p-d Orbital Hybridization Induced by Asymmetrical FeSn Dual Atom Sites Promotes the Oxygen Reduction Reaction.

With more flexible active sites and intermetal interaction, dual-atom catalysts (DACs) have emerged as a new frontier in various electrocatalytic reactions. Constructing a typical p-d orbital hybridization between p-block and d-block metal atoms may bring new avenues for manipulating the electronic properties and thus boosting the electrocatalytic activities. Herein, we report a distinctive heteronuclear dual-metal atom catalyst with asymmetrical FeSn dual atom sites embedded on a two-dimensional C2N nanosheet (FeSn-C2N), which displays excellent oxygen reduction reaction (ORR) performance with a half-wave potential of 0.914 V in an alkaline electrolyte. Theoretical calculations further unveil the powerful p-d orbital hybridization between p-block stannum and d-block ferrum in FeSn dual atom sites, which triggers electron delocalization and lowers the energy barrier of *OH protonation, consequently enhancing the ORR activity. In addition, the FeSn-C2N-based Zn-air battery provides a high maximum power density (265.5 mW cm-2) and a high specific capacity (754.6 mA h g-1). Consequently, this work validates the immense potential of p-d orbital hybridization along dual-metal atom catalysts and provides new perception into the logical design of heteronuclear DACs.

Active Oxygenated Structure-Intensified CO2 Capture Enables Efficient Electrochemical Ethylene Production Over Carbon Nanofibers.

The pursuit of high efficacy C-C coupling during the electrochemical CO2 reduction reaction remains a tremendous challenge owing to the high energy barrier of CO2 activation and insufficient coverage of the desired intermediates on catalytic sites. Inspired by the concept of capture-coupled CO2 activation, we fabricated quinone-grafted carbon nanofibers via an in situ oxidative carbonylation strategy. The quinone functionality of carbon nanofibers promotes the capture of CO2 followed by activation. At a current density of 400 mA cm-2, the Faradaic efficiency of ethylene reached 62.9 %, and a partial current density of 295 mA cm-2 was achieved on the quinone-rich carbon nanofibers. The results of in situ spectroscopy and theoretical calculations indicated that the remarkable selectivity enhancement in ethylene originates from the quinone structure, rather than the electronic properties of Cu particles. The interaction of quinone with CO2 increases the local *CO coverage and simultaneously hinders the co-adsorption of *H on Cu sites, which greatly reduces the energy barrier for C-C coupling and restrains subsequent *CO protonation. The modulation strategy involving specific oxygenated structure, as an independent degree of freedom, guides the design of functionalized carbon materials for tailoring the selectivity of desired products during the CO2 capture and reduction.

Atomic Printing Strategy Achieves Precise Anchoring of Dual-Copper Atoms on C2N Structure for Efficient CO2 Reduction to Ethylene.

Isolated metal sites catalysts (IMSCs) play crucial role in electrochemical CO2 reduction, with potential industrial applications. However, tunable synthesis strategies for IMSCs are limited. Herein, we present an atomic printing strategy that draws inspiration from the ancient Chinese "movable-type printing technology". Selecting customizable combinations of metal atoms as metal precursors from an extensive binuclear metal library. A series of dual-atom catalysts were prepared by utilizing the edge nitrogen atoms in the C2N cavity as anchoring "pincers" to capture metal atoms. To prove utility, the dual atom catalyst Cu2-C2N is investigated as electrocatalytic CO2RR catalyst. The synergistic interaction of dual Cu atoms promotes C-C coupling and guarantees FEC2+ (90.8 %) and FEC2H4. (71.7 %) at -1.10 V vs RHE. DFT calculations revealed the Cu2 site would be subtly flipped during CO2RR for enhancing *CO adsorption and dimerization. We validate that atomic printing strategies are applicable to wide range of metal combinations, representing a significant advancement in the development of IMSCs.

Engineering Isolated Mn-N2C2 Atomic Interface Sites for Efficient Bifunctional Oxygen Reduction and Evolution Reaction.

