Inside-out regulation of MnO toward fast reaction kinetics in aqueous zinc ion batteries.

An "inside-out regulation" strategy is proposed to improve the Zn2+ storage of MnO by Ni doping into the lattice and graphene wrapping outside the nanoparticles. The as-prepared Ni-MnO@rGO exhibits 112 mA h g-1 at 2.0 A g-1 over 800 cycles, due to the improved transport of electrons and ions from the synergistical function of intrinsic doping and external graphene encapsulation.

Synthesis of Cu Nanoparticles Incorporated Mesoporous C/SiO2 for Efficient Tetracycline Degradation.

In this study, a Cu NPs-incorporated carbon-containing mesoporous SiO2 (Cu/C-SiO2) was successfully synthesized through a grinding-assisted self-infiltration method followed by an in situ reduction process. The obtained Cu/C-SiO2 was then employed as a Fenton-like catalyst to remove tetracycline (TC) from aqueous solutions. TEM, EDS, XRD, N2 adsorption-desorption, FTIR, and XPS methods were used to characterize the crystal structure, morphology, porosity, chemical composition, and surface chemical properties of the catalyst. The effects of initial TC concentration, catalyst dosage, H2O2 dosage, solution pH, HA addition, and water media on the TC degradation over Cu/C-SiO2 were investigated. Scavenging and electrochemical experiments were then carried out to analyze the TC degradation mechanism. The results show that the Cu/C-SiO2 can remove 99.9% of the concentrated TC solution (C0 = 500 mg·L-1), and it can be used in a wide pH range (R.E. = 94-99%, pH = 3.0-11.0). Moreover, hydroxyl radicals (•OH) were detected to be the dominant reactive species in this catalytic system. This study provides a simple and promising method for the synthesis of heteroatom-containing mesoporous catalysts for the decomposition of antibiotics in wastewater.

Vertical 3D Nanostructures Boost Efficient Hydrogen Production Coupled with Glycerol Oxidation Under Alkaline Conditions.

Hydrogen production from electrolytic water is an important sustainable technology to realize renewable energy conversion and carbon neutrality. However, it is limited by the high overpotential of oxygen evolution reaction (OER) at the anode. To reduce the operating voltage of electrolyzer, herein thermodynamically favorable glycerol oxidation reaction (GOR) is proposed to replace the OER. Moreover, vertical NiO flakes and NiMoNH nanopillars are developed to boost the reaction kinetics of anodic GOR and cathodic hydrogen evolution, respectively. Meanwhile, excluding the explosion risk of mixed H2/O2, a cheap organic membrane is used to replace the expensive anion exchange membrane in the electrolyzer. Impressively, the electrolyzer delivers a remarkable reduction of operation voltage by 280 mV, and exhibits good long-term stability. This work provides a new paradigm of hydrogen production with low cost and good feasibility.

Engineering Amorphous/Crystalline Ru(OH)3/CoFe-Layered Double Hydroxide for Hydrogen Evolution at 1000 mA cm-2.

For large-scale industrial applications, it is highly desirable to create effective, economical electrocatalysts with long-term stability for the hydrogen evolution reaction (HER) at a large current density. Herein, we report a unique motif with crystalline CoFe-layered hydroxide (CoFe-LDH) nanosheets enclosed by amorphous ruthenium hydroxide (a-Ru(OH)3/CoFe-LDH) to realize the efficient hydrogen production at 1000 mA cm-2, with a low overpotential of 178 mV in alkaline media. During the continuous HER process for 40 h at such a large current density, the potential remains almost constant with only slight fluctuations, indicating good long-term stability. The remarkable HER performance can be attributed to the charge redistribution caused by abundant oxygen vacancies in a-Ru(OH)3/CoFe-LDH. The increased electron density of states lowers the charge-transfer resistance and promotes the formation and release of H2 molecules. The water-splitting electrolyzer with a-Ru(OH)3/CoFe-LDH as both an anode and a cathode in 1.0 M KOH demonstrates stable hydrogen production and a 100% faradic efficiency. The design strategy of interface engineering in this work will inspire the design of practical electrocatalysts for water splitting on an industrial scale.

Suppressing Local Dendrite Hotspots via Current Density Redistribution Using a Superlithiophilic Membrane for Stable Lithium Metal Anode.

