Rigid Ligand Confined Synthesis of Carbon Supported Dimeric Fe Sites with High-performance Oxygen Reduction Reaction Activity for Quasi-solid-state Rechargeable Zn-air Batteries.

Dimeric metal sites (DiMSs) in carbon-based single atom catalysts (SACs) offer distinct advantages in optimizing the adsorption energies of the catalytic intermediates and reaction pathways over single atom sites, and thus inspires the investigations on the rational design of DiMSs-based SACs and the accurate discernment of catalytic mechanisms. Here, dimeric Fe sites on carbon blacks (DiFe-N/CBs) are prepared using the precursor of metal-organic complex with a controlled structure, and the rigid ligand confinement secures the preservation of dimeric Fe sites during the thermal treatment. DiFe-N/CBs shows excellent electrocatalytic performance for oxygen reduction reaction (ORR) with a positive half-wave potential of 0.917 V, and excellent durability with negligible activity decay. Theoretical studies reveal that the dimeric Fe sites have an optimal adsorption of OOH* with the Yeager-type binding, illustrating the advantages of DiMSs over SAs in catalyzing ORR. The rechargeable aqueous and quasi-solid-state Zn-air battery assembled using DiFe-N/CBs-based air cathodes achieve small voltage gaps after long term charge/discharge test, showing great promises for practical applications. This synthetic strategy serves a novel platform to produce a scope of catalysts incorporating multimeric metal sites, and studies on the catalytic mechanism lay the foundation for establishing cooperative effect for multidentate adsorption reactions.

Ultra-Small High-Entropy Alloy as Multi-Functional Catalyst for Ammonia Based Fuel Cells.

Ammonia fuel cells using carbon-neutral ammonia as fuel are regarded as a fast, furious, and flexible next-generation carbon-free energy conversion technology, but it is limited by the kinetically sluggish ammonia oxidation reaction (AOR), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER). Platinum can efficiently drive these three types of reactions, but its scale-up application is limited by its susceptibility to poisoning and high cost. In order to reduce the cost and alleviate poisoning, incorporating Pt with various metals proves to be an efficient and feasible strategy. Herein, PtFeCoNiIr/C trifunctional high-entropy alloy (HEA) catalysts are prepared with uniform mixing and ultra-small size of 2 ± 0.5 nm by Joule heating method. PtFeCoNiIr/C exhibits efficient performance in AOR (Jpeak = 139.8 A g-1 PGM), ORR (E1/2 = 0.87 V), and HER (E10 = 20.3 mV), outperforming the benchmark Pt/C, and no loss in HER performance at 100 mA cm-2 for 200 h. The almost unchanged E1/2 in the anti-poisoning test indicates its promising application in real fuel cells powered by ammonia. This work opens up a new path for the development of multi-functional electrocatalysts and also makes a big leap toward the exploration of cost-effective device configurations for novel fuel cells.

Boosting urea-assisted water splitting over P-MoO2@CoNiP through Mo leaching/reabsorption coupling CoNiP reconstruction.

Combining the urea oxidation reaction (UOR) with the hydrogen evolution reaction (HER) is an effective technology for energy-saving hydrogen production. Herein, a bifunctional electrocatalyst with CoNiP nanosheet coating on P-doped MoO2 nanorods (P-MoO2@CoNiP) is obtained via a two-step hydrothermal followed a phosphorization process. The catalyst demonstrates exceptional alkaline HER performance due to the formation of MoO2 and the dissolution/absorption of Mo. Meanwhile, the inclusion of Co and P in the P-MoO2@CoNiP catalyst facilitated the formation of NiOOH, enhancing UOR performance. Density functional theory calculations reveal that the hydrogen adsorption Gibbs free energy (ΔGH*) of P-MoO2@CoNiP is closer to 0 eV than CoNiP, favoring the HER. The catalyst only needs -0.08 and 1.38 V to reach 100 mA cm-2 for catalyzing the HER and UOR, respectively. The full urea electrolysis system driven by P-MoO2@CoNiP requires 1.51 V to achieve 100 mA cm-2, 120 mV lower than the traditional water electrolysis.

