Construction of cyclobutane-fused tetracyclic skeletons via substrate-dependent EnT-enabled dearomative [2+2] cycloaddition of benzofurans (benzothiophenes)/maleimides.

Herein, a novel and facile organic photosensitizer (thioxanthone)-mediated energy-transfer-enabled (EnT-enabled) dearomative [2+2] cycloaddition of aromatic heterocycles/maleimides for green synthesis of cyclobutane-fused polycyclic skeletons is reported. Mechanistic investigations revealed that different EnT pathways by triplet thioxanthone were initiated when different aromatic heterocycles participated in the reaction, giving the corresponding excited intermediates, which underwent the subsequent intermolecular [2+2] cycloaddition to access the desired highly functionalized cyclobutane-fused polycyclic skeletons.

A defect-enriched PdMo bimetallene for ethanol oxidation reaction and 4-nitrophenol reduction.

A defect-enriched PdMo bimetallene (d-PdMo) was prepared by a one-pot wet chemical reaction followed by post-treatment of oxidative etching. The introduction of defects can tailor the electronic structure of PdMo bimetallene and the prepared d-PdMo bimetallene exhibited excellent performance in the ethanol oxidation reaction (EOR) and 4-nitrophenol (4-NP) reduction reaction.

Photomediated Hydro(deutero)acylation of Olefins by Decarboxylative Addition of α-Oxocarboxylic Acids.

Acyl radicals have been generated from the decarboxylation of α-oxocarboxylic acids by using a readily accessible organic pyrimidopteridine photoredox catalyst under ultraviolet-A (UV-A) light irradiation. These reactive acyl radicals were smoothly added to olefins such as styrenes and diverse Michael acceptors, with the assistance of H2O/D2O as hydrogen donors, enabling easy access to a diverse range of ketones/ß-deuterio ketones. A wide range of α-oxocarboxylic acids are compatible with this reaction, which shows a reliable, atom-economical, and eco-friendly protocol. Furthermore, postsynthetic diversifications and applications are presented.

Lattice Defects and Electronic Modulation of Flower-Like Zn3 In2 S6 Promote Photocatalytic Degradation of Multiple Antibiotics.

Photocatalysis is an effective technique to remove antibiotic residues from aquatic environments. Typical metal sulfides like Zn3 In2 S6 have been applied to a wide range of photocatalytic applications. However, there are currently no readily accessible methods to increase its antibiotic-degrading activity. Here, a facile hydrothermal approach is developed for the preparation of flower-like Zn3 In2 S6 with tunable sulfur lattice defects. Photogenerated carriers can be separated and transferred more easily when there is an adequate amount of lattice defects. Moreover, lattice defect-induced electronic modulation enhances light utilization and adsorption properties. The modified Zn3 In2 S6 demonstrates outstanding photocatalytic degradation activity for levofloxacin, ofloxacin, and tetracycline. This work sheds light on exploring metal sulfides with sulfur lattice defects for enhancing photocatalytic activity.

A Durable and High-Voltage Mn-Graphite Dual-Ion Battery Using Mn-Based Hybrid Electrolytes.

Rechargeable Mn-metal batteries (MMBs) can attract considerable attention because Mn has the intrinsic merits including high energy density (976 mAh g-1 ), high air stability, and low toxicity. However, the application of Mn in rechargeable batteries is limited by the lack of proper cathodes for reversible Mn2+ intercalation/de-intercalation, thus leading to low working voltage (<1.8 V) and poor cycling stability (≤200 cycles). Herein, a high-voltage and durable MMB with graphite as the cathode is successfully constructed using a LiPF6 -Mn(TFSI)2 hybrid electrolyte, which shows a high discharge voltage of 2.34 V and long-term stability of up to 1000 cycles. Mn(TFSI)2 can reduce the plating/stripping overpotential of Mn ions, while LiPF6 can efficiently improve the conductivity of the electrolyte. Electrochemical in-situ characterization implies the dual-anions intercalation/de-intercalation at the cathode and Mn2+ plating/stripping reaction at the anode. Theoretical calculations unveil the top site of graphite is the energetically favorable for anions intercalation and TFSI- shows the low migration barrier. This work paves an avenue for designing high-performance rechargeable MMBs towards electricity storage.

Multi-d Electron Synergy in LaNi1-x Cox Ru Intermetallics Boosts Electrocatalytic Hydrogen Evolution.

