Controlling and Stabilization of Ru Nanoparticles by Tuning the Nitrogen Content of the Support for Enhanced H₂ Production through Aqueous-Phase Reforming of Glycerol

Abstract

The stable activity of catalysts is an important issue in catalysis, particularly aqueous-phase reforming (APR) of renewable oxygenates, of biomass origin, to get H2. Sintering of metal nanoparticles on supports affects catalyst stability. To alleviate this problem, a series of highly stable Ru-supported catalysts with controlled metal nanoparticle sizes have been prepared via the easy incipient wetness impregnation method. These catalysts were used for APR of glycerol to produce H2. Nitrogen-doped mesoporous carbons (NMCs) were utlized as supports and found to have a strong influence on the catalytic performance of the catalysts. Incorporation of nitrogen in the carbon framework significantly enhanced the catalytic activity compared to Ru catalysts on nitrogen-free supports. Notably, the catalyst (5 wt % Ru-NMC-3) with optimal N content (10.9 wt %) demonstrated improved stability and H2 selectivity, which are better than those of many state-of-the-art catalysts. Nitrogen in the carbon framework has a dual relationship with the activity of the catalyst: (i) it creates basic environment over the catalysts support and (ii) it acts as an anchoring site for metal nanoparticles. Anchoring of metal nanoparticles has helped to curb their sintering, thus leading to better stability of the catalysts under APR reaction conditions. Various characterization techniques were employed to understand the nature of active catalytic sites responsible for higher H2 production while minimizing CO formation. In situ CO-FTIR studies showed that the higher catalytic activity of 5 wt % Ru-NMC-3 catalyst was attributed to the enhanced WGS activity over this catalyst. Density functional theory calculations were performed to understand the stabilization of metal nanoparticles by different types of N present on the support and provide insights into the prefered sites of glycerol adsorption on the NMC support. Since 5 wt % Ru-NMC-3 was the relatively best catalyst, it was selected for the preparation of bimetallic catalysts. Accordingly, addition of Pt to this system helped to increase the stability of the catalyst. This bimetallic catalyst may, therefore, find application for wide use in APR of biomass oxygenates.

Active and Recyclable Gold Metal Nanoparticles Catalyst Supported on Nitrogen‐Doped Mesoporous Carbon for Chemoselective Hydrogenation of Cinnamaldehyde to Cinnamyl Alcohol

“…The D‐band to the G‐band intensity ratios (I D /I G , understood via the collective areas of the band) are 1.62, 1.72, 2.31, 2.42, 2.40 and 2.38 for MC, Au‐MC‐SI, NMC, Au‐NMC‐SI, Au‐NMC‐DP and Au‐NMC‐IW, respectively. This result revealed that imperfection in the graphite‐like sheets was raised on increasing the N‐content of the catalyst as well as after Au metal loading [67,76–79] …”

“…This can be elucidated by means of enhance in the “d electrons density” with shrinking Au nanoparticles size [89] . Additionally, Au nanoparticles are possibly electronically rich due to the transfer of electron density from nitrogen atoms [67,76,84b] . The higher electron density on Au nanoparticles can appreciably affects the binding energies [84b] .…”

“…Recently, we have also discuss the efficiency of NMC supported active Ru metal nanoparticles catalysts for the conversion of biomass‐derived 5‐hydroxymethylfurfural to 2,5‐dimethylfuran and furfural to 2‐methylfuran as a result of catalytic transfer hydrogenation using 2‐propanol as source of hydrogen [77] . Moreover, our research group also discuss efficacy of NMC supported Ru metal catalysts for H 2 generation owing to aqueous phase reforming of glycerol [67] . At this moment, we report the advantage of Au metal nanoparticles catalyst supported on NMC prepared by sol‐immobilization process for the selective hydrogenation of CA to CAL.…”

“…Nitrogen‐doped carbon materials have fascinated universal interest attributable to their astonishing accomplishment in abundant purposes, for hydrogenation and oxidation reactions, as catalyst support for development of active heterogeneous catalysts, in supercapacitors, for H 2 production via aqueous phase reforming of glycerol, in case of electrochemical cell for the oxygen reduction without employing a metal, in ammonia decomposition reaction, for the hydrogenation of biosourced furanic compound, etc [60–69] . Research investigations (experimental, spectroscopic and theoretical studies) have announced that the nitrogen‐doping has several beneficial effects such as enhanced metal nanoparticles binding interaction with the support, amplifies the number of catalytic active sites, raised metal dispersion, better resistance to metal sintering via improving stability of metal nanoparticles, increased in the percentage of metal in zero oxidation state (metallic state), enhanced the basicity of catalyst, modify the chemical and electronic interactions with the metal nanoparticles, etc [60–72] . All these important attributes of nitrogen‐doped carbon supported metal catalysts can assist to boost the catalytic performance in addition to desired product selectivity [72–75] …”

The Size‐Dependent Catalytic Performances of Supported Metal Nanoparticles and Single Atoms for the Upgrading of Biomass‐Derived 5‐Hydroxymethylfurfural, Furfural, and Levulinic acid

“…[103] The N-doped mesoporous carbon-supported Ru nanoparticles showed higher stability compared to the undoped carbon support during glycerol reforming. [104] The Ndoped CNT-supported Pd nanoparticles showed stability against sintering during nitrobenzene hydrogenation reaction. [105] The functionalization of the support materials has also been shown to improve the metal-support interactions and the metal nanoparticles stability in several important chemical transformations.…”