Adjusting the Crystallinity of Mesoporous Spinel CoGa2O4 for Efficient Water Oxidation

The role of Co-Ga2O3 interfaces in methane dry reforming

As the combination of Co with other non-noble metals is a viable way to improve the catalytic properties of Co in methane dry reforming (DRM), we studied an impregnated Co3O4/β-Ga2O3 powder catalyst to understand the influence of Ga and the catalytic role of the Co-Ga2O3 interface and the intermetallic compound CoGa in DRM. Co3O4/β-Ga2O3 undergoes a series of structural transformations during activation by reduction in hydrogen and under DRM conditions. Contact to the CO2/CH4 mixture without hydrogen pre-reduction yields CoGa2O4 spinel particles encrusting β-Ga2O3 without significant DRM activity. Hydrogen reduction transforms Co3O4/β-Ga2O3 initially to α-Co/β-Ga2O3, before it induces reactive metal-support interaction leading to the formation of bimetallic CoGa particles on β-Ga2O3. Subsequent improved DRM activity can be correlated to the decomposition of the intermetallic compound CoGa: according to operando X-ray diffraction CoGa re-transforms into α-Co/β-Ga2O3 during DRM. Hydrogen pre-reduction is a prerequisite for high DRM activity on Co3O4/β-Ga2O3, where intermediarily formed CoGa is decomposed under reaction conditions yielding a pronounced increase in the activity rivalling established noble metal and non-noble metal catalysts. A particular advantage of β-Ga2O3 is the suppression of coking and Co deactivation, as observed on a Ga-free Co/SiO2 catalyst.

Construction of Co1-xZnxFe2xGa2-2xO4 (0<x≤0.6) Solid Solutions for Improving Solar Fuels Production in Photocatalytic CO2 Reduction by H2O Vapour

Solid solutions are garnering substantial attention in the realm of solar energy utilization due to their tunable electronic properties, encompassing band edge positions and charge-carrier mobilities. In this study, we designed and synthesized Co1-xZnxFe2xGa2-2xO4 (0 Collapse

Key Words

• CO2 conversion
• Co1-xZnxFe2xGa2–2xO4
• Solid solution
• molten salts
• photosynthesis

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Grants

• 2023AAC02002 Natural Science Foundation of Ningxia Province
• 21862015, 21865022 Innovative Research Group Project of the National Natural Science Foundation of China

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Affiliation(s)

Qiang Wang State Key Laboratory of High-efficiency, Utilization of Coal and Green Chemical Engineering, College of Chemistry and Chemical Engineering, Ningxia University, Yinchuan, 750021, China
Li Li State Key Laboratory of High-efficiency, Utilization of Coal and Green Chemical Engineering, College of Chemistry and Chemical Engineering, Ningxia University, Yinchuan, 750021, China
Jiaxue Lu State Key Laboratory of High-efficiency, Utilization of Coal and Green Chemical Engineering, College of Chemistry and Chemical Engineering, Ningxia University, Yinchuan, 750021, China
Yao Chai State Key Laboratory of High-efficiency, Utilization of Coal and Green Chemical Engineering, College of Chemistry and Chemical Engineering, Ningxia University, Yinchuan, 750021, China
Jinni Shen State Key Lab of Photocatalysis on Energy and Environment, College of Chemistry, Fuzhou University, Fuzhou, 350116, P. R. China
Jun Liang State Key Laboratory of High-efficiency, Utilization of Coal and Green Chemical Engineering, College of Chemistry and Chemical Engineering, Ningxia University, Yinchuan, 750021, China

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Synthesis of Iron Gallate (FeGa2O4) Nanoparticles by Mechanochemical Method

The study was focused on optimizing the procedure of synthesizing iron gallate (FeGa2O4) nanoparticles by mechanochemical techniques. Due to a lack of information in the literature about the sequence of synthesis procedures of FeGa2O4 structures, the study is based on the establishment of a recipe for FeGa2O4 synthesis using mechanochemical techniques. Rotation speed, grinding media, and milling durations were the optimized parameters. At the end of each step, the structure of the resulting samples was investigated using the X-ray diffraction (XRD) patterns of samples. At the end of the processes, the XRD patterns of the samples milled under an air atmosphere were coherent with the XRD pattern of the FeGa2O4 structure. XRD patterns were analyzed employing Rietveld refinements to determine lattice parameters under the assumption of an inverse spinel crystal formation. Furthermore, a fluctuation at band gap values in the range of 2.39 to 2.55 eV was realized and associated with the excess Fe atoms in the lattice, which settled as defects in the crystal structures.

