Construction of a built-in electric field has been identified as an attractive improvement strategy for photoelectrochemical (PEC) water splitting by facilitating the carrier extraction from the inside to the surface. However, the promotion effect of the electric field is still restrained by the confined built-in area. Herein, we construct a microscale built-in electric field via gradient oxygen doping. The octahedral configuration of the synthesized CdIn2S4 (CIS) provides a structural basis, which enables the subsequent oxygen doping to reach a depth of similar to 100 nm. Accordingly, the oxygen-doped CIS (OCIS) photoanode exhibits a microscale built-in electric field with band bending. Excellent PEC catalytic activity with a photocurrent density of 3.69 mA cm(-2) at 1.23 V vs. RHE is achieved by OCIS, which is 3.1 times higher than that of CIS. Combining the results of thorough characterization and theoretical calculations, accelerating migration and separation of charge carriers have been determined as the reasons for the improvement. Meanwhile, the recombination risk at the doping centers has also been reduced to the minimum via optimal experiments. This work provides a new-generation idea for constructing a built-in electric field from the view point of bulky configuration towards PEC water splitting.

Electrocatalytic nitrogen (N 2 ) reduction reaction (eNRR) is a promising route for sustainable ammonia (NH 3 ) generation, but the eNRR efficiency is dramatically impeded by sluggish reaction kinetics. Herein, inspired by the dynamic extension-contraction of sea anemone tentacles in response to environmental changes, we propose a biomimetic elastic Mo single-atom protrusion on vanadium oxide support (pSA Mo/VOH) electrocatalyst featuring a symmetry-breaking Mo site and an elastic Mo−O 4 pyramid for efficient eNRR. In situ spectroscopy and theoretical calculations reveal that the protruding Mo-induced symmetry-breaking structure optimizes the d-electron filling of Mo, enhancing the back-donation to the π* antibonding orbital, effectively polarizing the N≡N bond and reducing the barrier from *N 2 to *N 2 H. Notably, the elastic Mo−O 4 pyramidal structure of pSA Mo provides a dynamic Mo−O microenvironment during continuous eNRR processes. This optimizes the electronic structure of the Mo sites based on different reaction intermediates, enhancing the adsorption of various N intermediates and maintaining low barriers throughout the six-step hydrogenation process. Consequently, the elastic pSA Mo/VOH exhibits an excellent NH 3 yield rate of 50.71±1.12 μg h −1  mg −1 and a Faradaic efficiency of 35.38±1.03 %, outperforming most electrocatalysts.

Bi-based metal-organic frameworks (Bi-MOFs) as efficient catalysts for the CO2 electroreduction reaction (CRR) have been extensively investigated. It has been established that Bi-MOFs usually undergo in-situ transformation during the CRR, ultimately converting into Bi nanostructures. However, the effect of the MOF precursors on the structure of the derived Bi catalysts and consequently on their electrocatalytic properties has not been clearly elucidated. In this work, we prepared four variants of a novel Bi-MOF with different morphologies and dimensions, and explored the effects of the precursors on the resulting Bi catalysts and their CRR performance. A precursor-dependent in-situ transformation and its profound impact on tuning the CO2-formate FE towards ∼100

Supramolecular chemistry during the synthesis of carbon-nitrogen-based materials has recently experienced a renaissance in the arena of photocatalysis and electrocatalysis. In this review, we start with the discussion of supramolecular assemblies-derived carbon-nitrogen-based materials’ regulation from the aspect of morphology, chemical composition, and micro/nanostructural control. Afterwards the recent advances of these materials in energy and environment related applications, including degradation of pollutants, water splitting, oxygen reduction reactions, CO2 reduction reactions along with organic synthesis are summarized. The correlations between the structural features and physicochemical properties of the carbon-nitrogen-based materials and the specific catalytic activity are discussed in depth. By highlighting the opportunities and challenges of supramolecular assembly strategies, we attempt an outlook on possible future developments for highly efficient carbon-based photo/electrocatalysts.

In-situ generated hydroxides and oxyhydroxides have been gradually recognized as the real active sites of metal organic frameworks (MOFs) towards the oxygen evolution reaction (OER). Nevertheless, the fine phase evolution process is still less of concern and elusive. Herein, we successfully construct serious of Ni-MOFs with differing thickness ranging from 1 nm to 270 nm through a competitive coordination strategy. Utilizing the operando resonance spectroscopy, an accurate phase inversion behavior of the Ni-MOFs has been witnessed during the OER, and demonstrated as a thickness-dependent process. Ultrathin architecture is identified as a positive factor to promote the exchange between MOFs ligands and applied electrolyte during the electrochemical test. Hence, after removing most of the internal ligands, 2D MOFs favor to be transformed as beta-NiOOH, which is more active than the generated gamma-NiOOH in bulky system. The density function theory (DFT) calculation alongside with the in-situ electrochemistry tests further affirm the beta/gamma-NiOOH transformation behavior. This work offers a new understanding of the electrocatalytic mechanism from the view point of phase evolution in 2D MOFs.

