Carbon‐Layer Modulation of CoOx@C‐350 Nanoreactors Stabilizing Co0‐Co2+ Dual‐Active Site Ratio for High‐Efficiency Ambient‐Pressure Photothermal CO2 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.