Boron modification promoting electrochemical surface reconstruction of NiFe-LDH for efficient and stable freshwater/seawater oxidation catalysis.

Transition metal-based electrocatalysts generally take place surface reconstruction in alkaline conditions, but little is known about how to improve the reconstruction to a highly active oxyhydroxide surface for an efficient and stable oxygen evolution reaction (OER). Herein, we develop a strategy to accelerate surface reconstruction by combining boron modification and cyclic voltammetry (CV) activation. Density functional theory calculations and in-situ/ex-situ characterizations indicate that both B-doping and electrochemical activation can reduce the energy barrier and contribute to the surface evolution into highly active oxyhydroxides. The formed oxyhydroxide active phase can tune the electronic configuration and boost the OER process. The reconstructed catalyst of CV-B-NiFe-LDH displays excellent alkaline OER performance in freshwater, simulated seawater, and natural seawater with low overpotentials at 100 mA cm-2 (η100: 219, 236, and 255 mV, respectively) and good durability. This catalyst also presents outstanding Cl- corrosion resistance in alkalized seawater electrolytes. The CV-B-NiFe-LDH||Pt/C electrolyzer reveals prominent performance for alkalized freshwater/seawater splitting. This study provides a guideline for developing advanced OER electrocatalysts by promoting surface reconstruction.

Thermal Shock Synthesis for Loading Sub-2 nm Ru Nanoclusters on Titanium Nitride as a Remarkable Electrocatalyst toward Hydrogen Evolution Reaction.

Heterogeneous catalysts embracing metal entities on suitable supports are profound in catalyzing various chemical reactions, and substantial synthetic endeavors in metal-support interaction modulation are made to enhance catalytic performance. Here, it is reported the loading of sub-2 nm Ru nanocrystals (NCs) on titanium nitride support (HTS-Ru-NCs/TiN) via a special Ru-Ti interaction using the high-temperature shock (HTS) method. Direct dechlorination of the adsorbed RuCl3, ultrafast nucleation process, and short coalescence duration at ultrahigh temperatures contribute to the immobilization of Ru NCs on TiN support via producing the Ru-Ti interfacial perimeter. HTS-Ru-NCs/TiN shows remarkable activity toward hydrogen evolution reaction (HER) in alkaline solution, yielding ultralow overpotentials of 16.3 and 86.6 mV to achieve 10 and 100 mA cm-2, respectively. The alkaline and anion exchange membrane water electrolyzers assembled using HTS-Ru-NCs/TiN yield 1.0 A cm-2 at 1.65 and 1.67 V, respectively, which validate its applicability in the hydrogen production industry. Theoretical simulations reveal the favorable formation of Ru─O and Ti─H bonds at the interfacial perimeters between Ru NCs and TiN, which accelerates the prerequisite water dissociation kinetics for enhanced HER activity. This exemplified work motivates the design of specific interfacial perimeters via the HTS strategy to improve the performance of diverse catalysis.

Unraveling the crucial contribution of additive chromate to efficient and stable alkaline seawater oxidation on Ni-based layered double hydroxides.

Seawater electrolysis to generate hydrogen offers a clean, green, and sustainable solution for new energy. However, the catalytic activity and durability of anodic catalysts are plagued by the corrosion and competitive oxidation reactions of chloride in high concentrations. In this study, we find that the additive CrO42- anions in the electrolyte can not only promote the formation and stabilization of the metal oxyhydroxide active phase but also greatly mitigate the adverse effect of Cl- on the anode. Linear sweep voltammetry, accelerated corrosion experiments, corrosion polarization curves, and charge transfer resistance results indicate that the addition of CrO42- distinctly improves oxygen evolution reaction (OER) kinetics and corrosion resistance in alkaline seawater electrolytes. Especially, the introduction of CrO42- even in the highly concentrated NaCl (2.5 M) electrolyte prolongs the durability of NiFe-LDH to almost five times the case without CrO42-. Density functional theory calculations also reveal that the adsorption of CrO42- can tune the electronic configuration of active sites of metal oxyhydroxides, enhance conductivity, and optimize the intermediate adsorption energies. This anionic additive strategy can give a better enlightenment for the development of efficient and stable oxygen evolution reactions for seawater electrolysis.