To satisfy the emergency demand of clean and renewable energy sources, developing highly efficient electrochemical energy storage and conversion technologies, such as rechargeable batteries, electrochemical capacitors, electrolyzers, and fuel cells, has become one of the greatest assignments for the sustainable development of society. Despite their different working principles, the two electrodes (cathode and anode), where the major electrochemical processes take place, such as charge storage in batteries/capacitors and electrocatalytic reactions in electrolyzers/fuel cells, are the key components for these electrochemical devices. Consequently, the design and construction of high-performance electrode materials has been a primary quest for the development of future electrochemical energy-related technologies. As a new class of porous materials, hydrogen-bonded organic frameworks (HOFs) have generated tremendous interests from researchers in widespread areas. Since most H-bonding interactions are essentially weak, flexible, and of low directionality, the morphology and structure of HOFs can be easily modulated depending on the precursors and synthesis solvents or conditions. In addition, the remarkably high porosity with large specific area and abundant functional groups endows the HOFs with rapid ion transport channels, specific ion sieving, considerable electrochemical active area, and highly exposed catalytic active sites. These features trigger extensive research interest to explore HOFs and their derivatives for electrochemical energy storage and conversion. Nevertheless, the electrochemical instability of hydrogen bonding and low electronic conductivity hampers their adaptation as electrode materials and electrocatalysts. To solve these issues, researchers have proposed some feasible schemes such as utilizing multiple hydrogen bonds and changing the electrolyte. In addition, converting HOFs into HOF-derived materials such as metal compounds, carbonaceous materials, or their composites has also been extensively investigated as alternative methods. These HOFs derivatives usually exhibit remarkable advantages originating from their microstructures or nanostructures, showing great potential in electrochemical energy related technologies. From this perspective, we summarized the latest developments of pristine HOFs and HOFs-derived materials as the electrodes or catalysts for electrochemical applications such as rechargeable batteries, electrochemical supercapacitors and electrocatalysis. We aim to provide an overview for this highly interdisciplinary area and discuss the significant breakthroughs that HOFs-related materials have brought to the field of electrochemical energy storage and conversion. The effects of morphology, structure and composition of these promising HOFs related materials on the electrochemical applications are systemically discussed. By highlighting the advantages and challenges of each class of materials for different applications, we hope to shed some light on the future development of HOFs related materials in the electrochemical applications.

Constructing donor-acceptor structures in polymeric carbon nitride (CN) provides an attractive pathway for facilitating charge carrier separation in photocatalytic reactions. However, achieving the implantation of donor or acceptor moieties at molecule level precision remains challenging. Here we develop a three-dimensional (3D) porous thiophene implanted carbon nitride (TCN) with donor-acceptor structure via a supramolecular assembly strategy. The specific-designed triazine derivatives with similar hydrogen bonding sites allow for the uniform introduction of thiophene groups at molecule level precision during the supramolecular assemble stage. The electron-donating thiophene groups in TCN can continuously tune electronic band structure, expand visible light absorption range, and promote charge carriers' separation. The optimized properties enable TCN-3 an outstanding H2 evolution rate of 5620 μmol h-1 g-1, greatly exceeding bulk CN (95 μmol h-1 g-1). Briefly, our work may offer opportunities to prepare highly active photocatalysts with molecule level precise donor-acceptor structure.

Ultrafine Fe 3 N nanocrystals (less than 1.5 nm) embedded in nitrogen-doped carbon are synthesized via a supramolecular confinement strategy for the efficient electrocatalytic ORR in Zn–air batteries.

