Carbon‐Layer Modulation of CoO _x @C‐350 Nanoreactors Stabilizing Co ⁰ ‐Co ²⁺ Dual‐Active Site Ratio for High‐Efficiency Ambient‐Pressure Photothermal CO ₂ Methanation

Abstract The design of novel cobalt‐coated catalysts featuring synergistic dual‐active‐sites that facilitate coupled proton‐electron transfer has emerged as a pivotal strategy in ambient‐pressure photothermal catalysis. However, these catalysts often face the critical challenge of single active site deactivation under strong H ₂ ‐reducing atmospheres. Herein, carbon‐coated CoO _x @C‐x novel nanoreactors via a two‐step pyrolysis method is developed. The optimized CoO _x @C‐350 demonstrates remarkable photothermal catalytic performance under light irradiation at 200 °C, achieving 96.15% CH ₄ selectivity, 2.89 mmol·h ⁻¹ production rate, and 51.88% CO ₂ conversion. In situ characterization and calculations reveal that dual‐site synergy enables coupling between Co ²⁺ ‐rich active domains and metallic Co, facilitating proton‐electron transfer to drive the formation of crucial ^* COOH intermediates. Notably, the outer carbon layer serves dual functions as both a photothermal conversion medium (generating localized heating) and a charge redistribution modulator for stabilizing Co ²⁺ species, establishing the cooperative mechanism of “Co ²⁺ /Co ⁰ dual‐active site synergy‐charge redistribution‐thermal localization”. Comparative studies demonstrate that CoO _x @C‐230 (Co ₃ O ₄ ‐dominated) suffers from deactivation due to excessive hydrogen consumption by surface hydroxyl groups, while CoO _x @C‐600 (Co ⁰ ‐enriched) shows limited CO ₂ activation capability, highlighting that optimal valence control is critical. This work provides a novel paradigm for microenvironment engineering in photothermal synergistic catalysts.