Despite the fact that d-band center theory links the d electron structure of transition metals to their catalytic activity, it is yet unknown how the synergistic effect of multi-d electrons impacts catalytic performance. Herein, novel LaNi1-x Cox Ru intermetallics containing 5d, 4d, and 3d electrons were prepared. In these compounds, the 5d orbital of La transfers electrons to the 4d orbital of Ru, which provides adsorption sites for H*. The 3d orbitals of Ni and Co interact with the 5d and 4d orbitals to generate an anisotropic electron distribution, which facilitates the adsorption and desorption of OH*. The synergistic effect of multi-d electrons ensures efficient catalytic activity. The optimized LaNi0.5 Co0.5 Ru has an overpotential of 43mV at 10 mA cm-2 for alkaline electrocatalytic hydrogen evolution reaction. Beyond offering a variety of new electrocatalysts, this work reveals the multi-d electron synergy in promoting catalytic reaction.

Local electronic structure engineering of vanadium-doped nickel phosphide nanosheet arrays for efficient hydrogen evolution.

Local electronic structure engineering is an effective approach for optimizing the catalytic performance of electrocatalysts. Herein, a dual-phase vanadium-doped nickel phosphide (NiVxP) catalyst supported on nickel foam (NF) was synthesized via a successive hydrothermal and phosphorization process with interconnected nanosheet structures and homogeneous distributions. The catalyst's stable phase and strong adhesion to the substrate ensure good electrochemical stability. The incorporation of V effectively promotes initial H2O adsorption and H* formation, leading to a lower overpotential. As a result, the fabricated NiVxP@NF demonstrates favorable hydrogen evolution reaction (HER) activity and stability, with only 85 mV overpotential needed to reach 10 mA·cm-2 and showing no significant increase in the overpotential during the long-term 78-hour stability test.

Nontrivial Topological Surface States in Ru3 Sn7 toward Wide pH-Range Hydrogen Evolution Reaction.

Nontrivial topological surface states (TSSs), which possess extraordinary carrier mobility and are protected by the bulk symmetry, have emerged as an innovative platform to search for efficient electrocatalysts toward hydrogen evolution reaction (HER). Here, a Sn-based nontrivial metal Ru3 Sn7 is prepared using electrical arc melting method. The results indicate that the (001) crystal family of Ru3 Sn7 possesses nontrivial TSSs with linear dispersion relation and large nontrivial energy window. Experimental and theoretical results demonstrate that nontrivial TSSs of Ru3 Sn7 can significantly boost charge transfer kinetics and optimize adsorption of hydrogen intermediates due to bulk symmetry-protected band structures. As expected, nontrivial Ru3 Sn7 exhibits superior HER activity to Ru, Pt/C, and trivial counterparts (e.g., Ru2 Sn3 , IrSn2 , and Rh3 Sn2 ) with higher ratios of noble metals. Furthermore, the wide pH-range activity of topologically nontrivial Ru3 Sn7 implies the robustness of its TSSs against pH variation during the HER. These findings provide a promising approach to the rational design of topologically nontrivial metals as highly efficient electrocatalysts.

Charge Redistribution of Co9S8/MoS2 Heterojunction Microsphere Enhances Electrocatalytic Hydrogen Evolution.

The electrocatalytic hydrogen evolution activity of transition metal sulfide heterojunctions are significantly increased when compared with that of a single component, but the mechanism behind the performance enhancement and the preparation of catalysts with specific morphologies still need to be explored. Here, we prepared a Co9S8/MoS2 heterojunction with microsphere morphology consisting of thin nanosheets using a facile two-step method. There is electron transfer between the Co9S8 and MoS2 of the heterojunction, thus realizing the redistribution of charge. After the formation of the heterojunction, the density of states near the Fermi surface increases, the d-band center of the transition metal moves downward, and the adsorption of both water molecules and hydrogen by the catalyst are optimized. As a result, the overpotential of Co9S8/MoS2 is superior to that of most relevant electrocatalysts reported in the literature. This work provides insight into the synergistic mechanisms of heterojunctions and their morphological regulation.

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

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

Phosphorus-modified cobalt single-atom catalysts loaded on crosslinked carbon nanosheets for efficient alkaline hydrogen evolution reaction.

Efficient and low-cost transition metal single-atom catalysts (TMSACs) for hydrogen evolution reaction (HER) have been recognized as research hotspots recently with advances in delivering good catalytic activity without noble metals. However, the high-cost complex preparation of TMSACs and insufficient stability limited their practical applications. Herein, a simple top-down pyrolysis approach to obtain P-modified Co SACs loaded on the crosslinked defect-rich carbon nanosheets was introduced for alkaline hydrogen evolution, where Co atoms are locally confined before pyrolysis to prevent aggregation. Thereby, the abundant defects and the unsaturated coordination formed during the pyrolysis significantly improved the stability of the monatomic structure and reduced the reaction barrier. Furthermore, the synergy between cobalt atoms and phosphorus atoms was established to optimize the decomposition process of water molecules, which delivers the key to promoting the slow reaction kinetics of alkaline HER. As the result, the cobalt SAC exhibited excellent catalytic activity and stability for alkaline HER, with overpotentials of 70 mV and 192 mV at current densities of -10 mA cm-2 and -100 mA cm-2, respectively.

