Space-confined preparation of high surface area tungsten oxide and tungsten nitride inside the pores of mesoporous silica SBA-15

•Space-confined synthesis of W2N in the pores of ordered mesoporous silica SBA-15.•Two-step synthesis via mesoporous WO3 to phase-pure mesoporous W2N.•Mesoporous tungsten nitride with small particle sizes and high surface area.•Strong influence of template removal from WO3 before and after ammonolysis.•Reduction of particle sintering during nitridation by order of template removal.

For the direct preparation of high surface area nitride materials, a lack of suitable precursors exists. Indirect preparation by gas phase nitridation (e.g. by ammonia) requires high temperatures and often results in sintering. The present work demonstrates that the space-confined preparation of W2N inside the pores of ordered mesoporous silica SBA-15 offers a possibility to reduce sintering phenomena and thus to obtain smaller particles, porous structures and a higher surface area material. The preparation was pursued in a two-step approach. First, WO3 was introduced into the channels of SBA-15 and second, ammonolysis was conducted for its conversion to W2N. When performed in the presence of the exotemplate, SBA-15 acts as a stabilizer and small W2N particles (6–7 nm) with a high specific surface area (40 m2 g−1) are obtained after template removal. When the template is, however, removed before nitridation, it cannot stabilize the W2N particles and enhanced sintering occurs.

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