Experimental Evaluation and Density Functional Theory Analysis of Activation Barriers in Dry Reforming Reaction Using Ni Nanoparticle-Supported CeO2 Novel Flower-like Catalyst
Authors: Fujisaki Takaya , Tsuji Yuta , Tu Phuc Hoan , Doan Tin , Trinh Dinh Duc Minh , Rivera Rocabado D. S. , Staykov Aleksandar , Yashiro Keiji , Shiratori Yusuke 
Published: December 2024

Introduction

In the realm of renewable energy, biomass emerges as a crucial resource, capable of generating methane through anaerobic fermentation. This methane, in its role as a hydrogen carrier, presents an opportunity for fuel cells to leverage their high efficiency in electricity generation. Recent studies have illuminated the potential of biomass utilization, particularly in converting waste from shrimp farming into methane[1][2]. The prospect of utilizing revenue from shrimp farming to offset investments in fuel cells underscores the symbiotic relationship between these industries and drives interest in exploring new avenues for sustainable energy production.

Efficient extraction of hydrogen from methane is an important factor in optimizing the fuel cell systems described above. Consequently, there has been a burgeoning focus on improving the efficiency of the dry reforming of methane (DRM) reaction. Within this context, CeO2 loaded with Ni nanoparticles has emerged as a promising catalyst, holding the potential to innovate methane utilization in fuel cells. This study embarks on a meticulous investigation into the dissociation reactions of methane and carbon dioxide, key steps in the DRM reaction, aiming to elucidate the underlying mechanisms and enhance reaction efficiency.

Methodology

The methodology employed in this study density functional theory (DFT) to calculate activation barriers for each dissociation reaction. Leveraging the plane-wave DFT method within the Vienna ab initio simulation package (VASP), the study explores diverse configurations of tetrahedral Ni nanoparticles on CeO2(111) surfaces. Through the nudged elastic band (NEB) method, activation barriers for methane and carbon dioxide dissociation were determined for each configuration. To validate these computational findings, experimental DRM reaction tests were conducted utilizing a Ni nanoparticle-supported flower-shaped CeO2 catalyst specifically synthesized for this study. Then, the activation barriers were calculated from the amount of hydrogen gas produced and methane consumed, offering a comprehensive understanding of reaction kinetics.

Results and discussion

Results from the study reveal intriguing insights into methane dissociation kinetics. The activation barrier for methane dissociation is found to range from 0.80 eV to 1.03 eV, depending on the loading site of Ni nanoparticles, closely mirroring the value derived from experimental methane consumption rates (=0.67 eV). On the other hand, the dissociation of carbon dioxide exhibits higher activation barriers compared to methane dissociation, suggesting its role as a rate-limiting step in the DRM reaction. Particularly noteworthy is the study's suggestion that augmenting the positive charge of Ni nanoparticles may enhance methane dissociation, offering a promising avenue for catalyst optimization in DRM processes.

[1] Y. Shiratori et al., Biogas Power Generation with SOFC to Demonstrate Energy Circulation Suitable for Mekong Delta, Vietnam. Fuel Cells 19, 346-353 (2019).

[2] P. H. Tu et al., Paper‐structured catalyst with a dispersion of ceria‐based oxide support for improving the performance of an SOFC fed with simulated biogas. Fuel Cells, 1-11 (2024).