Searching for cheaper catalysts with high activity and stability in Ce–M–O systems (M = Fe, Co, Ni)

Abstract

For almost all catalysts, doping with cheaper transition metal ions could reduce the application price necessary, however usually a catalytic activity degradation occurs. This work reports on the preparation of Ce–M–O solid solutions (M = transition metal) with the aim to achieve cheaper catalysts with high activity and stability. Systematic sample characterizations indicate that the existence of more transition metal hydroxides is beneficial for the formation of Ce–M–O solid solutions and that the formation reaction involves a complicated process (e.g., nucleation, dehydration, Ostwald attachment, doping in ceria lattice, and oriented growth). When tested as the catalysts for CO oxidation, the solid solutions of M = Fe maintained excellent catalytic performance, much higher than ever reported, even when Fe doping levels reach 15%. No sign of deactivation was detected for M = Fe after 100 h reaction, which compares to the apparent decrease in catalytic activity for M = Co or Ni. By studying the doping effect on structure, reducibility, oxygen storage capacity and catalytic performance, it is demonstrated that Fe doping led to lattice crystal shrinking, lattice distortion and restrained grain growth of CeO₂, yielding a synergistic effect in promoting oxygen storage capacity and catalytic activity. The results reported herein may provide some direction for exploring advanced catalysts at lower prices.