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Electrochemical reduction reactions, as cathodic processes in many energy-related devices, significantly impact the overall efficiency determined mainly by the performance of electrocatalysts. Metal-organic frameworks (MOFs) derived carbon-supported metal materials have become one of star electrocatalysts due to their tunable structure and composition through ligand design and metal screening. However, for different electroreduction reactions, the required active metal species vary in phase component, electronic state, and catalytic center configuration, hence requiring effective customization. From this perspective, this review comprehensively analyzes the structural design principles, metal loading strategies, practical electroreduction performance, and complex catalytic mechanisms, thereby providing insights and guidance for the future rational design of such electroreduction catalysts., (© 2024 The Author(s). Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The controllable photocatalytic C-C coupling of methanol to produce ethylene glycol (EG) is a highly desirable but challenging objective for replacing the current energy-intensive thermocatalytic process. Here, we develop a metal-free porous boron nitride catalyst that demonstrates exceptional selectivity in the photocatalytic production of EG from methanol under mild conditions. Comprehensive experiments and calculations are conducted to thoroughly investigate the reaction mechanism, revealing that the OB 3 unit in the porous BN plays a critical role in the preferential activation of C-H bond in methanol to form ⋅CH 2 OH via a concerted proton-electron transfer mechanism. More prominent energy barriers are observed for the further dehydrogenation of the ⋅CH 2 OH intermediate on the OB 3 unit, inhibiting the formation of some other by-products during the catalytic process. Additionally, a small downhill energy barrier for the coupling of ⋅CH 2 OH in the OB 3 unit promotes the selective generation of EG. This study provides valuable insights into the underlying mechanisms and can serve as a guide for the design and optimization of photocatalysts for efficient and selective EG production under mild conditions., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Exploring unique single-atom sites capable of efficiently reducing O 2 to H 2 O 2 while being inert to H 2 O 2 decomposition under light conditions is significant for H 2 O 2 photosynthesis, but it remains challenging. Herein, we report the facile design and fabrication of polymeric carbon nitride (CN) decorated with single-Zn sites that have tailorable local coordination environments, which is enabled by utilizing different Zn salt anions. Specifically, the O atom from acetate (OAc) anion participates in the coordination of single-Zn sites on CN, forming asymmetric Zn-N 3 O moiety on CN (denoted as CN/Zn-OAc), in contrast to the obtained Zn-N 4 sites when sulfate (SO 4 ) is adopted (CN/Zn-SO 4 ). Both experimental and theoretical investigations demonstrate that the Zn-N 3 O moiety exhibits higher intrinsic activity for O 2 reduction to H 2 O 2 than the Zn-N 4 moiety. This is attributed to the asymmetric N/O coordination, which promotes the adsorption of O 2 and the formation of the key intermediate *OOH on Zn sites due to their modulated electronic structure. Moreover, it is inactive for H 2 O 2 decomposition under both dark and light conditions. As a result, the optimized CN/Zn-OAc catalyst exhibits significantly improved photocatalytic H 2 O 2 production activity under visible light irradiation., (© 2023 Wiley-VCH GmbH.)

Layered manganese dioxide is a promising cathode candidate for aqueous Zn-ion batteries. However, the narrow interlayer spacing, inferior intrinsic electronic conductivity and poor structural stability still limit its practical application. Herein, we report a two-step strategy to incorporate ammonium ions into manganese dioxide (named as AMO) nanosheets as a cathode for boosted Zn ion storage. K + -intercalated δ-MnO 2 nanosheets (KMO) grown on carbon cloth are chosen as the self-involved precursor. Of note, ammonium ions could replace K + ions via a facile hydrothermal reaction to enlarge the lattice space and form hydrogen-bond networks. Compared with KMO, the structural stability and the ion transfer kinetics of the layered AMO are enhanced. As expected, the obtained AMO cathode exhibits remarkable electrochemical properties in terms of high reversible capacity, decent rate performance and superior cycling stability over 10000 cycles., (© 2023 Wiley-VCH GmbH.)

Precise manipulation of the coordination environment of single-atom catalysts (SACs), particularly the simultaneous engineering of multiple coordination shells, is crucial to maximize their catalytic performance but remains challenging. Herein, we present a general two-step strategy to fabricate a series of hollow carbon-based SACs featuring asymmetric Zn-N 2 O 2 moieties simultaneously modulated with S atoms in higher coordination shells of Zn centers (n≥2; designated as Zn-N 2 O 2 -S). Systematic analyses demonstrate that the synergetic effects between the N 2 O 2 species in the first coordination shell and the S atoms in higher coordination shells lead to robust discrete Zn sites with the optimal electronic structure for selective O 2 reduction to H 2 O 2 . Remarkably, the Zn-N 2 O 2 moiety with S atoms in the second coordination shell possesses a nearly ideal Gibbs free energy for the key OOH* intermediate, which favors the formation and desorption of OOH* on Zn sites for H 2 O 2 generation. Consequently, the Zn-N 2 O 2 -S SAC exhibits impressive electrochemical H 2 O 2 production performance with high selectivity of 96 %. Even at a high current density of 80 mA cm -2 in the flow cell, it shows a high H 2 O 2 production rate of 6.924 mol g cat -1  h -1 with an average Faradaic efficiency of 93.1 %, and excellent durability over 65 h., (© 2023 Wiley-VCH GmbH.)

