Charge-Polarized Alloy for Robust Co-Production of H₂ and C₂₊ from Photocatalytic Nonoxidative Coupling of Methane

Direct selective conversion of methane under mild conditions remains a challenge. Photocatalytic nonoxidative coupling of methane (NOCM) offers a sustainable route to value-added hydrocarbons and hydrogen yet suffers from intrinsic trade-offs between activity, selectivity, and stability. Here, we report a charge-polarized Pt-Au nanoalloy on TiO₂ that enables synergistic C₂₊ and H₂ production in a continuous-flow photoreactor. The optimized Pt-Au/TiO₂ exhibits C₂₊ and H₂ yield rates of 22.3 ± 0.1 μmol h⁻¹ (1115 ± 5 μmol g⁻¹ h⁻¹) and 21.2 ± 0.1 μmol h⁻¹ (1060 ± 5 μmol g⁻¹ h⁻¹), respectively, with a C₂₊ selectivity of 99.0 ± 0.4% and stability over 210 h under light irradiation. The catalyst delivers an optimal balance of high product yields, near-quantitative C₂₊ selectivity, and stability under mild conditions, outperforming reported photocatalytic NOCM systems. In situ studies reveal that light-induced carriers partition at the bimetallic interface, where electrons preferentially localize on Pt sites and holes on Au sites, thereby establishing a Lewis acid-base-like, charge-polarized heterointerface. Au sites preferentially mediate *CH₃ adsorption and selective C−C coupling, while Pt sites facilitate H₂ evolution; the Pt-Au alloy synergy underpins C−C bond formation. This dual-site strategy harmonizes catalytic activity, selectivity, and stability, offering a generalizable approach for next-generation photocatalysts aimed at methane valorization.