In situ carbon-induced electronic regulation of CuCo₂O₄ for significantly enhanced water-resistant DeNO_X

Copper- and cobalt-based oxides are promising catalysts for sustainable NO_X abatement. However, their practical application is severely limited by the unavoidable presence of water vapor in exhaust gases. Herein, we demonstrate that trace, frequently overlooked ethylene glycol (EG)-derived in situ carbon can be deliberately exploited as an effective electron donor to regulate the electronic structure of CuCo₂O₄. As a result, both water tolerance and high-temperature DeNO_X efficiency are significantly improved. Integrated characterizations and DFT calculations demonstrate that synthesis temperature dictates metal-EG coordination, thereby regulating the in situ carbon content. Acting as an intrinsic electron donor, this residual carbon promotes the formation of low-valent Cu⁺ and Co²⁺ species and markedly increases the concentration of oxygen vacancies. In situ DRIFTS, NO-TPD-MS, and characterization of the control sample demonstrate that these oxygen vacancies facilitate the formation of abundant and thermally stable NO_X species through the continuous generation of reactive oxygen. While abundant and stable NO_X species limit low-temperature activity by suppressing Cu⁺-CO intermediates, they enable a direct reaction with CO at elevated temperatures, boosting catalytic performance. More importantly, these stable NO_X species effectively inhibit the competitive adsorption of H₂O on active sites, thereby significantly enhancing water resistance. Consequently, this work highlights the potential of EG-derived in situ carbon as an efficient electronic modulator for CuCo₂O₄, offering a simple, one-pot, and cost-effective pathway for developing water-resistant DeNO_X catalysts.