Electrochemical conversion of CO 2 into useful fuels provides tremendous potential for renewable energy storage. This study investigated a predominant nanostructure-dependent catalytic electroreduction of CO 2 into formate on Bi 2 O 3 electrode in 0.5 M KHCO 3 electrolyte. Compared with nano-particle Bi catalyst derived from Bi 2 O 3 nanorods (Bi 2 O 3 -R) electrode, the nano-flowered Bi in situ prepared via reduction of etched Bi 2 O 3 nanorods (Bi 2 O 3 -E) exhibited an enhanced catalytic activity for CO 2 electroreduction to formate. A relatively low overpotential of 530 mV was observed over Bi 2 O 3 -E electrode for formate generation, and the maximum faradaic efficiency (FE) was achieved 99.2% at −1.5 V vs SCE with operating at a current density of 7.5 mA cm −2 , which was superior to that of Bi 2 O 3 -R (FE = 67.9%). Experimental results revealed that the electrochemical active surface area and catalytic activity over reduced Bi 2 O 3 -E electrode were originated from the nano-flowered structure with abundant edge sites. The durability of catalytic activity over Bi 2 O 3 -E lasted at least for 20 h of continuous reaction with negligible decline of FE and current density. This insight may benefit for the further design of surface morphology and structure devoting to improving the catalytic efficiency for CO 2 electroreduction.

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A Nafion/phosphotungstic heteropolyacid/polypyrrole modified glassy carbon electrode (Nf/PW12/PPY/GCE) was prepared in this paper. The electrochemical behaviours of nitric oxide at the Nf/PW12/PPY/GCE were investigated by cyclic voltammetry. The experimental results indicated that the phosphotungstic heteropolyacid doped in polypyrrole film possessed obvious catalysis for the electroxidation of nitric oxide. In 0.1mol/L sulfuric acid, the anodic peak current of nitric oxide at the sensors linearly increased with nitric oxide concentration over the range of 1.0×10-7～2.5×10-5mol/L with a detection limit of 3.0×10-8mol/L. The Nafion layer modified on the surface of electrocatalyst could effectively eliminate the inferences from common species in biological samples such as ascorbate, uric acid and nitrite. The presented methods of determing nitric oxide exhibited high sensitivity and good reproducibility.