Boron-doped graphene as a high-efficiency counter electrode for dye-sensitized solar cells

Cost effective dye sensitized solar cell based on novel Cu polypyrrole multiwall carbon nanotubes nanocomposites counter electrode

In order to replace Pt CE in dye sensitized solar cell (DSSC) with simple and low cost, copper polypyyrol functionalized multiwall carbon nanotubes (Cu-PPy-FWCNTS) nanocomposite CE was fabricated by two step electrodeposition method on the stainless-steel substrate. The surface morphology, electrical conductivity, electrochemical properties of Cu-PPy-FWCNTS nanocomposite CE electrodes were observed by using verity of techniques such as scanning electron microscopy, a four-probe method and electrochemical workstation. The Fourier transform infrared (FTIR) spectroscopy confirms the presence of FMWCNTS into PPy-FMWCNTS nanocomposite and XRD analysis verified the Cu nanostructures had come into being. The cyclic voltammogram and Tafel polarization measurement demonstrated that solution processed Cu-PPy-FWCNTS nanocomposites CE had smaller charge transfer resistance Rct (4.31 Ω cm2) and higher electrocatalytic performance for I3-/I- redox solution. Finally, the photovoltaic efficiency of DSSC assembled with Cu-PPy-FWCNTS nanocomposite CE and Platinized CE were compared. The results revealed that the photovoltaic efficiency of DSSC with Cu-PPy-FWCNTS nanocomposites CE reached (7.1%), which is superior to Platinized CE (6.4%). The higher photovoltaic efficiency of the Cu-PPy-FMWCNTS film is due to copper nanostructures that lead to higher cathodic current density (2.35 mA/cm2). The simple fabrication method, excellent electrocatalytic and photovoltaic properties permit the Cu-PPy-FWCNTS nanocomposites credible alternative CE to save the cost of DSSC.

Tailorable boron-doped carbon nanotubes as high-efficiency counter electrodes for quantum dot sensitized solar cells

1. Tunable BCNTs are prepared by the pre-oxidation strategy. 2. B-Doped CNTs exhibit excellent activity for S_n²⁻ reduction. 3. The QDSSC based on CdS/CdSe QDs and BCNT1 shows a PCE of 4.55% under one sunlight illumination.

Metal-Free Synthesis of Boron-Doped Graphene Glass by Hot-Filament Chemical Vapor Deposition for Wave Energy Harvesting

Property modulation of graphene glass by heteroatom doping such as boron (B) and nitrogen (N) is important to extend its practical applications. However, unlike N doping, research studies about the metal-free synthesis of B-doped graphene on glass through the chemical vapor deposition (CVD) method are rarely reported. Herein, we report a hot-filament CVD approach to prepare B-doped graphene glass using diborane (B₂H₆) as the B dopant. The synthesized B-doped graphene was uniform on a large-scale and composed of nanocrystalline graphene grains. By raising the B₂H₆ flow from 0 to 15 sccm, the B content of graphene was facilely modulated from 0 to 5.3 at. %, accompanied with the improvement of both transparency and conductivity. The B-doped graphene prepared on glass at 15 sccm B₂H₆ flow presented the optimal transparent conductive performance superior to those of most reported graphene glass fabricated by other state-of-the-art approaches. Furthermore, for the first time, the performance of graphene glass for wave energy harvesting has been elaborated. It was found that the output power produced by inserting graphene glass into 0.6 M sodium chloride (NaCl) solution could be improved by more than 6 times through B doping. The significant enhancement resulted from the higher waving voltage and smaller resistance of B-doped graphene on glass than the pristine ones. In addition, the waving voltage inversed the polarity after B doping, which was due to the opposite variation of surface potential of pristine and B-doped graphene after NaCl immersion. This work would pave ways for the metal-free preparation and expand the energy-harvesting applications of B-doped graphene materials.

Tuning the properties of boron-doped reduced graphene oxide by altering the boron content

Boron-doping enhanced the occurrence of the energy bandgap, the pore structure and interfacial charge transfer characteristics.