Constructing multifunctional interphases to suppress the rampant Zn dendrite growth and detrimental side reactions is crucial for Zn anodes. Herein, a phytic acid (PA)-ZnAl coordination compound is demonstrated as a versatile interphase layer to stabilize Zn anodes. The zincophilic PA-ZnAl layer can manipulate Zn 2+ flux and promote rapid desolvation kinetics, ensuring the uniform Zn deposition with dendrite-free morphology. Moreover, the robust PA-ZnAl protective layer can effectively inhibit the hydrogen evolution reaction and formation of byproducts, further contributing to the reversible Zn plating/stripping with high Coulombic efficiency. As a result, the Zn@PA-ZnAl electrode shows a lower Zn nucleation overpotential and higher Zn 2+ transference number compared with bare Zn. The Zn@PA-ZnAl symmetric cell exhibits a prolonged lifespan of 650 h tested at 5 mA cm -2 and 5 mAh cm -2 . Furthermore, the assembled Zn battery full cell based on this Zn@PA-ZnAl anode also delivers decent cycling stability even under harsh conditions., (© 2023 Wiley-VCH GmbH.)

Developing highly efficient catalytic sites for O 2 reduction to H 2 O 2 , while ensuring the fast injection of energetic electrons into these sites, is crucial for artificial H 2 O 2 photosynthesis but remains challenging. Herein, we report a strongly coupled hybrid photocatalyst comprising polymeric carbon nitride (CN) and a two-dimensional conductive Zn-containing metal-organic framework (Zn-MOF) (denoted as CN/Zn-MOF(lc)/400; lc, low crystallinity; 400, annealing temperature in °C), in which the catalytic capability of Zn-MOF(lc) for H 2 O 2 production is unlocked by the annealing-induced effects. As revealed by experimental and theoretical calculation results, the Zn sites coordinated to four O (Zn-O 4 ) in Zn-MOF(lc) are thermally activated to a relatively electron-rich state due to the annealing-induced local structure shrinkage, which favors the formation of a key *OOH intermediate of 2e - O 2 reduction on these sites. Moreover, the annealing treatment facilitates the photoelectron migration from the CN photocatalyst to the Zn-MOF(lc) catalytic unit. As a result, the optimized catalyst exhibits dramatically enhanced H 2 O 2 production activity and excellent stability under visible light irradiation., (© 2023 Wiley-VCH GmbH.)

Lithium-sulfur (Li-S) batteries are considered as promising candidates for next-generation energy storage systems in view of the high theoretical energy density and low cost of sulfur resources. The suppression of polysulfide diffusion and promotion of redox kinetics are the main challenges for Li-S batteries. Herein, we design and prepare a novel type of ZnCo-based bimetallic metal-organic framework nanoboxes (ZnCo-MOF NBs) to serve as a functional sulfur host for Li-S batteries. The hollow architecture of ZnCo-MOF NBs can ensure fast charge transfer, improved sulfur utilization, and effective confinement of lithium polysulfides (LiPSs). The atomically dispersed Co-O 4 sites in ZnCo-MOF NBs can firmly capture LiPSs and electrocatalytically accelerate their conversion kinetics. Benefiting from the multiple structural advantages, the ZnCo-MOF/S cathode shows high reversible capacity, impressive rate capability, and prolonged cycling performance for 300 cycles., (© 2023 Wiley-VCH GmbH.)

Gas-liquid-solid triple-phase interfaces (TPI) are essential for promoting electrochemical CO 2 reduction, but it remains challenging to maximize their efficiency while integrating other desirable properties conducive to electrocatalysis. Herein, we report the elaborate design and fabrication of a superhydrophobic, conductive, and hierarchical wire membrane in which core-shell CuO nanospheres, carbon nanotubes (CNT), and polytetrafluoroethylene (PTFE) are integrated into a wire structure (designated as CuO/F/C(w); F, PTFE; C, CNT; w, wire) to maximize their respective functions. The realized architecture allows almost all CuO nanospheres to be exposed with effective TPI and good contact to conductive CNT, thus increasing the local CO 2 concentration on the CuO surface and enabling fast electron/mass transfer. As a result, the CuO/F/C(w) membrane attains a Faradaic efficiency of 56.8 % and a partial current density of 68.9 mA cm -2 for multicarbon products at -1.4 V (versus the reversible hydrogen electrode) in the H-type cell, far exceeding 10.1 % and 13.4 mA cm -2 for bare CuO., (© 2023 Wiley-VCH GmbH.)

The exploration of earth-abundant and efficient electrocatalysts toward the oxygen evolution reaction (OER) is critical for sustainable energy storage and conversion devices. In this work, we report a self-engaged strategy to fabricate a yolk-shelled OER electrocatalyst. Starting with a metal-organic framework, Co-Fe layered double hydroxide (LDH)@zeolitic imidazolate framework-67 (ZIF-67) yolk-shelled structures are formed in one step. Afterwards, these ZIF-67 building blocks are transformed into Ni-Co LDH nanocages to form the Ni-Co-Fe hydr(oxy)oxide@Ni-Co LDH yolk-shelled microrods (NiCoFe-HO@NiCo-LDH YSMRs) through an ion-exchange reaction. Owing to the structural and compositional merits, the NiCoFe-HO@NiCo-LDH YSMR electrocatalyst exhibits an overpotential of 278 mV to reach the current density of 10 mA cm -2 , a small Tafel slope of 49.7 mV dec -1 , and good stability in alkaline media., (© 2022 Wiley-VCH GmbH.)

Prussian blue analogs (PBAs) are promising candidates for aqueous Zn-ion batteries due to their unique open-framework structures. However, they suffer from limited capacity and severe capacity decay originating from insufficient redox sites and structural instability. Herein, Cu-substituted Mn-PBA double-shelled nanoboxes (CuMn-PBA DSNBs) prepared by tannic acid etching and cation exchange approaches are demonstrated for efficient Zn ion storage. The unique hollow structures can expose abundant active sites and alleviate the volume change during the cycling test. Moreover, partial Cu substitution and induced Mn vacancies might inhibit the Jahn-Teller distortions of Mn-N 6 octahedra, thus contributing to the prolonged lifespan. As a result, CuMn-PBA DSNBs exhibit high reversible capacity, decent rate performance and superior cycling stability for 2000 cycles. Furthermore, ex situ characterizations reveal that the charge storage mechanism of CuMn-PBA DSNBs mainly involves the reversible redox reactions of transition metals and Zn 2+ ion insertion/extraction processes., (© 2022 Wiley-VCH GmbH.)

