Enhanced CO* Adsorption on Ni Nanoparticles via Medium‐Entropy Oxide Nanosheets to Boost High‐Temperature Photothermal CO ₂ Methanation

Abstract Photothermal CO 2 methanation offers a promising route toward carbon neutrality. However, maintaining high methane (CH 4 ) selectivity under high‐temperature conditions remains challenging. Ni nanoparticles in situ exsolved from NiMnSiAlO nanosheets (Ni/MnSiAlO) are proposed as efficient photothermal catalysts. The exsolved Ni nanoparticles are embedded onto the medium‐entropy MnSiAlO support and act as active catalytic sites. The Ni/MnSiAlO catalyst performs exceptionally well at 432 °C, achieving a CH 4 generation rate of 328.4 mmol g cat −1 h −1 and demonstrating a CH 4 selectivity of up to 97.6%, with stable performance maintained over 100 reaction cycles. This outstanding performance stems from the unique properties of the medium‐entropy MnSiAlO support. It effectively reduces the local electron density of Ni nanoparticles, optimizes CO* adsorption strength, and accelerates hydrogenation kinetics, while also stabilizing Ni active sites, thereby maintaining high CH 4 selectivity and structural integrity under high‐temperature conditions. This study highlights the importance of tuning CO* adsorption for CO 2 methanation and demonstrates the potential of designing thermally stable catalysts for efficient high‐temperature photothermal applications.