Constructing Fe-N4 Sites through Anion Exchange-mediated Transformation of Fe Coordination Environments in Hierarchical Carbon Support for Efficient Oxygen Reduction.

Metal single atoms (SAs) anchored in carbon support via coordinating with N atoms are efficient active sites to oxygen reduction reaction (ORR). However, rational design of single atom catalysts with highly exposed active sites is challenging and urgently desirable. Herein, an anion exchange strategy is presented to fabricate Fe-N4 moieties anchored in hierarchical carbon nanoplates composed of hollow carbon spheres (Fe-SA/N-HCS). With the coordinating O atoms are substituted by N atoms, Fe SAs with Fe-O4 configuration are transformed into the ones with Fe-N4 configuration during the thermal activation process. Insights into the evolution of central atoms demonstrate that the SAs with specific coordination environment can be obtained by modulating in situ anion exchange process. The strategy produces a large quantity of electrochemical accessible site and high utilization rate of Fe-N4 . Fe-SA/N-HCS shows excellent ORR electrocatalytic performance with half-wave potential of 0.91 V (vs. RHE) in 0.1 M KOH, and outstanding performance when used in rechargeable aqueous and flexible Zn-air batteries. The evolution pathway for SAs demonstrated in this work offers a novel strategy to design SACs with various coordination environment and enhanced electrocatalytic activity.

Synthesis of dual-metal single atom in porous carbon with efficient oxygen reduction reaction in both acidic and alkaline electrolytes.

The rational design and fabrication of platinum group metal-free (PGM-free) electrocatalysts for oxygen reduction reaction (ORR) via economically feasible approach is essential for reducing the cost of fuel cells and metal-air batteries. Catalysts must have very high activity, and excellent mass diffusion of reactants. Herein, we display a high-performing dual-metal single atom catalyst (DM-SAC) composed of Fe and Ni SA active sites immobilized in porous carbon nanospheres (Fe/Ni-N-PCS), prepared via defects/vacancies anchoring strategy. The abundant and accessible edge-hosted Fe and Ni SA active sites can promote the adsorption/desorption behavior for ORR intermediates attributing to possible synergistic effects between dual-metal SA active sites. Thus, the as-developed Fe/Ni-N-PCS DM-SAC exhibits impressive ORR electrocatalytic performance in both alkaline (Eonset = 1.04 V, E1/2 = 0.9 V) and acid solutions (Eonset = 0.87 V, E1/2 = 0.71 V), and high stability, outperforming SACs with solo Fe-Nx or Ni-Nx active sites, and benchmark PGM. Fe/Ni-N-PCS also exhibits superior oxygen evolution reaction (OER) performance with low overpotential and long-term stability. Zn-air battery with Fe/Ni-N-PCS cathode yields encouraging performance, including working potential, peak power density, and the stability of charge and discharge cycles. Our synthesis method may promote the fabrication of other DM-SAC and the great promise in practical applications.

Rich edge-hosted single-atomic Cu-N4 sites for highly efficient oxygen reduction reaction performance.