Physicochemical confinement and catalytic conversion of lithium polysulfides (LiPSs) are crucial to suppress the shuttle effect and enhance the redox kinetics of lithium-sulfur (Li-S) batteries. In this study, a NH 4 Cl-assisted pyrolysis strategy is developed to fabricate highly mesoporous N-rich carbon (designed as NC(p)) featuring thin outer shells and porous inner networks, on which single-Ni atoms are anchored to form an excellent sulfur host (designed as Ni-NC(p)) for Li-S batteries. During pyrolysis, the pyrolytic HCl from confined NH 4 Cl within ZIF-8 will in situ etch ZIF-8 to produce rich mesoporous in the carbonized product NC(p). The mesoporous Ni-NC(p) enables favorable electron/ion transfer, high sulfur loading, and effective confinement of LiPSs, while the catalytic effect of single-Ni species enhances the redox kinetics of LiPSs. As a result, the sulfur cathode based on the Ni-NC(p) host delivers obviously improved Li-S battery performance with high specific capacity, good rate capability, and cycling stability., (© 2022 Wiley-VCH GmbH.)

Trapping the active sites on the exterior surface of hollow supports can reduce mass transfer resistance and enhance atomic utilization. Herein, we report a facile chemical vapor deposition strategy to synthesize single-Ni atoms decorated hollow S/N-doped football-like carbon spheres (Ni SAs@S/N-FCS). Specifically, the CdS@3-aminophenol/formaldehyde is carbonized into S/N-FCS. The gas-migrated Ni species are anchored on the surface of S/N-FCS simultaneously, yielding Ni SAs@S/N-FCS. The obtained catalyst exhibits outstanding performance for alkaline oxygen evolution reaction (OER) with an overpotential of 249 mV at 10 mA cm -2 , a small Tafel slope of 56.5 mV dec -1 , and ultra-long stability up to 166 hours without obvious fading. Moreover, the potential-driven dynamic behaviors of Ni-N 4 sites and the contribution of the S dopant at different locations in the matrix to the OER activity are revealed by the operando X-ray absorption spectroscopy and theoretical calculations, respectively., (© 2022 Wiley-VCH GmbH.)

Single-atom catalysts (SACs) are being pursued as economical electrocatalysts. However, their low active-site loading, poor interactions, and unclear catalytic mechanism call for significant advances. Herein, atomically dispersed Ni/Co dual sites anchored on nitrogen-doped carbon (a-NiCo/NC) hollow prisms are rationally designed and synthesized. Benefiting from the atomically dispersed dual-metal sites and their synergistic interactions, the obtained a-NiCo/NC sample exhibits superior electrocatalytic activity and kinetics towards the oxygen evolution reaction. Moreover, density functional theory calculations indicate that the strong synergistic interactions from heteronuclear paired Ni/Co dual sites lead to the optimization of the electronic structure and the reduced reaction energy barrier. This work provides a promising strategy for the synthesis of high-efficiency atomically dispersed dual-site SACs in the field of electrochemical energy storage and conversion., (© 2022 Wiley-VCH GmbH.)

Simultaneous transformation of CO 2 and H 2 O into syngas (CO and H 2 ) using solar power is desirable for industrial applications. Herein, an efficient photocatalyst based on double-shelled nanoboxes, with an outer shell of hydroxy-rich nickel cobaltite nanosheets and an inner shell of Cu 2 S (Cu 2 S@R OH -NiCo 2 O 3 ), is prepared via a multistep templating strategy. The high performance of Cu 2 S@R OH -NiCo 2 O 3 (7.1 mmol g -1  h -1 for CO; 2.8 mmol g -1  h -1 for H 2 ) is attributed to the hierarchical hollow geometry and p-n heterojunction to promote light absorption and charge separation. Spectroscopic and theoretical analyses elucidate that the R OH -NiCo 2 O 3 surface enhances *CO 2 adsorption and lowers energy barriers for CO 2 -to-CO. Therefore, modulating the hydroxy contents of R OH -NiCo 2 O 3 can achieve broad CO/H 2 ratios from 0.51 to 1.24. This work offers in-depth insights into adjustable syngas photosynthesis and generalized concepts of selective heterogeneous CO 2 photoreduction beyond cobalt-based oxides., (© 2022 Wiley-VCH GmbH.)

The rational design of single-atom catalysts featuring excellent conductivity, highly accessible discrete active sites and favorable mass transfer is crucial for electrocatalysis but remains challenging. In this study, a reliable Ni-catalyzed and Ni-templated strategy is developed to synthesize a single-atom catalyst by transforming metallic Ni into single-Ni atoms anchored on hollow porous urchin-like (HPU) N-doped carbon (NC) (designated as Ni-NC(HPU)), which possesses high crystallinity and sufficient Ni-N 4 moiety (2.4 wt %). The unique hollow thorns on the surface, good conductivity and large external surface area facilitate electron/mass transfer and exposure of single-Ni sites. As a result, the Ni-NC(HPU) catalyst exhibits remarkable activity and high stability for CO 2 electroreduction. Moreover, this synthetic strategy can also be facilely extended to prepare distinct hollow porous architectures with similar components, such as the wire- and sphere-like ones., (© 2022 Wiley-VCH GmbH.)

Uncontrolled growth of Zn dendrites and side reactions are the major restrictions for the commercialization of Zn metal anodes. Herein, we develop a TiO x /Zn/N-doped carbon inverse opal (denoted as TZNC IO) host to regulate the Zn deposition. Amorphous TiO x and Zn/N-doped carbon can serve as the zincophilic nucleation sites to prevent the parasitic reactions. More importantly, the highly ordered IO host homogenizes the local current density and electric field to stabilize Zn deposition. Furthermore, the three-dimensional open networks could regulate Zn ion flux to enable stable cycling performance at large current densities. Owing to the abundant zincophilic sites and the open structure, granular Zn deposits could be realized. As expected, the TZNC IO host guarantees the steady Zn plating/stripping with a long-term stability over 450 h at the current density of 1 mA cm -2 . As a proof-of-concept demonstration, a TZNC@Zn||V 2 O 5 full cell shows long lifespan over 2000 cycles at 5.0 A g -1 ., (© 2021 Wiley-VCH GmbH.)

