Congcong Liu

Liquid Exfoliated Graphene as Dopant for Improving the Thermoelectric Power Factor of Conductive PEDOT:PSS Nanofilm with Hydrazine Treatment

UNLABELLED Here, we fabricated a highly conductive poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) ( PEDOT PSS) nanofilm via vacuum filtration with enhanced thermoelectric power factor by doping of liquid exfoliated graphene (GE) and hydrazine treatment. The effect of GE exfoliated in dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP) on the electrical conductivity and thermopower of PEDOT PSS was investigated. Although electrical conductivity decreased with increasing GE, thermoelectric power factors of PEDOT PSS nanofilms were improved with 3 wt % GE in DMF (38.6 μW m(-1) K(-2)) and in NMP (28.0 μW m(-1) K(-2)) compared to pure PEDOT PSS (11.5 μW m(-1) K(-2)). The mechanism of improvement was proposed to be the removal of PSS and the good interaction between PEDOT and GE. With hydrazine treatment, 3 wt % GE-doped PEDOT PSS nanofilm (PG3) showed a further enhanced power factor of 53.3 μW m(-1) K(-2) (∼5 times higher than that of pristine PEDOT PSS nanofilm). The effects of hydrazine containing concentration, treatment time, and temperature on the electrical conductivity and Seebeck coefficient of PG3 were investigated systematically. An estimated thermoelectric figure of merit (ZT) is 0.05 with the optimized power factor at room temperature.

Amorphous Metallic NiFeP: A Conductive Bulk Material Achieving High Activity for Oxygen Evolution Reaction in Both Alkaline and Acidic Media

The intrinsic catalytic activity at 10 mA cm-2 for oxygen evolution reaction (OER) is currently working out at overpotentials higher than 320 mV. A highly efficient electrocatalyst should possess both active sites and high conductivity; however, the loading of powder catalysts on electrodes may often suffer from the large resistance between catalysts and current collectors. This work reports a class of bulk amorphous NiFeP materials with metallic bonds from the viewpoint of electrode design. The materials reported here perfectly combine high macroscopic conductivity with surface active sites, and can be directly used as the electrodes with active sites toward high OER activity in both alkaline and acidic electrolytes. Specifically, a low overpotential of 219 mV is achieved at the geometric current density 10 mA cm-2 in an alkaline electrolyte, with the Tafel slope of 32 mV dec-1 and intrinsic overpotential of 280 mV. Meanwhile, an overpotential of 540 mV at 10 mA cm-2 is attained in an acidic electrolyte and stable for over 30 h, which is the best OER performance in both alkaline and acidic media. This work provides a different angle for the design of high-performance OER electrocatalysts and facilitates the device applications of electrocatalysts.

Facile Fabrication of PEDOT:PSS/Polythiophenes Bilayered Nanofilms on Pure Organic Electrodes and Their Thermoelectric Performance

A pure organic PEDOT:PSS nanofilm was used as a working electrode for the first time to electrodeposit polymer films of polythiophene (PTh) and its derivatives in a boron trifluoride diethyl ether (BFEE) solution, fabricating a novel generation of bilayered nanofilms. Cyclic voltammetry (CV) demonstrated good electrochemical stability of the as-formed films. Structures and surface morphologies were systematically investigated by the characterizations of cross-section SEM, FT-IR, UV-vis, SEM, and AFM. The resulting films revealed stable and enhanced thermoelectric (TE) performances. The electrical conductivity values of PEDOT:PSS/PTh, PEDOT:PSS/P3MeT, and PEDOT:PSS/P3HT nanofilms were determined to be 123.9, 136.5, and 200.5 S cm(-1), respectively. The power factor reached up to be a maximum value of 5.79 μW m(-1) k(-2). Thus, this technique offers a facile approach to a class of bilayered nanofilms, and it may provide a general strategy for fabricating a new generation of conducting polymers for more practical applications.

Toward Superior Capacitive Energy Storage: Recent Advances in Pore Engineering for Dense Electrodes

With the rapid development of mobile electronics and electric vehicles, future electrochemical capacitors (ECs) need to store as much energy as possible in a rather limited space. As the core component of ECs, dense electrodes that have a high volumetric energy density and superior rate capability are the key to achieving improved energy storage. Here, the significance of and recent progress in the high volumetric performance of dense electrodes are presented. Furthermore, dense yet porous electrodes, as the critical precondition for realizing superior electrochemical capacitive energy, have become a scientific challenge and an attractive research focus. From a pore-engineering perspective, insight into the guidelines of engineering the pore size, connectivity, and wettability is provided to design dense electrodes with different porous architectures toward high-performance capacitive energy storage. The current challenges and future opportunities toward dense electrodes are discussed and include the construction of an orderly porous structure with an appropriate gradient, the coupling of pore sizes with the solvated cations and anions, and the design of coupled pores with diverse electrolyte ions.