Potassium Coordination Stabilized Ru δ+ State on Potassium Titanate Nanowire for Efficient Photothermal CO 2 Methanation

Abstract Photothermal CO 2 methanation offers a solution to achieve both the decarbonization targets and the substitution of fossil fuel feedstocks using renewable energy. The slightly oxidized Ru (Ru δ+ ) site is an active site for low‐temperature CO 2 activation. However, the susceptibility of Ru δ+ to reduction under the photothermal reaction process is a key limitation to the stabilization. Herein, the K 2 RuO 3 with high Ru─O bond strength via potassium coordination stabilized onto K 2 Ti 6 O 13 is constructed (KTO‐Ru δ+ /Ru 0 ). Benefiting from reducing activation energy by the Ru δ+ as Lewis active sites, the CO 2 hydrogenation path for KTO‐Ru δ+ /Ru 0 tends to favor a more advantageous formate pathway. In addition, K ions in K 2 RuO 3 and K 2 Ti 6 O 13 as alkaline promoters facilitate the adsorption of CO 2 and suppress dehydration to stablize the Ru δ+ . The KTO‐Ru δ+ /Ru 0 exhibits remarkable photothermal CO 2 methanation activity (CH 4 yield of 526 ± 5.5 mmol g cat −1 h −1 ), and CH 4 selectivity reaches over 99.9%. Taking advantage of thin KTO‐Ru δ+ /Ru 0 inorganic porous paper, the flow reactor system with the efficient contact among the KTO‐Ru δ+ /Ru 0 , flowing gas and the solar illumination obtains an ultrahigh photothermal CH 4 production rate of 0.99 mol g cat −1 h −1 at a gas flow rate of 35 mL min −1 (gas hourly space velocity of 210 000 mL g cat −1 h −1 ) with ≈96.6% CH 4 selectivity. This work suggests alternative perspectives for designing stabilized oxidation‐state photothermal catalysts for flow photothermal CO 2 methanation.