Mn-modified phosphomolybdates by hydrothermal route for pseudocapacitor application

In this study, hydrothermal method was used to synthesize Mn modified organic-inorganic phosphomolybdates, Product-1 and 2, as considered to be, Mn x (Imi) y PMo 12 O 40, Mn x (Imi) y P 2 Mn 2 Mo 12 O 50 with Product-3, which was considered to be mixed by-products, might have Mn x (Imi) y P 2 Mn 2 Mo 12 O 50 (Imi) 4 Na 4 (OH) 8 (OH) z (majority) in its structure, (imi = imidazole). Product-1 was the main product, Product-2 and 3 were prepared from the by-product using only heating followed by concentrating technique. All products had high temperature resistance. According to XPS data, the percentages of Mo, Mn, C, O, P, N and Na were 3. 91, 23. 30, 13. 54, 47. 83, 7. 9, 2. 30, and 1. 15%, 20. 10, 2. 39, 22. 98, 41. 53, 3. 53, 6. 83, and 2. 6%, and 15. 51, 1. 06, 31. 29, 43. 56, 1. 84, 5. 58, and 0. 58%, in Product-1, 2 and 3, respectively (by the no. of atoms), along with the average valency states of Mn were 2. 26, 2. 39, and 2. 14, respectively. Product-1 was considered having polyoxo kegging clusters, Product-2 and 3 were considered having polyoxohexamolybdate units in their structures, as well as Product-2 was deliberately assumed to be the polymer or a derivative of Product-3. Cyclic voltammetry (CV) showed all three compounds having different reversible pseudo-capacitor character. At 2. 0 Ag -1 current density, Product-1, 2 and 3@GCE showed specific discharge capacitance of 37. 01, 380. 45, and 635. 37 Fg -1, respectively. In galvanostatic charging-discharging (GCD), Product-1@GCE showed comparatively higher retention as compared to other electrodes.