Effect of thermal treatment on the charge storage properties of graphene oxide/12-tungstophosphoric acid nanocomposite

Modification of Keggin anion structure with ion beams—A new spectroscopic insights into the effects of keV‐ and MeV‐ion beam irradiation on 12‐tungstophosphoric acid

“…In IR spectra, the Keggin anion also exhibits characteristic bands that are in the case of 120‐nm‐thick WPA assigned as follows: Band at 1083 cm −1 is assigned to asymmetric P‐O a vibration, band at 1003 with the shoulder at 987 cm −1 is assigned to asymmetric W=O d vibration, band at 899 cm −1 to asymmetric W‐O b ‐W vibration, and band at 844 cm −1 is assigned to asymmetric W‐O c ‐W vibration. [ 11 ] These bands in ATR‐FTIR spectra of 20‐μm‐thick WPA are also observed at 1079, 980, 909, and 810 cm −1 , respectively.…”

“…Raman spectroscopy is a commonly used tool for monitoring structural changes in POMs caused by interactions with the support, [ 11 ] thermal treatment, [ 10 ] or decomposition in solutions. [ 22 ] The ability of precise structural probing comes from a fact that there is a direct impact of any symmetry change on Raman spectra.…”

“…The assignation of bands is quite straight‐forward: 1005 and 990 cm −1 are assigned to symmetric and asymmetric W=O d vibration, respectively, 982 cm −1 to stretching P‐O a vibration, 903 cm −1 to asymmetric stretching W‐O b ‐W vibration, 544 cm −1 to symmetric stretching W‐O c ‐W vibration, and the Raman band at 214 cm −1 is assigned to stretching W‐O a vibration. [ 11 ]…”

“…The inset part of Figure 1a shows in greater detail these changes: intensity ratio of symmetric and asymmetric W=O d bands changes with decreasing thickness, whereas symmetric W=O d band appears as a doublet with an additional shoulder at 1002 cm −1 . It is known that interactions of HPAs with the platinum [ 23 ] and zeolite [ 11 ] through terminal W=O d bond change the position of its symmetric vibration. In the latter case, red shift of W=O d bond indicates possible hydrogen bonding between terminal (O d ) oxygen of Keggin anion and hydrogen atoms of the support.…”

“…[ 10 ] In our recent work, thermal treatment of 12‐tungstophosphoric acid (WPA) and the effect of the interaction with the graphene oxide support were proven beneficial for the charge storage capacity of the nanocomposite. [ 11 ] Therein, the thermal treatment up to 500°C caused structural modification of Keggin anion, which was observed by splitting of characteristic infrared (IR) bands in WPA spectrum. Although these methods produce structurally modified HPAs, the appearance of interesting properties can be expected from the unique structures, which justifies the applications of novel methods for their structural modification.…”