In recent years, CO2 reforming of methane (dry reforming of methane, DRM) has become an attractive research area because it converts two major greenhouse gasses into syngas (CO and H2 ), which can be directly used as fuel or feedstock for the chemical industry. Ni-based catalysts have been extensively used for DRM because of its low cost and good activity. A major concern with Ni-based catalysts in DRM is severe carbon deposition leading to catalyst deactivation, and a lot of effort has been put into the design and synthesis of stable Ni catalysts with high carbon resistance. One effective and practical strategy is to introduce a second metal to obtain bimetallic Ni-based catalysts. The synergistic effect between Ni and the second metal has been shown to increase the carbon resistance of the catalyst significantly. In this review, a detailed discussion on the development of bimetallic Ni-based catalysts for DRM including nickel alloyed with noble metals (Pt, Ru, Ir etc.) and transition metals (Co, Fe, Cu) is presented. Special emphasis has been provided on the underlying principles that lead to synergistic effects and enhance catalyst performance. Finally, an outlook is presented for the future development of Ni-based bimetallic catalysts.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/cphc.201700529

A Review on Bimetallic Nickel‐Based Catalysts for CO2 Reforming of Methane

Catalytic conversion of CO2 to produce fuels and chemicals is attractive in prospect because it provides an alternative to fossil feedstocks and the benefit of converting and cycling the greenhouse gas CO2 on a large scale. In today's technology, CO2 is converted into hydrocarbon fuels in Fischer-Tropsch synthesis via the water gas shift reaction, but processes for direct conversion of CO2 to fuels and chemicals such as methane, methanol, and C2+ hydrocarbons or syngas are still far from large-scale applications because of processing challenges that may be best addressed by the discovery of improved catalysts-those with enhanced activity, selectivity, and stability. Core-shell structured catalysts are a relatively new class of nanomaterials that allow a controlled integration of the functions of complementary materials with optimised compositions and morphologies. For CO2 conversion, core-shell catalysts can provide distinctive advantages by addressing challenges such as catalyst sintering and activity loss in CO2 reforming processes, insufficient product selectivity in thermocatalytic CO2 hydrogenation, and low efficiency and selectivity in photocatalytic and electrocatalytic CO2 hydrogenation. In the preceding decade, substantial progress has been made in the synthesis, characterization, and evaluation of core-shell catalysts for such potential applications. Nonetheless, challenges remain in the discovery of inexpensive, robust, regenerable catalysts in this class. This review provides an in-depth assessment of these materials for the thermocatalytic, photocatalytic, and electrocatalytic conversion of CO2 into synthesis gas and valuable hydrocarbons.

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Core–shell structured catalysts for thermocatalytic, photocatalytic, and electrocatalytic conversion of CO2

Chemical-looping reforming of methane (CLRM) offers an effective approach for coproducing syngas and pure hydrogen. In this work, CeO2 nano particles (2–3 nm) are well dispersed on the wall surface of three-dimensional ordered macroporous (3DOM) LaFeO3, obtaining a highly efficient oxygen carrier for the CLRM technology. The physical and chemical properties of the oxygen carriers were characterized by SEM, TEM, H2-TPR, XPS, XRD, CH4-TPR and CH4-TPD techniques. It is found that the presence of CeO2 on LaFeO3 results in the formation of Ce3+ and Fe2+ due to the CeO2-LaFeO3 interaction. The coexistence of Ce3+ and Fe2+ irons induces abundant oxygen vacancies on the mixed oxides, which strongly improves the reducibility, oxygen mobility and reactivity for methane oxidation. The presence of CeO2 also improves the resistance towards carbon deposition formation, and this allows the CeO2/LaFeO3 materials own high available oxygen storage capacity (available OSC, the maximum amount of oxygen consumed by methane reduction without the formation of carbon deposition). It is also noted that the agglomeration of CeO2 nano particles would reduce the reactivity of oxygen carriers. Among all the obtained samples, the 10% CeO2/LaFeO3 sample exhibits the highest yields of syngas (9.94 mmol g−1) and pure hydrogen (3.38 mmol g−1) without the formation of carbon deposition, which are much higher than that over the pure LaFeO3 sample (5.73 mmol g−1 for syngas yield and 2.00 mmol g−1 for hydrogen yield). In addition, the CeO2/LaFeO3 oxygen carrier also showed high stability during the successive CLRM testing either in the activity (yields of syngas and pure hydrogen) or structure (macroporous frameworks) aspect.

