The Kinetics of Reduction of Dense Synthetic Nickel Oxide in H2-N2 and H2-H2O Atmospheres

Hidayat, Taufiq; Rhamdhani, M. Akbar; Jak, Evgueni; Hayes, Peter C.

doi:10.1007/s11663-008-9212-0

Cited by 28 publications

(36 citation statements)

References 20 publications

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“…The loss of oxygen during reduction leads to a volume decrease by 41 % resulting in a restructuring of the overall morphology of the solid and can lead to pore formation in the Ni [17][18][19]. A delay in the reduction onset, a so-called incubation or induction period is reported, which decreases with reaction temperature [6,8,10,12] and increasing number of defects on the NiO surface [10].…”

Section: Introductionmentioning

confidence: 99%

“…On the contrary, the produced H 2 O influences the reaction rate negatively, possibly by poisoning of the active sites for H 2 adsorption [6,18]. In addition it has been reported that the reaction rate scales with the H 2 pressure [8,10,17].…”

Section: Introductionmentioning

confidence: 99%

“…In addition, local information has been obtained using post mortem electron microscopy [12,13,14,17,18]. However, nanoscale dynamics, such as initiation of the reduction, crystal growth/decay or morphological changes of NiO and Ni during reduction can only be indirectly probed with these techniques.…”

Section: Introductionmentioning

confidence: 99%

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Environmental TEM study of the dynamic nanoscaled morphology of NiO/YSZ during reduction

Simonsen¹,

Agersted²,

Jacobsen³

et al. 2015

Applied Catalysis A: General

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The reduction of a metal oxide is often a critical preparation step for activating catalytic behavior.This study addresses the reduction process of NiO in pure form and in a composite of NiO/yttriastabilized zirconia (YSZ) in hydrogen relevant for solid oxide electrochemical cells by comparing results from environmental transmission electron microscopy (ETEM) with thermogravimetric analysis (TGA). The temperature dependent reduction profiles obtained from TGA confirm an inhibitive effect from YSZ on the NiO reduction. The ETEM images show the growth of Ni in decaying NiO and reveal the nanoscale morphological changes such as pore formation in NiO above 280°C and densification and collapse of the pore structures above 400°C. The accelerated Ni front in NiO illustrates the autocatalysis of the reaction. A rapid temperature ramping from room temperature to 780°C in hydrogen in 1 second resulted in immediate morphological changes at the nanoscale from dense NiO to dense Ni. The analysis suggests that the inhibitive effect of YSZ on the NiO reduction reaction is not due to a direct local interaction between YSZ and NiO, but instead due to gas and/or mass transport limitations.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Environmental TEM study of the dynamic nanoscaled morphology of NiO/YSZ during reduction

Simonsen¹,

Agersted²,

Jacobsen³

et al. 2015

Applied Catalysis A: General

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show abstract

“…This can be partly explained by the framework of YSZ surrounding the Ni for Ni/YSZ samples (1), but also for initially dense samples of pure NiO, micropores have been observed in the Ni after reduction (19,20). We suggest that the larger pores observed at high temperatures are due to collapse of the Ni nanopores and coarsening of the Ni particles.…”

Section: Etem Resultsmentioning

confidence: 83%

NiO/YSZ Reduction for SOFC/SOEC Studied In Situ by Environmental Transmission Electron Microscopy

Simonsen¹,

Agersted²,

Jacobsen³

et al. 2014

ECS Trans.

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A typical anode for solid oxide fuel cells (SOFC) or cathode for solid oxide electrolysis cells (SOEC) is a complex porous structure of Ni and yttria-stabilized zirconia (YSZ). The porous Ni/YSZ is usually prepared from powder mixtures of NiO and YSZ, tape casted and sintered into a dense structure and finally reduced during start-up of the SOFC/SOEC in H 2 at the operating temperature of the cell (ca. 800 °C). This contribution presents environmental transmission electron microscopy (ETEM) nanoscale observations of the reduction process of a NiO/YSZ powder in H 2 at temperatures up to almost 1000 °C. The study focusses on the temperature dependent dynamical morphology of the NiO/YSZ and on the possible influence of YSZ on the NiO reduction.

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“…As an estimation, the unreacted shrinking-core model (USCM) is widely used in the literature to simplify the grain diffusion process [4,58,65,68,72,73], in which a product layer is formed around an unreacted core inside the grain, as seen in Figure 6. The gaseous reactant is assumed to diffuse through the product layer, and react with the unreacted core.…”

Section: Grain Diffusion Controlsmentioning

confidence: 99%

Design of a rotary reactor for chemical-looping combustion. Part 1: Fundamentals and design methodology

Zhao

Iloeje

Chen

et al. 2014

Fuel

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Chemical-looping combustion (CLC) is a novel and promising option for several applications including carbon capture (CC), fuel reforming, H 2 generation, etc. Previous studies demonstrated the feasibility of performing CLC in a novel rotary design with micro-channel structures. In the reactor, a solid wheel rotates between the fuel and air streams at the reactor inlet, and depleted air and product streams at exit. The rotary wheel consists of a large number of micro-channels with oxygen carriers (OC) coated on the inner surface of the channel walls. In the CC application, the OC oxidizes the fuel while the channel is in the fuel zone to generate undiluted CO 2 , and is regenerated while the channel is in the air zone. In this two-part series, the effect of the reactor design parameters is evaluated and its performance with different oxygen carriers (OC) is compared. In Part 1, the design objectives and criteria are specified and the key parameters controlling the reactor performance are identified. The fundamental effect of the OC  Corresponding author. Tel.: +1 617 253 2295. E-mail address: ghoniem@mit.edu (A.F. Ghoniem) 2 characteristics, the design parameters, and the operating conditions are studied. The design procedures are presented on the basis of the relative importance of each parameter, enabling a systematic methodology of selecting the design parameters and the operating conditions with different OCs. Part 2 presents the application of the methodology to the designs with the three commonly used OCs, i.e., nickel, copper, and iron, and compares the simulated performances of the designs.

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The Kinetics of Reduction of Dense Synthetic Nickel Oxide in H2-N2 and H2-H2O Atmospheres

Cited by 28 publications

References 20 publications

Environmental TEM study of the dynamic nanoscaled morphology of NiO/YSZ during reduction

Environmental TEM study of the dynamic nanoscaled morphology of NiO/YSZ during reduction

NiO/YSZ Reduction for SOFC/SOEC Studied In Situ by Environmental Transmission Electron Microscopy

Design of a rotary reactor for chemical-looping combustion. Part 1: Fundamentals and design methodology

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