“…Synthesis of Nb 2 O 5 : The Nb 2 O 5 was synthesized using the hydrothermal procedure described elsewhere. 25 In a typical synthesis route, ammonium niobate(V) oxalate hydrate (Sigma-Aldrich, C 4 H 4 NNbO 9 •H 2 O, 99.99%) (9.0894 g, 30 mmol) was dissolved in 200 mL of deionized water. Following 1 h of vigorous stirring, the pellucid solution was sealed in a Teflonlined stainless steel autoclave and heated for 24 h at 175 °C.…”