Oxygen-involved electrochemical reactions are crucial for plenty of energy conversion techniques. Herein, we rationally designed a carbon-based Mn-N2C2 bifunctional electrocatalyst. It exhibits a half-wave potential of 0.915 V versus reversible hydrogen electrode for oxygen reduction reaction (ORR), and the overpotential is 350 mV at 10 mA cm-2 during oxygen evolution reaction (OER) in alkaline condition. Furthermore, by means of operando X-ray absorption fine structure measurements, we reveal that the bond-length-extended Mn2+-N2C2 atomic interface sites act as active centers during the ORR process, while the bond-length-shortened high-valence Mn4+-N2C2 moieties serve as the catalytic sites for OER, which is consistent with the density functional theory results. The atomic and electronic synergistic effects for the isolated Mn sites and the carbon support play a critical role to promote the oxygen-involved catalytic performance, by regulating the reaction free energy of intermediate adsorption. Our results give an atomic interface strategy for nonprecious bifunctional single-atom electrocatalysts.

In Situ Phosphatizing of Triphenylphosphine Encapsulated within Metal-Organic Frameworks to Design Atomic Co1-P1N3 Interfacial Structure for Promoting Catalytic Performance.

The engineering coordination environment offers great opportunity in performance tunability of isolated metal single-atom catalysts. For the most popular metal-Nx (MNx) structure, the replacement of N atoms by some other atoms with relatively weak electronegativity has been regarded as a promising strategy for optimizing the coordination environment of an active metal center and promoting its catalytic performance, which is still a challenge. Herein, we proposed a new synthetic strategy of an in situ phosphatizing of triphenylphosphine encapsulated within metal-organic frameworks for designing atomic Co1-P1N3 interfacial structure, where a cobalt single atom is costabilized by one P atom and three N atoms (denoted as Co-SA/P-in situ). In the acidic media, the Co-SA/P-in situ catalyst with Co1-P1N3 interfacial structure exhibits excellent activity and durability for the hydrogen evolution reaction (HER) with a low overpotential of 98 mV at 10 mA cm-2 and a small Tafel slope of 47 mV dec-1, which are greatly superior to those of catalyst with Co1-N4 interfacial structure. We discover that the bond-length-extended high-valence Co1-P1N3 atomic interface structure plays a crucial role in boosting the HER performance, which is supported by in situ X-ray absorption fine structure (XAFS) measurements and density functional theory (DFT) calculation. We hope this work will promote the development of high performance metal single-atom catalysts.

Design of a Single-Atom Indiumδ+ -N4 Interface for Efficient Electroreduction of CO2 to Formate.

Main-group element indium (In) is a promising electrocatalyst which triggers CO2 reduction to formate, while the high overpotential and low Faradaic efficiency (FE) hinder its practical application. Herein, we rationally design a new In single-atom catalyst containing exclusive isolated Inδ+ -N4 atomic interface sites for CO2 electroreduction to formate with high efficiency. This catalyst exhibits an extremely large turnover frequency (TOF) up to 12500 h-1 at -0.95 V versus the reversible hydrogen electrode (RHE), with a FE for formate of 96 % and current density of 8.87 mA cm-2 at low potential of -0.65 V versus RHE. Our findings present a feasible strategy for the accurate regulation of main-group indium catalysts for CO2 reduction at atomic scale.

From Indium-Doped Ag2 S to AgInS2 Nanocrystals: Low-Temperature In Situ Conversion of Colloidal Ag2 S Nanoparticles and Their NIR Fluorescence.

