Holey Graphitic Carbon Nitride Nanosheets with Carbon Vacancies for Highly Improved Photocatalytic Hydrogen Production

Abstract

2D graphitic carbon nitride (GCN) nanosheets have attracted tremendous attention in photocatalysis due to their many intriguing properties. However, the photocatalytic performance of GCN nanosheets is still restricted by the limited active sites and the serious aggregation during the photocatalytic process. Herein, a simple approach to produce holey GCN (HGCN) nanosheets with abundant in‐plane holes by thermally treating bulk GCN (BGCN) under an NH3 atmosphere is reported. These formed in‐plane holes not only endow GCN nanosheets with more exposed active edges and cross‐plane diffusion channels that greatly speed up mass and photogenerated charge transfer, but also provide numerous boundaries and thus decrease the aggregation. Compared to BGCN, the resultant HGCN has a much higher specific surface area of 196 m2 g−1, together with an enlarged bandgap of 2.95 eV. In addition, the HGCN is demonstrated to be self‐modified with carbon vacancies that make HGCN show much broader light absorption extending to the near‐infrared region, a higher donor density, and remarkably longer lifetime of charge carriers. As such, HGCN has a much higher photocatalytic hydrogen production rate of nearly 20 times the rate of BGCN.

Reduced-sized monolayer carbon nitride nanosheets for highly improved photoresponse for cell imaging and photocatalysis

“…Compared with GCNNs (Fig. 3a), the (002) peak at about 27.5°is much weaker and broader, and the (100) peak at 13.2°has disappeared, indicating that the stacking of the conjugated aromatic systems and the in-plane repeat units of GCN are obviously disrupted after the exfoliation [20,26,37]. A Fourier transform infrared (FTIR) spectrum measurement was conducted to verify the chemical structure of the NMGCNs.…”

“…Compared with bulk graphitic carbon nitride (GCN), the remarkable optical and catalytic properties of the GCNNs are mainly associated with the QCE and their larger specific surface area (SSA) [18,20]. On one hand, the wider energy bandgap arising from the QCE accompanied by the different photo-physical behavior of photogenerated electron-hole pairs is very helpful for improving their redox performance.…”

“…Thus far, GCNNs prepared with various techniques, such as mechanical milling [24,25], chemical oxidation thermal or etching [20,26,27], physical and liquid exfoliation [22,28,29], and electrochemical synthesis [30] usually show wide distributions in both the number of layers and lateral size. In particular, due to many advantages of easy operation, low-cost, environmental benignity, and no reason for interfacial defects, liquid-phase exfoliation, usually in conjunction with ultrasonic treatment has been intensively explored for producing ultrathin GCNNs by delaminating bulk GCN [28,31,32].…”

2D/2D Graphitic Carbon Nitride (g-C3N4) Heterojunction Nanocomposites for Photocatalysis: Why Does Face-to-Face Interface Matter?

“…Additionally, it has been proven that 2D semiconductor possessed improved mobility of charge carriers and reduced charge recombination as compared to the 0D and 1D nanomaterials (Meng et al, 2012;Ida and Ishihara, 2014). In spite of the fascinating properties possessed by 2D g-C3N4, pristine g-C3N4 demonstrated several shortfalls such as sluggish separation of electron-hole pairs, limited visible-light absorption beyond 460 nm, small specific surface area, and low electrical conductivity (Liang et al, 2015b;Hou et al, 2016;Shi et al, 2016;Zhang et al, 2016g;Li et al, 2017;Xia et al, 2017). To overcome these bottlenecks, modification of bare g-C3N4 such as nanostructure design (Niu et al, 2012;Liang et al, 2015c;Zheng et al, 2015), intercalation with Li + and Cl − (Liang et al, 2015a), elemental doping Huang et al, 2015;She et al, 2016), copolymerization (Fan et al, 2016;Rahman et al, 2016), coupling with metals or noble metals (Tonda et al, 2014;Ong et al, 2015b), incorporation with other semiconductors Putri et al, 2016a;Zhang et al, 2016g;Ye et al, 2017), hybridization with metal phosphides (Pan et al, 2017;Wen et al, 2017;Yi et al, 2017;Zhao et al, 2017a,b), and many more has been widely investigated to enhance the photocatalytic efficiency for practical benefits.…”

Polar Ultrathin Self‐Doping Carbon Nitride Nanosheets with Intrinsic Polysulfide Adsorption for High Performance Lithium‐Sulfur Batteries

“…[38,39] The peak area ratio of N-C=N/CÀC in CNB and CÀCNN were 2.17 and 1.68 respectively, and the significant decrease in the ratio suggested the loss of N and the doping of C. Meanwhile, the N 1s spectra of the two samples in Figure 5c were resolved to four peaks at the binding energy of 398.7, 399.7, 401.1, and 404.1 eV, which were attributed to N species in N=CÀN, N-(C) 3 , NÀN, and positive charge localization in heptazine rings. [40] The peak area percentages of the N=CÀN and NÀN decreased from 73.78 % and 10.44 % for CNB to 71.70 % and 7.75 % for CÀCNN, respectively. Meanwhile, the peak area percentage of the NÀ(C) 3 obviously increased from 13.61 % for CNB to 18.96 % for CÀCNN.…”