The development of efficient oxygen electrocatalysts and understanding their underlying catalytic mechanism are of significant importance for the high-performance energy conversion and storage technologies. Herein, we report novel CoCu-based bimetallic metal-organic framework nanoboxes (CoCu-MOF NBs) as promising catalysts toward efficient electrochemical oxygen evolution reaction (OER), fabricated via a successive cation and ligand exchange strategy. With the highly exposed bimetal centers and the well-designed architecture, the CoCu-MOF NBs show excellent OER activity and stability, with a small overpotential of 271 mV at 10 mA cm -2 and a high turnover frequency value of 0.326 s -1 at an overpotential of 300 mV. In combination of quasi in situ X-ray absorption fine structure spectroscopy and density-functional theory calculations, the post-formed CoCu-based oxyhydroxide analogue during OER is believed to account for the high OER activity of CoCu-MOF NBs, where the electronic synergy between Co and neighbouring Cu atoms promotes the O-O bond coupling toward fast OER kinetics., (© 2021 Wiley-VCH GmbH.)

Mn-based oxides have sparked extensive scientific interest for aqueous Zn-ion batteries due to the rich abundance, plentiful oxidation states, and high output voltage. However, the further development of Mn-based oxides is severely hindered by the rapid capacity decay during cycling. Herein, a two-step metal-organic framework (MOF)-engaged templating strategy has been developed to rationally synthesize heterostructured Mn 2 O 3 -ZnMn 2 O 4 hollow octahedrons (MO-ZMO HOs) for stable zinc ion storage. The distinctive composition and hollow heterostructure endow MO-ZMO HOs with abundant active sites, enhanced electric conductivity, and superior structural stability. By virtue of these advantages, the MO-ZMO HOs electrode shows high reversible capacity, impressive rate performance, and outstanding electrochemical stability. Furthermore, ex situ characterizations reveal that the charge storage of MO-ZMO HOs mainly originates from the highly reversible Zn 2+ insertion/extraction reactions., (© 2021 Wiley-VCH GmbH.)

Exploring earth-abundant electrocatalysts with excellent activity, robust stability, and multiple functions is crucial for electrolytic hydrogen generation. Porous phosphorized CoNi 2 S 4 yolk-shell spheres (P-CoNi 2 S 4 YSSs) were rationally designed and synthesized by a combined hydrothermal sulfidation and gas-phase phosphorization strategy. Benefiting from the strengthened Ni 3+ /Ni 2+ couple, enhanced electronic conductivity, and hollow structure, the P-CoNi 2 S 4 YSSs exhibit excellent activity and durability towards hydrogen/oxygen evolution and urea oxidation reactions in alkaline solution, affording low potentials of -0.135 V, 1.512 V, and 1.306 V (versus reversible hydrogen electrode) at 10 mA cm -2 , respectively. Remarkably, when used as the anode and cathode simultaneously, the P-CoNi 2 S 4 catalyst merely requires a cell voltage of 1.544 V in water splitting and 1.402 V in urea electrolysis to attain 10 mA cm -2 with excellent durability for 100 h, outperforming most of the reported nickel-based sulfides and even noble-metal-based electrocatalysts. This work promotes the application of sulfides in electrochemical hydrogen production and provides a feasible approach for urea-rich wastewater treatment., (© 2021 Wiley-VCH GmbH.)

Prussian blue analogs (PBAs) are considered as reliable and promising cathode materials for aqueous Zn-ion batteries (AZIBs), but they suffer from low capacity and poor cycling stability due to insufficient active sites and structural damage caused by the ion insertion/extraction processes. Herein, a template-engaged ion exchange approach has been developed for the synthesis of Co-substituted Mn-rich PBA hollow spheres (CoMn-PBA HSs) as cathode materials for AZIBs. Benefiting from the multiple advantageous features including hollow structure, abundant active sites, fast Zn 2+ ion diffusion, and partial Co substitution, the CoMn-PBA HSs electrode shows efficient zinc ion storage properties in terms of high capacity, decent rate capability and prolonged cycle life., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The unique structural characteristics of one-dimensional (1D) hollow nanostructures result in intriguing physicochemical properties and wide applications, especially for electrochemical energy storage applications. In this Minireview, we give an overview of recent developments in the rational design and engineering of various kinds of 1D hollow nanostructures with well-designed architectures, structural/compositional complexity, controllable morphologies, and enhanced electrochemical properties for different kinds of electrochemical energy storage applications (i.e. lithium-ion batteries, sodium-ion batteries, lithium-sulfur batteries, lithium-selenium sulfur batteries, lithium metal anodes, metal-air batteries, supercapacitors). We conclude with prospects on some critical challenges and possible future research directions in this field. It is anticipated that further innovative studies on the structural and compositional design of functional 1D nanostructured electrodes for energy storage applications will be stimulated., (© 2021 Wiley-VCH GmbH.)

Highly efficient electrocatalysts are essential for the production of green hydrogen from water electrolysis. Herein, a metal-organic framework-assisted pyrolysis-replacement-reorganization approach is developed to obtain ultrafine Pt-Co alloy nanoparticles (sub-10 nm) attached on the inner and outer shells of porous nitrogen-doped carbon nanotubes (NCNT) with closed ends. During the thermal reorganization, the migration of Pt-Co nano-alloys to both surfaces ensures the maximized exposure of active sites while maintaining the robust attachment to the porous carbon matrix. Density functional theory calculations suggest a nearly thermodynamically-neutral free energy of adsorption for hydrogen intermediates and diversified active sites induced by alloying, thus resulting in a great promotion in intrinsic activity towards the hydrogen evolution reaction (HER). Benefiting from the delicate structural design and compositional modulation, the optimized Pt 3 Co@NCNT electrocatalyst manifests outstanding HER activity and superior stability in both acidic and alkaline media., (© 2021 Wiley-VCH GmbH.)