Focusing on ternary I-III-VI2 colloidal nanocrystals (NCs) synthesized with precise control of the composition (from doping to ternary composition) and NIR fluorescence performance, monodisperse binary In3+ -doped Ag2 S NCs and ternary AgInS2 NCs have been achieved successfully by facile low-temperature in situ conversion of colloidal Ag2 S nanoparticles. In3+ ions were inserted into the crystal lattice of Ag2 S NCs at a relatively low temperature as dopant and ternary AgInS2 NCs were obtained at a higher temperature following a phase transition. These doped Ag2 S and AgInS2 NCs based on different indium precursor concentrations were explored with respect to the position and intensity of the near-infrared photoluminescent emission at different doping levels and crystal phase evolution.

Encapsulating Ammonia Borane in Cobalt Decorated Kaolinite Monolith Aerogel for Hydrogen Storage and Controllable Release.

Achieving the "on-off" control of hydrogen release remains a huge challenge in efficiently harnessing hydrogen energy on demand. In this work, a controlled hydrogen production strategy is proposed. Hydrogen carrier ammonia borane (AB) and Co catalyst are loaded into kaolinite aerogel (KA) to obtain a composite AB@Co/KA monolith. The results show that Co particles with surface-oxidized species are uniformly decorated on the surface of aerogel, and AB can fill the pores of aerogel to form a composite hydrogen storage material. Hydrogen generation is modulated on AB@Co/KA by tuning the amount of water added, which achieves an "on-off" hydrogen release on demand. The Co-modified KA (Co/KA) can be repackaged multiple times for recycling use after the AB is completely hydrolyzed. This work provides a promising approach for controlling the release of hydrogen neither the input of additional energy nor foreign reagents added to the reaction system.

Surface fluorination of BiVO4 for the photoelectrochemical oxidation of glycerol to formic acid.

The C-C bond cleavage of biomass-derived glycerol to generate value-added C1 products remains challenging owing to its slow kinetics. We propose a surface fluorination strategy to construct dynamic dual hydrogen bonds on a semiconducting BiVO4 photoelectrode to overcome the kinetic limit of the oxidation of glycerol to produce formic acid (FA) in acidic media. Intensive spectroscopic characterizations confirm that double hydrogen bonds are formed by the interaction of the F-Bi-F sites of modified BiVO4 with water molecules, and the unique structure promotes the generation of hydroxyl radicals under light irradiation, which accelerates the kinetics of C-C bond cleavage. Theoretical investigations and infrared adsorption spectroscopy reveal that the double hydrogen bond enhances the C=O adsorption of the key intermediate product 1,3-dihydroxyacetone on the Bi-O sites to initiate the FA pathway. We fabricated a self-powered tandem device with an FA selectivity of 79% at the anode and a solar-to-H2 conversion efficiency of 5.8% at the cathode, and these results are superior to most reported results in acidic electrolytes.

High Coverage Sub-Nano Iridium Cluster on Core-Shell Cobalt-Cerium Bimetallic Oxide for Highly Efficient Full-pH Water Splitting.

The construction of sub-nanometer cluster catalysts (<1 nm) with almost complete exposure of active atoms serves as a promising avenue for the simultaneous enhancement of atom utilization efficiency and specific activity. Herein, a core-shell cobalt-cerium bimetallic oxide protected by high coverage sub-nanometer Ir clusters (denoted as Ir cluster@CoO/CeO2) is constructed by a confined in situ exsolution strategy. The distinctive core-shell structure endows Ir cluster@CoO/CeO2 with enhanced intrinsic activity and high conductivity, facilitating efficient charge transfer and full-pH water splitting. The Ir cluster@CoO/CeO2 achieves low overpotentials of 49/215, 52/390, and 54/243 mV at 10 mA cm-2 for hydrogen evolution reaction/oxygen evolution reaction (HER/OER) in 0.5 m H2SO4, 1.0 m PBS, and 1.0 m KOH, respectively. The small decline in performance after 300 h of operation renders it one of the most effective catalysts for full-pH water splitting. DFT calculations indicate that oriented electron transfer (along the path from Ce to Co and then to Ir) creates an electron-rich environment for surface Ir clusters. The reconstructed interface electronic environment provides optimized intermediates adsorption/desorption energy at the Ir site (for HER) and at the Ir-Co site (for OER), thus simultaneously speeding up the HER/OER kinetics.

