Adsorption and dissociation of H2S on nitrogen-doped TiO2 anatase nanoparticles: Insights from DFT computations

We have investigated the adsorption and dissociation of hydrogen sulfide (H2S) molecule on the pristine and nitrogen-doped TiO2 anatase nanoparticles using first-principles calculations in order to obtain insights into the adsorption behaviors of H2S molecules. We have investigated different adsorption geometries of H2S over the nanoparticles. We have found that the H2S adsorption is not energetically more favorable on the pristine nanoparticle surface, but H2S is preferentially adsorbed on the N-doped nanoparticles with a higher favorability in energy. H2S molecule adsorbs on the dangling oxygen, doped nitrogen and fivefold coordinated titanium sites of the TiO2 nanoparticle. The hydrogen atom in the H2S molecule forms a hydrogen bond with the surface oxygen or doped nitrogen atom of TiO2. We have reported the results of DFT calculations including the bond lengths/angles, adsorption energies, electronic density of states and molecular orbitals. Charge analysis based on Mulliken charges reveals a significant charge transfer from the molecule to the TiO2 anatase particle. The inclusion of the vdW interactions results in considerable enhancement of H2S-TiO2 interaction, thereby increasing the adsorption energies of the molecules. The N-doped nanoparticles have stronger adsorption ability than the undoped ones, indicating the higher sensing capability of N-doped nanoparticles for H2S detection. Our results suggest a great potential of N-doped TiO2 for application as a highly sensitive H2S sensor.