Formate and CO* Radicals Intermediated Atmospheric CO₂ Conversion over Co–Ni Bimetallic Catalysts Assembled on Diatomite

There exists an imperative exigency to ascertain catalysts of cost-effectiveness and energy efficiency for the facilitation of industrial CO₂ methanation. In this area, the dual metal synergistic enhancement of the metal-support interaction emerges as a highly promising strategy. Here, Diatomite (Dt) was used as the support, and a series of CoyNi/Dt (Co as the first component and Ni as the second component) composite catalysts were constructed using an ultrasound-assisted coimpregnation method. Different Co/Ni molar ratios had a significant impact on the phase structure, chemical properties, morphological characteristics, and NiCo crystal structure of the <i>x</i>Co<i>y</i>Ni/Dt materials. When the Co/Ni molar ratio was set to 2.0, a Ni-Co alloy was obtained, which is the key to improve the catalytic activity. Compared to the other <i>x</i>Co<i>y</i>Ni/Dt catalysts, the bimetallic catalyst 2Co1Ni/Dt exhibited superior CO₂ catalytic performance and stability, achieving a 76% CO₂ conversion and 98% CH₄ selectivity at 425 °C. The <i>in situ</i> DRIFTS results indicated that CO₂ methanation over the 2Co1Ni/Dt catalyst followed the reaction pathway with formate and CO* radicals as the intermediates.