Interface engineering of three-phase nickel-cobalt sulfide/nickel phosphide/iron phosphide heterostructure for enhanced water splitting and urea electrolysis.

Rational designing efficient transition metal-based multifunctional electrocatalysts is highly desirable for improving the efficiency of hydrogen production from water cracking. Herein, a self-supported three-phase heterostructure electrocatalyst of nickel-cobalt sulfide/nickel phosphide/iron phosphide (CoNi5S8-Ni2P-FeP2) was prepared by a two-step gas-phase sulfurization/phosphorization strategy. The heterostructure in CoNi5S8-Ni2P-FeP2 provides a favorable interfacial environment for electron transfer and synergistic interaction of multiphase active components, while the introduced electronegative P/S not only serves as a carrier for proton capture in the hydrogen evolution reaction (HER) process but also promotes the metal-electron outflow, which in turn accelerates the generation of high-valent Ni3+ species to enhance the catalytic activity of oxygen evolution reaction (OER) and urea oxidation reaction (UOR). As expected, CoNi5S8-Ni2P-FeP2 reveals excellent multifunctional electrocatalytic properties. An overpotential of 35/215 mV is required to reach 10 mA cm-2 for HER/OER. More encouragingly, a current of 100 mA cm-2 requires only 1.36 V for UOR with CoNi5S8-Ni2P-FeP2 as anode, which is much lower as compared to the OER (1.50 V). Besides, a two-electrode water/urea electrolyzer assembled based on CoNi5S8-Ni2P-FeP2 has a voltage of only 1.59/1.48 V when the system reaches 50 mA cm-2. This work provides a new idea for the design of energy-efficient water/urea-assisted water-splitting multifunctional catalysts with multi-component heterostructure synergistic interface engineering.

A replacement strategy for regulating local environment of single-atom Co-SxN4-x catalysts to facilitate CO2 electroreduction.

The performances of single-atom catalysts are governed by their local coordination environments. Here, a thermal replacement strategy is developed for the synthesis of single-atom catalysts with precisely controlled and adjustable local coordination environments. A series of Co-SxN4-x (x = 0, 1, 2, 3) single-atom catalysts are successfully synthesized by thermally replacing coordinated N with S at elevated temperature, and a volcano relationship between coordinations and catalytic performances toward electrochemical CO2 reduction is observed. The Co-S1N3 catalyst has the balanced COOH*and CO* bindings, and thus locates at the apex of the volcano with the highest performance toward electrochemical CO2 reduction to CO, with the maximum CO Faradaic efficiency of 98 ± 1.8% and high turnover frequency of 4564 h-1 at an overpotential of 410 mV tested in H-cell with CO2-saturated 0.5 M KHCO3, surpassing most of the reported single-atom catalysts. This work provides a rational approach to control the local coordination environment of the single-atom catalysts, which is important for further fine-tuning the catalytic performance.

Double solvent synthesis of ultrafine Pt nanoparticles supported on halloysite nanotubes for chemoselective cinnamaldehyde hydrogenation.

The development of highly active, low cost and durable catalysts for selective hydrogenation of aldehydes is imperative and challenging. In this contribution, we rationally constructed ultrafine Pt nanoparticles (Pt NPs) supported on the internal and external surfaces of halloysite nanotubes (HNTs) by a facile double solvent strategy. The influence of Pt loading, HNTs surface properties, reaction temperature, reaction time, H2 pressure and solvents on the performance of cinnamaldehyde (CMA) hydrogenation was analyzed. The optimal catalysts with the Pt loading of 3.8 wt% and the average Pt particle size of 2.98 nm exhibited outstanding catalytic activity for the hydrogenation of CMA to cinnamyl alcohol (CMO) with 94.1% conversion of CMA and 95.1% selectivity to CMO. More impressively, the catalyst showed excellent stability during six cycles of use. The ultra-small size and high dispersion of Pt NPs, the negative charge on the outer surface of HNTs, the -OH on the inner surface of HNTs, and the polarity of anhydrous ethanol solvent account for the outstanding catalytic performance. This work offers a promising way to develop high-efficiency catalysts with high CMO selectivity and stability by combining clay mineral halloysite and ultrafine nanoparticles.

