Yuanxing Fang

Tri-s-triazine-Based Crystalline Carbon Nitride Nanosheets for an Improved Hydrogen Evolution

Tri-s-triazine-based crystalline carbon nitride nanosheets (CCNNSs) have been successfully extracted via a conventional and cost-effective sonication-centrifugation process. These CCNNSs possess a highly defined and unambiguous structure with minimal thickness, large aspect ratios, homogeneous tri-s-triazine-based units, and high crystallinity. These tri-s-triazine-based CCNNSs show significantly enhanced photocatalytic hydrogen generation activity under visible light than g-C3 N4 , poly (triazine imide)/Li+ Cl- , and bulk tri-s-triazine-based crystalline carbon nitrides. A highly apparent quantum efficiency of 8.57% at 420 nm for hydrogen production from aqueous methanol feedstock can be achieved from tri-s-triazine-based CCNNSs, exceeding most of the reported carbon nitride nanosheets. Benefiting from the inherent structure of 2D crystals, the ultrathin tri-s-triazine-based CCNNSs provide a broad range of application prospects in the fields of bioimaging, and energy storage and conversion.

A Facile Steam Reforming Strategy to Delaminate Layered Carbon Nitride Semiconductors for Photoredox Catalysis

The delamination of layered crystals that produces single or few-layered nanosheets while enabling exotic physical and chemical properties, particularly for semiconductor functions in optoelectronic applications, remains a challenge. Here, we report a facile and green approach to prepare few-layered polymeric carbon nitride (PCN) semiconductors by a one-step carbon/nitrogen steam reforming reaction. Bulky PCN, obtained from typical precursors including urea, melamine, dicyandiamide, and thiourea, are exfoliated into few-layered nanosheets, while engineering its surface carbon vacancies. The unique sheet structures with strengthened surface properties endow PCNs with more active sites, and an increased charge separation efficiency with a prolonged charge lifetime, drastically promoting their photoredox performance. After an assay of a H2 evolution reaction, an apparent quantum yield of 11.3 % at 405 nm was recorded for the PCN nanosheets, which is much higher than those of PCN nanosheets. This delamination method is expandable to other carbon-based 2D materials for advanced applications.

Metal‐Free Boron‐Containing Heterogeneous Catalysts

Metal-free catalysts have distinct advantages over metal and metal oxide catalysts, such as lower cost as well as higher reliability and sustainability. Among the nonmetal compounds used in catalysis, boron-containing compounds with a few unique properties have been developed. In this Minireview, the recent advances in the field of boron-containing metal-free catalysts are presented, including binary and ternary boron-containing catalytic materials. Additionally, the three main applications in catalysis are considered, namely, electrocatalysis, thermal catalysis, and photocatalysis, with the role of boron discussed in depth for each specific catalytic application. Boron-containing compounds could have a substantial impact on the field of metal-free catalysts in the future.

Biomimetic Donor–Acceptor Motifs in Conjugated Polymers for Promoting Exciton Splitting and Charge Separation

Natural photosynthesis serves as a model for energy and chemical conversions, and motivates the search of artificial systems that mimic natures energy- and electron-transfer chains. However, bioinspired systems often suffer from the partial or even large loss of the charge separation state, and show moderate activity owing to the fundamentally different features of the multiple compounds. Herein, a selenium and cyanamide-functionalized heptazine-based melon (DA-HM) is designed as a unique bioinspired donor-acceptor (D-A) light harvester. The combination of the photosystem and electron shuttle in a single species, with both n- and p-type conductivities, and extended spectral absorption, endows DA-HM with a high efficiency in the transfer and separation of photoexcited charge carriers, resulting in photochemical activity. This work presents a unique conjugated polymeric system that shows great potential for solar-to-chemical conversion by artificial photosynthesis.

Coating Polymeric Carbon Nitride Photoanodes on Conductive Y:ZnO Nanorod Arrays for Overall Water Splitting

Polymeric carbon nitride (PCN) photosensitizers are proposed replacements for their inorganic counterparts in solar-to-fuel conversion via photoelectrochemical water splitting. However, intense charge recombination, primarily because of surface defects, limits the use of PCN in PEC systems. Now, photoanodes are designed by coating PCN films onto highly conductive yttrium-doped zinc oxide (Y:ZnO) nanorods (NRs) serving as charge collectors. The generation of charge carriers can therefore be promoted by this type II alignment. The charge collectors would be kept nearby for charge separation and transport to be used in the interfacial redox reactions. The photocurrent density of the polymer electrode is improved to 0.4 mA cm-2 at 1.23 V vs. the reversible hydrogen electrode in a Na2 SO4 electrolyte solution under AM 1.5 illumination. The result reveals a more than 50-fold enhancement over the PCN films achieved by powder; the efficiency can be preserved at 95 % for 160 minutes.

Efficient development of Type-II TiO 2 heterojunction using electrochemical approach for an enhanced photoelectrochemical water splitting performance

Abstract Type-II-heterojunction TiO2 nanorod arrays (NAs) are achieved by a combination of reduced and pristine TiO2 NAs through a simple electrochemical reduction. The heterojunction-structured TiO2 NAs exhibit an enhanced photo-efficiency, with respect to those of pristine TiO2 NAs and completely reduced black TiO2. The improved efficiency can be attributed to a synergistic effect of two contributions of the partially reduced TiO2 NAs. The light absorption is significantly increased, from the UV to the visible spectrum. Moreover, the type II structure leads to enhanced separation and transport of the electrons and charges. The proposed electrochemical approach could be applied to various semiconductors for a control of the band structure and improved photoelectrochemical performance.

LiCl as Phase-Transfer Catalysts to Synthesize Thin Co2P Nanosheets for Oxygen Evolution Reaction

Inorganic salts have been widely studied as templates for the synthesis of 2D layer structures. However, these salts normally can only serve as templates without any catalytic activity. Here, we report that LiCl used for the synthesis of ultrathin nanosheets not only serves as template for the synthesis of ultrathin Co2 P nanosheets with a thickness of 0.7 nm but also acts as a catalyst that induces the phase-transfer from CoP to Co2 P. The Co2 P nanosheets have a high electrochemical performance for oxygen evolution reaction.