Construction of Cobalt Molybdenum Diselenide Three-phase Heterojunctions for Electrocatalytic Hydrogen Evolution in Acid Medium.

Molybdenum diselenide and cobalt diselenide have been commonly implemented in electrocatalytic hydrogen evolution reaction (HER). However, there have been few research on the creation of their three-phase heterojunctions and the associated HER process. Herein, we constructed a three-phase heterostructure sample consisting of orthorhombic CoSe2 , cubic CoSe2 and MoSe2 and we investigated its HER performance. The sample shows microsphere morphology composed of nanosheets with interfacial interactions between the components. It possesses an overpotential of -136 mV at -10 mA cm-2 in acid medium, which is superior to that of single component and most two-phase heterostructures. Especially, the overpotential at -200 mA cm-2 is smaller than that of Pt/C. The excellent performance can be attributed to the d-orbital upshift of the Co active sites due to charge redistribution between the three-phase heterojunction and the optimization of the hydrogen free energy. This work provides inspiration for exploring the application of other multi-component heterojunctions in electrocatalytic hydrogen evolution.

Interlayer Spacing Regulation of Molybdenum Selenide Promotes Electrocatalytic Hydrogen Evolution in Alkaline Media.

The construction of heterostructures is a versatile tactic to enhance catalytic activity. However, it is still elusive to realize the modulation of the interlayer spacing in this way to further improve the performance. Here, strong interfacial coupling between CoSe2 and MoSe2 by constructing CoSe2 /MoSe2 heterostructures is achieved. The interlayer spacing of MoSe2 is compressed by 0.3 Å. The enhanced charge transfer is validated by X-ray absorption spectroscopy and X-ray photoelectron spectroscopy. Coupled with the morphology of hollow microtubes, which can facilitate the exposure of active sites, CoSe2 /MoSe2 heterostructures reported here exhibit high activity (119 mV at 10 mA cm-2 ) and excellent stability with small degradation after 50 h operation, surpassing other analogous powdered electrocatalysts. This work sheds light on the importance of tuning the interlayer spacing to improve electrocatalytic activity.

Highly Active Si Sites Enabled by Negative Valent Ru for Electrocatalytic Hydrogen Evolution in LaRuSi.

The discovery and identification of novel active sites are paramount for deepening the understanding of the catalytic mechanism and driving the development of remarkable electrocatalysts. Here, we reveal that the genuine active sites for the hydrogen evolution reaction (HER) in LaRuSi are Si sites, not the usually assumed Ru sites. Ru in LaRuSi has a peculiar negative valence state, which leads to strong hydrogen binding to Ru sites. Surprisingly, the Si sites have a Gibbs free energy of hydrogen adsorption that is near zero (0.063 eV). The moderate adsorption of hydrogen on Si sites during the HER process is also validated by in situ Raman analysis. Based on it, LaRuSi exhibits an overpotential of 72 mV at 10 mA cm-2 in alkaline media, which is close to the benchmark of Pt/C. This work sheds light on the recognition of real active sites and the exploration of innovative silicide HER electrocatalysts.

Crystalline-Amorphous Interfaces Coupling of CoSe2 /CoP with Optimized d-Band Center and Boosted Electrocatalytic Hydrogen Evolution.

Amorphous and heterojunction materials have been widely used in the field of electrocatalytic hydrogen evolution due to their unique physicochemical properties. However, the current used individual strategy still has limited effects. Hence efficient tailoring tactics with synergistic effect are highly desired. Herein, the authors have realized the deep optimization of catalytic activity by a constructing crystalline-amorphous CoSe2 /CoP heterojunction. Benefiting from the strong electronic coupling at the interfaces, the d-band center of the material moves further down compared to its crystalline-crystalline counterpart, optimizing the valence state and the H adsorption of Co and lowering the kinetic barrier of hydrogen evolution reaction (HER). The heterojunction shows an overpotential of 65 mV to drive a current density of 10 mA cm-2 in the acidic medium. Besides, it also shows competitive properties in both neutral and basic media. This work provides inspiration for optimizing the catalytic activity through combining a crystalline and amorphous heterojunction, which can be implemented for other transition metal compound electrocatalysts.

PtSe2 /Pt Heterointerface with Reduced Coordination for Boosted Hydrogen Evolution Reaction.

