Interfacial π-p Electron Coupling Prompts Hydrogen Evolution Reaction Activity in Acidic Electrolyte.

The thermodynamically stable 2H-phase MoS2 is a brilliant material toward hydrogen evolution reaction (HER) owing to its excellent Gibbs free energy of hydrogen adsorption. Nevertheless, the poor intrinsic properties of 2H-MoS2 limit its electrocatalytic performances toward HER. In this work, graphitic carbon nitride covalently bridging 2H-MoS2 (MoS2/GCN) is proposed to construct robust HER electrocatalysts. The strong π-p electron coupling between the delocalized π electrons of GCN and the localized p electrons of S atoms sufficiently expose active sites and accelerate the reaction kinetics. To be specific, MoS2/GCN exhibits remarkable HER activity (160 mV at 10 mA·cm-2) and long-term durability. Importantly, MoS2/GCN also provides great potential for industrial application. Density functional theory (DFT) calculations disclose that the π-p electron coupling at the MoS2/GCN interface regulates the electronic structure of S atoms, consequently providing enhanced HER performance. This work presents a feasible pathway to develop advanced electrocatalysts for energy conversions.

Interfacial Co-O-Cu bonds prompt electrochemical nitrate reduction to ammonia in neutral electrolyte.

In this work, the formed interfacial Co-O-Cu bonds in Co-doped Cu(OH)2 (Co2-Cu(OH)2) sufficiently expose active sites and improve the reaction kinetics. As a result, the optimal Co2-Cu(OH)2 provides an amazing faradaic efficiency (91.6%), high selectivity (93.2%) and robust stability toward the NO3RR.

Regulating charge distribution of Cu3PdN nanocrystals for nitrate electroreduction to ammonia.

As-synthesized Cu3PdN nanocrystals displayed high faradaic efficiency and selectivity for nitrate-to-ammonia conversion. The excellent performances can be attributed to the charge redistribution in Cu3PdN as a result of modulations of the electronic structures of Pd and Cu atoms, which altered the adsorption activation energy of the intermediates during the nitrate reduction reaction process.

Long-Lasting Zinc-Iodine Batteries with Ultrahigh Areal Capacity and Boosted Rate Capability Enabled by Nickel Single-Atom Electrocatalysts.

Zinc-iodine (Zn-I2) batteries have garnered significant attention for their high energy density, low cost, and inherent safety. However, several challenges, including polyiodide dissolution and shuttling, sluggish iodine redox kinetics, and low electrical conductivity, limit their practical applications. Herein, we designed a highly efficient electrocatalyst for Zn-I2 batteries by uniformly dispersing Ni single atoms (NiSAs) on hierarchical porous carbon skeletons (NiSAs-HPC). In situ Raman analysis revealed that the conversion of soluble polyiodides (I3- and I5-) was significantly accelerated using NiSAs-HPC because of the remarkable electrocatalytic activity of NiSAs. The resulting Zn-I2 batteries with NiSAs-HPC/I2 cathodes delivered exceptional rate capability (121 mAh g-1 at 50 C), and ultralong cyclic stability (over 40 000 cycles at 50 C). Even under 11.6 mg cm-2 iodine, Zn-I2 batteries still exhibited an impressive cyclic stability with a capacity retention of 93.4% and 141 mAh g-1 after 10 000 cycles at 10 C.

A general strategy to generate oxygen vacancies in bimetallic layered double hydroxides for water oxidation.

A general electrocatalyst design for water splitting through generating oxygen vacancies in bimetallic layered double hydroxides by using carbon nitride is proposed. The excellent OER activity of the achieved bimetallic layered double hydroxides is attributed to oxygen vacancies, which reduce the energy barrier of the rate-determining step.

Single-atom Fe-N4 site for the hydrogenation of nitrobenzene: theoretical and experimental studies.

The hydrogenation of nitrobenzene to aniline is an important process in the industry of fine chemicals, but developing inexpensive catalysts with expected activity and selectivity still remains a challenge. By using density functional theory calculations, we demonstrated that the isolated Fe atom not only can weaken the adsorption of reactants and reaction intermediates as compared to Fe nanoparticles, but also remarkably decrease the reaction barrier for the hydrogenation of nitrobenzene to aniline. Thus, the Fe single-atom (Fe SA) catalyst is considered as an ideal catalyst for this reaction. This theoretical prediction has been subsequently confirmed by experimental results obtained for the Fe SAs loaded on N-doped hollow carbon spheres (Fe SAs/NHCSs) which achieved a conversion of 99% with a selectivity of 99% for the hydrogenation of nitrobenzene. The results significantly outperformed the Fe nanoparticles for this reaction. This work provides theoretical insight for the rational design of new catalytic systems with excellent catalytic properties.

Copper single-atom catalysts with photothermal performance and enhanced nanozyme activity for bacteria-infected wound therapy.

Nanozymes have become a new generation of antibiotics with exciting broad-spectrum antibacterial properties and negligible biological toxicity. However, their inherent low catalytic activity limits their antibacterial properties. Herein, Cu single-atom sites/N doped porous carbon (Cu SASs/NPC) is successfully constructed for photothermal-catalytic antibacterial treatment by a pyrolysis-etching-adsorption-pyrolysis (PEAP) strategy. Cu SASs/NPC have stronger peroxidase-like catalytic activity, glutathione (GSH)-depleting function, and photothermal property compared with non-Cu-doped NPC, indicating that Cu doping significantly improves the catalytic performance of nanozymes. Cu SASs/NPC can effectively induce peroxidase-like activity in the presence of H2O2, thereby generating a large amount of hydroxyl radicals (•OH), which have a certain killing effect on bacteria and make bacteria more susceptible to temperature. The introduction of near-infrared (NIR) light can generate hyperthermia to fight bacteria, and enhance the peroxidase-like catalytic activity, thereby generating additional •OH to destroy bacteria. Interestingly, Cu SASs/NPC can act as GSH peroxidase (GSH-Px)-like nanozymes, which can deplete GSH in bacteria, thereby significantly improving the sterilization effect. PTT-catalytic synergistic antibacterial strategy produces almost 100% antibacterial efficiency against Escherichia coli (E. coli) and methicillin-resistant Staphylococcus aureus (MRSA). In vivo experiments show a better PTT-catalytic synergistic therapeutic performance on MRSA-infected mouse wounds. Overall, our work highlights the wide antibacterial and anti-infective bio-applications of Cu single-atom-containing catalysts.