Solid-state redox couple mediated water splitting

The solid-state redox couple is a vital charge transfer medium for electrochemical water splitting. In this Frontiers article, we summarize the versatile application of redox couples in promoting OER kinetics, in decoupling the HER and OER, and in combined electrochemical-thermochemical water splitting. These new ideas unlock vast potential for applying redox-couple-mediated water splitting to the storage of the intermittent and fluctuating energy derived from renewable sources.

Fabrication of cobalt gallium oxide with zinc iron oxide on nickel foam for a high-performance asymmetric supercapacitor

A straightforward method is proposed for the synthesis of CoGa₂O₄ on nickel foam with excellent durability for practical applications in asymmetric supercapacitors.

Balancing Catalytic Activity and Interface Energetics of Electrocatalyst-Coated Photoanodes for Photoelectrochemical Water Splitting

For photoelectrochemical (PEC) water splitting, the interface interactions among semiconductors, electrocatalysts, and electrolytes affect the charge separation and catalysis in turn. Here, through the changing of the bath temperature, Co-based oxygen evolution catalysts (OEC) with different crystallinities were electrochemically deposited on Ti-doped Fe₂O₃ (Ti-Fe₂O₃) photoanodes. We found: (1) the OEC with low crystallinity is highly ion-permeable, decreasing the interactions between OEC and photoanode due to the intimate interaction between semiconductor and electrolyte; (2) the OEC with high crystallinity is nearly ion-impermeable, is beneficial to form a constant buried junction with semiconductor, and exhibits the low OEC catalytic activity; and (3) the OEC with moderate crystallinity is partially electrolyte-screened, thus contributing to the formation of ideal band bending underneath surface of semiconductor for charge separation and the highly electrocatalytic activity of OEC for lowering over-potentials of water oxidation. Our results demonstrate that to balance the water oxidation activity of OEC and OEC-semiconductor interface energetics is crucial for highly efficient solar energy conversion; in particular, the energy transducer is a semiconductor with a shallow or moderate valence-band level.

Molten salt-assisted a-axis-oriented growth of Ta3N5 nanorod arrays with enhanced charge transport for efficient photoelectrochemical water oxidation

Molten salt-assisted a-axis-oriented growth of Ta₃N₅ nanorod arrays with enhanced charge transport for efficient photoelectrochemical water oxidation.

Anchoring CoFe2O4 Nanoparticles on N-Doped Carbon Nanofibers for High-Performance Oxygen Evolution Reaction

The exploration of earth-abundant and high-efficiency electrocatalysts for the oxygen evolution reaction (OER) is of great significant for sustainable energy conversion and storage applications. Although spinel-type binary transition metal oxides (AB2O4, A, B = metal) represent a class of promising candidates for water oxidation catalysis, their intrinsically inferior electrical conductivity exert remarkably negative impacts on their electrochemical performances. Herein, we demonstrates a feasible electrospinning approach to concurrently synthesize CoFe2O4 nanoparticles homogeneously embedded in 1D N-doped carbon nanofibers (denoted as CoFe2O4@N-CNFs). By integrating the catalytically active CoFe2O4 nanoparticles with the N-doped carbon nanofibers, the as-synthesized CoFe2O4@N-CNF nanohybrid manifests superior OER performance with a low overpotential, a large current density, a small Tafel slope, and long-term durability in alkaline solution, outperforming the single component counterparts (pure CoFe2O4 and N-doped carbon nanofibers) and the commercial RuO2 catalyst. Impressively, the overpotential of CoFe2O4@N-CNFs at the current density of 30.0 mA cm-2 negatively shifts 186 mV as compared with the commercial RuO2 catalyst and the current density of the CoFe2O4@N-CNFs at 1.8 V is almost 3.4 times of that on RuO2 benchmark. The present work would open a new avenue for the exploration of cost-effective and efficient OER electrocatalysts to substitute noble metals for various renewable energy conversion/storage applications.