六氰合铁酸铜钴薄膜修饰铂电极的电化学、XRD及XPS研究

采用循环伏安法在铂电极上电聚合了六氰合铁酸铜钴薄膜，并用电化学、XRD 和XPS对该薄膜进行了表征。研究表明此薄膜属于取代型的多核六氰合铁酸盐，由 Cu~(2+)，Co~(2+)和Fe~(2+)共同占据晶格格点。通过改变Cu~(2+)，Co~(2+)和 Fe~(3+)在沉积液中的比例可以改变聚合膜的性质。随沉积液中Cu~(2+)含量的增加 ，聚合膜中铜的含量相应增加而晶格常数则逐渐减小，但保持着面心立方的晶格对 称性。当沉积液中Cu~(2+):Co~(2+):Fe~(3+) = 1:1:2时，得到的聚合膜具有比较 典型的性质，该薄膜修饰的铂电极在pH 4～10之间均能保持着稳定的电化学响应。 其对一价阳离子的选择性顺序为K~+ > Li~+ > Na~+ > NH_4~+，与单组分的六氰铁 酸酮和六氰合铁酸钴都存在着较大的差别。XPS实验表明氧化态薄膜中铁元素以Fe (III)存在，并且在X射线的照射下很快转化为Fe(II)。

Electrochemistry, XRD and XPS of a Platinum Electrode Modified with Hybrid Hexacyanoferrate Films of Copper and Cobalt

Hybrid hexacyanoferrate films of copper and cobalt (CuCoHCF) were electrodeposited on a platinum electrode by cyclic voltammetry from 0. 0 V to + 1.0 V (vs. SCE) at 50 mV/s in a solution mixture containing 0. 25 mol/L KNO_3, 1.25 * 10~(-4) mol/L CuSO_4, 1.25 * 10~(-4) mol/L Co (NO_3)_2 and 2.5 * 10~(-4) mol/L K_3Fe-(CN)_6, and characterized with electrochemistry, XRD and XPS. The results demonstrate that CuCoHCF is not a simple mixture of copper hexacyanoferrate and cobalt hexacyanoferrate, but a new compound with cyano moiety bridge between two adjacent lattice sites, Cu~(2+) and Co~(2+) coordinated to nitrogen atom and Fe~(2+) to carbon atom. With the increase of Cu~(2+) concentration in the deposition solution, Cu~(2+) content in the films increased, while the lattice constant of the films decreased gradually. Typical properties were obtained for the films electrodeposited from a solution mixture with content ratio of Cu~(2+), Co~(2+) and Fe~(3+) being 1:1:2. The CuCoHCF modified platinum electrode exhibited stable electrochemical response in pH range 4 ～ 10 and permeability for monovalent cations in the order of K~+ > Li~+ > Na~+ > NH_4~+, all of which were different from that of the respective single component hexacyanoferrates. XPS reveals that the iron atom exists in the form of Fe(III) in oxidized films, which is reduced to Fe~(2+) during X-ray scanning.