Kezhong Wu

TiC/Pt composite catalyst as counter electrode for dye-sensitized solar cells with long-term stability and high efficiency

Titanium carbide/platinum (TiC/Pt) composites were prepared by a simple chemical route and subsequently introduced into dye-sensitized solar cells (DSCs) as counter electrode (CE) catalysts to improve the catalytic activity and reduce the cost of DSCs. The DSC using TiC/Pt (containing 0.12 wt% of Pt) CE showed high power conversion efficiency (PCE) of 7.63%, higher than those of DSCs using TiC and Pt CEs (6.40% and 7.16%, respectively). After a long-term (one year) stability test, the PCE of the DSC using this CE retained 86.9% of its highest value, proving the outstanding durability of the TiC/Pt composite. In large-scale DSCs (55 mm × 75 mm), the DSC using TiC/Pt CE yielded a PCE of 4.98%, comparable to that of a DSC using Pt CE (4.94%). This work points out the feasibility of using TiC/Pt composite CEs in practical applications.

Mo2C microspheres and nanorods as counter electrode catalysts for iodide-free redox couples in dye-sensitized solar cells

In this work, molybdenum carbide microspheres (Mo2C-Ms) and nanorods (Mo2C-Nr) are synthesized for use as counter electrode (CE) catalysts in dye-sensitized solar cells (DSSCs), specifically towards the regeneration of iodide-free redox couples of T2/T− and Co3+/2+. In the T2/T− based DSSCs, the prepared Mo2C-Ms and Mo2C-Nr both show high catalytic behavior, and the devices generate power conversion efficiency (PCE) values of 5.50% (Mo2C-Ms) and 4.86% (Mo2C-Nr), respectively, much higher than the Pt CE based counterpart (3.73%). Electrochemical impedance spectroscopy, cyclic voltammetry, and Tafel polarization curve measurements reveal that Mo2C-Ms also show higher catalytic activity for the Co3+/2+ redox couple that is competitive with the traditional Pt CE. The device using a Mo2C-Ms CE achieves a high PCE of 8.70%, indicating great potential to replace the expensive Pt CE.

Effect of Transition-Metal Ion Doping on Electrocatalytic Activities of graphene/polyaniline-M2+ (Mn2+, Co2+, Ni2+, and Cu2+) Composite Materials as Pt-Free Counter Electrode in Dye-Sensitized Solar Cells

ABSTRACT A series of graphene/polyaniline-M2+ (M2+ = Mn2+, Co2+, Ni2+, and Cu2+) composite counter electrodes were synthesized by doping transition-metal ions in polyaniline and graphene for dye-sensitized solar cells (DSSCs). The counter electrodes showed significantly high photoelectric conversion efficiency of 5.38% (Mn2+), 4.65% (Co2+), 4.00% (Ni2+), and 2.49% (Cu2+). The catalytic activities of graphene/polyaniline-M2+ electrodes were evaluated using cyclic voltammetry, Nyquist plots, and Tafel polarization. The chemical characteristics and surface morphology of graphene/polyaniline-M2+ composite materials were determined by infrared spectroscopy and scanning electron microscopy. These results indicate a potential application of ion-doped polyaniline as the counter electrode in cost-effective DSSCs.

Synthesis of transition-metal (VIB)-compound catalysts as counter electrodes in dye-sensitized solar cells

Transition-metal (VIB) carbides (TMCs) and oxides (TMOs) were prepared by a simple acetamide–metal route for use as counter electrodes (CEs) in dye-sensitized solar cells (DSSCs). Acetamide served as the source of carbon and oxygen because it is cost-effective and a good chelating agent, as well as it does not pollute the environment. The carbides and oxides thus prepared were characterized by X-ray diffraction, scanning electron microscopy, and nitrogen sorption. These catalysts comprising Cr3C2, Cr2O3, WC, WO2, Mo2C, and MoO2 exhibited satisfactory catalytic activities for the reduction of I3− to I− in DSSCs, as evidenced by the results obtained from cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel polarization measurements. WC exhibited the best catalytic activity with the maximum photoelectric conversion efficiency. A power conversion efficiency (PCE) of up to 4.83% was obtained for the device using WC as the CE, among other materials, while those of 3.24% (Mo2C), 4.44% (Cr3C2), 4.67% (WO2), 2.73% (Cr2O3), and 2.53% (MoO2) were obtained for other DSSCs.

Synthesis and performance of La 2 O 3 @MWCNT composite materials as Pt-free counter electrodes for dye-sensitized solar cells

Pt-free composite counter electrode (CE) composed of La2O3 was successfully synthesized by a simple pyrolysis of Lanthanum acetate hydrate (La(CH3COO)3·xH2O) in a high-temperature solid phase. Furthermore, three proportion composite catalysts of La2O3@MWCNTs based on La2O3 and multiwall carbon nanotubes (MWCNTs) were prepared and characterized as Pt-free catalysts for CE in dye-sensitized solar cells (DSSCs). The morphology and structure of La2O3@MWCNT composites were determined by scanning electron microscopy and X-ray diffraction. The electrochemical performance of La2O3@MWCNT composite catalysts for CEs was determined by photocurrent-voltage measurements, cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel polarization. The experimental results showed that the power conversion efficiencies of 5.20, 5.12, and 4.70% were obtained for La2O3: MWCNTs with mass ratios of 5:1, 3:1, and 1:1 as counter electrode towards the reduction of I3−/I− ions respectively in the encapsulation of DSSC batteries, which were higher than that of MWCNTs (3.94%) and La2O3 (0.77%) electrode under the similar conditions. The enhanced electrode performance was attributed to relatively larger surface area and higher conductivity of La2O3@MWCNT composite catalysts.