Facile C–C Coupling of Aqueous Ethanol to High-Carbon Alcohols over Hierarchical Ni@C-CeO₂ Catalysts: Synergistic Effects of Confined Ni Nanoparticles and Oxygen Vacancy

The one-step hydrothermal reconstruction of bioethanol into higher alcohols represents a pivotal advancement in green chemistry, addressing both environmental sustainability and energy regeneration. Herein, a rational design of Ni@C-CeO2 catalysts via a sol–gel method for efficient aqueous-phase ethanol C–C coupling was reported. Systematic investigation of Ni loading and precursor carbonization temperature revealed their critical roles in modulating catalyst microstructure and performance. The optimized Ni-2@C-CeO2-500 catalyst demonstrated exceptional activity under 190 °C and 12 h, achieving ethanol conversion of 72.0% and C4+ alcohol yield of 55.6%. Advanced characterization techniques unveiled structure-performance relationships: (1) controlled Ni loading ensured optimal nanoparticle dispersion, while excessive loading induced aggregation; (2) carbonization at 500 °C balanced carbon matrix architecture and CeO2 reducibility. XPS analysis revealed that oxygen vacancy concentration critically modulates strong metal–support interactions through Ce3+-induced charge redistribution, facilitating interfacial electron transfer during reaction. Furthermore, the Ni-2@C-CeO2-500 catalyst demonstrated excellent stability with sustained activity retention over five consecutive cycles. This work establishes a renewable and technologically viable alternative to conventional petroleum-derived chemicals widely utilized in the chemical industry, demonstrating significant potential for applications in green and sustainable chemistry.