XiangLiu+-+Log

The final paper, I will writing something about first-principle calculation of doping of perovskite.

The paper I summarized for is : Zhou, X.; Shi, J.; Li, C., Effect of Metal Doping on Electronic Structure and Visible Light Absorption of SrTiO3 and NaTaO3 (Metal = Mn, Fe, and Co). //The Journal of Physical Chemistry C// **2011,** //115// (16), 8305-8311. [|doi:10.1021/jp200022x] **[Full Marks JCB]**

1 Introduction Perovskite is proven to be active for photocatalytical water splitting reaction. The low efficiency of perovskite can be improved by doping other elements.

The writer reviewed some previous experimental work of various different perovskite doped with new metals.

Some previous work pointed out that transition metal doping in anatase TiO2 would introduce d states within the bandgap. Then the writer shows interests in what about the doping in SrTiO3.

2 Experimental Section 2.1 Computational details The general computation method is given in this paragraph, as DFT with GGA. The cutoff energy is 400eV. The k-point in Brillouin zone is 8*8*8

The 2*2*2 and 2*2*5 supercells are used. The modeled structures are as Sr1-xMxTiO3, SrTi1-xMxO3(x=0.0125,0.05, and M=Mn, Fe, and Co)

2.2 Synthesis and Charaterization The methods of synthesizing and doping NaTaO3 powder are given. The ultraviolet-visible absorption spectra were done.

3 Results and Discussion 3.1 Relaxed Structure The writer showed the calculated lattice parameter for pure Pm3M SrTiO3 and the influence of doping upon M-O and M-Ti bond lengths.

The writer pointed out the definition of formation energy Ef of the doped system.

The Ef values for different systems showed the substitution for Ti has lower energy due to their similar ion radius.

3.2 Electronic Structures 3.2.1 pure SrTiO3 The density of states and projected density of states of pure SrTiO3 are shown and explained. And the writer pointed out the shortcoming of GGA that it will underestimate the band gap of strong correlated system will not influence his research. 3.2.2 doping system The DOS and PDOS of doped system are given and explained.

When doping occurs on Sr site, the band gap is nearly not affected.

When doping occurs on Ti site, the band gap will be narrowed. And some details about the DOS were given here.

The writer concluded that metal doping at Ti site is favored and responsible for the observed phenomenon. Furthermore, the writer said the 40-atom smaller supercell is enough for calculation without any significant error.

3.2.3 Evaluation of photocatalytic activity The ability of a semiconductor to work as catalyst depends on the potential of its band structure compared to the potential of oxygen and hydrogen.

The writer used a “scissors operator” to compensate the error derived from local functionals of DFT.

The CBM and VBM of different system were compared to the NHE potential.

The comparison showed that except for Co-doped SrTiO3, all of the others have higher CBM than H+/H2 and lower VBM than O2/H2O. And the Fe and Mn doped SrTiO3 shows a better activity according to the writer’s method.

3.3 Effects on NaTaO3 Similar work had been done on NaTaO3. The computation details are given in this paragraph.

The DOS and PDOS of doped NaTaO3 are explained in details in this paragraph. The 3d-like states of Mn and Fe contributing to the CBM can narrow the band gap.

The potentials of VBM and CBM of pure NaTaO3 and doped NaTaO3 are compared to the H+/H2 and O2/H2O potentials to indicate that Fe-doped NaTaO3 can be an active catalyst.

UV-vis spectrum of Fe-doped NaTaO3 is shown where the pure NaTaO3 only gives a high absorption in UV region while the absorption band of Fe-doped NaTaO3 can extend to visible region.

The writer pointed out that dopant in TiO2 will decrease the efficient since the dopant will play as a recombination center. The situation is different for SrTiO3 and NaTaO3, of which the reason might be their different crystal structures.

4. Conclusion Conclusion is given that metal doping at Ti site is energetically favorable and both the doped SrTiO3 and NaTaO3 shows absorption in visible region.