Nano-Ru Supported on Ni Nanowires for Low-Temperature Carbon Dioxide Methanation

Abstract

In this study, we investigated the catalytic performance of Ru nanoparticles (NPs) supported on Ni-nanowires for the first time. This appears to be a highly efficient catalyst for low-temperature methanation, e.g., ca. 100% conversion and 100% of CH4 selectivity can be achieved at ca. 179 °C, while the turnover frequency (TOF) value was 2479.2 h−1. At the same time, the onset of a reaction was observed at a temperature as low as 130 °C. The comparison of nano-Pd and nano-Ru supported on Ni-nanowires enabled us to prove that oxidized surface metals are highly important for the high activity of the investigated nano-Ru@nanowired-Ni. Moreover, similar to the microscopic Sabatier rule, which indicates that some optimal reactivity level of a catalyst exists, we showed that Ni-nanowires (a higher specific surface area than a standard metal surface, e.g., in the form of a metal foam, but lower than nano-sized materials) significantly enhances the performance of the Ru-Ni catalytic system.

Bimetallic Ni-Based Catalysts for CO2 Methanation: A Review

“…The prepared catalyst exhibited a greatly enhanced lowtemperature activity with about 100% CO 2 conversion being achieved at a temperature as low as 200 • C. Carbon deposition was shown to deactivate the catalyst over time, with the initial activity being regained upon treatment under H 2 atmosphere. In a followup work, Siudyga et al [110] synthesized 1.5% Ru catalysts supported on Ni nanowires via a similar preparation method. The higher surface area of the 1D nanostructure of the Ni support provided an additional advantage, with around 100% CO 2 conversion being reached at 179 • C and the onset temperature for the reaction being observed at just 130 • C. Siudyga et al [111] also observed that Ru/Ni catalysts are highly active for CO methanation from syngas, with 100% CO conversion being reached at 178 • C and observable CO conversion being detected even at −7 • C.…”

Ru and Ni—Privileged Metal Combination for Environmental Nanocatalysis

“…They can also easily get deactivated at high temperatures by sintering and/or coke deposition and are particularly susceptible to sulfur poisoning, e.g., from H 2 S [80,91,97]. There are several solutions that can improve the performance and life span of this type of catalyst, for instance, using a support [83,91,[98][99][100], catalytic promoters [91,99,100], coupling with other non-noble elements into alloys or spinel structures [100,101], or composing bimetallics with noble metals [10,53,[74][75][76]84]. Ruthenium is one of the most used noble metals for this purpose.…”

“…Ru/Ni conjugate appeared highly active at low temperature (entry 6 in Table 3) [53]. Interestingly, a special method for preparing a catalyst produces an unalloyed bimetallic construct [38,53,75,108].…”

“…We recently discovered a nano-Ru/nanowired-Ni system that is active starting from ca. 125 • C (onset of the reaction) and at 179 • C. In such conditions, 100% conversion and 100% selectivity to methane could be achieved for the TOF value of 2479.2 [75]. A bimetallic catalyst was constructed of the oxidized forms of the metals.…”

“…The presence of the non-stoichiometric oxides RuO x apparently plays a role in a high catalytic activity of Ru/Ni systems because generally catalyst's activity is often positively affected by non-stoichiometric compounds [6]. The high activity of a nano-Ru/nanowired-Ni system is additionally supported due to the high porosity of the Ni nanowires, which amounts to 99.31% and reaches a level of aerogels [75].…”