Seawater electrolysis offers a renewable, scalable, and economic means for green hydrogen production. However, anode corrosion by Cl
pose great challenges for its commercialization. Herein, different ...from conventional catalysts designed to repel Cl
adsorption, we develop an atomic Ir catalyst on cobalt iron layered double hydroxide (Ir/CoFe-LDH) to tailor Cl
adsorption and modulate the electronic structure of the Ir active center, thereby establishing a unique Ir-OH/Cl coordination for alkaline seawater electrolysis. Operando characterizations and theoretical calculations unveil the pivotal role of this coordination state to lower OER activation energy by a factor of 1.93. The Ir/CoFe-LDH exhibits a remarkable oxygen evolution reaction activity (202 mV overpotential and TOF = 7.46 O
s
) in 6 M NaOH+2.8 M NaCl, superior over Cl
-free 6 M NaOH electrolyte (236 mV overpotential and TOF = 1.05 O
s
), with 100% catalytic selectivity and stability at high current densities (400-800 mA cm
) for more than 1,000 h.
Highlights
A hybrid electrocatalyst consisting of PtNi-W alloy nanocrystals loaded on carbon surface with atomically dispersed W sites was realized.
Single-atomic W formed protonic acid sites and ...established an extended proton transport network at the catalyst surface.
Peak power density is enhanced by 64.4% compared to that with the commercial Pt/C catalyst in fuel cell as cathode at ultra-low loading of 0.05 mg
Pt
cm
−2
.
The performance of proton exchange membrane fuel cells is heavily dependent on the microstructure of electrode catalyst especially at low catalyst loadings. This work shows a hybrid electrocatalyst consisting of PtNi-W alloy nanocrystals loaded on carbon surface with atomically dispersed W sites by a two-step straightforward method. Single-atomic W can be found on the carbon surface, which can form protonic acid sites and establish an extended proton transport network at the catalyst surface. When implemented in membrane electrode assembly as cathode at ultra-low loading of 0.05 mg
Pt
cm
−2
, the peak power density of the cell is enhanced by 64.4% compared to that with the commercial Pt/C catalyst. The theoretical calculation suggests that the single-atomic W possesses a favorable energetics toward the formation of *OOH whereby the intermediates can be efficiently converted and further reduced to water, revealing a interfacial cascade catalysis facilitated by the single-atomic W. This work highlights a novel functional hybrid electrocatalyst design from the atomic level that enables to solve the bottle-neck issues at device level.
In this study, we developed a novel confinement-synthesis approach to layered double hydroxide nanodots (LDH-NDs) anchored on carbon nanoparticles, which formed a three-dimensional (3D) ...interconnected network within a porous carbon support derived from pyrolysis of metal-organic frameworks (C-MOF). The resultant LDH-NDs@C-MOF nonprecious metal catalysts were demonstrated to exhibit super-high catalytic performance for oxygen evolution reaction (OER) with excellent operation stability and low overpotential (∼230 mV) at an exchange current density of 10 mAcm
−2
. The observed overpotential for the LDH-NDs@C-MOF is much lower than that of large-sized LDH nanosheets (321 mV), pure carbonized MOF (411 mV), and even commercial RuO
2
(281 mV). X-ray absorption measurements and density functional theory (DFT) calculations revealed partial charge transfer from Fe
3+
through an O bridge to Ni
2+
at the edge of LDH-NDs supported by C-MOF to produce the optimal binding energies for OER intermediates. This, coupled with a large number of exposed active sides and efficient charge and electrolyte/reactant/product transports associated with the porous 3D C-MOF support, significantly boosted the OER performance of the LDH-ND catalyst with respect to its nanosheet counterpart. Apart from the fact that this is the first active side identification for LDH-ND OER catalysts, this work provides a general strategy to enhance activities of nanosheet catalysts by converting them into edge-rich nanodots to be supported by 3D porous carbon architectures.
Recent progress of the soft X-ray magnetic circular dichroism (XMCD) techniques and relevant applications at beamline 4B7B in Beijing Synchrotron Radiation Facility are reported here. The key ...progress of the XMCD techniques include i) improvements in the accuracy and sensitivity of XMCD measurements by fast-reversing magnetic field with electromagnet, and ii) establishment an angle-dependent experimental method for obtaining the magnetic anisotropy information. These techniques have been applied to investigate the interface ferromagnetism and magnetic anisotropy of two Mn-based materials, i.e. Fe/(Ga,Mn)As and La2/3Sr1/3MnO3/SrTiO3 bilayer heterostructures. An enhanced XMCD signal has been observed at the Fe L2,3-edges whereas a relative small but unambiguous Mn XMCD signal with opposite sign has been detected which indicates an antiferromagnetic coupling at Fe/(Ga,Mn)As interfaces. A comparative study of the stoichiometric and nonstoichiometric La2/3Sr1/3MnO3/SrTiO3 bilayers clearly demonstrates that the oxygen vacancies degrade the magnetic properties of the perovskite manganese oxide film. These achievements benefit from the established field-reversal and angle-dependent XMCD techniques, which will make it possible to extend the research field of our devices from ferromagnetic to paramagnetic or diluted magnetic semiconductor system.
