Defect pyrochlore oxides: as photocatalyst materials for environmental and energy applications ‐ a review

Jitta, Raju Reddy; Ravi, G.; Veldurthi, Naveen Kumar; Guje, Ravinder; Vithal, M.

doi:10.1002/jctb.4745

Cited by 76 publications

(24 citation statements)

References 120 publications

(116 reference statements)

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“…However, the energy consumption associated with electrolysis must be significantly reduced before this process becomes competitive at large scales. Photocatalytic generation of H 2 from organic solutions or H 2 O, although considered a minor source in terms of produced H 2 volume, appears to be a complementary and renewable way for simultaneous H 2 generation and wastewater remediation …”

Section: State Of the Art Of Photocatalytic Generation Of Hydrogenmentioning

confidence: 99%

Comprehensive review and future perspectives on the photocatalytic hydrogen production

Corredor

Rivero

Rangel

et al. 2019

J of Chemical Tech & Biotech

174

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Hydrogen represents a renewable energy alternative that may positively contribute to get over the global energy crisis while at the same time reducing its environmental burden. Overcoming the challenge of reaching this potential could be helped by careful choice of hydrogen (H2) sources. Photocatalytic generation of H2, although a minor alternative, appears to be a very good option at the time that liquid wastes are being degraded; therefore, this approach has given rise to an increasing number of interesting studies. Here, we aim to provide an integrated overview of the different photocatalytic, heterogeneous, homogeneous and hybrid systems. First, we categorize the units and mechanisms that take part in the photocatalytic process, and secondly we analyze their role and draw comparative conclusions. Thus, we analyze the role of (i) the electron source to carry out proton reduction, (ii) the proton source, which can be free protons in the medium or a proton donor compound, (iii) the catalyst nature and concentration, and (iv) the photosensitizer nature and concentration. We also provide an analysis of the influence of the solvent, especially in homogenous systems as well as the influence of pH. We provide a comparison of the photocatalytic performance, highlighting the advantages and disadvantages, of different systems. Thus, this review is, on the one hand, an update on the state of the art of photocatalytic generation of H2 from a full perspective that integrates homogeneous, heterogeneous and hybrid systems, and, on the other, a source of useful information for future research. © 2019 Society of Chemical Industry

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Section: State Of the Art Of Photocatalytic Generation Of Hydrogenmentioning

confidence: 99%

Comprehensive review and future perspectives on the photocatalytic hydrogen production

Corredor

Rivero

Rangel

et al. 2019

J of Chemical Tech & Biotech

174

View full text Add to dashboard Cite

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“…The pyrochlore oxides with the general formula of A 2 3+ B 2 4+ O 7 , where A 3+ is a rareearth ion and B 4+ is usually a transition metal, have attracted great attention as materials for nuclear waste disposal [1][2][3], thermal barrier coating materials [4][5][6], catalysts [7,8], and for other important technological applications such as solid electrolytes [9,10], electrodes [11], and magnets [12][13][14].…”

Section: Introductionmentioning

confidence: 99%

The Gd2−xMgxZr2O7−x/2 Solid Solution: Ionic Conductivity and Chemical Stability in the Melt of LiCl-Li2O

et al. 2022

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Materials with pyrochlore structure A2B2O7 have attracted considerable attention owing to their various applications as catalysts, sensors, electrolytes, electrodes, and magnets due to the unique crystal structure and thermal stability. At the same time, the possibility of using such materials for electrochemical applications in salt melts has not been studied. This paper presents the new results of obtaining high-density Mg2+-doped ceramics based on Gd2Zr2O7 with pyrochlore structure and comprehensive investigation of the electrical properties and chemical stability in a lithium chloride melt with additives of various concentrations of lithium oxide, performed for the first time. The solid solution of Gd2−xMgxZr2O7−x/2 (0 ≤ x ≤ 0.10) with the pyrochlore structure was obtained by mechanically milling stoichiometric mixtures of the corresponding oxides, followed by annealing at 1500 °C. The lattice parameter changed non-linearly as a result of different mechanisms of Mg2+ incorporation into the Gd2Zr2O7 structure. At low dopant concentrations (x ≤ 0.03) some interstitial positions can be substituted by Mg2+, with further increasing Mg2+-content, the decrease in the lattice parameter occurred due to the substitution of host-ion sites with smaller dopant-ion. High-density ceramics 99% was prepared at T = 1500 °C. According to the results of the measurements of electrical conductivity as a function of oxygen partial pressure, all investigated samples were characterized by the dominant ionic type of conductivity over a wide range of pO2 (1 × 10–18 ≤ pO2 ≤ 0.21 atm) and T < 800 °C. The sample with the composition of x = 0.03 had the highest oxygen-ion conductivity (10−3 S·cm−1 at 600 °C). The investigation of chemical stability of ceramics in the melt of LiCl with 2.5 mas.% Li2O showed that the sample did not react with the melt during the exposed time of one week at the temperature of 650 °C. This result makes it possible to use these materials as oxygen activity sensors in halide melts.

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“…It is known that oxygen vacancies are generally formed preferentially at the interstitial O′ sites rather than at the O sites . Thanks to the compositional flexibility of the A and B sites to manipulate their wide spectrum of properties, including electrical, magnetic, dielectric, optical, and electrocatalytic properties, pyrochlores have been used in a variety of applications, such as ionic/electrical conductors, anode materials for solid electrolyte fuel cells, radioactive waste immobilization, high-temperature thermal barrier coatings, photocatalysts, electrocatalysts for oxygen reduction reaction (ORR), and OER. − In particular, pyrochlore oxides with metallic conduction behavior are attractive candidates for OER catalysts due to their high conductivity, fast charge transfer through the oxygen vacancies, and structural stability. In addition, the ability to substitute different ions into the A- and B-site elements while maintaining the same crystal structure provides another powerful strategy to tune the concentration of oxygen vacancies and electronic structures, and thus the OER activity and stability.…”

Section: Introductionmentioning

confidence: 99%

Toward Efficient Electrocatalytic Oxygen Evolution: Emerging Opportunities with Metallic Pyrochlore Oxides for Electrocatalysts and Conductive Supports

et al. 2020

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The design of active and stable electrocatalysts for oxygen evolution reaction is a key enabling step toward efficient utilization of renewable energy. Along with efforts to develop high-performance electrocatalysts for oxygen evolution reaction, pyrochlore oxides have emerged as highly active and stable materials that function as catalysts as well as conductive supports for hybrid catalysts. The compositional flexibility of pyrochlore oxide provides many opportunities to improve electrocatalytic performance by manipulating material structures and properties. In this Outlook, we first discuss the recent advances in developing metallic pyrochlore oxides as oxygen evolution catalysts, along with elucidation of their reaction mechanisms, and then introduce an emerging area of using pyrochlore oxides as conductive supports to design hybrid catalysts to further improve the OER activity. Finally, the remaining challenges and emerging opportunities for pyrochlore oxides as electrocatalysts and conductive supports are discussed.

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Defect pyrochlore oxides: as photocatalyst materials for environmental and energy applications ‐ a review

Cited by 76 publications

References 120 publications

Comprehensive review and future perspectives on the photocatalytic hydrogen production

Comprehensive review and future perspectives on the photocatalytic hydrogen production

The Gd2−xMgxZr2O7−x/2 Solid Solution: Ionic Conductivity and Chemical Stability in the Melt of LiCl-Li2O

Toward Efficient Electrocatalytic Oxygen Evolution: Emerging Opportunities with Metallic Pyrochlore Oxides for Electrocatalysts and Conductive Supports

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