Single-atom electrocatalysts with metal-nitrogen-carbon (MNC SACs) moieties in carbon support display outstanding electrocatalytic performance towards oxygen reduction reaction (ORR) and have received widespread attentions. Only active sites on the edges of pores in carbon support are electrochemically accessible and contribute to ORR. Herein, we report a combined hydroxyl-functionalized and NH4Cl-assisted etching strategy to effectively promote the yield of edge-hosted Cu SAs. Thus, well-defined SAs with Cu-N4 configuration are generated into the defect of carbonaceous nanospheres (CuSAs@DCSs). Impressively, the obtained SACs renders outstanding electrocatalytic ORR activity with onset, half-wave potentials of 1.02 V, 0.90 V, and extremely high stability, which transcends the noble-metals and most of the previously reported catalysts. When used in rechargeable Zn-air batteries, CuSAs@DCSs achieves ultralong cycle life at the large current density of 10 mA cm-2 (over 260 h) with low charge-discharge potential gap. Our study demonstrates that the creation of abundant micropores enriches the electrochemically accessible SAs, which locate at the edge-defects and are responsible for the remarkable ORR performance. This work sheds a facile strategy for designing and developing efficient electrocatalyst for various energy-related electrocatalytic reactions.

Coupling of N-Doped Mesoporous Carbon and N-Ti3 C2 in 2D Sandwiched Heterostructure for Enhanced Oxygen Electroreduction.

2D heterostructures provide a competitive platform to tailor electrical property through control of layer structure and constituents. However, despite the diverse integration of 2D materials and their application flexibility, tailoring synergistic interlayer interactions between 2D materials that form electronically coupled heterostructures remains a grand challenge. Here, the rational design and optimized synthesis of electronically coupled N-doped mesoporous defective carbon and nitrogen modified titanium carbide (Ti3 C2 ) in a 2D sandwiched heterostructure, is reported. First, a F127-polydopamine single-micelle-directed interfacial assembly strategy guarantees the construction of two surrounding mesoporous N-doped carbon monolayers assembled on both sides of Ti3 C2 nanosheets. Second, the followed ammonia post-treatment successfully introduces N elements into Ti3 C2 structure and more defective sites in N-doped mesoporous carbon. Finally, the oxygen reduction reaction (ORR) and theoretical calculation prove the synergistic coupled electronic effect between N-Ti3 C2 and defective N-doped carbon active sites in the 2D sandwiched heterostructure. Compared with the control 2D samples (0.87-0.88 V, 4.90-5.15 mA cm-2 ), the coupled 2D heterostructure possesses the best onset potential of 0.90 V and limited density current of 5.50 mA cm-2 . Meanwhile, this catalyst exhibits superior methanol tolerance and cyclic durability. This design philosophy opens up a new thought for tailoring synergistic interlayer interactions between 2D materials.

Formation of V6O11@Ni(OH)2/NiOOH hollow double-shell nanoflowers for the excellent cycle stability of supercapacitors.

The rational design of multi-shelled hollow structured electrode materials is of great importance and has met with fundamental challenges in recent years. Herein, we demonstrate a combination approach of self-templating and sacrificial templating method for synthesizing double-shelled hollow nanoflower-structured V6O11@Ni(OH)2/NiOOH. Firstly, highly uniform vanadium-glycerate (VG) solid nanospheres are controllably synthesized and employed as the template, then Ni(OH)2/NiOOH nanosheets grow vertically on it, following with VG solid nanospheres changing to the V6O11 hollow structure. By controlling the amount of Ni(OH)2/NiOOH nanosheets, the optimized V6O11@Ni(OH)2/NiOOH-6 (VN-6) delivers high performance for supercapacitors. Specifically, the specific capacitance of VN-6 is 1018.2 F g-1 at the current density of 1 A g-1 and the energy density is 24.3 W h kg-1 at the power density of 850 W kg-1. Impressively, an outstanding cycling stability of over 120% specific capacitance retention can be obtained after 5000 cycles in the three-electrode and two-electrode systems. The excellent performance can be ascribed to the compositional and structural advantages.

Porous organic polymer supported rhodium as a heterogeneous catalyst for hydroformylation of alkynes to α,ß-unsaturated aldehydes.

A new porous organic polymer supported rhodium catalyst (Rh/POL-BINAPa&PPh3) has been developed for the hydroformylation of various alkynes to afford the corresponding α,ß-unsaturated aldehydes with high chem- and stereoselectivity, excellent catalytic activity and good reusability (10 cycles). The heterogeneous catalyst exhibited more catalytic activity than the comparable homogeneous Rh/BINAPa/PPh3 system.

