Mechanochemical Synthesis of Ni–Y/CeO₂ Catalyst for Nonthermal Plasma Catalytic CO₂ Methanation

Abstract

Nonthermal plasma (NTP)-assisted CO2 methanation can activate and convert stable CO2 molecules under ambient conditions as compared to conventional thermal catalysis (normal operation temperature up to 450 °C), which is a good technique to reduce CO2 emissions and simultaneously utilize the renewable energies like solar and wind. It is critical to develop a robust catalyst with good catalytic performance in order to make NTP catalytic CO2 methanation more competitive. Herein, we present a simple yet efficient synthesis of CeO2-supported Ni catalysts with yttrium (Y) as the promoter (i.e., Ni–Y/CeO2) via mechanochemical synthesis for efficient NTP catalytic CO2 methanation. The developed 7.5Ni–1Y/CeO2 catalyst demonstrated the highest energy efficiency values for CO2 conversion and CH4 yield, i.e., ∼57 gCO2 kWh–1 and ∼17 gCH4 kWh–1, respectively. The CO2-TPD and HRTEM results confirmed that the doped Y positively enhanced the basicity of the catalysts and also decreased the particle size of Ni nanoparticles, thus promoting the NTP catalytic activity of CO2 methanation. The catalyst displayed excellent short-term stability for plasma catalytic CO2 methanation over a 12 h on-stream evaluation, showing a CO2 conversion of 84.2 ± 1.8% and a CH4 selectivity of 83.3 ± 1.9%.

Mechanochemical Synthesis of Bimetallic NiCo Supported on a CeO2 Catalyst with Less Metal Loading for Non-Thermal Plasma Catalytic CO2 Hydrogenation

“…NTP-catalytic CO 2 methanation over the catalysts under investigation was performed in a dielectric barrier discharge (DBD) reactor in a laboratory-scale plasma rig at ambient temperature (viz. 25 °C) described previously . Before the experiment, ∼300 mg of as-synthesized catalyst was in situ pre-treated in a 20% H 2 /Ar atmosphere for 30 min under the plasma condition at an applied peak voltage and a frequency of 9 kV and 7.7 kHz, respectively.…”

“…NTP activation has the unslective nature, thus rational design of catalysts is considered one of the important aspects in the development of selective NTP-catalysis, which has been proposed and proved by us and other colleagues previously. − For example, previously we have partially showed the effect of the catalyst physiochemical properties (such as pore structure, support size, and surface acidity/basicity) and active site accessibility on the interactions between the active metal sites and the plasma-induced active species and thus the performance of NTP-catalytic CO 2 hydrogenation. , In addition to catalyst development, in situ methods such as diffuse reflectance infrared Fourier transform spectroscopy and X-ray absorption fine-structure were developed as well to enable the mechanistic understanding of the surface phenomena of relevant NTP-catalytic systems, which helps the rational design and development of tailored catalysts. ,,− In detail, in NTP-catalytic CO 2 hydrogenation, in situ studies showed that plasma-induced vibrationally excited CO 2 molecules could readily interact with dissociated H 2 species adsorbed on metal surface via the Eley–Rideal (E–R) pathway, which can overcome the kinetic limitation in CO 2 conversion. ,− Accordingly, to promote such interfacial interactions in NTP-catalysis, rational tailoring of active metal species is key to advance NTP-catalytic systems.…”

“…25 °C) described previously. 19 Before the experiment, ∼300 mg of assynthesized catalyst was in situ pre-treated in a 20% H 2 /Ar atmosphere for 30 min under the plasma condition at an applied peak voltage and a frequency of 9 kV and 7.7 kHz, respectively. Subsequently, the NTP catalysis was conducted with a feed gas of associated discharged power was calculated to be 9.9 W according to Q−V Lissajous curves (Figure S1) using the method detailed elsewhere.…”

“…In both thermal and NTP-catalytic systems, Ni-based catalysts are commonly used for CO 2 hydrogenation to produce methane (i.e., CO 2 methanation). ,,,− The activity and stability of Ni-based catalysts in CO 2 methanation is normally related to support properties (e.g., surface acidity/basicity), − metal particle size (which is mainly controlled by metal loading), − and metal composition (e.g., monometallic Ni and bimetallic NiFe and NiCo). , For NTP-catalytic CO 2 hydrogenation over the Ni-based catalyst, modification of surface basicity via rare-earth elements doping (e.g., La and Y) was demonstrated as an effective way to enhance the affinity of the catalysts for CO 2 , and hence promote CO 2 conversion and CH 4 selectivity. , Notably, CeO 2 -supported Ni catalyst is demonstrated as the most active and selective catalyst in the thermally catalytic CO 2 methanation system owing to the unique oxygen mobility of the CeO 2 support (viz. Ce 4+ ↔ Ce 3+ cycle). , Also, alloying of Ni with other transition metals (e.g., Fe, Co, and Cu) to form bimetallic catalysts is an effective method to improve the electronic and geometric properties of Ni, being able to tune the activity in CO/CO 2 methanation. − For example, Fe doping leads to the improved electron donating effect and excellent reducibility of the FeNi catalysts, which was beneficial to NTP-catalytic CO 2 methanation .…”

Alkaline Earth Metal-Induced Hydrogenation of the CaO-Captured CO2 to Methane at Room Temperature

“…Therefore, the conversion of the produced CaCO 3 is the indirect utilization of the CaO-captured CO 2 . To date, conversion of CO 2 /carbonate to value-added chemicals or fuels has become a hot research field. − However, efficient, selective, and energy-saving conversion of CO 2 /carbonate into methane (CH 4 ) is still a challenge due to their stabilities …”