Designed oxygen carriers from macroporous LaFeO3 supported CeO2 for chemical-looping reforming of methane

Low-temperature catalytic CO2 dry reforming of methane on Ni-based catalysts: A review

Funded by: National Natural Science Foundation of China. Grant Numbers: 21701043, 21573066, 51402100; Provincial Natural Science Foundation of Hunan. Grant Numbers: 2016JJ1006, 2016TP1009; Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province; Shenzhen Science and Technology Program, Grant Number: JCYJ20170306141659388

Rational Design of Transition Metal-Based Materials for Highly Efficient Electrocatalysis

In recent decades, increasing interests have been put on improving the stability and selectivity of nanocatalysts for clean energy production due to the decrease of fossil fuels. Despite the prominent feature of high catalytic activity, nanocatalysts are prone to sintering. Structural design of nanocatalysts to form core/yolk shell structure has been proven to be the most effective method to enhance their catalytic stability. In this review, design strategies for core/yolk shell nanocatalysts to attain high stability in energy related applications at high temperatures such as hydrocarbon reforming reactions for syngas production and high temperature fuel cells such as SOFC and MCFC are summarized and exemplified with the advancements made in the recent three years. In addition, measures taken to obtain outstanding selectivity for F-T synthesis and C C bond hydrogenation reactions are also presented. Further, excellent shape and size selectivity design examples are also introduced. Finally, unsolved problems and challenges for core/yolk shell nanocatalysts design are proposed as the final part of this review.

Design of highly stable and selective core/yolk–shell nanocatalysts—A review

NiCo@NiCo phyllosilicate@CeO2 hollow core shell catalysts for steam reforming of toluene as biomass tar model compound

CO2 (dry) reforming of CH4 (DRM) reaction is an attractive measure to not only mitigate the environmental problems such as global warming but also produce the syngas as feedstock for liquid fuel production. Great achievements have been made in various DRM processes such as thermally-driven DRM, plasma-assisted DRM and solar-driven DRM together with the corresponding catalyst design strategies. Herein, the merits and demerits of these three processes as well as these design strategies are compared and analyzed. We start with thermally-driven DRM which accounts for the large majority of researches being reported in the recent five years (2016–2020). Four typical measures to achieve sintering and carbon resistant catalysts including designing catalysts with strong MSI, bimetallic catalysts, layered doubled hydroxide catalysts and core shell structured catalysts are summarized. Thereafter, for plasma-assisted DRM, the effect of operating parameters to the performance of classical plasma reactors as well as the influence of different packing materials for these packed plasma reactors are analyzed. After this, for solar-driven DRM, the application and design of solar reactors are discussed for solar thermocatalysis, which is followed by the discussion of solar photocatalysis and hybrid photothermo catalysis. Finally, we propose potential challenges and research directions of these three processes to give a comprehensive understanding of DRM reaction.

Recent advances in process and catalyst for CO2 reforming of methane

Major issues in photocatalysis include improving charge carrier separation efficiency at the interface of semiconductor photocatalysts and rationally developing efficient hierarchical heterostructures. Surface continuous growth deposition is used to make hollow Cu2-x S nanoboxes, and then simple hydrothermal reaction is used to make core-shell Cu2-x S@ZnIn2 S4 S-scheme heterojunctions. The photothermal and photocatalytic performance of Cu2-x S@ZnIn2 S4 is improved. In an experimental hydrogen production test, the Cu2-x S@ZnIn2 S4 photocatalyst produces 4653.43 µmol h-1 g-1 of hydrogen, which is 137.6 and 13.8 times higher than pure Cu2-x S and ZnIn2 S4 , respectively. Furthermore, the photocatalyst exhibits a high tetracycline degradation efficiency in the water of up to 98.8%. For photocatalytic reactions, the hollow core-shell configuration gives a large specific surface area and more reactive sites. The photocatalytic response range is broadened, infrared light absorption enhanced, the photothermal effect is outstanding, and the photocatalytic process is promoted. Meanwhile, characterizations, degradation studies, active species trapping investigations, energy band structure analysis, and theoretical calculations all reveal that the S-scheme heterojunction can efficiently increase photogenerated carrier separation. This research opens up new possibilities for future S-scheme heterojunction catalyst design and development.

Hollow Nanoboxes Cu2-x S@ZnIn2 S4 Core-Shell S-Scheme Heterojunction with Broad-Spectrum Response and Enhanced Photothermal-Photocatalytic Performance.

Min Li

Papers

Design of highly stable and selective core/yolk–shell nanocatalysts—A review

NiCo@NiCo phyllosilicate@CeO2 hollow core shell catalysts for steam reforming of toluene as biomass tar model compound

Recent advances in process and catalyst for CO2 reforming of methane

Hollow Nanoboxes Cu2-x S@ZnIn2 S4 Core-Shell S-Scheme Heterojunction with Broad-Spectrum Response and Enhanced Photothermal-Photocatalytic Performance.

Electrocatalyst design strategies for ammonia production via N2 reduction