Aqueous-Phase Reforming of Methanol for Hydrogen Production on Nitrogen-Doped Ceria: The Effect of the Doping Method
Songqi Leng, T. H. Shen, Shuting Li, Haoyu Wang, Shahzad Barghi, Dan Wu, Chunbao Xu
Abstract
This study first compares the effects of three nitrogen doping methods, namely, solvothermal, hydrothermal, and coheat treatments, on the catalytic performance of Pt/CeO 2 catalysts for aqueous-phase reforming (APR) of methanol to produce hydrogen. Characterization techniques (X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), H 2 temperature-programmed reduction (H 2 -TPR), temperature-programmed desorption of O 2 (O 2 -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, Ce 3+ 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 CeO 2 nanorods. This study highlights the importance of selecting suitable N-doping strategies to improve the activity and stability of Pt/CeO 2 catalysts for hydrogen production.