Dual‐Gas Activation Nanodomains Enable Solar‐Powered Selective Methane Conversion

Abstract

ABSTRACT Photocatalytic oxidation of methane to formaldehyde at concentrations compatible with direct fuel‐cell use remains a critical yet unmet challenge. Here we introduce a “dual‐gas coadsorption domain” architecture discovered through a high‐throughput screen of 37 earth‐abundant transition metals and their oxides. Reduced nickel oxide (NiO 1‐x ) emerged as the optimal co‐catalyst, decorating the pore edges of vacancy‐rich porous ZnO (pZnO). Oxygen vacancies in pZnO act as oxygen pumps, while adjacent NiO 1‐x nanoclusters chemisorb and polarize methane, lowering the C‐H activation barrier and steering the radical cascade toward methyl hydroperoxide instead of methanol. Methyl hydroperoxide quantitatively decomposes to formaldehyde, delivering 28.5 mmol g −1 (3 mM in solution, 88.5% selectivity). An outdoor reactor powered only by natural sunlight (peak 72.8 mW cm −2 ) produced 12.3 mmol g −1 formaldehyde in 6 h without detectable by‐products. The concentrated effluent feeds an alkaline formaldehyde fuel cell directly—no purification—co‐generating 0.2 kWh of electricity and valuable formate at a peak power density of 32.6 mW cm −2 . The work establishes a scalable, solar‐driven pathway for simultaneous methane valorization and on‐site energy conversion.