Li metal anode is considered as one of the most desirable candidates for next-generation battery due to its lowest electrochemical potential and high theoretical capacity. However, undesirable dendrite growth severely exacerbates the interfacial stability, thus damaging battery performance and bringing safety concerns. Here, an efficient strategy is proposed to stabilize Li metal anode by digesting dendrites sprout using a 3D flexible superlithiophilic membrane consisting of poly(vinylidene fluoride) (PVDF) and ZnCl2 composite nanofibers (PZEM) as a protective layer. Both the experimental studies and theoretical calculations show the origin of superlithiophilicity ascribed to a strong interaction between ZnCl2 and PVDF to form the ZnF bonds. The multifield physics calculation implies effective removal of local dendrite hotspots by PZEM via a more homogeneous Li+ flux. The PZEM-covered Li anode (PZEM@Li) exhibits superior Li deposition/stripping performance in a symmetric cell over 1100 cycles at a high current density of 5 mA cm-2 . When paired with LiFePO4 (LFP), PZEM@Li|LFP full cell remains stable over 1000 cycles at 2 C with a degradation rate of 0.0083% per cycle. This work offers a new route for efficient protection of Li metal anode for practical applications.

Recent progress in emergent two-dimensional silicene.

Although graphene is by far the most famous example of two-dimensional (2D) materials, which exhibits a wealth of exotic and intriguing properties, it suffers from a severe drawback. In this regard, the exploration of silicene, the silicon analog of the graphene material, has attracted substantial interest in the past decade. This review therefore provides a comprehensive survey of recent theoretical and experimental works on this 2D material. We first overview the distinctive structures and properties of silicene, including mechanical, electronic, and spintronic properties. We then discuss the growth and experimental characterization of silicene on Ag(111) and other different substrates, providing insights into the different phases or atomic arrangements of silicene observed on the metallic surfaces as well as on its electronic structures. Then, the recent state-of-the-art applications of silicene are summarized in section 4 with the aim to break the scientific and engineering barriers for application in nanoelectronics, sensors, energy storage devices, electrode materials, and quantum technology. Finally, the concluding remarks and the future prospects of silicene are also provided.

N-doped graphene for electrocatalytic O2 and CO2 reduction.

The electrocatalytic CO2 reduction reaction (CO2RR) and oxygen reduction reaction (ORR) are important approaches to realize energy conversion and sustainable development. However, sluggish reaction kinetics severely hinders the practical application of devices related to these reactions. N-doped graphene (NG) with unique properties exhibits great potential in catalyzing the CO2RR and ORR, which is attributed to the electron redistribution. In this review, we start from the fundamental properties of NG, especially emphasizing the changes caused by N doping. Then the synthetic methods are summarized by classifying them into top-down strategies and bottom-up strategies. Subsequently, the applications of NG in the ORR and CO2RR are discussed and the effects of electronic structure on the electrocatalytic activity are highlighted. Finally, we give our own perspective on the future research direction of NG in the applications of the ORR and CO2RR.

Cross-Linking Network of Soft-Rigid Dual Chains to Effectively Suppress Volume Change of Silicon Anode.

Polyacrylic acid (PAA) is a promising binder for the high-capacity Si anode. However, the one-dimensional structure of PAA could cause the linear molecular chains to slide from the Si surface during the charge-discharge processes, leading to insufficient suppression of the massive volume expansion of the Si anode. Herein, a soft-rigid dual chains' network of PAA-sodium silicate (PAA-SS) was successfully constructed by cross-linking PAA and SS in situ at room temperature. The soft chains of PAA and the rigid chains of polysilicic acid synergistically ensure the enhanced adhesion property and mechanical strength. Therefore, the Si electrode with PAA-SS binder delivers a discharge capacity of 1559 mAh/g after 150 cycles at 4.2 A/g (1C) with an initial Coulombic efficiency of 93.2%. Moreover, the PAA-SS based SiC-500 electrode exhibits a discharge capacity of 441 mAh/g with the capacity retention of 88.2% after 500 cycles at 0.5 A/g, implying the PAA-SS binder's great industrial prospect in Si based electrodes.

Spin engineering of single-site metal catalysts.

