Liqiang Hou

Insight into the topological defects and dopants in metal-free holey graphene for triiodide reduction in dye-sensitized solar cells

Exploiting highly active and stable counter electrodes (CEs) has been a persistent challenge for the practical application of dye-sensitized solar cells (DSSCs). Herein, we present an edge-enhanced modification to fabricate nitrogen doped holey graphene (NHG) by rationally employing N2 plasma treatment at the exposed edge sites of holey graphene. The as-synthesized NHG exhibits a highly conductive and unique holey scaffold with a large surface area, along with abundant edge-induced topological defects and nitrogen dopants. Benefiting from such unique features, NHG exhibits outstanding electrocatalytic activity and high electrochemical stability for the I−/I3− redox reaction. Furthermore, density functional theory calculations are performed to further elucidate the underlying mechanism behind this encouraging performance, in particular the effect of edge-induced topological defects. The DSSCs based on NHG CEs display a power conversion efficiency of 9.07%, which is even superior to that of Pt (8.19%). These results strongly indicate possibilities for the large-scale fabrication of low-cost and metal-free NHG materials for DSSCs with an I-complex redox couple.

Large-scale preparation of B/N co-doped graphene-like carbon as an efficient metal-free catalyst for the reduction of nitroarenes

Boron and nitrogen co-doped graphene-like carbon (BNG) is a metal-free catalyst that has been synthesized by combining ball-milling with thermal treatment. Firstly, the edge-selectively-functionalized graphene nanoplatelets (EFGnPs) were prepared by ball milling of the pristine graphite, which can facilitate boron incorporation. BNG catalysts with a high content of boron and nitrogen can then be obtained by pyrolysis of a mixture of EFGnPs and boric acid. We found that the reduction of nitroarenes can be catalyzed using a low BNG loading and a small amount of N2H4 in ethanol to form aminoarenes in high yields. The type of boron species in the BNG catalyst has an important effect on the reduction reaction. Furthermore, the catalyst containing the most B/N shows the highest catalytic activity during the reduction of nitroarenes, indicating that the doped B/N within the BNG is a key active site in impelling this reaction. Moreover, the BNG catalyst can be used six times, and no dehalogenation phenomenon occurs during the reduction process for halogen-substituted nitroarenes in contrast to the case when conventional metal catalysts are used.

Shear-Assisted Production of Few-Layer Boron Nitride Nanosheets by Supercritical CO 2 Exfoliation and Its Use for Thermally Conductive Epoxy Composites

Boron nitride nanosheets (BNNS) hold the similar two-dimensional structure as graphene and unique properties complementary to graphene, which makes it attractive in application ranging from electronics to energy storage. The exfoliation of boron nitride (BN) still remains challenge and hinders the applications of BNNS. In this work, the preparation of BNNS has been realized by a shear-assisted supercritical CO2 exfoliation process, during which supercritical CO2 intercalates and diffuses between boron nitride layers, and then the exfoliation of BN layers is obtained in the rapid depressurization process by overcoming the van der Waals forces. Our results indicate that the bulk boron nitride has been successfully exfoliated into thin nanosheets with an average 6 layers. It is found that the produced BNNS is well-dispersed in isopropyl alcohol (IPA) with a higher extinction coefficient compared with the bulk BN. Moreover, the BNNS/epoxy composite used as thermal interface materials has been prepared. The introduction of BNNS results in a 313% enhancement in thermal conductivity. Our results demonstrate that BNNS produced by supercritical CO2 exfoliation show great potential applications for heat dissipation of high efficiency electronics.

Catalytically enhanced thin and uniform TaS2 nanosheets for hydrogen evolution reaction

Though the transition-metal dichalcogenides (TMDs) were proven to have a better performance on the hydrogen evolution reaction (HER), the bulk production of active TMD materials remains a challenging work. This report overcomes those barriers by showing a simple procedure to synthesize TaS2 nanosheets through modifying the arc discharge process. The usage of chloride as the transporting agent reduces the growth period of the formed TaS2 with active edge sites. TaS2 is found to have a uniform thickness (4 nm) with high crystallinity and adopt a 2H polytype (double-layered hexagonal) structure. The as-synthesized TaS2 has superior activity for HER with the potential of 280 mV.