The adjustment of hierarchical micro-nanostructure and morphology has been identified as an effective strategy to optimize photocatalytic performance of carbon nitrides (CNs). Nevertheless, environmental and additive-free construction of CNs with hierarchical structures is still challenging. Herein, a nucleation processable strategy is proposed to construct hierarchically intercalated CNs with unique morphologies (planar, donuts-like, flower-like), free of harmful additions. In this strategy, nucleation process (homogenous or heterogenous nucleation) and crystal growth degree of supramolecular precursors (cyanuric acid-melamine aggregates) can be controlled via tuning the initial supersaturation in the crystallization. Moreover, the formation mechanism of unique morphologies is illustrated in this article, based on the understanding of nucleation and crystal growth. Among the as-prepared CNs, owing to its hierarchically intercalated structure and unique morphology, the flower-like CN0.25 display the optimal charge separation and excellent photocatalytic hydrogen evolution performance of 1880 μmol h-1 g-1, which is 27 times higher than that of the bulk CN. Additionally, the apparent quantum yield of CN0.25 is achieved 6.7% at 420 nm. The experimental results demonstrate that the nucleation processable strategy developed herein may provide a new pathway in the design of hierarchically structured CNs with desirable photocatalytic performance.

Carbon materials with the merits of superior conductivity and wide available resources have emerged as promising anode candidates for sodium-ion batteries (SIBs). However, the inferior capacitance and the limited interlayer spacing restrain their practical application. Herein, we report an atom-adjustable doping strategy to fabricate the N/P dual-doped porous carbon nanosheet anodes (NP-PCN) via the in situ pyrolysis of supermolecules. Nitrogen atoms and phosphorus atoms are introduced to the skeleton with the monomers assembled incrementally. Benefiting from its monomer processability, the supermolecules demonstrate a rationally designed topological structure, endowing the derived carbon anode with a homogeneous heteroatom dispersion with 25.00 at. % of nitrogen and 6.37 at. % of phosphor, an expanded interlayer spacing of 0.47 nm, as well as an optimized configuration of more pyridinic N. Accordingly, the resulting NP-PCN achieves an enhanced reversible capacity of 223 mAh g(-1) at 100 mA g(-1), a robust rate capability of 114 mAh g(-1) at 1000 mA g(-1), and a long cycle life of 4000 cycles with a capacity retention of 92.60%. The storage mechanism is also explored by in situ Raman spectra and galvanostatic intermittent titration technique. This work may inspire new possibility of designing high-performance carbon anodes toward rechargeable alkali-metal-ion batteries at an atomic level.

2D metal coordination polymers have emerged as a new serious of efficient electrocatalysts in OER for their abundant unsaturated coordination centers and high charge-carrier mobility. However, the synthetic routes are mostly depending on the top-down exfoliation with unavoidable structural fragmentation and the annoying sheets' re-stacking. Here, an electrocatalytic poly (triazine imide) ligand is firstly synthesized and successfully applied to construct the 2D Ni/Fe coordination polymers nanosheets (Ni/Fe-CPNs) through a bottom-up strategy. Average thickness of the nanosheets is around 5 nm, enabling the highly exposed reactive centers. Further benefiting from the ligand promotion effect, absorption of the oxygen species during the OER is effectively accelerated, thus improving the reaction kinetics. Accordingly, the Ni/Fe-CPNs reveals an adorable overpotential of 244 mV at the current density of 10 mA cm(-2), and the Tafel value of 65.8 mv dec(-1). Both values are much better than that of commercial RuO2, and competitive to most of the reported catalysts. The ex-situ techniques, including Raman, FT-IR and XPS analysis alongside with applied potential, are also applied to elaborate the catalytic mechanism. This work offers a new point of view to improve the catalysts' activity. (C) 2021 Elsevier Ltd. All rights reserved.

An interstitial vacancy on molybdenum nitride has been determined as a negative factor towards the alkaline hydrogen evolution reaction (HER) by reason of upraising the d orbitals of Mo. Nevertheless, investigations aiming to eliminate the vacancies are rarely reported. Here, an interstitial reconfiguration method for the design of stoichiometric molybdenum carbonitride (Mo 2 CN) is proposed, in which the vacancies are fulfilled by lattice carbon. Multiple fine structural analyses alongside with the theoretical calculations indicate that beyond lower the d orbitals of Mo by the hybridization of additive p‐d orbitals, lattice carbon also behaves as the extra active center with exceptional H adsorption/desorption energy. Mo 2 CN reveals an adorable overpotential of − 84 mV at a current density of 10 mA cm −2 with a long‐term electrochemical stability by accompanying the nitrogen‐doped carbon substrate. It is anticipated that the vacancy‐eliminating concept will provide a constructive entry point for the rational design of electro‐catalysts and beyond.