Single-site metal atoms (SMAs) on supports are attracting extensive interest as new catalytic systems because of maximized atom utilization and superior performance. However, rational design of configuration-optimized SMAs with high activity from the perspectives of fundamental electron spin is highly challenging. Herein, N-coordinated Fe single atoms are successfully distributed over axial carbon micropores to form dangling-FeN4 centers (d-FeN4). This unique d-FeN4 demonstrates much higher intrinsic activity toward oxygen reduction reaction (ORR) in HClO4 than FeN4 without micropore underneath and commercial Pt/C. Both theoretical calculation and electronic structure characterization imply that d-FeN4 endows central Fe with medium spin (t2g 4 eg 1), which provides a spin channel for electron transition compared with FeN4 with low spin. This leads to the facile formation of the singlet state of oxygen-containing species from triplet oxygen during the ORR, thus showing faster kinetics than FeN4. This work provides an in-depth understanding of spin tuning on SMAs for advanced energy catalysis.

Coordination environment tuning of nickel sites by oxyanions to optimize methanol electro-oxidation activity.

To achieve zero-carbon economy, advanced anode catalysts are desirable for hydrogen production and biomass upgrading powered by renewable energy. Ni-based non-precious electrocatalysts are considered as potential candidates because of intrinsic redox attributes, but in-depth understanding and rational design of Ni site coordination still remain challenging. Here, we perform anodic electrochemical oxidation of Ni-metalloids (NiPx, NiSx, and NiSex) to in-situ construct different oxyanion-coordinated amorphous nickel oxyhydroxides (NiOOH-TOx), among which NiOOH-POx shows optimal local coordination environment and boosts electrocatalytic activity of Ni sites towards selective oxidation of methanol to formate. Experiments and theoretical results demonstrate that NiOOH-POx possesses improved adsorption of OH* and methanol, and favors the formation of CH3O* intermediates. The coordinated phosphate oxyanions effectively tailor the d band center of Ni sites and increases Ni-O covalency, promoting the catalytic activity. This study provides additional insights into modulation of active-center coordination environment via oxyanions for organic molecules transformation.

Flower-like MOF-74 nanocomposites directed by selenylation towards high-efficient oxygen evolution.

Sluggish kinetics of the oxygen evolution reaction during the water splitting requires high-performance electrocatalysts with low cost and good stability. Metal-organic frameworks (MOFs) have attracted much attention as electrocatalysts owing to their unique properties. To improve their electrocatalytic activity and stability, we report a selenylation method to modulate the morphology and interfaces by forming flower-like MOF-selenide nanocomposites. The optimal sample exhibits high activity with an overpotential of 260 mV at 10 mA cm-2, much better than commercial RuO2 and the control samples. Moreover, the optimal sample has the lowest Tafel slope of 54.3 mV dec-1, indicating the fast reaction kinetics, which can be attributed to the lower charge-transfer resistance and high intrinsic activity. Chronoamperometry shows that the optimal sample can maintain the current density for 60 h at 10 mA cm-2 after the initial surface reconstruction, demonstrating good stability. This study provides a new perspective on the development of highly efficient electrocatalysts based on polymetallic MOFs.

Surface Engineering of Cr-Doped Cobalt Molybdate toward High-Performance Hydrogen Evolution.

Replacing commercial noble metal catalysts with earth-abundant metal catalysts for hydrogen production is an important research direction for electrolytic water. Improving the catalytic performance of non-noble metals while maintaining stability is a key challenge for alkaline hydrogen evolution. Herein, we combined alkali etching and surface phosphating to regulate the properties of Cr-doped CoMoO4 material, forming a surface structure in which amorphous cobalt phosphate and Cr-doped Co(Mo)Ox coexist. As expected, the as-prepared catalytic material exhibits remarkable hydrogen evolution activity in 1.0 M KOH, only requiring a low overpotential of 52.7 mV to achieve a current density of 10 mA cm-2, and can maintain this current density for 24 h. The characterization and analysis of the catalyst before and after the stability test reveal that the Cr doping and surface engineering (i.e., alkali etching and phosphating) synergistically increase the adsorption and dissociation of water, optimize the desorption of H, and ultimately accelerate hydrogen evolution. This work provides a new strategy for tailoring nonprecious metal materials to improve the hydrogen production from water electrolysis.

