Photocatalytic Conversion of Methane to Ethane and Propane Using Cobalt-Cluster-Activated GaN Nanowires

Abstract

The photocatalytic nonoxidative coupling of methane (PNOCM) offers a promising route to synthesize valuable C2+ hydrocarbons while minimizing side reactions. Oxide-based photocatalysts have been predominant in this field, but suffering from limited conversion rates, selectivity, and durability due to poor C-C coupling as well as overoxidation of CH4 by lattice oxygen. Here, we introduce an advancement in PNOCM for methane conversion into ethane and propane using GaN, one of the most produced semiconductors, together with trace amounts of metallic cobalt clusters (0.1 wt%). The photocatalytic system exhibits outstanding stability, maintaining performance over 110 hours, achieving conversion rates of approximately 192.3 mmol g-1 h-1 for ethane and ~17.9 mmol g-1 h-1 for propane, with virtually no coke byproducts detected, representing the highest activity and stability ever reported to our knowledge. This high activity is attributed to the critical methane activation and C-C coupling on Co cluster, which can be greatly accelerated via the ultrafast photogenerated charge transfer from p-GaN to Co cluster. Additionally, the GaN support further synergistically enhances methane activation by in situ generating N-H and O-H species under reaction, as well as provides a vital anti-overoxidation effect to CH4 for high selectivity and stability.