Hydrogenation of CO2 on Nickel–Iron Nanoparticles Under Sunlight Irradiation

Abstract

Nickel-iron oxide nanoparticles were prepared by a simple mixed oxalate precursor decomposition method and used as catalysts for the sunlight-promoted CO2 hydrogenation reaction. The composition of the NiyFe1−yOx materials was designed to cover the entire Ni/Fe ratio range (y = 1, 0.9, 0.75, 0.5, 0.25, 0.1, 0). Characterisation was undertaken by means of elemental analyses, X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). The pure nickel material (NiOx) contained crystalline NiO nanoparticles. Upon introducing lower proportions of iron in Ni9FeOx and Ni3FeOx, NiO was the only crystalline phase, along with increasing amounts of amorphous iron oxides. Higher iron contents resulted in the coexistence of NiO and γ-Fe2O3 domains at the nanoscale in NiFeOx, NiFe3Ox and NiFe9Ox, whereas the pure iron material (FeOx) was composed of α-Fe2O3 as the only crystalline phase and a significant fraction of amorphous iron oxides. The hydrogenation of carbon dioxide was tested on the materials under simulated sunlight irradiation, and the activities and selectivities investigated as initial CO2 conversion rates and product distributions, respectively. The introduction of iron was beneficial for the activation of CO2, due to the known ability of this metal for promoting the reverse water-gas shift (rWGS) reaction. On the other hand, it was proven that nickel and iron favoured hydrogenation and chain growth processes, respectively. Moreover, the lack of hydrogenation sites in the pure iron material results in the expected preferential generation of olefins. Results for the entire compositional range draw a clear trend towards the enhanced formation of short-chain alkanes at middle iron contents, most likely owing to the existence of junctions of nickel and iron oxides at the nanoscale, and the related interfaces providing rWGS, chain growth and hydrogenation sites in close vicinity. The

Mono- and bimetallic metal catalysts based on Ni and Ru supported on alumina-coated monoliths for CO2 methanation

“…This is consistent with fact that Fe is known to catalyze the rWGS reaction. 16,20 The kinetic rate constants (k) were calculated from the results in Fig. 1A.…”

“…14 Elsewhere, iron catalysts have proven the ability to promote the water gas-shift reaction 15 and the oligomerization to C 2+ . 16 The addition of Fe to a Ni catalyst has been found to promote the CO 2 methanation reaction. 12,16,17 Bimetallic Ni-Fe alloy nanoparticles have been prepared from a hydrotalcite precursor and the bimetallic catalyst exhibited higher activities and stabilities than a monometallic catalyst in CO 2 hydrogenation.…”

“…16 The addition of Fe to a Ni catalyst has been found to promote the CO 2 methanation reaction. 12,16,17 Bimetallic Ni-Fe alloy nanoparticles have been prepared from a hydrotalcite precursor and the bimetallic catalyst exhibited higher activities and stabilities than a monometallic catalyst in CO 2 hydrogenation. 18 Nevertheless, the best catalyst was that with the lowest amount of Fe.…”

Substitution of Zinc(II) in Nickel(II) Oxide as Proficient Copper-Free Catalysts for Selective CO2 Electroreduction

“…In cases of Zn-substituted NiO, no additional peak corresponding to Zn metal or ZnO is observed. There may be some chance for the presence of undetectected crystallites or amorphous domains of zinc, which are nondominant, because of the formation of a stable solid solution . The observed XRD pattern shows an observable shift toward lower 2θ in Ni 0.9 Zn 0.1 O catalysts, in comparison to pure NiO.…”

High-Performance, Scalable, and Low-Cost Copper Hydroxyapatite for Photothermal CO2 Reduction

“…In recent years, the intensification of climate change and increasing demand for renewable chemicals and clean energy have triggered enormous research attention. − Among many possible solutions to these issues, the gas-phase photoreduction of CO 2 to CO via the reverse water gas shift (RWGS) reaction stands out, due in part to the ability of CO to serve as a feedstock in the production of both value-added chemicals and renewable fuels. − Unfortunately, the best-performing catalysts for this reaction often contain expensive or toxic elements. − Thus, the development of a catalyst with high performance, industrially relevant scalability, and competitive cost is a pivotal challenge for photocatalytic gas-phase hydrogenation of CO 2 . − ,− − ,− As a result, one of the greatest obstacles to the further development of this technology is the identification of a suitable catalyst material.…”