Two-dimensional (2D) 2,6-naphalene dicarboxylic acid-based nickel iron metal-organic frameworks (NiFe-NDC MOFs) have been widely deemed as promising electrocatalysts by virtue of their adorable specific surface area and the highly-exposed reactive metal centers. However, the practical performance of the pristine NiFe-NDC MOFs is far from satisfaction towards the electrocatalytic water oxidation for the sluggish ion-transport. Herein, we report a co-coordination approach to afford dual-ligand NiFe electrocatalysts (NiFe-NDCxBDC1-x) with striking oxygen evolution reaction (OER) performance. Except for the 2,6-naphalene dicarboxylic acid (NDC), 1,4-terephthalic acid (BDC) is adopted as the co-coordination ligand to tune the electronic and structural configuration of the catalysts via the unique ligand processability of the MOFs. The optimal NiFe-NDC0.9BDC0.1 displays a superior performance for OER catalysis with an overpotential of 295 mV when current density arrives at 10 mA cm(-2) and the Tafel slope is 69.4 mV dec(-1), as well as excellent stability in alkaline media. In-situ Raman and ex-situ X-ray photoelectron spectroscopy further indicates that introduction of BDC ligands not only strengthen the interaction between Ni and Fe atoms, but also facilitate the deeper conversion from MOF to active NiOOH species, especially the higher proportion of beta-NiOOH species which can greatly promote the OER performance.

With a remarkable advantage of high theoretical capacity and excellent rate performance, zinc selenide (ZnSe) has been regarded as a high-potential electrode for sodium-ion batteries (SIBs). Nevertheless, the practical use of ZnSe as the anode for SIBs is severely limited by the large volumetric expansion and sluggish kinetics during the conversion/alloying reaction process. Herein, we develop a dual-type carbon approach to afford a 3D hierarchical ZnSe@N-doped carbon/reduced graphene oxide (ZnSe@NC/rGO) using simple selenization of ZIF-8 and subsequent incorporation process. Alongside with buffering the volume variation by the in-situ generated NC, the electron and ion transfer can also be accelerated on account of the interconnected graphene network. Therefore, the ZnSe@NC/rGO offers a splendid discharge capacity of 455.3 mAh g-1 at 0.1 A g-1, and exhibits a superior rate capability of 195.1 mAh g-1 at 5 A g-1. Besides, the capacity retains as high as 170.1 mAh g-1 after 500 cycles at 5 A g-1, indicating an outstanding cyclic ability. A full-cell sodium ion hybrid capacitor (SIHC) constructed using a ZnSe@NC/rGO anode and a commercial activated carbon (AC) cathode (ZnSe@NC/rGO//AC SIHC) shows a high energy output of 117.8 Wh kg-1 at 105 W kg-1, and a long lifespan with 86.4% capacity retention over 3000 cycles.

The vigorous development of photocatalytic water splitting technology has laid the foundation for the photo catalytic transfer hydrogenation of organic substrates to produce the high value-added chemicals using water as hydrogen source. Nevertheless, the high dissociation energy of the O-H bond impedes its academic progress and the practical applications. Herein, we synthesize a 3D hierarchical porous loofah-like carbon nitride sponge (LCN) with ultrathin thickness via the supramolecular pre-organization coupling with the oxidation etching process, in which the heterogeneous oxygen atoms and the nitrogen vacancies are in-situ engineered. On top of the adorable photocatalytic H2 evolution (4812 mu mol h(-1) g(-1)), LCN associated with Pt cocatalyst reveals a conversion rate of 96.5 % towards the hydrogenation of 4-nitrophenol, substantially superior to the reference experiment (8.3 %). Further based on the isotope-labeling tests and the density functional theory calculations, the photo-generated H0 from water is clarified to be the direct reducing agent, tactfully skipping the hydrogen extraction step in the traditional path. This work provides a green and sustainable methodology to transfer the solar energy to the valuable fine chemicals, as well as highlights the importance of the 3D hierarchical porous structure to the catalytic activity.

Crystal facet engineering has been proved as a dramatically efficient strategy to optimize the intrinsic catalytic property of catalysts. However, because of the difficulty in precise construction, facet engineering of two-dimensional metal-organic frameworks (2D MOFs) is rarely reported. Herein, we propose a new and facile coordination modulation method to realize the controllable synthesis of 2D NiFe-MOFs with a highly exposed (001) crystal facet. Specifically, acetate ions, which possess the same coordination groups with the participated terephthalic ligand, have been adopted into the MOF construction as the morphology and facet regulator. Through competitive coordination effect and ion-induced self-assembly, the fabricated NiFe-MOFs reveal a hierarchical microsphere architecture consisting of ultrathin nanosheets with thickness similar to 5 nm. Further benefiting from the structural advantages, e.g., abundant active sites, highly exposed catalytic facet, and enhanced mass/charge transport, the hierarchical NiFe- MOF nanosheets exhibit an attractive overpotential of 240 mV at the current density of 10 mA cm(-2), a small Tafel slope of 73.44 mV dec(-1), and satisfactory stability for 16 h toward oxygen evolution reaction (OER). Besides, the increased exposure of the (001) facet will increase the proportion of high-valent nickel oxyhydroxides during OER, which will enhance the electrocatalytic performance. The universality of the modulation method is further verified by the successful synthesis of a series of 2D MOFs (Ni, Co, Cu, Zn, and corresponding bimetal MOFs). This method may serve as an important inspiration for the preparation and crystal facet engineering of 2D MOFs.