Developing electrocatalytic energy conversion technologies for replacing the traditional energy source is highly expected to resolve the fossil fuel exhaustion and related environmental problems. Exploring stable and high-efficiency electrocatalysts is of vital importance for the promotion of these technologies. Single-atom catalysts (SACs), with atomically distributed active sites on supports, perform as emerging materials in catalysis and present promising prospects for a wide range of applications. The rationally designed near-range coordination environment, long-range electronic interaction and microenvironment of the coordination sphere cast huge influence on the reaction mechanism and related catalytic performance of SACs. In the current Review, some recent developments of atomically dispersed reactive centers for electrocatalytic CO 2 reduction and water splitting are well summarized. The catalytic mechanism and the underlying structure-activity relationship are elaborated based on the recent progresses of various operando investigations. Finally, by highlighting the challenges and prospects for the development of single-atom catalysis, we hope to shed some light on the future research of SACs for the electrocatalytic energy conversion., (© 2020 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The development of efficient and low-cost electrocatalysts toward the oxygen evolution reaction (OER) is critical for improving the efficiency of several electrochemical energy conversion and storage devices. Here, we report an elaborate design and synthesis of porous Co-based trimetallic spinel oxide nanoboxes (NiCo 2-x Fe x O 4 NBs) by a novel metal-organic framework engaged strategy, which involves chemical etching, cation exchange, and subsequent thermal oxidation processes. Owing to the structural and compositional advantages, the optimized trimetallic NiCo 2-x Fe x O 4 NBs (x is about 0.117) deliver superior electrocatalytic performance for OER with an overpotential of 274 mV at 10 mA cm -2 , a small Tafel slope of 42 mV dec -1 , and good stability in alkaline electrolyte, which is much better than that of Co-based bi/monometallic spinel oxides and even commercial RuO 2 ., (© 2021 Wiley-VCH GmbH.)

The application of lithium metal anodes for practical batteries is still impeded by safety issues and low Coulombic efficiency caused mainly by the uncontrollable growth of lithium dendrites. Herein, two types of free-standing nitrogen-doped amorphous Zn-carbon multichannel fibers are synthesized as multifunctional hosts for lithium accommodation. The 3D macroporous structures endow effectively reduced local current density, and the lithiophilic nitrogen-doped carbon and functional Zn nanoparticles serve as preferred deposition sites with low nucleation barriers to guide uniform lithium deposition. As a result, the developed anodes exhibit remarkable electrochemical properties in terms of high Coulombic efficiency for more than 500 cycles at various current densities from 1 to 5 mA cm -2 , and symmetric cells show long-term cycling duration over 2000 h. Moreover, full cells based on the developed anode and a LiFePO 4 cathode also demonstrate superior rate capability and stable cycle life., (© 2021 Wiley-VCH GmbH.)

Confining nanostructured electrode materials in porous carbon represents an effective strategy for improving the electrochemical performance of lithium-ion batteries. Herein, we report the design and synthesis of hybrid hollow nanostructures composed of highly dispersed Co 3 O 4 hollow nanoparticles (sub-20 nm) embedded in the mesoporous walls of carbon nanoboxes (denoted as H-Co 3 O 4 @MCNBs) as an anode material for lithium-ion batteries. The facile metal-organic framework (MOF)-engaged strategy for the synthesis of H-Co 3 O 4 @MCNBs involves chemical etching-coordination and subsequent two-step annealing treatments. Owing to the unique structural merits including more active interfacial sites, effectively alleviated volume variation, good and stable electrical contact, and easy access of Li + ions, the H-Co 3 O 4 @MCNBs exhibit excellent lithium-storage performance in terms of high specific capacity, excellent rate capability, and cycling stability., (© 2020 Wiley-VCH GmbH.)

Developing noble-metal-free bifunctional oxygen electrocatalysts is of great significance for energy conversion and storage systems. Herein, we have developed a transformation method for growing NiMn-based bimetal-organic framework (NiMn-MOF) nanosheets on multi-channel carbon fibers (MCCF) as a bifunctional oxygen electrocatalyst. Owing to the desired components and architecture, the MCCF/NiMn-MOFs manifest comparable electrocatalytic performance towards oxygen reduction reaction (ORR) with the commercial Pt/C electrocatalyst and superior performance towards oxygen evolution reaction (OER) to the benchmark RuO 2 electrocatalyst. X-ray absorption fine structure (XAFS) spectroscopy and density functional theory (DFT) calculations reveal that the strong synergetic effect of adjacent Ni and Mn nodes within MCCF/NiMn-MOFs effectively promotes the thermodynamic formation of key *O and *OOH intermediates over active NiO 6 centers towards fast ORR and OER kinetics., (© 2020 Wiley-VCH GmbH.)