Carbon-based single-atom catalysts: impacts of atomic coordination on the oxygen reduction reaction.

Slow oxygen reduction reaction (ORR) kinetics is the main factor restricting the development of fuel cells and metal-air batteries. Carbon-based single-atom catalysts (SACs) have the advantages of high electrical conductivity, maximal atom utilization, and high mass activity, thus showing great potential in exploring low-cost and high-efficiency ORR catalysts. For carbon-based SACs, the defects in the carbon support, the coordination of non-metallic heteroatoms, and the coordination number have a great influence on the adsorption of the reaction intermediates, thus significantly affecting the catalytic performance. Consequently, it is of vital importance to summarize the impacts of atomic coordination on the ORR. In this review, we focus on the regulation of the central atoms and coordination atoms of carbon-based SACs for the ORR. The survey involves various SACs, from noble metals (Pt) to transition metals (Fe, Co, Ni, Cu, etc.) and major group metals (Mg, Bi, etc.). At the same time, the influence of defects in the carbon support, the coordination of non-metallic heteroatoms (such as B, N, P, S, O, Cl, etc.), and the coordination number of the well-defined SACs on the ORR were put forward. Then, the impact of the neighboring metal monomers for SACs on the ORR performance is discussed. Finally, the current challenges and prospects for the future development of carbon-based SACs in coordination chemistry are presented.

Complementary Operando Spectroscopy identification of in-situ generated metastable charge-asymmetry Cu2-CuN3 clusters for CO2 reduction to ethanol.

Copper-based materials can reliably convert carbon dioxide into multi-carbon products but they suffer from poor activity and product selectivity. The atomic structure-activity relationship of electrocatalysts for the selectivity is controversial due to the lacking of systemic multiple dimensions for operando condition study. Herein, we synthesized high-performance CO2RR catalyst comprising of CuO clusters supported on N-doped carbon nanosheets, which exhibited high C2+ products Faradaic efficiency of 73% including decent ethanol selectivity of 51% with a partial current density of 14.4 mA/cm-2 at -1.1 V vs. RHE. We evidenced catalyst restructuring and tracked the variation of the active states under reaction conditions, presenting the atomic structure-activity relationship of this catalyst. Operando XAS, XANES simulations and Quasi-in-situ XPS analyses identified a reversible potential-dependent transformation from dispersed CuO clusters to Cu2-CuN3 clusters which are the optimal sites. This cluster can't exist without the applied potential. The N-doping dispersed the reduced Cun clusters uniformly and maintained excellent stability and high activity with adjusting the charge distribution between the Cu atoms and N-doped carbon interface. By combining Operando FTIR and DFT calculations, it was recognized that the Cu2-CuN3 clusters displayed charge-asymmetric sites which were intensified by CH3* adsorbing, beneficial to the formation of the high-efficiency asymmetric ethanol.

Ag/Ultrathin-Layered Double Hydroxide Nanosheets Induced by a Self-Redox Strategy for Highly Selective CO2 Reduction.

