Spherical Fe7S8@rGO nanoflowers as electrodes with high electrocatalytic performance in dye-sensitized solar cells.

Dye-sensitized solar cells (DSSCs) can directly convert solar energy into electricity, and have aroused great research interest from researchers. Here, the spherical Fe7S8@rGO nanocomposites were expediently fabricated by facile methods, and applied in DSSCs as counter electrodes (CEs). The morphological features show the porous structure of Fe7S8@rGO, and it is beneficial to enhance the permeability of ions. Reduced graphene oxide (rGO) has a large specific surface area and good electrical conductivity, shortening the electron transfer path. The presence of rGO promotes the catalytic reduction of I3- ions to I- ions and reduces the charge transfer resistance (Rct). The experimental findings show that the power conversion efficiency (PCE) of Fe7S8@rGO as CEs for DSSCs can reach 8.40% (20 wt% for rGO), significantly higher than Fe7S8 (7.60%) and Pt (7.69%). Therefore, Fe7S8@rGO nanocomposite is expected to be an efficient and cost-effective CE material for DSSCs.

Quantum dot embedded N-doped functionalized multiwall carbon nanotubes boost the short-circuit current of Ru(ii) based dye-sensitized solar cells.

Here, we report zinc sulfide quantum dots, ZnS(QDs), moored on N-doped functionalized multiwall carbon nanotubes (MWCNTs) wrapped with reduced graphene oxide (rGO). The MWCNTs have a tangled network, a particular surface area, and a distinctive hollow structure that may be suitable for use as a counter electrode (CE) material. A ZnS@N.f-MWCNTs@rGO composite as the CE on a fluorine-doped tin oxide substrate in a dye-sensitized solar cell (DSSC) was fabricated using a doctor blade technique. The electrochemical performance showed that at the electrolyte/CE interface, the ZnS(QDs) and N-doped functionalized MWCNTs wrapped with rGO (ZnS@N.f-MWCNTs@rGO) electrode has a lower transfer charge resistance (Rct) and a greater catalytic capacity than naked ZnS(QDs). A power conversion efficiency (PCE) of 9.4% was attained for this DSSC gadget, which is higher than that of a DSSC gadget utilizing ZnS(QDs), ZnS@N.f-MWCNTs, ZnS@rGO and Pt. Also, the DSSC device using ZnS@N.f-MWCNTs@rGO had a fill factor (FF) that was better than the other counter electrodes. The cyclic voltammetry and electrochemical impedance spectra (EIS) electron transfer measurements showed that ZnS@N.f-MWCNTs@rGO films can provide fast electron transfer from the electrolyte to the CE and great electrocatalytic activity to reduce triiodide to a CE based on ZnS@N.f-MWCNTs@rGO in the DSSC.

Remarkable Enhancement in the Photoelectric Performance of Uniform Flower-like Mesoporous Fe3O4 Wrapped in Nitrogen-Doped Graphene Networks.

The porous structure and excellent specific surface area are superior for use as a counter electrode (CE) material. In addition, N-doped graphene possesses a remarkable electron-transfer pathway and many active sites. Therefore, a novel idea is to wrap uniform flower-like mesoporous Fe3O4 (Fe3O4UFM) in an N-doped graphene (N-RGO) network structure to enhance the power conversion efficiency (PCE). The hybrid materials of Fe3O4UFM@N-RGO are first used as a CE in dye-sensitized solar cells (DSSCs), showing a preeminent conductive interconnected 3D porous structure with more catalytic activity sites and a better ability for and a faster reaction rate of charge transfer, resulting in quicker reduction of I3- than Pt. A 9.26% photoelectric conversion efficiency has been achieved for the DSSCs with Fe3O4UFM@N-RGO as the CE, which is beyond the value of Pt (7.72%). The positive synergetic effect between Fe3O4 and N-RGO is mainly responsible for the remarkable photoelectric property enhancement of this uniform flower-like mesoporous Fe3O4 wrapped in N-doped graphene networks, as demonstrated by the Tafel polarization, electrochemical impedance spectra, and CV curves. These methods will provide a simple way to effectively reproduce CE materials.

Functional integration and self-template synthesis of hollow core-shell carbon mesoporous spheres/Fe3O4/nitrogen-doped graphene to enhance catalytic activity in DSSCs.

Excellent corrosion resistance is crucial for photovoltaic devices to acquire high and stable performance under high corrosive complicated environments. Creative inspiration comes from sandwich construction, whereby Fe3O4 nanoparticles were anchored onto hollow core-shell carbon mesoporous microspheres and wrapped by N-graphene nanosheets (HCCMS/Fe3O4@N-RGO) to obtain integrated high corrosive resistance and stability. The as-prepared multiple composite material possesses outstanding performance as a result of structure optimization, performance improvement, and interface synergy. Therefore, it can effectively suppress corrosion from the electrolyte in recycled tests many times, indicating the ultrahigh corrosion resistance life of this double carbon-based nanocomposite. Furthermore, the electrical conductivity and conversion efficiency of the composite are well maintained due to the triple synergistic interactions, which could serve as a guideline in establishing high-performance multifunctional HCCMS/Fe3O4@N-RGO with great prospects in energy devices, such as lithium batteries, supercapacitors and electrode materials, etc.

Origin of photoactivity in graphitic carbon nitride and strategies for enhancement of photocatalytic efficiency: insights from first-principles computations.

The origin of the photoactivity in graphitic carbon nitride (g-C3N4) and the strategies for improving its photocatalytic efficiency were systematically investigated using first-principles computations. We found that g-C3N4 composed of tri-s-triazine units (g-CN1) is preferable in photocatalysis, owing to its visible-light absorption and appropriate band edge potentials. Despite the benefit of nanocrystallization of g-CN1, excessively minimized and passivated g-CN1 nanosheets (g-CN1NSs) should be inhibited, due to the intensely broadened band gaps in these structures. C- or N-vacancies in g-CN1NSs lead to gap states and smaller band widths, which should also be restrained. Compared with C substitution in B doped g-CN1NSs, N-substitution is favourable for enhancing the photoactivity of g-CN1NSs, due to the red-shift light absorption and the absence of gap states within this structure. Both WTe2 coupled and CdSe cluster loaded g-CN1NSs have decreased band gaps and directly separated carriers, which are beneficial to promote the photoactivity of g-CN1NSs. Among these modified g-CN1NS photocatalysts, WTe2 coupled g-CN1NSs are more preferable, as a result of their smaller band gap, free gap states and more rapid migration of excitons.

Nanocomposite of tin sulfide nanoparticles with reduced graphene oxide in high-efficiency dye-sensitized solar cells.

A nanocomposite of SnS2 nanoparticles with reduced graphene oxide (SnS2@RGO) had been successfully synthesized as a substitute conventional Pt counter electrode (CE) in a dye-sensitized solar cell (DSSC) system. The SnS2 nanoparticles were uniformly dispersed onto graphene sheets, which formed a nanosized composite system. The effectiveness of this nanocomposite exhibited remarkable electrocatalytic properties upon reducing the triiodide, owning to synergistic effects of SnS2 nanoparticles dispersed on graphene sheet and improved conductivity. Consequently, the DSSC equipped with SnS2@RGO nanocomposite CE achieved power conversion efficiency (PCE) of 7.12%, which was higher than those of SnS2 nanoparticles (5.58%) or graphene sheet alone (3.73%) as CEs and also comparable to the value (6.79%) obtained with pure Pt CE as a reference.