Cooperative Catalysis of Nickel and Nickel Oxide for Efficient Reduction of CO₂ to CH₄

Abstract

The use of CO₂ to produce value‐added energy chemicals is a promising means for renewable CO₂ transformation in low‐carbon energy system, and CO₂ methanation has attracted ever‐increasing interest. Herein, we report that the Ni/MCM‐41 catalyst with prominent cooperative effect of Ni and NiO is efficient for CH₄ generation with CO₂ conversion of 73.2 % and CH₄ selectivity of 91.6 % at 400 °C and high gas hourly space velocity (GHSV) of 90000 mL g_cat⁻¹ h⁻¹. Combined methodologies of in situ X‐ray diffraction, diffuse reflectance infrared Fourier transform spectroscopy, and ambient‐pressure X‐ray photoelectron spectroscopy reflect the structural evolvements of Ni/MCM‐41 catalyst, the presence of carbonyl intermediates, the co‐existence of metallic and oxidized Ni species with sufficient molar ratio of Ni⁰/Ni²⁺ under working conditions. H₂ and CO₂ molecules are preferentially adsorbed and chemically activated over Ni⁰ and Ni²⁺ species, respectively. The possible four‐step reaction mechanism involved carbonyl pathway and the cleavage of C=O bond from CO₂ as the rate‐determining step over the engineered Ni/MCM‐41 catalyst was demonstrated.