Molybdenum diselenide (MoSe2) is emerging as a promising anode material for sodium-ion hybrid capacitors (SIHCs) due to its high theoretical capacity. However, the limited rate capability and the poor stability restrain its practical applications. Herein, we report a template approach to prepare two-dimensional (2D) few-layer MoSe2 embedded in nitrogen-doped carbon sheets (MoSe2@NCS). Specifically, graphitic carbon nitride is in situ transformed as the sacrificial template, which not only inhibits the accumulation of the MoSe2 but also endows the MoSe2@NCS composite with a 2D morphology. Benefiting from this architecture, the heterostructure reveals the accelerated ion diffusion rate, enhanced electronic conductivity, and well-controlled volume expansion. Consequently, the MoSe2@NCS delivers a high specific capacity of 398.9 mAh g(-1) at 0.1 A g(-1) and a good rate performance of 229 mAh g(-1) at 5 A g(-1). Meanwhile, an outstanding long cyclic stability with high capacity of 225.2 mAh g(-1) is maintained after 1000 cycles at 1 A g(-1). Hence, a SIHC based on the MoSe2@NCS anode is established and exhibits a high energy of 122.8 Wh kg(-1) at 105 W kg(-1) and power densities of 65.3 Wh kg(-1) at 10500 W kg(-1).

Sodium ion hybrid capacitors (SIHCs) have attracted considerable attentions due to their high-energy density of batteries and high-power output of supercapacitors. However, the slow intercalation kinetics of anode and low specific capacity of cathode greatly hinder the high-performance output of the SIHCs. Herein, we develop a facile chemical gas expansion method with chemical etching to prepare 3D nitrogen and sulfur co-doped porous carbon nanosheet (PCNS). As an anode material of SIBs, the PCNS displays a high reversible capacity of 205 mAh g(-1) at 0.5 A g(-1), outstanding rate capability of 96 mAh g(-1) at 20 A g(-1), and excellent cycle performance of 180 mAh g(-1) at 7 A g(-1 )after 10 000 cycles. Based on this good performance, a dual-carbon SIHC is assembled by battery-type anode material (PCNS) and capacitive-type cathode material (hierarchically porous carbon). This device exhibits high energy densities of 119 Wh kg(-1) and 53 Wh kg(-1) at power densities of 200 W kg(-1) and 20 kW kg(-1), respectively. Besides, it possesses a superior cycle life of 82% capacity retention after 8000 cycles. Moreover, this work provides a new idea for the synthesis of carbon materials as high-performance SIBs and SIHCs electrode materials.

Carbon nitride has drawn widespread attention as a low-cost alternative to metal-based materials in the field of photocatalysis. However, the traditionally synthesized carbon nitrides always suffer a bulky architecture, which limits their intrinsic activities. Here, a cycloaddition reaction is proposed to synthesize a triazine-based precursor with implanted sodium and cyano groups, which are mostly retained in the resulting carbon nitride after the following polymerization. Incorporated sodium and cyano defects can not only tune the band structure of the carbon nitride but also provide more additive active sites. The optimized properties enable it an adorable photocatalytic hydrogen evolution rate of 1070 mu mol h(-1) g(-1), varying by almost an order of magnitude from the pristine carbon nitride (79 mu mol h(-1) g(-1)). Moreover, a sequential self-assembly strategy has been adopted to further improve its architecture. As a consequence, a three-dimensional (3D) porous carbon nitride microtube cluster is constructed, indicating abundant exposed active sites and the faster separation of charge carriers. The corresponding photocatalytic hydrogen evolution rate is 1681 mu mol h(-1) g(-1), which is very competitive compared with the reported pure carbon nitride photocatalysts. Briefly, this new approach may offer opportunities to fabricate task-specific carbon- and nitrogen-based materials from the molecular level.