The growth of Li dendrites hinders the practical application of lithium metal anodes (LMAs). In this work, a hollow nanostructure, based on hierarchical MoS 2 coated hollow carbon particles preloaded with sulfur (C@MoS 2 /S), was designed to modify the LMA. The C@MoS 2 hollow nanostructures serve as a good scaffold for repeated Li plating/stripping. More importantly, the encapsulated sulfur could gradually release lithium polysulfides during the Li plating/stripping, acting as an effective additive to promote the formation of a mosaic solid electrolyte interphase layer embedded with crystalline hybrid lithium-based components. These two factors together effectively suppress the growth of Li dendrites. The as-modified LMA shows a high Coulombic efficiency of 98 % over 500 cycles at the current density of 1 mA cm -2 . When matched with a LiFePO 4 cathode, the assembled full cell displays a highly improved cycle life of 300 cycles, implying the feasibility of the proposed LMA., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Hierarchical FeCoS 2 -CoS 2 double-shelled nanotubes have been rationally designed and constructed for efficient photocatalytic CO 2 reduction under visible light. The synthetic strategy, engaging the two-step cation-exchange reactions, precisely integrates two metal sulfides into a double-shelled tubular heterostructure with both of the shells assembled from ultrathin two-dimensional (2D) nanosheets. Benefiting from the distinctive structure and composition, the FeCoS 2 -CoS 2 hybrid can reduce bulk-to-surface diffusion length of photoexcited charge carriers to facilitate their separation. Furthermore, this hybrid structure can expose abundant active sites for enhancing CO 2 adsorption and surface-dependent redox reactions, and harvest incident solar irradiation more efficiently by light scattering in the complex interior. As a result, these hierarchical FeCoS 2 -CoS 2 double-shelled nanotubes exhibit superior activity and high stability for photosensitized deoxygenative CO 2 reduction, affording a high CO-generating rate of 28.1 μmol h -1 (per 0.5 mg of catalyst)., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Photocatalysts with well-designed compositions and structures are desirable for achieving highly efficient solar-to-chemical energy conversion. Heterostructured semiconductor photocatalysts with advanced hollow structures possess beneficial features for promoting the activity towards photocatalytic reactions. Here we develop a facile synthetic strategy for the fabrication of Fe 2 TiO 5 -TiO 2 nanocages (NCs) as anode materials in photoelectrochemical (PEC) water splitting cells. A hydrothermal reaction is performed to transform MIL-125(Ti) nanodisks (NDs) to Ti-Fe-O NCs, which are further converted to Fe 2 TiO 5 -TiO 2 NCs through a post annealing process. Owing to the compositional and structural advantages, the heterostructured Fe 2 TiO 5 -TiO 2 NCs show enhanced performance for PEC water oxidation compared with TiO 2 NDs, Fe 2 TiO 5 nanoparticles (NPs) and Fe 2 TiO 5 -TiO 2 NPs., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Hybrid materials, integrating the merits of individual components, are ideal structures for efficient sodium storage. However, the construction of hybrid structures with decent physical/electrochemical properties is still challenging. Now, the elaborate design and synthesis of hierarchical nanoboxes composed of three-layered Cu 2 S@carbon@MoS 2 as anode materials for sodium-ion batteries is reported. Through a facile multistep template-engaged strategy, ultrathin MoS 2 nanosheets are grown on nitrogen-doped carbon-coated Cu 2 S nanoboxes to realize the Cu 2 S@carbon@MoS 2 configuration. The design shortens the diffusion path of electrons/Na + ions, accommodates the volume change of electrodes during cycling, enhances the electric conductivity of the hybrids, and offers abundant active sites for sodium uptake. By virtue of these advantages, these three-layered Cu 2 S@carbon@MoS 2 hierarchical nanoboxes show excellent electrochemical properties in terms of decent rate capability and stable cycle life., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In view of the clean and sustainable energy, metal-organic frameworks (MOFs) based materials, including pristine MOFs, MOF composites, and their derivatives are emerging as unique electrocatalysts for oxygen reduction reaction (ORR). Thanks to their tunable compositions and diverse structures, efficient MOF-based materials provide new opportunities to accelerate the sluggish ORR at the cathode in fuel cells and metal-air batteries. This Minireview first provides some introduction of ORR and MOFs, followed by the classification of MOF-based electrocatalysts towards ORR. Recent breakthroughs in engineering MOF-based ORR electrocatalysts are highlighted with an emphasis on synthesis strategy, component, morphology, structure, electrocatalytic performance, and reaction mechanism. Finally, some current challenges and future perspectives for MOF-based ORR electrocatalysts are also discussed., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The construction of hybrid architectures for electrode materials has been demonstrated as an efficient strategy to boost sodium-storage properties because of the synergetic effect of each component. However, the fabrication of hybrid nanostructures with a rational structure and desired composition for effective sodium storage is still challenging. In this study, an integrated nanostructure composed of copper-substituted CoS 2 @Cu x S double-shelled nanoboxes (denoted as Cu-CoS 2 @Cu x S DSNBs) was synthesized through a rational metal-organic framework (MOF)-based templating strategy. The unique shell configuration and complex composition endow the Cu-CoS 2 @Cu x S DSNBs with enhanced electrochemical performance in terms of superior rate capability and stable cyclability., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Materials for high-efficiency photocatalytic CO 2 reduction are desirable for solar-to-carbon fuel conversion. Herein, highly dispersed nickel cobalt oxyphosphide nanoparticles (NiCoOP NPs) were confined in multichannel hollow carbon fibers (MHCFs) to construct the NiCoOP-NPs@MHCFs catalysts for efficient CO 2 photoreduction. The synthesis involves electrospinning, phosphidation, and carbonization steps and permits facile tuning of chemical composition. In the catalyst, the mixed metal oxyphosphide NPs with ultrasmall size and high dispersion offer abundant catalytically active sites for redox reactions. At the same time, the multichannel hollow carbon matrix with high conductivity and open ends will effectively promote mass/charge transfer, improve CO 2 adsorption, and prevent the metal oxyphosphide NPs from aggregation. The optimized hetero-metal oxyphosphide catalyst exhibits considerable activity for photosensitized CO 2 reduction, affording a high CO evolution rate of 16.6 