**4. Conclusions**

Series Co-Ni bi-metallic catalysts supported on Ce-Al2O3 (CA) with different Co ratios are prepared for *n*-decane steam reforming towards H2 preparation, so as to screen appropriate Co content. N2 adsorption-desorption, XRD, NH3-TPD, SEM-EDS, and TEM were used to explain the relationship between catalytic activity and textural-structure properties, microscopic appearance and dispersion state of the catalysts. The activity test indicated that the addition of Co resulted in higher selectivity of hydrogen compared with NCA contrast catalyst. The results indicated that 12% Co showed better hydrogen selectivity (74%), *n*-decane conversion (100%), and anti-carbon ability (3.90 mg/g-fuel). Moreover, thermal stability and regeneration performance were also tested, and the results showed that reforming activity over C12-NCA catalyst was stable in 6 h, and the hydrogen selectivity and *n*-decane conversion over regenerated catalysts were almost close to the fresh ones.

The results were mainly interpreted on the basis of characterization studies, which revealed the significant role of textural and structural properties, microscopic appearance and dispersion state on reforming performance. Obviously, the dispersion state and the BET-specific surface area decrease caused by the formation of the carbon deposition are the main reasons for the activity difference among these catalysts.

**Author Contributions:** Q.Y., Y.J. and J.L. conceived and designed the experiments; Q.Y. and Y.J. performed the experiments; W.W., Y.D. and C.L. contributed with catalyst characterization; J.Y. analyzed the data; J.L. administrated the project; Q.Y. wrote original draft; Q.Y. and Y.J. reviewed and modified the manuscript.

**Funding:** The research was funded by the special program for Key Basic Research in China (Grant No. 0040202204) and the Key Research& Development Plan in Shaanxi Province (2017ZDXM-GY-042, 2017ZDXM-GY-070).

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