1 Department of Energy Conversion and Storage, Technical University of Denmark2 Proton conductors, Department of Energy Conversion and Storage, Technical University of Denmark3 Technische Universität München4 Department of Mechanical Engineering, Technical University of Denmark
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 exo-template, SBA-15 acts as a stabilizer and small W2N particles (6-7 nm) with a high specific surface area (40 m(2) 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. (C) 2015 Elsevier Inc. All rights reserved.
Microporous and Mesoporous Materials, 2015, Vol 211, p. 147-151