Effect Of Additives On Catalytic Properties Of Ni Anode In DBFC

As a new portable fuel cell with high specific energy, the direct borohydride fuel cell (DBFC) has become the research focus in the abroad field of fuel cell in recent years due to its advantages of high theoretical voltage and specific energy, convenient fuel storage and transportation and so on. Theoretically, the electrochemical oxidation of BH 4– is 8e reaction, but the actual released electrons are different because of using different anodic catalysts. Thus the research on anodic catalysts is particularly important for the application of DBFC. It is an important way for the reduction of DBFC cost that develops non-noble metal anode catalysts because noble metals are expensive. In this work, the performance of Ni anodic catalyst with low price was researched systematically.Firstly, the catalytic performance of Ni to electrochemical oxidation of BH₄^– in alkaline medium was studied by cyclic voltammetry. It was found that there was only one oxidized peak in the cyclic voltammetry of BH₄^– electro-oxidation on Ni electrode and the peak potential was about -0.7V without any peaks during the reduction, while two peaks existed in the electro-oxidation of BH₄^– on Pt electrode locating in the range of -0.4 0V and two peaks also emerged in the reduction. So the oxidation of BH₄^– was more simple and peak potential was more negative on Ni electrode than that on Pt electrode.Secondly, it was easy for Ni to lose the catalytic activity on electrochemical oxidation of BH₄^– due to corrosion in alkaline medium. So the effects of amine, alcohols, amino acids and alcohol amines organic additives on the catalytic performance of Ni were investigated in alkaline medium by cyclic voltammetry. The results demonstrated that the electro-oxidation of BH–4 was promoted by hexamethylenetetramine, triethylenetetramine and glycine but the corrosion of Ni metal was not inhibited. The catalytic stability of Ni and the electro-oxidation of BH–4 were not improved by ethanol and glycerol. Although the catalytic stability of Ni was improved effectively by ethanolamine, the electro-oxidation of BH₄^– was not enhanced.Lastly, the influences of ethanolamine (MEA), diethanolamine (DEA) and triethanolamine (TEA) on the catalytic performance of Ni were researched by cyclic voltammetry, electrochemical impedance spectroscopy, chronopotentiometry and so on. The results showed that the corrosion of Ni in alkaline medium was inhibited effectively by addition these additives. And the optimal concentration ranges of additives were 0.0494 0.0606mol / L, 0.0618 0.0759mol / L, 0.0643 0.0738mol / L, respectively. The results also demonstrated that TEA was the best additive, which not only inhibited effectively the corrosion of Ni in alkaline medium, but also promoted the electrochemical oxidation of BH₄^– . The inhibition of TEA on the corrosion of Ni in alkaline medium was confirmed further by X-ray diffraction. In addition, it was also found that the inhibition of the additives on the corrosion of Ni in alkaline medium was enhanced by elevating temperature. The effect of temperature on TEA was the least among additives.