Synthesis of High Surface Area W 2 N and Co–W–N Nitrides by Chemical Routes

This study investigates the synthesis of high surface area W₂N and Co–W–N nitrides by nitridation of various precursors obtained by chemical routes. For the synthesis of W₂N nitride, WO₃ precursors were obtained by acidifying Na₂WO₄·2H₂O (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 CoWO₄ synthesized by co-precipitation. W₂N and Co–W–N nitrides crystallize in β-W₂N structure. The single-point BET surface areas were estimated to be 58, 55 and 60 m²/g for the β-W₂N nitride materials synthesized using commercial WO₃ and WO₃ obtained from acid and citrate precursor, respectively. The maximum surface areas (40 m²/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.