The carbon-neutral photocatalytic CO2 reduction reaction (CO2RR) enables the conversion of CO2 into hydrocarbon fuels or value-added chemicals under mild conditions. Achieving high selectivity for the desired products of the CO2RR remains challenging. Herein, a self-redox strategy is developed to construct strong interfacial bonds between Ag nanoparticles and an ultrathin CoAl-layered double hydroxide (U-LDH) nanosheet support, where the surface hydroxyl groups associated with oxygen vacancies of U-LDH play a critical role in the formation of the interface structure. The supported Ag@U-LDH acts as a highly efficient catalyst for CO2 reduction, resulting in a high CO evolution rate of 757 µmol gcat-1 h-1 and a CO selectivity of 94.5% under light irradiation. Such a high catalytic selectivity may represent a new record among current photocatalytic CO2RR to CO systems. The Ag-O-Co interface bonding is confirmed by Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and FTIR CO2 adsorption studies. The in situ FTIR measurements indicate that the formation of the *COOH intermediate is accelerated and the mass transfer is improved during the CO2RR. Density functional theory calculations show that the Ag-O-Co interface reduces the formation energy of the *COOH intermediate and accumulates localized charge. Experimental and theoretical analysis collectively demonstrates that the strong interface bonding between Ag and U-LDH activates the interface structure as catalytically CO2RR active sites, effectively optimizing the binding energies with reacted intermediates and facilitating the CO2RR performance.

Atomic-dispersed platinum anchored on porous alumina sheets as an efficient catalyst for diboration of alkynes.

Atomic-dispersed Pt anchored on defect-rich porous alumina sheets (Pt/dp-Al2O3) was accessed via a wet impregnation combined with pyrolysis method. These nanosheets functionalized by atomic-dispersed Pt possess a high density of active sites, exhibiting an exceptional catalytic activity combined with cyclic performance in the diboration of alkynes. The selectivity and conversion yield could reach as high as 97% and 98%, respectively.

Engineering a metal-organic framework derived Mn-N4-C x S y atomic interface for highly efficient oxygen reduction reaction.

Atomic interface engineering is an effective pathway to regulate the performance of single metal atom catalysts for electrochemical reactions in energy applications. Herein, we construct a sulfur modified Mn-N-C single atom catalyst through a metal-organic framework derived atomic interface strategy, which exhibits outstanding ORR activity with a half-wave potential of 0.916 V vs. RHE in alkaline media. Moreover, operando X-ray absorption spectroscopy analysis indicates that the isolated bond-length extending the low-valence Mn-N4-C x S y moiety serves as an active site during the ORR process. These findings suggest a promising method for the advancement of single atom catalysis.

Engineering unsymmetrically coordinated Cu-S1N3 single atom sites with enhanced oxygen reduction activity.

Atomic interface regulation is thought to be an efficient method to adjust the performance of single atom catalysts. Herein, a practical strategy was reported to rationally design single copper atoms coordinated with both sulfur and nitrogen atoms in metal-organic framework derived hierarchically porous carbon (S-Cu-ISA/SNC). The atomic interface configuration of the copper site in S-Cu-ISA/SNC is detected to be an unsymmetrically arranged Cu-S1N3 moiety. The catalyst exhibits excellent oxygen reduction reaction activity with a half-wave potential of 0.918 V vs. RHE. Additionally, through in situ X-ray absorption fine structure tests, we discover that the low-valent Cuprous-S1N3 moiety acts as an active center during the oxygen reduction process. Our discovery provides a universal scheme for the controllable synthesis and performance regulation of single metal atom catalysts toward energy applications.

High-Performance Quantum Dots with Synergistic Doping and Oxide Shell Protection Synthesized by Cation Exchange Conversion of Ternary-Composition Nanoparticles.

The insertion of cation impurities into quantum dots (QDs) as a dopant has been proved to be an efficient way to tailor their optical, electronic, and magnetic properties; however, the low quantum yield (QY) and poor photostability strongly limit their further applications. We report a strategy to coat a thin oxide shell around the heterovalent doped QDs to enhance their QYs and photostabilities simultaneously. In the case of Ag+-doped CdS QDs, the controlled cation exchange reaction between Cd2+ and ternary Ag3SbS3 nanoparticles not only realizes the Ag+ doping in CdS QDs but also generates a thin Sb2O3 shell around the surface of the QDs. Enabled by such, as-prepared CdS:Ag@Sb2O3 QDs exhibited enhanced photostability and high QY of 66.5%. We envision that the findings presented here will inspire more novel protocols for advancing the practical applications of doped QDs.