Density functional theory (DFT) calculations are conducted to explore the interaction of H_2 with pure and Tidoped WO_3 (002) surfaces.Four top adsorption models of H_2 on pure and Ti-doped WO_3 (002) surfaces are investigated respectively,they are adsorption on bridging oxygen O_(1c),absorption on plane oxygen O_(2c),absorption on 5-fold W_(5c) (Ti),and absorption on 6-fold W_(6c).The most stable and H_2 possible adsorption structure in the pure surface is H-end oriented to the surface plane oxygen O_(2c) site,while the favourable adsorption sites for H_2 in a Ti-doped surface is not only an O_(2c) site but also a W_(6c) site.The adsorption energy,the Fermi energy level E_F,and the electronic population are investigated and the H_2-sensing mechanism of a pure-doped WO_3 (002) surface is revealed theoretically:the theoretical results are in good accordance with our existing experimental results.By comparing the above three terms,it is found that Ti doping can obviously enhance the adsorption of H_2.It can be predicted that the method of Ti-doped into a WO_3 thin film is an effective way to improve WO_3 sensor sensitivity to H_2 gas.
展开▼