Tunable-Deformed Graphene Layers for Actuation

Benefiting from unique planar structure, high flexibility, splendid thermal, and electric properties; graphene as a crucial component has been widely applied into smart materials and multi-stimulus responsive actuators. Moreover, graphene with easy processing and modification features can be decorated with various functional groups through covalent or non-covalent bonds, which is promising in the conversion of environmental energy from single and/or multi-stimuli, to mechanical energy. In this review, we present the actuating behaviors of graphene, regulated by chemical bonds or intermolecular forces under multi-stimuli and summarize the recent advances on account of the unique nanostructures in various actuation circumstances such as thermal, humidity, electrochemical, electro-/photo-thermal, and other stimuli.

Guiding Principles for Designing Highly Efficient Metal-Free Carbon Catalysts

Carbon nanomaterials are promising metal-free catalysts for energy conversion and storage, but the catalysts are usually developed via traditional trial-and-error methods. To rationally design and accelerate the search for the highly efficient catalysts, it is necessary to establish design principles for the carbon-based catalysts. Here, theoretical analysis and material design of metal-free carbon nanomaterials as efficient photo-/electrocatalysts to facilitate the critical chemical reactions in clean and sustainable energy technologies are reviewed. These reactions include the oxygen reduction reaction in fuel cells, the oxygen evolution reaction in metal-air batteries, the iodine reduction reaction in dye-sensitized solar cells, the hydrogen evolution reaction in water splitting, and the carbon dioxide reduction in artificial photosynthesis. Basic catalytic principles, computationally guided design approaches and intrinsic descriptors, catalytic material design strategies, and future directions are discussed for the rational design and synthesis of highly efficient carbon-based catalysts for clean energy technologies.

Catalysis with Two-Dimensional Materials Confining Single Atoms: Concept, Design, and Applications

Two-dimensional materials and single-atom catalysts are two frontier research fields in catalysis. A new category of catalysts with the integration of both aspects has been rapidly developed in recent years, and significant advantages were established to make it an independent research field. In this Review, we will focus on the concept of two-dimensional materials confining single atoms for catalysis. The new electronic states via the integration lead to their mutual benefits in activity, that is, two-dimensional materials with unique geometric and electronic structures can modulate the catalytic performance of the confined single atoms, and in other cases the confined single atoms can in turn affect the intrinsic activity of two-dimensional materials. Three typical two-dimensional materials are mainly involved here, i.e., graphene, g-C₃N₄, and MoS₂, and the confined single atoms include both metal and nonmetal atoms. First, we systematically introduce and discuss the classic synthesis methods, advanced characterization techniques, and various catalytic applications toward two-dimensional materials confining single-atom catalysts. Finally, the opportunities and challenges in this emerging field are featured on the basis of its current development.

Coaxial heterojunction carbon nanofibers with charge transport and electrocatalytic reduction phases for high performance dye-sensitized solar cells

Coaxial CNFs featured high conductivity derived from HP, and high N content and defective sites derived from PAN.

Carbon quantum dot tailored counter electrode for 7.01%-rear efficiency in a bifacial dye-sensitized solar cell

We present here a carbon quantum dot (CQD) tailored counter electrode (CE) for a bifacial dye-sensitized solar cell (DSSC).

Extraction of nano-silicon with activated carbons simultaneously from rice husk and their synergistic catalytic effect in counter electrodes of dye-sensitized solar cells

The extraction of renewable energy resources particularly from earth abundant materials has always been a matter of significance in industrial products. Herein, we report a novel simultaneous extraction of nano-silicon with activated carbons (nano-Si@ACs) from rice husk (RH) by chemical activation method. As-extracted nano-Si@ACs is then used as an energy harvesting materials in counter electrodes (CEs) of dye-sensitized solar cells (DSSCs). The morphology, structure and texture studies confirm the high surface area, abundant active sites and porous structure of nano-Si@ACs. Electrochemical impedance spectroscopy and cyclic voltammetry analyses reveal that the nano-Si@ACs is highly beneficial for fast I₃⁻ reduction and superior electrolyte diffusion capability. The nano-Si@ACs CE based DSSC exhibits enhanced power conversion efficiency of (8.01%) in contrast to pristine Pt CE (7.20%). These favorable results highlight the potential application of RH in low-cost, high-efficiency and Pt-free DSSCs.

