High Entropy Spinel Oxide (AlCrCoNiFe2)O as Highly Active Oxygen Evolution Reaction Catalysts
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PROVIDER: S-EPMC11209678 | biostudies-literature | 2024 Jun
REPOSITORIES: biostudies-literature
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Project description:The rational design principle of highly active catalysts for the oxygen evolution reaction (OER) is desired because of its versatility for energy-conversion applications. Postspinel-structured oxides, CaB 2O4 (B = Cr3+, Mn3+, and Fe3+), have exhibited higher OER activities than nominally isoelectronic conventional counterparts of perovskite oxides LaBO3 and spinel oxides ZnB 2O4. Electrochemical impedance spectroscopy reveals that the higher OER activities for CaB 2O4 series are attributed to the lower charge-transfer resistances. A density-functional-theory calculation proposes a novel mechanism associated with lattice oxygen pairing with adsorbed oxygen, demonstrating the lowest theoretical OER overpotential than other mechanisms examined in this study. This finding proposes a structure-driven design of electrocatalysts associated with a novel OER mechanism.
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Project description:The oxygen evolution reaction (OER) plays a key role in emerging energy conversion technologies such as rechargeable metal-air batteries, and direct solar water splitting. Herein, a remarkably low overpotential of ≈150 mV at 10 mA cm-2disk in alkaline solutions using one of the non-Fermi liquids, Hg2Ru2O7, is reported. Hg2Ru2O7 displays a rapid increase in current density and excellent durability as an OER catalyst. This outstanding catalytic performance is realized through the coexistence of localized d-bands with the metallic state that is unique to non-Fermi liquids. The findings indicate that non-Fermi liquids could greatly improve the design of highly active OER catalysts.
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Project description:Developing stable and efficient electrocatalysts is vital for boosting oxygen evolution reaction (OER) rates in sustainable hydrogen production. High-entropy oxides (HEOs) consist of five or more metal cations, providing opportunities to tune their catalytic properties toward high OER efficiency. This work combines theoretical and experimental studies to scrutinize the OER activity and stability for spinel-type HEOs. Density functional theory confirms that randomly mixed metal sites show thermodynamic stability, with intermediate adsorption energies displaying wider distributions due to mixing-induced equatorial strain in active metal-oxygen bonds. The rapid sol-flame method is employed to synthesize HEO, comprising five 3d-transition metal cations, which exhibits superior OER activity and durability under alkaline conditions, outperforming lower-entropy oxides, even with partial surface oxidations. The study highlights that the enhanced activity of HEO is primarily attributed to the mixing of multiple elements, leading to strain effects near the active site, as well as surface composition and coverage.
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Project description:High catalytic efficiency and long-term stability are two main components for the performance assessment of an electrocatalyst. Previous attention has been paid more to efficiency other than stability. The present work is focused on the study of the stability processed on the FeCoNiRu high-entropy alloy (HEA) in correlation with its catalytic efficiency. This catalyst has demonstrated not only performing the simultaneous hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with high efficiency but also sustaining long-term stability upon HER and OER. The study reveals that the outstanding stability is attributed to the spinel oxide surface layer developed during evolution reactions. The spinel structure preserves the active sites that are inherited from the HEA's intrinsic structure. This work will provide an insightful direction/pathway for the design and manufacturing activities of other metallic electrocatalysts and a benchmark for the assessment of their efficiency-stability relationship.
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Project description:High-entropy alloys (HEAs) have recently been applied in the field of heterogeneous catalysis benefiting from vast chemical space. However, huge chemical space also brings extreme challenges for the comprehensive study of HEAs by traditional trial-and-error experiments. Therefore, the machine learning (ML) method is presented to investigate the oxygen reduction reaction (ORR) catalytic activity of millions of reactive sites on HEA surfaces. The well-performed ML model is constructed based on the gradient boosting regression (GBR) algorithm with high accuracy, generalizability, and simplicity. In-depth analysis of the results demonstrates that adsorption energy is a mixture of the individual contributions of coordinated metal atoms near the reactive site. An efficient strategy is proposed to further boost the ORR catalytic activity of promising HEA catalysts by optimizing the HEA surface structure, which recommends a highly efficient HEA catalyst of Ir48Pt74Ru30Rh30Ag74. Our work offers a guide to the rational design and nanostructure synthesis of HEA catalysts.
| S-EPMC9481945 | biostudies-literature
Project description:The multi-element synergism in high-entropy materials (HEMs) provides great opportunities as multi-functional catalysts or for the promotion of tandem reactions. Herein, a strategy that utilizes a high entropy precursor is proposed to realize the formation of a unique high entropy metallic-high entropy non-metallic community (HEM-HENMC). Aminotriazole acts as a "bonding agent" for the high entropy precursor, and not only binds the five metals Cr, Mn, Fe, Co and Ni together, but also introduces nitrogen and carbon in situ. After simultaneous phosphorization and vulcanization and surface oxidation, the unique HEM-HENMC containing five metals (Cr, Mn, Fe, Co and Ni) and five non-metals (C, N, O, P and S) was successfully prepared. The synergistic effect of the various non-metal and metal ions imparts the HEM-HENMC with excellent electrochemical activity. When used as an OER electrocatalyst, the HEM-HENMC exhibits a low overpotential of 211.9 mV (@10 mA cm-2) and has excellent stability for over 25 h, while as an ORR electrocatalyst, a satisfactory initial voltage of 0.977 V, half wave potential of 0.841 V and excellent 25 h electrochemical stability are achieved. This work provides an important research basis for the development of high entropy metallic-high entropy nonmetallic materials.
