**4. Conclusions**

In summary, a series of Ni-Mo sulfide/Al2O3 catalysts with di fferent molar ratios of Ni/Mo were prepared and applied for the one-step conversion of CO2 and H2S into syngas in non-thermal plasma. According to the characterization results, the optical and structural properties of the as-synthesized catalysts were significantly influenced by the Ni/Mo molar ratio. The Ni/Mo molar ratio can e ffectively adjust the particle size and band gap. Additionally, the generated Mo vacancies are also favorable for the transfer and separation of holes and electrons. The experimental results indicated that the Ni-Mo sulfide/Al2O3 catalysts possessed excellent catalytic activities for CO2 and H2S conversion, compared to the single-component NiS2/Al2O3 and MoS2/Al2O3 catalysts. In particular, the Ni-Mo sulfide/Al2O3 catalyst with Ni/Mo molar ratio of 5/3 showed relatively higher CO2 and H2S conversions, and exhibited good stability in the long-term test for CO2 and H2S conversion to syngas.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2073-4344/9/6/525/s1, Figure S1: XPS spectra of Mo 3d (**a**) and Ni 2p (**b**) for the 5Ni-3Mo/Al2O3 catalyst before and after reaction; Figure S2: SEM images of the 5Ni-3Mo/Al2O3 catalyst before (**a**) and after (**b**) reaction; Figure S3: XRD patterns of the 5Ni-3Mo/Al2O3 catalyst before and after reaction.

**Author Contributions:** The project was conceived by L.Z.; X.L. performed the experiments and drafted the paper under the supervision of L.Z. and K.F.; Y.L. and M.W. helped to collect and analyze some characterization data. The manuscript was revised and checked through the comments of all authors. All authors have given approval for the final version of the manuscript.

**Funding:** This research was funded by the National Key R&D Program of China (2018YFB0604700), the National Natural Science Foundation of China (21603255, 21473230), and the Natural Science Foundation of Shanxi (201601D021052).

**Conflicts of Interest:** The authors declare no conflict of interest.
