Extending the promoter–carbide interface strategy: a comparative study of promoters for reverse water-gas shift catalysis

Abstract

Carbide-based catalysts have been widely studied for high-temperature reverse water-gas shift (RWGS) catalysis. The construction of oxide–carbide interfaces has been shown to enhance both catalytic activity and sintering resistance, but whether this strategy can be generalized to a broader range of oxide and oxycarbonate modifiers remains unclear. Here, we systematically investigate the promotional effects of four distinct modifiers—CeO₂, Y₂O₃, MgO, and La₂O₂CO₃ (LOC)—on the InNi₃C_0.5 carbide catalyst for RWGS. All modified catalysts exhibit significantly enhanced CO₂ conversion and improved stability compared to unmodified InNi₃C_0.5, while maintaining high CO selectivity (>97%), demonstrating the broad applicability of the promoter–carbide interface concept. Among the systems, LOC/InNi₃C_0.5 shows high long-term stability with only 1.3% activity loss over 100 hours at 600 °C and only minor deactivation after six thermal cycles (4.1% loss at 450 °C), attributed to a unique phase-transformation-induced particle refinement. MgO/InNi₃C_0.5 achieves the highest CO selectivity (>99%) by effectively suppressing Ni segregation. Mechanistic investigations reveal a dual-pathway synergy: all promoter–carbide interfaces operate via a classical redox pathway on the carbide, while simultaneously enabling an associative formate-mediated route at the interface, where oxides activate CO₂ to formate intermediates, and the carbide supplies dissociated hydrogen. This work establishes the promoter–carbide interface as a versatile and robust design paradigm for RWGS catalysis.