Plasma-Induced Catalyst Support Defects for the Photothermal Methanation of Carbon Dioxide

Abstract

The presence of defects in a catalyst support is known to benefit catalytic activity. In this work, a He-plasma treatment-based strategy for introducing and stabilising defects on a Ni/TiO2 catalyst for photothermal CO2 hydrogenation was established. The impact of pretreatment step sequence—which comprised He-plasma treatment and reduction/passivation—on defect generation and stabilisation within the support was evaluated. Characterisation of the Ni/TiO2 catalysts indicated that defects created in the TiO2 support during the initial plasma treatment stage were then stabilised by the reduction/passivation process, (P-R)Ni/TiO2. Conversely, performing reduction/passivation first, (R-P)Ni/TiO2, invoked a resistance to subsequent defect formation upon plasma treatment and consequently, poorer photothermal catalytic activity. The plasma treatment altered the metal-support interaction and ease of catalyst reduction. Under photothermal conditions, (P-R)Ni/TiO2 reached the highest methane production in 75 min, while (R-P)Ni/TiO2 required 165 min. Decoupling the impacts of light and heat indicated thermal dominance of the reaction with CO2 conversion observed from 200 °C onwards. Methane was the primary product with carbon monoxide detected at 350 °C (~2%) and 400 °C (~5%). Overall, the findings demonstrate the importance of pretreatment step sequence when utilising plasma treatment to generate active defect sites in a catalyst support.

Solar‐Driven Continuous CO2 Reduction to CO and CH4 using Heterogeneous Photothermal Catalysts: Recent Progress and Remaining Challenges

“…To increase the performance of another nickel CO 2 methanation catalyst, Scott, Lovell and co-workers utilized a plasma treatment to create a defective titania support. [146] Nickel nanoparticles were subsequently deposited on the support, and different combinations of reduction steps and plasma passivation treatments were studied. The authors reported that the plasma treatment resulted in extra oxygen vacancies, which increased the interaction between CO 2 and the support, leading to improved performance of the catalytic system.…”

“…To increase the performance of another nickel CO 2 methanation catalyst, Scott, Lovell and co‐workers utilized a plasma treatment to create a defective titania support [146] . Nickel nanoparticles were subsequently deposited on the support, and different combinations of reduction steps and plasma passivation treatments were studied.…”

Advances and Perspectives of Photopromoted CO2 Hydrogenation for Methane Production: Catalyst Development and Mechanism Investigations

“…(c and d) Influence of Ni/TiO 2 catalyst pretreatment on (c) CO 2 conversion and (d) methane selectivity during decoupled photo and thermal CO 2 methanation in a continuous flow reactor system. Reproduced with permission from ref . Copyright 2021 The Author(s).…”

“…For example, in the initial stage of plasma treatment, the time of the catalyst (P-R)Ni/TiO 2 (obtained by He-plasma treatment and then reduction/ passivation) to reach the maximum CH 4 generation amount in the full-spectrum batch cycle reactor system was shorter compared with the catalyst (R-P)Ni/TiO 2 (obtained by first reduction/passivation and then He-plasma treatment), as shown in Figure 9a−d. 116 Research indicated that the defects produced by plasma treatment of TiO 2 support could be stabilized by the reduction/passivation process, while reduction/passivation produced resistance to the formation of defects in plasma treatment. In addition, catalysts derived from precursors with MOF have also attracted great attention.…”

Photothermal methane coupling into liquid fuels with hydrogen evolution over nanocatalysts based on layered double hydroxide (LDH)

“…However, the consumption of fossil fuels has led to one of the greatest conflicts between reserves and demand in this century [3,4]. Transforming relatively abundant energy resources into high value-added energy resources through sustainable approaches has been considered as a powerful way to alleviate the above contradiction [5][6][7][8]. Among them, methane, as the main component of natural gas and shale gas with abundant reserves, has become the focus of the above research [9][10][11].…”