Nitrogen and phosphorus dual-doped graphene as a metal-free high-efficiency electrocatalyst for triiodide reduction

Alternative high-performance electrocatalysts for triiodide (I₃^-) reduction of low-cost dye-sensitized solar cells (DSSCs) are urgently sought after. To address the concerned issues, we report a facile strategy for engineering the nitrogen and phosphorus dual-doped graphene (NPG) via an efficient ball-milling process, followed by a simple thermal annealing approach utilizing melamine (C₃H₆N₆) and triphenylphosphine ((C₆H₅)₃P) as the N and P source, respectively. When employed as the counter electrode (CE) in DSSCs, such a metal-free material exhibits excellent electrocatalytic activity towards the I₃^-/I^- redox reaction. Dual-doping of N and P heteroatoms can markedly enhance the photovoltaic performance of DSSCs by a synergistic effect and a high conversion efficiency of 8.57% is achieved, which is superior to Pt CE, and much higher than that of the single-component N- or P-doped graphene electrodes. In addition, the NPG CE also shows an outstanding electrochemical stability. The present results demonstrate that the NPG as a low-cost and high-efficiency electrocatalyst for reduction of I₃^- will be one of the promising CE materials in DSSCs.

Plasma-induced highly efficient synthesis of boron doped reduced graphene oxide for supercapacitors

In this work, we presented a novel route to synthesize boron doped reduced graphene oxide (rGO) by using the dielectric barrier discharge (DBD) plasma technology under ambient conditions.

The effect of doped heteroatoms (nitrogen, boron, phosphorus) on inhibition thermal oxidation of reduced graphene oxide

The effect of doping different heteroatoms including nitrogen, boron and phosphorus on the thermal oxidation of RGO is investigated.

Boron-doped nanographene: Lewis acidity, redox properties, and battery electrode performance

The impact of boron doping on the nature of nanographene was investigated at the molecular level in terms of chemical adsorption with various Lewis bases, spin multiplicity of the two electron-reduced species, and performance as a battery electrode.

The preparation of boron-doped nanocarbon scaffolds with well-defined structures is important for the understanding of the impact of boron doping on their properties and behavior at the molecular level. We recently succeeded in the synthesis of a structurally well-defined nanographene molecule, bearing two boron atoms at the central positions. In this study, the characteristic properties and functions of this boron-doped nanographene were investigated in terms of (1) Lewis acidity, (2) redox properties, and (3) electrode performance in a battery. This boron-doped nanographene was susceptible to chemical adsorption with various Lewis bases, resulting in significant changes in the absorption and fluorescence properties, as well as in the conformation of the honeycomb framework. The two-electron reduction of this boron-doped nanographene produced a dianionic species that showed a substantial biradical character with a triplet ground state. A Li battery electrode, composed of a boron-doped nanographene with small peripheral substituents, displayed a stable performance in the 1.5–4.0 V range with a first discharge capacity of 160 mA h g^–1. These results provide important insights into the effect of boron doping on nanocarbon compounds.

Functionalized graphene and other two-dimensional materials for photovoltaic devices: device design and processing

2D materials have been successfully used in various types of solar cells as transparent electrodes, interfacial and active materials.

3 D single-walled carbon nanotube/graphene aerogels as pt-free transparent counter electrodes for high efficiency dye-sensitized solar cells

3D single-walled carbon nanotube (SWCNT)/graphene aerogel (NGS) was synthesized and used as an alternative to platinized fluorine-doped tin oxide (FTO) in dye-sensitized solar cells (DSSCs). An island-like structure formed on the FTO using the spin-coating method, leading to a transmittance (49.86 % at 671 nm). The resulting NGS-based counter electrodes (CEs) exhibited excellent power conversion efficiency (PCE) (8.31 %) compared to Pt (7.56 %). Surprisingly, PCE increased to 9.64 % under assisted by a mirror; The excellent performance of DSSCs can be attributed to the high electrical conductivity and good electrocatalytic activity induced by the SWCNTs and the excellent catalytic properties of graphene, coupled with the 3D structure with a larger surface area and good surface hydrophilicity for increased electrolyte-electrode interactions and electrolyte/reactant diffusion. Hence, our results demonstrate that 3D-NGS materials have considerable potential for DSSC-related applications and merit further investigation.

Two carboxyethyltin functionalized polyoxometalates for assembly on carbon nanotubes as efficient counter electrode materials in dye-sensitized solar cells

Two new POM-carboxyethyltin derivatives increased the electrocatalytic activity of single-walled carbon nanotubes toward triiodide reduction as counter electrodes in DSSCs.