Role of the Pr/Ni loading sequence in boosting the photothermal catalytic activity of CeO₂ for methane dry reforming

The dry reforming of methane (DRM) is an attractive process for the simultaneous utilization of two major greenhouse gases, CH₄ and CO₂, enabling the production of synthesis gas (CO and H₂) and contributing to environmental sustainability. However, conventional thermocatalytic DRM requires high temperatures and suffers from limited catalytic activity and stability. Here, we systematically explore the impact of the praseodymium (Pr) and nickel (Ni) loading sequence on the photothermal catalytic performance of CeO₂ for DRM. By synthesizing and thoroughly characterizing various Pr/Ni/CeO₂ catalysts with different architectural designs, we identified that pre-loading Pr followed by Ni deposition (Ni/Pr-Ce) yielded a catalyst with a superior concentration of oxygen vacancies, optimized Ni electron density, and enhanced metal-support interactions. Under light irradiation (3.51 W cm^-2), the Ni/Pr-Ce catalyst demonstrated exceptional performance, achieving CH₄ and CO₂ conversions of 80.1% and 83.1%, respectively, with a nearly ideal H₂/CO ratio approaching 1.0. Mechanistic investigations revealed that Pr pre-modification is crucial for promoting electron transfer, creating abundant oxygen vacancies, and facilitating the activation of CH₄ and CO₂, thereby synergistically boosting the photothermal response and catalytic reactivity. This work introduces a strategy for enhancing the photothermal performance of CeO₂-based catalysts through the controlled loading sequence of rare-earth and transition metals, offering insights for the development of high-efficiency, solar-driven methane reforming technologies.