Light‐Induced Nonoxidative Coupling of Methane Using Stable Solid Solutions

Abstract

Achieving efficient and direct conversion of methane under mild conditions is of great significance for innovations in the chemical industry. However, the efficiency and lifetime of most catalysts remain too far from practical requirements, since it is difficult to break the first C−H bond of methane as well as to suppress the following complete dehydrogenation (or overoxidation) and the resulting carbonaceous deposition (or CO2). Here, we report that wurtzite GaN:ZnO solid solutions exhibit unique and unprecedented photocatalytic performances for the nonoxidative coupling of methane at room temperature, exclusively generating ethane with nearly stoichiometric H2. High conversion rate (>330 μmol g−1 h−1), long‐term stability (>70 h), and superior coke‐resistance were achieved. At 293 K, the methane conversion exceeds 7 %, comparable to the equilibrium conversion of thermal catalysis at 910 K. Mechanistic studies revealed that the N‐ZnGa‐ON units and the absence of acid sites on the surface played crucial roles in reactivity and coke resistance, respectively.

High-energy Charge Separation State for Photocatalytic Nonoxidative Methane Conversion

“…On the other hand, Fig. 3d showed that the reaction order for methane over C@CZ was only 0.24, a value much smaller than other Ce-based catalysts (0.41-0.47) and other traditional NOCM semiconductors such as ZnO (0.46) and GaN (0.61), 22 suggesting that the surface of C@CZ can well adsorb methane, leading to very weak dependencies of the reaction rate on the gas-phase methane concentrations.…”

“…9 To date, only a few unsupported semiconductor photocatalysts can durably produce both ethane and H 2 under photocatalytic NOCM conditions. [21][22][23] In many cases, the H moieties detached from methane will combine with the lattice oxygen of catalysts and be released as water instead of H 2 . [15][16][17] Therefore, the oxidative regeneration of the catalyst at intervals is indispensable in these reactions.…”

Advances and Challenges of Photocatalytic Methane C—C Coupling

“…reported a GaN:ZnO solid solution for photocatalytic NOCM, which exhibits a productivity of 162 and 166 μmol·g −1 ·h −1 for ethane and hydrogen, respectively. [ 52 ] In addition to high catalytic activity superior to ZnO and GaN, GaN:ZnO solid solution achieves unique long‐term stability and superior coke‐resistance.…”