Porous Organic Polymer Supported Rhodium as a Reusable Heterogeneous Catalyst for Hydroformylation of Olefins.

A new porous organic polymer has been prepared via copolymerization of divinyl-functionalized phosphoramidite ligand and tris(4-vinylphenyl)phosphine. The porous polymer was loaded with Rh(acac)CO2 to yield a supported Rh catalyst, which demonstrated good regioselectivity ( l/ b = 6.7-52.8) and high catalytic activity (TON up to 45.3 × 104) in hydroformylation of terminal and internal olefins. Remarkably, the heterogeneous catalyst can be reused at least 10 cycles without losing activity and selectivity in hydroformylation of 1-hexene.

Lanthanide-Doped Photoluminescence Hollow Structures: Recent Advances and Applications.

Lanthanide-doped nanomaterials have attracted significant attention for their preeminent properties and widespread applications. Due to the unique characteristic, the lanthanide-doped photoluminescence materials with hollow structures may provide advantages including enhanced light harvesting, intensified electric field density, improved luminescent property, and larger drug loading capacity. Herein, the synthesis, properties, and applications of lanthanide-doped photoluminescence hollow structures (LPHSs) are comprehensively reviewed. First, different strategies for the engineered synthesis of LPHSs are described in detail, which contain hard, soft, self-templating methods and other techniques. Thereafter, the relationship between their structure features and photoluminescence properties is discussed. Then, niche applications including biomedicines, bioimaging, therapy, and energy storage/conversion are focused on and superiorities of LPHSs for these applications are particularly highlighted. Finally, keen insights into the challenges and personal prospects for the future development of the LPHSs are provided.

Cobalt hollow nanospheres: controlled synthesis, modification and highly catalytic performance for hydrolysis of ammonia borane.

Size tunable cobalt hollow nanospheres with high catalytic activity for the ammonia borane (AB) hydrolysis have been synthesized by using the solvothermal method. The complexation between Co2+ and ethylenediamine is observed to be critical for the formation of the cobalt hollow nanospherical structure. The morphology of the cobalt hollow nanospheres can be regulated by adjusting the original ethylenediamine/ethanol volume ratio, reaction time and temperature. Impressively, the magnetic property study reveals that the coercivity of the as-synthesized cobalt hollow nanospheres is much enhanced compared with that of bulk cobalt materials. Meanwhile, Co/Pt bimetal hollow nanospheres (CoPtHS) and graphene-cobalt hollow composite nanospheres (CoHS-rGO) have also been explored. In comparison with the cobalt hollow nanospheres, both the CoPtHS and CoHS-rGO show higher catalytic activities and better repeatability for the catalytic hydrogen generation from AB hydrolysis. Moreover, it is noted that these catalysts could be recycled by using the magnetic separation method.

Composite Yttrium-Carbonaceous Spheres Templated Multi-Shell YVO4 Hollow Spheres with Superior Upconversion Photoluminescence.

Complex oxide YVO4 multi-shell hollow spheres with uniform morphologies and controllable shell numbers are successfully prepared by using a newly developed and general composite yttrium-carbonaceous sphere templated approach. The prominent upconversion luminous intensity of the YVO4 :Yb3+ /Er3+ hollow spheres might be attributed to the enhanced near-infrared excitation light harvesting efficiency originated from the multiple reflections.

Y2O3:Yb³âº/Er³âº Hollow Spheres with Controlled Inner Structures and Enhanced Upconverted Photoluminescence.

Multishell Y2 O3 :Yb(3+) /Er(3+) hollow spheres with uniform morphologies and controllable inner structures are prepared successfully by using a glucose-template hydrothermal process followed by temperature-programmed calcination. Much enhanced upconverted photoluminescence of these Y2 O3 :Yb(3+) /Er(3+) are observed, which are due to the multiple reflections and the enhanced light-harvesting efficiency of the NIR light resulting from the special features of the multishell structures.