytic activity. N-doped reduced graphene oxide (N-RGO) serves as an efficient metal-free catalyst toward the hydrogenation of 4-nitrophenol (4-NP), as shown in Scheme 6 [80]. Fabrication of a series of N-RGO meshes was achieved through the etching of 3-5 nm sized nanopores with doping of N-dopants.…”

“…As supported by theoretical studies, active sites could be generated from C atoms, which are next to the doped N atoms on N-doped graphene (NG) surface; hence these NG meshes are a more useful candidate in the catalytic reduction of the nitro compound. N-doped reduced graphene oxide (N-RGO) serves as an efficient metal-free catalyst toward the hydrogenation of 4-nitrophenol (4-NP), as shown in Scheme 6 [80]. Fabrication of a series of N-RGO meshes was achieved through the etching of 3-5 nm sized nanopores with doping of N-dopants.…”