[THESIS DEFENSE] CASETE – Ganesh JABOTRA

Pr. Patrick Da Costa

Referee

Sorbonne University

Pr. Catherine Batiot-Dupeyrat

Referee

University of Poitiers

Dr. Nathalie Tanchoux

Examiner

University of Montpellier

Pr. Rose-Noëlle Vannier

(President) Examiner

Centrale Lille

Pr. Sébastien Royer

Invited

University of Côte d'Opale

Dr. Sudhanshu Sharma

Invited

IIT Gandhinagar

Dr. Jean-Philippe Dacquin

Thesis director

University of Lille

Dr. Axel Löfberg

Thesis co-director

CNRS, University of Lille

Dry methane reforming, chemical looping, LaFeO₃ perovskites, Cu-Ni-Co metal doping, oxygen carriers, redox behavior, CO₂ conversion, nanoparticle exsolution, syngas production, carbon suppression.

The transition towards a sustainable hydrogen based economy necessitates efficient, low-carbon methods for syngas production that utilize CO₂ while minimizing energy penalties. In this regard, chemical looping dry reforming of methane (CL-DRM) offers a promising alternative to traditional catalytic dry reforming of CH₄ by eliminating direct contact between CH₄ and CO₂, thus improving selectivity and optimizing thermal efficiency. This thesis explores the design, synthesis, and redox behaviour of LaFeO₃-based perovskites as oxygen carriers (OCs) for CL-DRM. The research adopts a three-tiered approach: (1) Cu-doped LaFeO₃ to understand the impact of Cu substitution on redox and structural dynamics; (2) a comparative analysis of Ni-, Co-, and Cu-doped LaFeO₃ systems to assess the influence of transition-metal dopants on methane activation and syngas composition; and (3) the development of bimetallic and trimetallic perovskites (Co-Ni, Co-Cu, Ni-Cu, and Co-Ni-Cu) to investigate synergistic effects and optimize redox performance. Comprehensive physicochemical characterization (XRD, XPS, Mössbauer, EPR, TEM, TPR, TGA) combined with catalytic activity tests under co-feed and chemical looping configurations revealed that Cu-doped LaFeO₃ facilitates the exsolution of stable Cu nanoparticles, suppressing methane over-cracking and achieving a stoichiometric H₂/CO ratio of 2 with excellent cyclic stability. Ni- and Co-doped systems showed higher CH₄ conversions but experienced carbon accumulation and H₂-rich syngas. The bimetallic LaFe_0.85Co_0.075Ni_0.075O₃ demonstrated the best balance between activity and stability, while the trimetallic LaFe_0.85Co_0.05Ni_0.05Cu_0.05O₃ achieved ideal selectivity and robust oxygen mobility. These findings illustrate that synergistic multi-metal substitution effectively tunes the balance between lattice oxygen activity and reducibility, enabling high CO₂ conversion and minimizing carbon deposition.