With the combination of a single crystal diamond anvil cell and a polycapillary half-lens, the local structural evolution around germanium in tetrahedrally networked quartz-like α-GeO2 has been ...investigated using extended x-ray absorption fine structure spectroscopy of up to 14 GPa by multiple-scattering analysis method. While the first shell Ge-O bond distances show a slight contraction with increasing pressure, the third shell Ge-O bond distances are found to decrease dramatically. The sluggish lengthening of the first shell Ge-O bond distances, initiated by coordination increase from fourfold to sixfold, occurs in the 7-14 GPa range just when the third shell Ge-O bond distances fall in the region of the second shell Ge-Ge bond distances. Moreover, these features are accompanied by the closing of intertetrahedral Ge-O-Ge angles and the opening of two intratetrahedral O-Ge-O angles, whose topological configuration surprisingly exhibits a helical chirality along the c axis that is opposite to the double helices of the corner-linked GeO4 tetrahedra. These results suggest that the high-pressure phase transitions in quartz and quartz-like materials could be associated with a structural instability that is driven by the drastic collapse of the next-nearest-neighbour anion shell, which is consistent with the emergence of high-symmetry anion sublattice. Our findings provide crucial insights into the densification mechanisms of quartz-like oxides, which would have broad implications for our understanding of the metastability of various post-quartz crystalline phases and pressure-induced amorphization.
The aluminum‐based metal–organic framework (MOF) made from 2‐aminoterephthalate is a photocatalyst for oxygen evolution. This MOF can be modified by incorporating Ni2+ cations into the pores through ...coordination to the amino groups, and the resulting MOF is an efficient photocatalyst for overall water splitting.
One catalyst, two reactions: The aluminum‐based metal–organic framework (MOF) made from 2‐aminoterephthalate, which is a photocatalyst for oxygen evolution, can be modified by incorporating Ni2+ cations into the pores through coordination to the amino groups. The resulting MOF is an efficient photocatalyst for overall water splitting.
Mn-based aqueous zinc-ion batteries (ZIBs) are promising candidate for large-scale rechargeable energy storage because of easy fabrication, low cost, and high safety. Nevertheless, the commercial ...application of Mn-based cathode is hindered by the challenging issues of low rate capability and poor cyclability. Herein, a manganese–vanadium hybrid, K–V2C@MnO2 cathode, featured with MnO2 nanosheets uniformly formed on a V2CTX MXene surface, is elaborately designed and synthesized by metal–cation intercalation and following in situ growth strategy. Benefiting from the hybrid structure with high conductivity, abundant active sites, and the synergistic reaction of Mn2+ electrodeposition and inhibited structural damage of MnO2, K–V2C@MnO2 shows excellent electrochemical performance for aqueous ZIBs. Specifically, it presents the high specific capacity of 408.1 mAh g–1 at 0.3 A g–1 and maintains the specific capacity of 119.2 mAh g–1 at a high current density of 10 A g–1 in a long-term cycle of up to 10000 cycles. It is superior to almost all reported Mn-based cathodes for ZIBs in the aqueous electrolyte. The superior electrochemical performance suggests that the Mn-based cathode materials designed in this work can be a rational approach to be applied for high-performance ZIBs cathodes.
To enhance the performance of semiconductor photocatalysts, cocatalysts are used to accelerate surface reactions. Herein, ultrasmall molybdenum-oxygen (MoO
) clusters are developed as a novel ...non-noble cocatalyst, which significantly promotes the photocatalytic hydrogen generation rate of CdS nanowires (NWs). As indicated by extended X-ray absorption fine structure analysis, direct bonds are formed between CdS NWs and MoO
clusters, which guarantee the migration of photo-generated charge carriers. Moreover, the MoO
clusters induce deep electron trap states owing to the unique atomic arrangement and configuration with the generation of long-lived electrons to enhance the activity. These findings may guide the design of efficient cocatalytic materials for solar water splitting and open a new avenue toward practical applications of ultrasmall clusters.
Although great progress has been made in artificial enzyme engineering, their catalytic performance is far from satisfactory as alternatives of natural enzymes. Here, we report a novel and efficient ...strategy to access high-performance nanozymes via direct atomization of platinum nanoparticles (Pt NPs) into single atoms by reversing the thermal sintering process. Atomization of Pt NPs into single atoms makes metal catalytic sites fully exposed and results in engineerable structural and electronic properties, thereby leading to dramatically enhanced enzymatic performance. As expected, the as-prepared thermally stable Pt single-atom nanozyme (PtTS-SAzyme) exhibited remarkable peroxidase-like catalytic activity and kinetics, far exceeding the Pt nanoparticle nanozyme. The following density functional theory calculations revealed that the engineered P and S atoms not only promote the atomization process from Pt NPs into PtTS-SAzyme but also endow single-atom Pt catalytic sites with a unique electronic structure owing to the electron donation of P atoms, as well as the electron acceptance of N and S atoms, which simultaneously contribute to the substantial enhancement of the enzyme-like catalytic performance of PtTS-SAzyme. This work demonstrates that thermal atomization of the metal nanoparticle-based nanozymes into single-atom nanozymes is an effective strategy for engineering high-performance nanozymes, which opens up a new way to rationally design and optimize artificial enzymes to mimic natural enzymes.
Abstract The monoclinic phase of Y2O3（B-RES） has been synthesized using a Kawai-type multi-anvil apparatus under 20 GPa at 1800℃. Samples of the cubic Y2O3（C-RES） and monoclinic Y2O3 phases were ...characterized by synchrotron radiation X-ray diffraction, X-ray absorption near edge structure and Raman spectroscopy. Crystal structures of the cubic and monoclinic phases have been examined using Rietveld refinement of the X-ray diffraction data. The cubic-to-monoclinic transition of Y2O3 was reconstructive and irreversible. The X-ray diffraction results were further confirmed by simulation of the X-ray absorption spectra.
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