聚乙烯亚胺-钴络合物对氧还原电流的影响

研究了聚乙烯亚胺 钴络合物 (PEI Co)在电解质溶液中的氧可逆结合特性及对氧还原电流的影响 .PEI Co络合物溶解于电解质的水溶液中 ,在氧气气氛中络合物与氧结合 ,UV Vis光谱在 310nm处出现了新的吸收峰 ,并在 2 80nm处观察到等吸光点 .PEI Co络合物与氧结合平衡曲线服从Langmuir行为 ,络合物与氧结合的亲和力 (p50 )为 0 6 6 7kPa .氧与PEI Co加成物的解离反应表观速率常数为 1 1× 10 5s- 1 ,表明络合物具有快速、可逆的氧结合特性 .在PEI Co络合物存在下 ,氧电极的还原电流显著增加 ,并且随PEI Co络合物的浓度以及气氛中氧浓度的增加而增加 .[PEI链节 ] [Co]=5 1时 ,氧还原电流达到极大值 ,说明PEI Co络合物与氧形成了结构为 [N5CoⅢ O2 CoⅢ N5]的加成物 .

EFFECT OF THE POLYETHYLENEIMINE-COBALT COMPLEX ON REDUCTION CURRENT OF OXYGEN

The reversible oxygen-binding properties of the polyethyleneimine-cobalt (PEI-Co) complex and the effect of the PEI-Co complex on the reduction current of oxygen were studied.The color of the PEI-Co complex in the electrolyte solution changed on exposure to oxygen atmosphere,which was?monitored by UV-visible absorption spectrometry.The UV-visible absorption spectra of the PEI-Co complex displayed a new adsorption band at 310?nm,with an isosbestic point at 280?nm.The spectral change was attributed to the reversible oxygen-adduct formation of the PEI-Co complex even in the electrolyte solution.The oxygen-binding equilibrium curve of the PEI-Co complex obeyed a Langmuir isotherm,to give the high oxygen-binding affinity (p_(50) = 0.667 kPa).And the apparent dissociation rate constant of oxygen from the PEI-Co complex (k_d = 1.1×10~5 s~(-1)) was also high.The aqueous solution of the PEI-Co complex that had rapid and reversible oxygen-binding properties functioned as an oxygen-enriching medium for oxygen electrode to enhance the diffusion-controlled current for the oxygen reduction.Based on the rapid release of oxygen from the PEI-Co complex,a high current was obtained for the reduction of oxygen in the presence of the PEI-Co complex,and the current increased with the increase of the concentration of the PEI-Co complex and the oxygen concentration in the atmosphere.The reduction current reached a saturated value near [ethyleneimine unit]/[Co] = 5,which suggested the structure of a six-coordinate μ-dioxo dinuclear complex [N_5Co~Ⅲ-O_2-Co~ⅢN_5].A new type of oxygen-diffusion electrode for metal/air batteries and fuel cells is proposed using the oxygen-enriching material immobilized at the electrode surface.