Aqueous-Phase Reforming of Methanol for Hydrogen Production on Nitrogen-Doped Ceria: The Effect of the Doping Method

This study first compares the effects of three nitrogen doping methods, namely, solvothermal, hydrothermal, and coheat treatments, on the catalytic performance of Pt/CeO2 catalysts for aqueous-phase reforming (APR) of methanol to produce hydrogen. Characterization techniques (X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), H2 temperature-programmed reduction (H2-TPR), temperature-programmed desorption of O2 (O2-TPD), and Fourier transform infrared spectroscopy (FT-IR)) were used to analyze the impact of the N-dopant type and content on oxygen vacancy formation, Ce3+ ratio, crystal structure, and active sites. Compared to the undoped sample, N-doping significantly enhanced the catalytic performance, increasing the turnover frequency (TOF) from 773 to 1290/h at 200 °C with 0.5 wt % Pt and a methanol-to-water molar ratio of 1:1. Hydrothermal treatment generated more oxygen vacancies due to Ce–N–O bond formation, while coheat treatment produced both Ce–N–O and Ce–N bonds. Triethanolamine (TEA) proved effective for hydrothermal N-doping, promoting oxygen vacancies via ethanol derivative formation. In contrast, solvothermal treatment was less effective due to inadequate N-doping and disruption of the CeO2 nanorods. This study highlights the importance of selecting suitable N-doping strategies to improve the activity and stability of Pt/CeO2 catalysts for hydrogen production.