New Opportunity for Carbon‐Supported Ni‐based Electrocatalysts: Gas‐Phase CO₂ Methanation

Abstract

The cost‐effectiveness and excellent performance of conductive‐carbon‐supported Ni‐based electrocatalysts make them attractive materials for hydrogen oxidation and evolution reactions. However, they were previously unused in gas‐phase hydrogenation reactions. In this work, we have expanded the applicability of commercially available advanced Ni/C, NiMo/C and NiRe/C materials from electrocatalysis to heterogeneous catalysis of CO2 methanation. Our catalytic testing efforts indicate that the monometallic Ni/C material demonstrates the best CO2 methanation properties, achieving an excellent CO2 conversion of 83 % at 400 °C with nearly complete selectivity to CH4 of 99.7 %, plus exhibiting intact performance during 90 h of time‐on‐stream testing. Such catalytic properties are among the highest reported to date among carbon‐supported Ni‐based methanation catalysts. Excellent performance of Ni/C stems from the good dispersion of the Ni nanoparticles over N‐containing carbon support material.

In situ investigation of the CO2 methanation on carbon/ceria-supported Ni catalysts using modulation-excitation DRIFTS

“…The lower energy component (853.0 ± 0.1 eV) is assigned to Ni 0 in metallic Ni species, while the components at 854.4 ± 0.2 eV and 856.4 ± 0.1 eV are consistent with Ni 2+ in nickel-oxide phase, and the ones at 861.3 ± 0.3 eV and 864.3 ± 0.1 eV are satellite peaks from Ni 2+ . The Ni 2p 3/2 spectral envelopes of the catalysts resemble the typical spectra for nanoscale oxidation layers on Ni and Ni compounds, being consistent with a thin, predominantly Ni 2+ , nickel oxide layer on metallic Ni [5,[28][29][30]. The binding energies (BEs) of fitting components are presented in Table S1 and the relative atomic percentages (at%) of Ni 0 and Ni 2+ are presented in Table S2.…”

“…Importantly, researchers continue to exploit different catalysts to achieve high CO 2 conversion and complete selectivity towards CH 4 . For example, a number of catalysts based on transition metals (Ni, Co, Fe) or platinumgroup metals (Ru, Rh) dispersed on porous supporting materials have been developed [2,[5][6][7][8][9][10][11][12]. Notably, Ni-based catalysts, compared to platinum-group metals, exhibit an optimal combination of activity, selectivity, and low price [2,5,6].…”

“…For example, a number of catalysts based on transition metals (Ni, Co, Fe) or platinumgroup metals (Ru, Rh) dispersed on porous supporting materials have been developed [2,[5][6][7][8][9][10][11][12]. Notably, Ni-based catalysts, compared to platinum-group metals, exhibit an optimal combination of activity, selectivity, and low price [2,5,6]. Despite the advances in using Ni catalysts for CO 2 methanation, a way to reduce the reaction temperature from the current ≥ 400 • C while preserving high catalytic performance remains a challenge.…”

“…Specifically, via modification of their surface chemistry, carbon materials can exhibit increased basicity, which improves the CO 2 coverage of the catalyst, since it is an acidic molecule, thus enhancing the CO 2 methanation performance at lower reaction temperatures [2]. Compared to the more common Ni supported on metal oxides, the research on Ni supported on carbon materials is less advanced, motivating a fundamental investigation of such alternative catalytic systems [2,5]. Among the metal-oxide supporting materials, despite being based on a rare-earth metal, ceria (CeO 2 ) has emerged as a promising alternative to Al 2 O 3 because it enhances the metal-support interactions, leading to high dispersion of the resultant Ni nanoparticles over the support.…”

“…Traditionally, alumina (Al 2 O 3 ) is used as supporting material for Ni methanation catalysts [13][14][15]. In contrast, we and other researchers have focused on carbon supporting materials [2,5,16,17]. An exciting feature of these high-surface-area porous supports are their versatile surface properties [18].…”