Design Strategies for Single-Atom Iron Electrocatalysts toward Efficient Oxygen Reduction.

The oxygen reduction reaction (ORR) is a pivotal half-reaction for full cells and metal-air batteries. However, the intrinsic sluggish kinetics of the ORR inhibits the practical applications of these environmentally friendly energy-conversion devices. Therefore, highly efficient electrocatalysts with low cost are required to promote the ORR process. Carbon materials with single-atom Fe coordinated with N and C (Fe-N-C) stand out from various non-precious electrocatalysts, and great progress of both catalysts design and mechanism understanding has been achieved in the past. In this Perspective, we start with the recent advance in design strategies of active sites in Fe-N-C and emphasize the importance of spatial configuration and electron distribution. We discuss diverse Fe-N-C species as well as their corresponding properties. At last, we give our outlook for the future development of advanced Fe-N-C electrocatalysts.

Hollow MoS2/Co nanopillars with boosted Li-ion diffusion rate and long-term cycling stability.

Hollow MoS2/Co-0.1 nanopillars were successfully synthesized by sulfurizing CoMoO4 and subsequent acid etching, which were used as the anode material for lithium ion batteries. The introduction of suitable metal Co into MoS2 nanopillars effectively accelerates electron/ion transport kinetics, leading to high specific capacity and superior rate capability and cycling stability.

Hollow MXene Sphere-Based Flexible E-Skin for Multiplex Tactile Detection.

Skin-like electronics that can provide comprehensively tactile sensing is required for applications such as soft robotics, health monitoring, medical treatment, and human-machine interfaces. In particular, the capacity to monitor the contact parameters such as the magnitude, direction, and contact location of external forces is crucial for skin-like tactile sensing devices. Herein, a flexible electronic skin which can measure and discriminate the contact parameters in real time is designed. It is fabricated by integrating the three-dimensional (3D) hollow MXene spheres/Ag NW hybrid nanocomposite-based embedded stretchable electrodes and T-ZnOw/PDMS film-based capacitive pressure sensors. To the best of our knowledge, it is the first stretchable electrode to utilize the 3D hollow MXene spheres with the essential characteristic, which can effectively avoid the drawbacks of stress concentration and shedding of the conductive layer. The strain-resistance module and the pressure-capacitance module show the excellent sensing performance in stability and response time, respectively. Moreover, a 6 × 6 sensor array is used as a demonstration to prove that it can realize the multiplex detection of random external force stimuli without mutual interference, illustrating its potential applications in biomimetic soft wearable devices, object recognition, and robotic manipulation.

Crystallinity Effect of NiFe LDH on the Growth of Pt Nanoparticles and Hydrogen Evolution Performance.

NiFe layered double hydroxides (LDHs) usually exhibit high water-dissociation ability in the alkaline media and also provide an ideal substrate for anchoring noble metals, such as platinum (Pt), due to the 2D microstructure. Appropriate regulation of the interaction between Pt and substrate could enhance the intrinsic activity of composite catalysts toward the hydrogen evolution reaction (HER) in the alkaline media. Herein, we electrodeposit Pt nanoparticles on amorphous NiFe LDH (Pt/NiFe-ED) or crystalline NiFe LDH (Pt/NiFe-HD) to regulate the interaction between Pt and NiFe LDH. Experimental results reveal that Pt nanoparticles on NiFe-ED are smaller than those on NiFe-HD and possess a narrower size distribution. Thus, Pt/NiFe-ED (300 µM) exhibits a much lower overpotential of 81 mV at 100 mA cm-2 than Pt/NiFe-HD. In contrast, Pt/NiFe-HD exhibits a higher intrinsic activity than Pt/NiFe-ED, which could be caused by the easily elongated Pt-O bond. These findings provide new opportunities to understand the relationship between activity and crystallinity of substrates in the composite electrocatalyst.

Spider Web-like Flexible Tactile Sensor for Pressure-Strain Simultaneous Detection.

