As a fascinating conjugated polymer, graphitic carbon nitride (g-C3N4) has become a new research hotspot and drawn broad interdisciplinary attention as a metal-free and visible-light-responsive photocatalyst in the arena of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability, and “earth-abundant” nature. This critical review summarizes a panorama of the latest progress related to the design and construction of pristine g-C3N4 and g-C3N4-based nanocomposites, including (1) nanoarchitecture design of bare g-C3N4, such as hard and soft templating approaches, supramolecular preorganization assembly, exfoliation, and template-free synthesis routes, (2) functionalization of g-C3N4 at an atomic level (elemental doping) and molecular level (copolymerization), and (3) modification of g-C3N4 with well-matched energy levels of another semiconductor or a metal as a cocatalyst to form heterojunction nanostructures. The constructi...

Graphitic Carbon Nitride (g-C3N4)-Based Photocatalysts for Artificial Photosynthesis and Environmental Remediation: Are We a Step Closer To Achieving Sustainability?

Engineering photocatalytic materials for renewable energy generation and environmental decontamination has always been a very exciting prospect to counter the global energy demands and pollution challenges. Graphitic carbon nitride (g-C 3 N 4 ), a polymeric, metal-free semiconductor with a mild band gap (2.7 eV) has become hot-spot in various scientific exploits such as environmental pollution mitigation, energy generation and storage, organic synthesis, sensors, etc. These applications exploit the interesting properties of g-C 3 N 4 such as good visible light absorption, graphene-like structure, good thermal and chemical stability and photocatalytic properties. In this review we begin with an overview of the fundamental aspects of photocatalysis as a pollution remediation strategy. This is followed by an introduction to graphitic carbon nitride as a photocatalyst, preparation strategies and its properties. Subsequently, a comprehensive and critical discussion of the various most recent developments towards enhancing the visible light photocatalytic properties of g-C 3 N 4 for pollution alleviation, selected results and important photocatalytic degradation mechanisms, is given. Summary remarks and future perspective conclude the review.

Graphitic carbon nitride (g-C3N4) nanocomposites: A new and exciting generation of visible light driven photocatalysts for environmental pollution remediation

Surface reaction kinetics and bulk charge separation are both critical to the efficiency of solar water splitting. In addition to the well-documented surface catalytic effect, the promotion of bulk charge separation upon loading of cocatalysts has rarely been reported. This paper describes the synergetic enhancement of surface reaction kinetics and bulk charge separation by introducing discrete nanoisland p-type Co3O4 cocatalysts onto n-type BiVO4, forming a p–n Co3O4/BiVO4 heterojunction with an internal electric field to facilitate charge transport. Being highly dispersed on the surface of photoanodes, the nanoisland cocatalysts could suppress the formation of recombination centers at the photoanode/cocatalyst interface. This cocatalyst-loading method achieved a charge separation efficiency of up to 77% in the bulk and 47% on the surface of catalysts. An AM 1.5G photocurrent of 2.71 mA/cm2 at 1.23 V versus the reversible hydrogen electrode for water oxidation was obtained, which is the highest photocurr...

Enhanced Surface Reaction Kinetics and Charge Separation of p-n Heterojunction Co3O4/BiVO4 Photoanodes.

A review on TiO 2 -based Z-scheme photocatalysts

Bismuth vanadate (BiVO4) is a promising visible-light driven semiconductor photocatalyst with various benefits such as low production cost, low toxicity, high photostability, resistance to photo-corrosion and narrow band gap with a good response to visible-light excite. However, the fast recombination of photoinduced charge carriers restricts their photocatalytic activity. In the past decades, many attempts were adopted to enhance the photocatalytic activity of BiVO4. Significant advances in understanding the fundamental issues and the development of an efficient photocatalyst have been made in current years. In this review, we have provided a comprehensive overview of the latest progress on the morphology control and growth mechanism of BiVO4 micro/nano-structures, doping with metal and non-metal elements and semiconductor coupling along with some highlights in the photodegradation of organic pollutants under visible-light illumination. This review may benefit the researchers and engineers in the arena of material chemistry for designing new BiVO4 based photocatalysts with low production cost and high efficiency.