μmol h -1 (per 0.1 mg of catalyst)., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Hierarchical hollow structures for electrode materials of supercapacitors could enlarge the surface area, accelerate the transport of ions and electrons, and accommodate volume expansion during cycling. Besides, construction of heterostructures would enhance the internal electric fields to regulate the electronic structures. All these features of hierarchical hollow heterostructures are beneficial for promoting the electrochemical properties and stability of electrode materials for high-performance supercapacitors. Herein, CoO/Co-Cu-S hierarchical tubular heterostructures (HTHSs) composed of nanoneedles are prepared by an efficient multi-step approach. The optimized sample exhibits a high specific capacity of 320 mAh g -1 (2300 F g -1 ) at 2.0 A g -1 and outstanding cycling stability with 96.5 % of the initial capacity retained after 5000 cycles at 10 A g -1 . Moreover, an all-solid-state hybrid supercapacitor (HSC) constructed with the CoO/Co-Cu-S and actived carbon shows a stable and high energy density of 90.7 Wh kg -1 at a power density of 800 W kg -1 ., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Bi 2 O 3 nanosheets were grown on a conductive multiple channel carbon matrix (MCCM) for CO 2 RR. The obtained electrocatalyst shows a desirable partial current density of ca. 17.7 mA cm -2 at a moderate overpotential, and it is highly selective towards HCOOH formation with Faradaic efficiency approaching 90 % in a wide potential window and its maximum value of 93.8 % at -1.256 V. It also exhibits a maximum energy efficiency of 55.3 % at an overpotential of 0.846 V and long-term stability of 12 h with negligible degradation. The superior performance is attributed to the synergistic contribution of the interwoven MCCM and the hierarchical Bi 2 O 3 nanosheets, where the MCCM provides an accelerated electron transfer, increased CO 2 adsorption, and a high ratio of pyrrolic-N and pyridinic-N, while ultrathin Bi 2 O 3 nanosheets offer abundant active sites, lowered contact resistance and work function as well as a shortened diffusion pathway for electrolyte., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Electrochemical reduction of CO 2 could mitigate environmental problems originating from CO 2 emission. Although grain boundaries (GBs) have been tailored to tune binding energies of reaction intermediates and consequently accelerate the CO 2 reduction reaction (CO 2 RR), it is challenging to exclusively clarify the correlation between GBs and enhanced reactivity in nanostructured materials with small dimension (<10 nm). Now, sub-2 nm SnO 2 quantum wires (QWs) composed of individual quantum dots (QDs) and numerous GBs on the surface were synthesized and examined for CO 2 RR toward HCOOH formation. In contrast to SnO 2 nanoparticles (NPs) with a larger electrochemically active surface area (ECSA), the ultrathin SnO 2 QWs with exposed GBs show enhanced current density (j), an improved Faradaic efficiency (FE) of over 80 % for HCOOH and ca. 90 % for C1 products as well as energy efficiency (EE) of over 50 % in a wide potential window; maximum values of FE (87.3 %) and EE (52.7 %) are achieved., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Metal sulfides have received considerable attention for efficient sodium storage owing to their high capacity and decent redox reversibility. However, the poor rate capability and fast capacity decay greatly hinder their practical application in sodium-ion batteries. Herein, an elegant multi-step templating strategy has been developed to rationally synthesize hierarchical double-shelled nanoboxes with the CoS 2 nanosheet-constructed outer shell supported on the CuS inner shell. Their structure and composition enable these hierarchical CuS@CoS 2 nanoboxes to show boosted electrochemical properties with high capacity, outstanding rate capability, and long cycle life., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Metal sulfides with excellent redox reversibility and high capacity are very promising electrode materials for sodium-ion batteries. However, their practical application is still hindered by the poor rate capability and limited cycle life. Herein, a template-based strategy is developed to synthesize nitrogen-doped carbon-coated Cu 9 S 5 bullet-like hollow particles starting from bullet-like ZnO particles. With the structural and compositional advantages, these unique nitrogen-doped carbon-coated Cu 9 S 5 bullet-like hollow particles manifest excellent sodium storage properties with superior rate capability and ultra-stable cycling performance., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We report the synthesis of cobalt sulfide multi-shelled nanoboxes through metal-organic framework (MOF)-based complex anion conversion and exchange processes. The polyvanadate ions react with cobalt-based zeolitic imidazolate framework-67 (ZIF-67) nanocubes to form ZIF-67/cobalt polyvanadate yolk-shelled particles. The as-formed yolk-shelled particles are gradually converted into cobalt divanadate multi-shelled nanoboxes by solvothermal treatment. The number of shells can be easily controlled from 2 to 5 by varying the temperature. Finally, cobalt sulfide multi-shelled nanoboxes are produced through ion-exchange with S 2- ions and subsequent annealing. The as-obtained cobalt sulfide multi-shelled nanoboxes exhibit enhanced sodium-storage properties when evaluated as anodes for sodium-ion batteries. For example, a high specific capacity of 438 mAh g -1 can be retained after 100 cycles at the current density of 500 mA g -1 ., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The design and synthesis of hierarchical microboxes, assembled from SnS nanoplates coated with nitrogen-doped carbon (NC) as an anode material for sodium-ion batteries, is demonstrated. The template-engaged multistep synthesis of the SnS@NC microboxes involves sequential phase transformation, polydopamine coating, and thermal annealing in N 2 . The SnS@NC composite with two-dimensional nano-sized subunits rationally integrates several advantages including shortening the diffusion path of electrons/Na + ions, improving electric conductivity, and alleviating volume variation of the electrode material. As a result, the SnS@NC microboxes show efficient sodium storage performance with high capacity, good cycling stability, and excellent rate capability., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Designing advanced structures for heterojunction photocatalysts is an effective approach to enhance their performance toward solar-energy conversion. Herein we develop a facile synthetic strategy for the fabrication of Fe 2 O 3 -TiO 2 microdumbbells. With the assistance of preferentially adsorbed hexadecylamine molecules, amorphous TiO 2 nanospheres with tunable size are grown at the two ends of Fe-based metal-organic compound microrods. Subsequent