Resistance of the electrode material play a vital role for applications in supercapacitors, where lowering the resistance leads to improved performance. Poly(3,4-ethylene dioxythiophene) (PEDOT) possesses high theoretical conductivity; however, the high density of grain boundaries, low accessible surface area, and low rate capability have been pervasive issues affecting the PEDOT-based supercapacitors. To this end, a hydrothermal method is proposed in this work where oxygen functional groups incorporated on the surface of carbon nanotubes (CNTs) are utilized to polymerize 3,4-ethylenedioxythio-phene (EDOT). PEDOT forms an ultrathin, well-aligned coating on the surface of CNTs. This arrangement minimizes the number of grain boundaries and increases the electrochemically active surface area. Additionally, a shear-thinning Xanthan gum-H 2 SO 4 gel electrolyte is introduced to overcome the low impregnation of the conventional polyvinyl-based electrolyte due to the hydrophobicity of the CNT-PEDOT composite.A supercapacitor based on this material showed a very low Equivalent Series Resistance (ESR) of 0.31 Ω which leads to a high power density of 74 W cm À 3 .

Oxygen reduction reaction (ORR) is one of the fundamental reactions that occur on the cathode of fuel cells. The sluggish kinetics of ORR and the high cost of the conventionally used ORR electrocatalyst mandate extensive research towards the development of inexpensive, high-performance and stable electrocatalysts. Various supported nanostructures of pristine noble metals and its alloys, transition metals/metal oxides (MOs), chalcogens/pnictogens doped metals/MOs, etc. have attracted great attention towards ORR in both acidic and alkaline electrolytes. This review primarily documents the recent advancements and challenges of supported nanomaterials with fascinating properties towards ORR. This study focuses on the use of carbon-based materials as support. The significant factors like size, morphology, hetero-atom doping, defects and interfaces (metal/metal, metal/oxide and metal/hydroxide) that can tailor ORR activity are portrayed elaborately. The electrochemical techniques and parameters that are adopted mainly during data collection and evaluation of ORR are also discussed.

No abstract

Pd-based electrocatalysts are considered as suitable replacement for Pt-based ones owing to the similar electronic structure of Pd, relatively low cost, and superior catalytic performance. The activity and utilization efficiency of Pd in electrochemical reactions can be increased by alloying with transition metals, like Cu and Co. Herein, we report the synthesis of a homogeneously embedded Pd 2 CuCo alloy in the carbon matrix. Compared with the benchmark Pt/C, the as-synthesized Pd alloy electrocatalyst exhibited an improved limiting current density (J m ; −5.65 mA cm −2 ), a smaller Tafel slope (58.7 mV dec −1 ), and a comparable onset potential (E onset ; 0.91 V vs RHE). Comparatively, the optimized Pd 2 CuCo showed a current retention of ∼96% after a 6 h stability test and only a 4 mV loss in the half-wave potential (E 1/2 ) after 10,000 redox cycles, while Pt/C showed a current retention of 72.5% and a loss of 5 mV in E 1/2 . Meanwhile, the Pd 2 CuCo alloy electrocatalyst also demonstrated excellent methanol tolerance compared to benchmark Pt/C. In addition, the electrocatalyst showed higher activity and long-term stability toward the formic acid oxidation reaction than Pd/C, signifying the potential for wide applicability.