Photocatalytic oxidative coupling of methane to C3+ hydrocarbons via nanopore-confined microenvironments

Abstract

Photocatalytic oxidative coupling of methane (POCM) enables the production of value-added fuels and chemicals using renewable solar energy. Unfortunately, despite recent advances in the production of C2 chemicals (for example, ethane), POCM systems that selectively produce industrially useful and transportable C3+ hydrocarbons remain elusive. Here we report that Au-embedded porous TiO2, activated by steam during the POCM process, enables efficient and selective flow synthesis of propane with a productivity of 1.4 mmol h−1. At this productivity, we achieve a high propane selectivity of 91.3% and an apparent quantum efficiency of 39.7% at a wavelength of 365 nm. Mechanistic studies reveal that the tensile-strained Au and the nanopore-confined catalytic microenvironment jointly stabilize key ethane intermediates, boosting deeper C2–C1 coupling to form propane. Meanwhile, the steam-activated surface lattice oxygen on TiO2 accelerates hydrogen species transfer, thus enhancing POCM kinetics. This approach is economically feasible for practical application under concentrated solar light. Methane can be converted into other useful chemicals and fuels via photocatalytic oxidative coupling, yet producing molecules with more than two carbon atoms remains difficult. Here the authors show that highly strained Au confined within the nanopores of TiO2 can convert methane to propane with high selectivity.