annealing of the hybrid obtained leads to the formation of a novel heterostructured Fe 2 O 3 -TiO 2 microdumbbell photocatalyst. Owing to the heterojunction formed and the unique structure, Fe 2 O 3 -TiO 2 microdumbbells with optimized composition and morphology show enhanced performance for photoelectrochemical water oxidation, compared to monophasic Fe 2 O 3 and TiO 2 materials as well as physical mixtures thereof., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We have designed and synthesized novel hollow Ni/Fe layered double hydroxide (LDH) polyhedrons as an advanced sulfur host for enhancing the performance of lithium-sulfur (Li-S) batteries. The Ni/Fe LDH host shows multiple advantages. First, the Ni/Fe LDH shells can provide sufficient sulfiphilic sites for chemically bonding with polysulfides. Second, the hollow architecture can provide sufficient inner space for both loading a large amount of sulfur and accommodating its large volumetric expansion. Moreover, once the active material is confined within the host, the shells could easily restrict the outward diffusion of polysulfides, guaranteeing prolonged cycle life even with high sulfur loading. As a result, the S@Ni/Fe LDH cathode has successfully solved the main issues related to sulfur electrodes, and it exhibits significantly improved electrochemical performances with prolonged life over 1000 cycles and excellent rate properties., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Antimony-based electrode materials with high specific capacity have aroused considerable interest as anode materials for sodium-ion batteries (SIBs). Herein, we develop a template-engaged ion-exchange method to synthesize Sb 2 Se 3 microclips, and the as-obtained Sb 2 Se 3 microclips are further in situ coated with polypyrrole (PPy). Benefiting from the structural and compositional merits, these PPy-coated Sb 2 Se 3 microclips exhibit enhanced sodium-storage properties in terms of high reversible capacity, superior rate capability, and stable cycling performance., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Herein we report a simple dual-soft-template approach to prepare walnut-shaped macro-/mesoporous polydopamine particles with diameter of ca. 270 nm, highly accessible bicontinuous channels and wide pore size distribution from ca. 20 nm to ca. 95 nm. This approach provides great opportunities to tailor the soft template-directed assembly processes and generate various polydopamine particles with controllable mesophase curvature. Walnut-shaped mesoporous carbon particles with large open mesochannels in the range of ca. 13 nm to ca. 50 nm can be fabricated by subsequent thermal treatment under nitrogen atmosphere. Lastly, we demonstrate that the as-derived walnut-shaped carbon particles manifest enhanced electrocatalytic performance for oxygen reduction reaction in alkaline electrolyte., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Complex nanostructures with multi-components and intricate architectures hold great potential in developing high-performance electrode materials for lithium-ion batteries (LIBs). Herein, we demonstrate a facile self-templating strategy for the synthesis of metal vanadate nanomaterials with complex chemical composition of NiCo 2 V 2 O 8 and a unique yolk-double shell structure. Starting with the Ni-Co glycerate spheres, NiCo 2 V 2 O 8 yolk-double shell spheres are synthesized through an anion-exchange reaction of Ni-Co glycerate templates with VO 3 - ions, followed by an annealing treatment. By virtue of compositional and structural advantages, these NiCo 2 V 2 O 8 yolk-double shell spheres manifest outstanding lithium storage properties when evaluated as anodes for LIBs. Impressively, an extra-high reversible capacity of 1228 mAh g -1 can be retained after 500 cycles at a high current density of 1.0 Ag -1 ., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The oxygen evolution reaction (OER) is involved in various renewable energy systems, such as water-splitting cells and metal-air batteries. Ni-Fe layered double hydroxides (LDHs) have been reported as promising OER electrocatalysts in alkaline electrolytes. The rational design of advanced nanostructures for Ni-Fe LDHs is highly desirable to optimize their electrocatalytic performance. Herein, we report a facile self-templated strategy for the synthesis of novel hierarchical hollow nanoprisms composed of ultrathin Ni-Fe LDH nanosheets. Tetragonal nanoprisms of nickel precursors were first synthesized as the self-sacrificing template. Afterwards, these Ni precursors were consumed during the hydrolysis of iron(II) sulfate for the simultaneous growth of a layer of Ni-Fe LDH nanosheets on the surface. The resultant Ni-Fe LDH hollow prisms with large surface areas manifest high electrocatalytic activity towards the OER with low overpotential, small Tafel slope, and remarkable stability., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The introduction of a certain proportion of selenium into sulfur-based cathodes is an effective strategy for enhancing the integrated battery performance. However, similar to sulfur, selenium sulfide cathodes suffer from poor cycling stability owing to the dissolution of reaction intermediate products. In this study, to exploit the advantages of SeS 2 to the full and avoid its shortcomings, we designed and synthesized a hollow mesoporous carbon@titanium nitride (HMC@TiN) host for loading 70 wt % of SeS 2 as a cathode material for Li-SeS 2 batteries. Benefiting from both physical and chemical entrapment by hollow mesoporous carbon and TiN, the HMC@TiN/SeS 2 cathode manifests high utilization of the active material and excellent cycling stability. Moreover, it exhibits promising areal capacity (up to 4 mAh cm -2 ) with stable cell performance in the high-mass-loading electrode., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

SeS 2 shows attractive advantages beyond bare S and Se as a cathode material for lithium storage. Here, a freestanding lotus root-like carbon fiber network decorated with CoS 2 nanoparticles (denoted as CoS 2 @LRC) has been designed and prepared as the SeS 2 host for enhancing the lithium storage performance. The integrated electrode is constructed by three-dimensional interconnected multichannel carbon fibers, which can not only accommodate high content of SeS 2 (70 wt %), but also promise excellent electron and ion transport for achieving high capacity utilization of 1015 mAh g -1 at 0.2 A g -1 . What is more, there are numerous CoS 2 nanoparticles decorated all over the inner walls and surfaces of the carbon fibers, providing efficient sulfiphilic sites for restricting the dissolution of polysulfides and polyselenides during the electrochemical processes, thus successfully suppressing the shuttle effect and maintaining excellent cycling stability over 400 cycles at 0.5 A g -1 ., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)