PtSe2 is a typical noble metal dichalcogenide (NMD) that holds promising possibility for next-generation electronics and photonics. However, when applied in hydrogen evolution reaction (HER), it exhibits sluggish kinetics due to the insufficient capability of absorbing active species. Here, we construct PtSe2 /Pt heterointerface to boost the reaction dynamics of PtSe2 , enabled by an in situ electrochemical method. It is found that Se vacancies are induced around the heterointerface, reducing the coordination environment. Correspondingly, the exposed Pt atoms at the very vicinity of Se vacancies are activated, with enhanced overlap with H 1s orbital. The adsorption of H. intermediate is thus strengthened, achieving near thermoneutral free energy change. Consequently, the as-prepared PtSe2 /Pt exhibits extraordinary HER activity even superior to Pt/C, with an overpotential of 42 mV at 10 mA cm-2 and a Tafel slope of 53 mV dec-1 . This work raises attention on NMDs toward HER and provides insights for the rational construction of novel heterointerfaces.

Laser ablation in air and its application in catalytic water splitting and Li-ion battery.

Pulse laser has been widely used in both fundamental science and practical technologies. In this perspective, we highlight the employment of pulse laser ablation in air (LAA) in energy-related catalytic reactions. With LAA, samples are directly ablated in ambient air, which makes this technology facile to conduct. Materials can be modified by LAA in multiple aspects, such as morphology modulation, heterojunction fabrication, or defects engineering, which are desired features for energy-related catalytic reactions. We begin this perspective with a brief introduction of this technology, including the mechanism, the experimental setup, and the characteristic of laser-ablated materials. The recent works utilizing LAA are then summarized to prove the promising prospects of LAA in the energy field. Finally, several opportunities about the future usage of LAA are proposed and discussed.

Reversed Active Sites Boost the Intrinsic Activity of Graphene-like Cobalt Selenide for Hydrogen Evolution.

Optimizing the hydrogen adsorption Gibbs free energy (ΔGH ) of active sites is essential to improve the overpotential of the electrocatalytic hydrogen evolution reaction (HER). We doped graphene-like Co0.85 Se with sulfur and found that the active sites are reversed (from cationic Co sites to anionic S sites), which contributed to an enhancement in electrocatalytic HER performance. The optimal S-doped Co0.85 Se composite has an overpotential of 108 mV (at 10 mA cm-2 ) and a Tafel slope of 59 mV dec-1 , which exceeds other reported Co0.85 Se-based electrocatalysts. The doped S sites have much higher activity than the Co sites, with a hydrogen adsorption Gibbs free energy (ΔGH ) close to zero (0.067 eV), which reduces the reaction barrier for hydrogen production. This work provides inspiration for optimizing the intrinsic HER activity of other related transition metal chalcogenides.

RhSe2 : A Superior 3D Electrocatalyst with Multiple Active Facets for Hydrogen Evolution Reaction in Both Acid and Alkaline Solutions.

Layered 2D materials are a vital class of electrocatalys for the hydrogen evolution reaction (HER), due to their large area, excellent activity, and facile fabrication. Theoretical caculations domenstrate, however, that only the edges of the 2D nanosheets act as active sites, while the much larger basal plane exhibits passive activity. Here, from a distinguishing perspective, RhSe2 is reported as a "3D" electrocatalyst for HER with top-class activity, synthesized by a facile solid-state method. Superior to 2D materials, multiple crystal facets of RhSe2 exhibit near-zero free energy change of hydrogen adsorption (ΔGH ), which guarantees high performance in most common morphologies. Density functional theory calculations reveal that the low-coordinated Rh atoms act as the active sites in acid, which enables the modified Kubas-mediated pathway, while the Se atoms act as the active sites in an alkaline medium. The overpotentials of HER activity of RhSe2 are measured to be 49.9 and 81.6 mV at 10 mA cm-2 in acid and alkaline solutions, respectively. This work paves the way to new transition metal chalcogenide catalysts.

2D Transition Metal Dichalcogenides: Design, Modulation, and Challenges in Electrocatalysis.

Hydrogen has been deemed as an ideal substitute fuel to fossil energy because of its renewability and the highest energy density among all chemical fuels. One of the most economical, ecofriendly, and high-performance ways of hydrogen production is electrochemical water splitting. Recently, 2D transition metal dichalcogenides (also known as 2D TMDs) showed their utilization potentiality as cost-effective hydrogen evolution reaction (HER) catalysts in water electrolysis. Herein, recent representative research efforts and systematic progress made in 2D TMDs are reviewed, and future opportunities and challenges are discussed. Furthermore, general methods of synthesizing 2D TMDs materials are introduced in detail and the advantages and disadvantages for some specific methods are provided. This explanation includes several important regulation strategies of creating more active sites, heteroatoms doping, phase engineering, construction of heterostructures, and synergistic modulation which are capable of optimizing the electrical conductivity, exposure to the catalytic active sites, and reaction energy barrier of the electrode material to boost the HER kinetics. In the last section, the current obstacles and future chances for the development of 2D TMDs electrocatalysts are proposed to provide insight into and valuable guidelines for fabricating effective HER electrocatalysts.