Multiparameter integrated sensors are required for the next generation of flexible wearable electronics. However, mutual interference between detected signals is a technical bottleneck for a flexible tactile sensor to realize pressure-strain monitoring simultaneously and sensitively. Herein, a flexible dual-parameter pressure-strain sensor based on the three-dimensional (3D) tubular graphene sponge (TGS) and spider web-like stretchable electrodes is designed and fabricated. As the pressure-sensitive module, the unique 3D-TGS with an uninterrupted network of tubular graphene and high graphitic degree demonstrates great robust compressibility, supporting compression to ∼20% without shape collapse. The spider web-like stretchable electrodes as the strain-sensitive module are fabricated by a spray-embedded process based on the hierarchical multiscale hybrid nanocomposite of Ag nanowires (NWs) and carbon nanotubes (CNTs) with an optimal mass ratio. By comparing the output signals of spider web-like flexible electrodes, the magnitude and direction of the applied force can be effectively monitored simultaneously. Moreover, the potential applications of the flexible dual-parameter pressure-strain device in human-machine interaction are also explored, showing great promise in artificial intelligence and wearable systems.

A Glass-Ceramic with Accelerated Surface Reconstruction toward the Efficient Oxygen Evolution Reaction.

The effective non-precious metal catalysts toward the oxygen evolution reaction (OER) are highly desirable for electrochemical water splitting. Herein, we prepare a novel glass-ceramic (Ni1.5 Sn@triMPO4 ) by embedding crystalline Ni1.5 Sn nanoparticles into amorphous trimetallic phosphate (triMPO4 ) matrix. This unique crystalline-amorphous nanostructure synergistically accelerates the surface reconstruction to active Ni(Fe)OOH, due to the low vacancy formation energy of Sn in glass-ceramic and high adsorption energy of PO4 3- at the VO sites. Compared to the control samples, this dual-phase glass-ceramic exhibits a remarkably lowered overpotential and boosted OER kinetics after surface reconstruction, rivaling most of state-of-the-art electrocatalysts. The residual PO4 3- and intrinsic VO sites induce redistribution of electron states, thus optimizing the adsorption of OH* and OOH* intermediates on metal oxyhydroxides and promoting the OER activity.

Dual-Metal Interbonding as the Chemical Facilitator for Single-Atom Dispersions.

Atomically dispersed catalysts, with maximized atom utilization of expensive metal components and relatively stable ligand structures, offer high reactivity and selectivity. However, the formation of atomic-scale metals without aggregation remains a formidable challenge due to thermodynamic stabilization driving forces. Here, a top-down process is presented that starts from iron nanoparticles, using dual-metal interbonds (RhFe bonding) as a chemical facilitator to spontaneously convert Fe nanoparticles to single atoms at low temperatures. The presence of RhFe bonding between adjacent Fe and Rh single atoms contributes to the thermodynamic stability, which facilitates the stripping of a single Fe atom from the Fe nanoparticles, leading to the stabilized single atom. The dual single-atom Rh-Fe catalyst renders excellent electrocatalytic performance for the hydrogen evolution reaction in an acidic electrolyte. This discovery of dual-metal interbonding as a chemical facilitator paves a novel route for atomic dispersion of chemical metals and the design of efficient catalysts at the atomic scale.

Engineering Hierarchical CoO Nanospheres Wrapped by Graphene via Controllable Sulfur Doping for Superior Li Ion Storage.

The inferior conductivity and large volume expansion impair the widespread applications of metal oxide-based anode materials for lithium-ion batteries. To address these issues, herein an efficient strategy of structural engineering is proposed to improve lithium storage performance of hierarchical CoO nanospheres wrapped by graphene via controllable S-doping (CoOS0.1   @ G). S-doping promotes the Li+ diffusion kinetics of CoO by expanding the interplanar spacing of CoO, lowering the activation energy, and improving the pseudocapacitance contribution. Meanwhile, the electronic structure of CoO is adjusted by S-doping as confirmed by density functional theory calculations, thus enhancing the conductivity. Finite element analysis reveals that the produced Li2 S during lithiation improves the structural stability of the S-doped electrode, which is further confirmed by experimental observation. As expected, CoOS0.1   @ G exhibits excellent lithium storage performance with an initial discharge capacity of 1974 mAh g-1 at 100 mA g-1 , and high discharge capacity of 1573 mAh g-1 after 400 cycles at 500 mA g-1 . It is believed that the insights into the structural doping enlighten research to explore other metal oxides for fast and stable Li ion storage.