A review on BiVO4 photocatalyst: Activity enhancement methods for solar photocatalytic applications

The invention provides a preparation method for fusiform rod-shaped hexagonal phase BiPO4 powder. The method comprises the steps that Bi(NO3)3.5H2O, Na3PO4.12H2O and (NH4)2TiF6 serve as raw materials, the raw materials are added into water and stirred evenly, the pH value is regulated to be in faintly acid, and a precursor solution is formed; a microwave hydrothermal method is adopted to enable the precursor solution to be reacted, after the reaction is completed, cooling is performed, sediment in a reaction kettle is taken out, washed and dried, and then the fusiform rod-shaped hexagonal phase BiPO4 powder is obtained. The preparation method for the fusiform rod-shaped hexagonal phase BiPO4 powder has the advantages that devices are simple, and low temperature (about 200 DEG C) and high efficiency (the reaction time is about 60 min) are achieved; the synthesized powder is higher in purity and better in appearance; the preparation method is simple in technology, high in efficiency, low in energy consumption and cost and friendly to environment.

Preparation method for fusiform rod-shaped hexagonal phase BiPO4 powder

The thin films of BFO, binary-doped Bi0.96Sr0.04Fe0.98Co0.02O3, and multi-doped Bi0.96Sr0.04Fe0.94Mn0.04Co0.02O3 are fabricated using the sol–gel method. To study the mechanism for the enhanced intrinsic ferroelectricity in multi-doped BFO, this work uses related aspects including the electrostatic potential energy, the Fermi level, and the Schottky interface barrier. Using multi-doped BFO can reduce the height of the electrostatic barrier and change the Fermi level so that the Schottky barrier height is increased to reduce the leakage current, thereby improving the intrinsic ferroelectricity. Also, using multivalent Mn with a double-exchange effect improves the ferromagnetism. These improved intrinsic ferroelectric and ferromagnetic properties make BFO applicable in various practical devices and fields.

Mechanism for enhanced ferroelectricity in multi-doped BiFeO 3 thin films

Heterostructured CNT-RuSx Nanomaterials for Efficient Electrochemical Hydrogen Evolution Reaction

Local surface plasmon resonance promotion of photogenerated electrons to hot electrons for enhancing photothermal CO2 hydrogenation over Ni(OH)2/Ti3C2 catalysts

Bi0.88Gd0.09Sr0.03Fe0.94Mn0.04Co0.02O3/Co1−xNixFe2O4 (BGSFMC/CNxFO, x = 0.1–0.5) composite films were successfully prepared by the sol–gel method. The structure and performance changes of BGSFMC/CNxFO composite film were studied. The results show that after the Ni2+-doped CNxFO magnetic bottom layer is combined with the upper BGSFMC, stress is generated in the film interface, which makes the upper BGSFMC layer phase structure change from a single R3c:H phase to the coexistence of R3c:H and R3m:R phases. The change of the structure causes the Fe–O bond length and Fe–O–Fe bond angle of the upper layer of the BGSFMC to change, the internal oxygen vacancy concentration decreases and the Fe3+ concentration increases. As a result, the inclination of the upper BGSFMC layer octahedron changes, limiting spatial modulation and releasing magnetism. At the same time, the change of structure also inhibits the conversion of Fe3+ to Fe2+ and strengthens the spin tilt and Fe–O–Fe super exchange interaction to enhance ferromagnetism. The ferromagnetic properties of the BGSFMC/CNxFO composite film are significantly enhanced, and the residual magnetization of 48.29–56.94 emu/cm3 is obtained. The reduction of defect complexes makes the ferroelectric domains of the BGSFMC/CNxFO composite film easier to flip under an external electric field, the symmetry and peak sharpness of the C–V characteristic curve increase, and the intrinsic polarization increases. The BGSFMC/CN0.1FO composite film obtained an increased Pr = 112 μC/cm2, a polarization switching current Is = 0.081 mA, a ferroelectric domain switching capacitance peak CS = 24.9 μF/cm2, and a reduced leakage conductivity CL = 4.73 μF/cm2. Through the ion doping of the magnetic layer, the ferromagnetic and ferroelectric properties of the BFO film can be adjusted and improved.

Huijun Ren

Papers

Preparation method for fusiform rod-shaped hexagonal phase BiPO4 powder

Mechanism for enhanced ferroelectricity in multi-doped BiFeO 3 thin films

Heterostructured CNT-RuSx Nanomaterials for Efficient Electrochemical Hydrogen Evolution Reaction

Local surface plasmon resonance promotion of photogenerated electrons to hot electrons for enhancing photothermal CO2 hydrogenation over Ni(OH)2/Ti3C2 catalysts

The enhanced multiferroic properties of BiFeO3 composite film by doping ions in the magnetic layer