(182b) Atomic Layer Deposition Nano-Engineered Ni/Al2O3 Catalyst for Bi-Reforming of Methane

CeO_x-overcoated Ni/Al₂O₃ catalysts were prepared by atomic layer deposition (ALD) for bi-reforming of methane (BRM), as the combination of dry reforming of methane (DRM) and steam reforming of methane (SRM). Ni nanoparticles were deposited on alpha-Al₂O₃ nanoparticles by ALD, followed by deposition of non-stoichiometric CeO_x thin films on Ni/ Al₂O₃ particles by ALD, which constructed a beneficial Ni-CeO_x interface and modified the catalyst property. Ascribed to the unique ALD growth mode, a high amount of Ce(III) and oxygen vacancies existed in the ALD-deposited CeO_x overcoating. A reduction process before the BRM reaction contributed to the further reduction of Ce(IV) to Ce(III), resulting in more oxygen vacancies. The oxygen vacancies at the Ni-CeO_x interface enabled a high rate of CO₂ activation and enabled the balance between the activation of CO₂ and H₂O for BRM. Due to its oxygen vacancies as activation sites for CO₂ and H₂O, CeO_x ALD overcoating significantly improved the activity of Ni/Al₂O₃ catalyst and achieved a better control in the H₂/CO ratio with a suitable ratio of H₂O/CO₂/CH₄ feed. CeOx overcoatings enhanced the reducibility of Ni(II) sites and assisted in preventing Ni from oxidation during the BRM reaction. Less carbon deposition was achieved by the Ni/Al₂O₃ catalyst with CeO_x overcoating as ascribed to its better reactant activation capacity.