Synthesis of High Surface Area WN and Co–W–N Nitrides by Chemical Routes

Abstract

This study investigates the synthesis of high surface area W 2 N and Co–W–N nitrides by nitridation of various precursors obtained by chemical routes. For the synthesis of W 2 N nitride, WO 3 precursors were obtained by acidifying Na 2 WO 4 ·2H 2 O (acid route) and by thermal decomposition of the tungstate–citrate precursor. The solid-state reactivity, BET surface areas and pore structures of the nitride materials have been investigated in detail. Co–W–N nitride was obtained from CoWO 4 synthesized by co-precipitation. W 2 N and Co–W–N nitrides crystallize in β-W 2 N structure. The single-point BET surface areas were estimated to be 58, 55 and 60 m 2 /g for the β-W 2 N nitride materials synthesized using commercial WO 3 and WO 3 obtained from acid and citrate precursor, respectively. The maximum surface areas (40 m 2 /g) are obtained for Co–W–N nitrides synthesized at 700 °C. We have investigated the change in pore volume and pore diameter when the synthesis conditions are changed. The thermogravimetric and differential thermal analysis studies corroborate the fine particle nature of the materials.