Cold plasma activated Ni0/Ni2+ interface catalysts for efficient electrocatalytic methane oxidation to low-carbon alcohols

Abstract

The field of converting methane into valuable products using renewable energy sources under ambient conditions is both appealing and highly demanding. The inherent inertness of methane (CH₄) necessitates the selective breaking of its first C–H bond while avoiding excessive oxidation, in order to transform CH₄ into high-value products. Herein we present a novel approach for creating a highly concentrated Ni⁰/Ni²⁺-on-Cu interface using an O₂ cold plasma in situ method to enhance the activity and stability of the CH₄OR to low-carbon alcohol. The Cu@Ni–NiO electrocatalyst exhibits excellent performance for the CH₄OR to low-carbon alcohol, showcasing a high faradaic efficiency (FE) of 86.7%, an impressive low-carbon alcohol yield of 1215.2 μmol g⁻¹ h⁻¹, remarkable durability (66 h) and a notable C₂H₅OH selectivity of 59.8% at 1.9 V vs. RHE. The ATRSEIRAS spectroscopy and DFT calculations further reveal that the synergistic effect of the Ni⁰/Ni²⁺-on-Cu interface can enhance the *O and *CH₂ generation on Ni⁰, and the *CH₂ spillover from Ni⁰ to Ni²⁺ atoms can also improve the C–C coupling reaction. Additionally, the in situ treatment with O₂ cold plasma can enhance the formation of NiO, leading to a high concentration of the Ni⁰/Ni²⁺-on-Cu interface, which effectively prevents the oxidation of Ni⁰ during the CH₄OR process. Furthermore, we developed a general oxidation strategy for the direct synthesis of transition metal nitrides by O₂ cold plasma treatment of Ni⁰. Compared with the previous methods used for the preparation of NiO, the Ni-based metal oxide synthesis method offers several advantages, including simplicity and practicality, low cost, high throughput, pollution-free nature, low energy consumption and the capability to prepare metal oxides with controllable coordination number of the O atom. This work provides new insights into the highly efficient CH₄OR process and presents an innovative, cost-effective method for preparing electrocatalysts.