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Electronic engineering of gallium nitride (GaN) is critical for enhancement of its electrode performance. In this work, copper (Cu) cation substituted GaN (Cu-GaN) nanowires were fabricated to understand the electronically engineered electrochemical performance for Li ion storage. Cu cation substitution was revealed at atomic level by combination of X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (XAFS), density functional theory (DFT) simulation, and so forth. The Cu-GaN electrode delivered high capacity of 813.2 mA h g−1 at 0.1 A g−1 after 200 cycles, increased by 66% relative to the unsubstituted GaN electrode. After 2000 cycles at 10 A g−1, the reversible capacity was still maintained at 326.7 mA h g−1. The DFT calculations revealed that Cu substitution introduced the impurity electronic states and efficient interatomic electron migration, which can enhance the charge transfer efficiency and reduce the Li ion adsorption energy on the Cu-GaN electrode. The ex-situ SEM, TEM, HRTEM, and SAED analyses demonstrated the reversible intercalation Li ion storage mechanism and good structural stability. The concept of atomic-arrangement-assisted electronic engineering strategy is anticipated to open up opportunities for advanced energy storage applications.

Coulombic efficiency (CE) and cycle life of metal anodes (lithium, sodium, zinc) are limited by dendritic growth and side reactions in rechargeable metal batteries. Here, we proposed a concept for constructing an anion concentration gradient (ACG)-assisted solid-electrolyte interphase (SEI) for ultrahigh ionic conductivity on metal anodes, in which the SEI layer is fabricated through an in situ chemical reaction of the sulfonic acid polymer and zinc (Zn) metal. Owing to the driving force of the sulfonate concentration gradient and high bulky sulfonate concentration, a promoted Zn

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 RuO2 (281 mV). X-ray absorption measurements and density functional theory (DFT) calculations revealed partial charge transfer from Fe3+ through an O bridge to Ni2+ 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.

Tungsten carbide (WC) with imperfect structures determined by phase engineering and heteroatom doping has attracted a great deal of attention with respect to hydrogen evolution reaction (HER). Howe...

Lithium–sulfur (Li–S) battery, as an emerging rechargeable energy-storage system, sparks intensive research enthusiasm owing to its high theoretical energy density. However, the sulfur cathode undergoes the low coulombic efficiency, poor rate and cycling performance, caused by the polysulfides shuttle, low conductivity and sluggish redox kinetics. To address the above issues, various hybrid sulfur cathodes are developed based on two-dimensional (2D) materials. Recently, 2D transition metal carbides and nitrides (MXenes) are receiving intensive interest as matrix materials for sulfur cathodes owing to their favorable properties, such as superior electrical conductivity, abundant active sites and adjustable surface functional groups. In this review, we mainly summarize the development of novel hybrid sulfur cathodes by taking advantage of unique properties of MXenes. The different roles MXenes played in sulfur cathodes, including facilitating the electron transfer, tuning the adsorption of polysulfides and catalyzing polysulfides conversion, are well discussed. Finally, we propose the future strategies on the rational design of MXene-based sulfur cathodes with high performances.

Single‐atom sites on MXenes (SASs‐MXenes) have attracted widespread attention for energy storage and conversion due to their highest atom utilization efficiency, intriguing intrinsic properties, unusual performance, and improved robustness. In addition, the large surface area and abundant anchor sites make MXenes ideal substrates for supporting single atoms via covalent interaction. Herein, the main strategies for synthesis of SASs‐MXenes are first summarized, which cover capturing single atoms by cation vacancies, coordinating single atoms with heterodopants, and inheriting single atoms from MAX phases. Then, disclosing the crucial roles SASs‐MXenes play in tuning the kinetics and thermodynamics of various catalytic reactions, i.e., hydrogen evolution reaction, nitrogen reduction reaction, CO2 reduction reaction, CO2 functionalization, polysulfide conversion, and other redox reactions involved in rechargeable batteries, is focused on. Finally, the challenges and future opportunities for developing highly active SASs‐MXenes are discussed.

Here, we demonstrate that structural defects can induce catalytic reactivity in simple metal oxides to deliver cost-effective alternatives to noble metal group catalysts. We detail a strategy for introducing multiple defect sites in a binary TiO2–SiO2 composite to invoke synergism for oxygen activation. Hydrogenation and UV light pretreatment were applied to generate two distinct and adjacent defect sites, Ti3+ and silica-based nonbridging oxygen hole centers (NBOHC)—which work in unison to activate oxygen and oxidize formic acid under ambient conditions without light. The hydrogenation step was found to be crucial for rupturing Ti–O–Si bonds while first-principles calculations indicated that Si-doped TiO2 lowered the energy barrier for oxygen activation and formic acid dehydrogenation on the defect sites. Activity lost during the reaction was recoverable by catalyst reillumination. Defective metal oxides represent an appealing prospect in the pursuit of simple and readily accessible catalyst materials.

Single atom catalysts possess attractive electrocatalytic activities for various chemical reactions owing to their favorable geometric and electronic structures compared to the bulk counterparts. Herein, we demonstrate an efficient approach to producing single atom copper immobilized MXene for electrocatalytic CO

Two-dimensional (2D) transition metal carbides, nitrides and carbonitrides (MXenes) have been extensively studied in catalysis due to their high specific surface area, favorable electrochemical properties, excellent corrosion resistance, high mechanical strength, superior electrical and thermal conductivity. Additionally, the unique 2D features with adjustable surface properties of MXene enable its structure to be engineered as catalyst towards a range of the electro-, photo- and thermal-catalytic reactions. In this review, we summarize the advanced engineering strategies that have been developed for MXenes to achieve desirable catalytic performance, including termination engineering, atomic engineering, interfacial engineering and hybrid engineering. We focus on disclosing the origin of enhanced catalytic activity realized by different engineering strategies from the mechanism perspective. Then the limitations and challenges of MXenes engineering under various conditions are discussed. Furthermore, some advanced in situ techniques are recommended to elucidate the active sites in MXenes. Finally, we point out the future directions in MXenes engineering towards highly active catalysts at industrial standard.

Hierarchical porous carbon nanosheets (HPCS) were prepared by using thermoplastic phenolic formaldehyde resin as the carbon source and copper nitrate as the template precursor. The effects of Cu(NO 3 ) 2 loading content on the pore property and electrochemical performance of HPCS as anode material for lithium ion batteries were investigated. It was found that, with the addition of Cu(NO 3 ) 2 , both the specific surface area and mesopore percentage increase. Correspondingly, the electrochemical performances of HPCS electrodes in terms of the specific capacity and rate performance improve for lithium ion batteries. The reasons were deduced and discussed from the view point of different pore size, especially the function of mesopores.