Metal(ii) complex based on 5-[4-(1H-imidazol-1-yl)phenyl]-2H-tetrazole: the effect of the ligand on the electrodes in a lead-acid battery

Abstract

Based on 5-[4-(1H-imidazol-1-yl)-phenyl]-2H-tetrazole (HL), three metal(II) complexes formulated as PbL₂(H₂O) (1) and ML₂(H₂O)₄·2H₂O (M = Ni 2 and Co 3) were synthesized and structurally characterized by single-crystal X-ray diffraction. A stable mononuclear metal(II) fragment was observed in the three complexes. The cyclic voltammograms (CVs) of complex 1 were investigated. In 0.5 M H₂SO₄ aqueous solution with and without the HL ligand, the Pb (or PbO₂) electrode showed a similar electrochemical response but with less redox current in the presence of HL, which is most likely due to the formation of the Pb(II) complex upon the addition of HL, and it probably can decrease the redox rates of the two electrodes to some extent. The galvanostatic charge–discharge plot of the lead-acid battery shows a longer discharge time in the presence of HL. After CV or charge–discharge cycles, the Pb electrode consists of Pb and PbSO₄ but with a lower PbSO₄ content upon the addition of HL.