| S-EPMC11575638 | biostudies-literature
Project description:Herein, a new high entropy material is reported, i.e., a noble metal-free high entropy glycerate (HEG), synthesized via a simple solvothermal process. The HEG consists of 5 different metals of Fe, Ni, Co, Cr, and Mn. The unique glycerate structure exhibits an excellent oxygen evolution reaction (OER) activity with a low overpotential of 229 and 278 mV at current densities of 10 and 100 mA cm-2, respectively, in 1 m KOH electrolyte, outperforming its subsystems of binary-, ternary-, and quaternary-metal glycerates. The HEG also shows outstanding stability and durability in the alkaline electrolyte. The result demonstrates the significance of synergistic effect that gives additional freedoms to modify the electronic structure and coordination environment. Moreover, HEG@HEG electrolyzer shows a good overall water splitting performance and durability, requiring a cell voltage of 1.63 V to achieve a current density of 10 mA cm-2.
| S-EPMC7967045 | biostudies-literature
Project description:Developing effective and long-lasting electrocatalysts for oxygen evolution reaction (OER) is critical for increasing sustainable hydrogen production. This paper describes the production and characterization of CoFeP nanoparticles (CFP NPs) as high-performance electrocatalysts for OER. The CFP NPs were produced using a simple hydrothermal technique followed by phosphorization, yielding an amorphous/crystalline composite structure with improved electrochemical characteristics. Our results reveal that CFP NPs have a surprisingly low overpotential of 284 mV at a current density of 100 mA cm-2, greatly exceeding the precursor CoFe oxide/hydroxide (CFO NPs) and the commercial RuO2 catalyst. Furthermore, CFP NPs demonstrate exceptional stability, retaining a constant performance after 70 h of continuous operation. Post-OER characterization analysis revealed transformations in the catalyst, including the formation of cobalt-iron oxides/oxyhydroxides. Despite these changes, CFP NPs showed superior long-term stability compared to native metal oxides/oxyhydroxides, likely due to enhanced surface roughness and increased active sites. This study proposes a viable strategy for designing low-cost, non-precious metal-based OER catalysts, which will help advance sustainable energy technology.
| S-EPMC11396991 | biostudies-literature
Project description:Spinel oxides are considered as promising low-cost non-precious metal electrocatalysts for oxygen evolution reaction (OER) due to their desirable catalytic activities and fast kinetics. However, as a result of the structural complexity of spinel oxides, systematic and in-depth studies on enhancing the OER performance of spinel oxides remain inadequate. In particular, the construction of active sites regarding the large number of unoccupied octahedral interstices has not yet been explored. Herein, more octahedral sites with high OER activities are constructed on the surface of spinel oxides via a cationic misalignment, which is induced by the defects in the spinel oxide solutions, i.e., MoFe2 O4 and CoFe2 O4 nanosheets supported on an iron foam (MCFO NS/IF). With increased active sites and modified electronic structure, the state-of-the-art electrocatalyst exhibits the excellent OER catalytic activity with an onset potential of 1.41 V versus RHE and an overpotential of 290 mV to achieve a current density of 500 mA cm-2 . Moreover, such an electrocatalyst also demonstrates fast kinetics with the Tafel slope of 38 mV dec-1 and superior durability by maintaining the OER activity at 250 mA cm-2 for 1000 h.
| S-EPMC8425945 | biostudies-literature
Project description:The three-dimensional (3D) distribution of individual atoms on the surface of catalyst nanoparticles plays a vital role in their activity and stability. Optimising the performance of electrocatalysts requires atomic-scale information, but it is difficult to obtain. Here, we use atom probe tomography to elucidate the 3D structure of 10 nm sized Co2FeO4 and CoFe2O4 nanoparticles during oxygen evolution reaction (OER). We reveal nanoscale spinodal decomposition in pristine Co2FeO4. The interfaces of Co-rich and Fe-rich nanodomains of Co2FeO4 become trapping sites for hydroxyl groups, contributing to a higher OER activity compared to that of CoFe2O4. However, the activity of Co2FeO4 drops considerably due to concurrent irreversible transformation towards CoIVO2 and pronounced Fe dissolution. In contrast, there is negligible elemental redistribution for CoFe2O4 after OER, except for surface structural transformation towards (FeIII, CoIII)2O3. Overall, our study provides a unique 3D compositional distribution of mixed Co-Fe spinel oxides, which gives atomic-scale insights into active sites and the deactivation of electrocatalysts during OER.
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