One-dimensional nitrogen doped porous carbon nano-array arranged by carbon nanotubes for electrochemical sensing ascorbic acid, dopamine and uric acid simultaneously.

In this work, one-dimensional nitrogen doped porous carbon nano-arrays arranged by carbon nanotube (1D CNTs@NPC) were first constructed, using a coating technology at room temperature and followed by high temperature carbonization. It was expected that the resulting glassy carbon electrodes modified by 1D CNTs@NPC (CNTs@NPC/GCE) could express different electrochemical responses to ascorbic acid (AA), dopamine (DA), uric acid (UA), by virtue of the synergistic-improved effect between CNTs and NPC. Under the optimized conditions, there were excellent analytical parameters for CNTs@NPC/GCE to detect AA, DA and UA, i.e. a wide linear range of 40-2100µM for AA, 0.5-49µM for DA and 3-50µM for AA with low detection limits of 0.36µM, 0.02µmol l-1and 0.57µM respectively. Importantly, the proposed CNTs@NPC/GCE was efficiently applied to determine AA, DA and UA in some real samples with high stability, reproducibility and selectivity. This work will offer an efficient potential for diagnosing ascorbic acid, dopamine or uric acid-related diseases on clinical testing in future.

Dopamine polymer derived isolated single-atom site metals/N-doped porous carbon for benzene oxidation.

Isolated single-atom site metals/nitrogen-doped porous carbon (ISAS M/NPC, M = Fe, Co, Ni) catalysts are successfully prepared by a top-down polymerization-pyrolysis-etching-activation (PPEA) strategy, which uses dopamine as the precursor. Due to the isolated single atom Fe active sites and porous structure, the ISAS Fe/NPC catalyst displays a high benzene conversion up to 42.6% and nearly 100% phenol selectivity.

Synergistically Interactive Pyridinic-N-MoP Sites: Identified Active Centers for Enhanced Hydrogen Evolution in Alkaline Solution.

For electrocatalysts for the hydrogen evolution reaction (HER), encapsulating transition metal phosphides (TMPs) into nitrogen-doped carbon materials has been known as an effective strategy to elevate the activity and stability. Yet still, it remains unclear how the TMPs work synergistically with the N-doped support, and which N configuration (pyridinic N, pyrrolic N, or graphitic N) contributes predominantly to the synergy. Here we present a HER electrocatalyst (denoted as MoP@NCHSs) comprising MoP nanoparticles encapsulated in N-doped carbon hollow spheres, which displays excellent activity and stability for HER in alkaline media. Results of experimental investigations and theoretical calculations indicate that the synergy between MoP and the pyridinic N can most effectively promote the HER in alkaline media.

Three-dimensional open nano-netcage electrocatalysts for efficient pH-universal overall water splitting.

High-efficiency water electrolysis is the key to sustainable energy. Here we report a highly active and durable RuIrOx (x ≥ 0) nano-netcage catalyst formed during electrochemical testing by in-situ etching to remove amphoteric ZnO from RuIrZnOx hollow nanobox. The dispersing-etching-holing strategy endowed the porous nano-netcage with a high exposure of active sites as well as a three-dimensional accessibility for substrate molecules, thereby drastically boosting the electrochemical surface area (ECSA). The nano-netcage catalyst achieved not only ultralow overpotentials at 10 mA cm-2 for hydrogen evolution reaction (HER; 12 mV, pH = 0; 13 mV, pH = 14), but also high-performance overall water electrolysis over a broad pH range (0 ~ 14), with a potential of mere 1.45 V (pH = 0) or 1.47 V (pH = 14) at 10 mA cm-2. With this universal applicability of our electrocatalyst, a variety of readily available electrolytes (even including waste water and sea water) could potentially be directly used for hydrogen production.

Regulating the coordination structure of single-atom Fe-NxCy catalytic sites for benzene oxidation.

Atomically dispersed metal-N-C structures are efficient active sites for catalyzing benzene oxidation reaction (BOR). However, the roles of N and C atoms are still unclear. We report a polymerization-regulated pyrolysis strategy for synthesizing single-atom Fe-based catalysts, and present a systematic study on the coordination effect of Fe-NxCy catalytic sites in BOR. The special coordination environment of single-atom Fe sites brings a surprising discovery: Fe atoms anchored by four-coordinating N atoms exhibit the highest BOR performance with benzene conversion of 78.4% and phenol selectivity of 100%. Upon replacing coordinated N atoms by one or two C atoms, the BOR activities decrease gradually. Theoretical calculations demonstrate the coordination pattern influences not only the structure and electronic features, but also the catalytic reaction pathway and the formation of key oxidative species. The increase of Fe-N coordination number facilitates the generation and activation of the crucial intermediate O=Fe=O species, thereby enhancing the BOR activity.

Isolated Iron Single-Atomic Site-Catalyzed Chemoselective Transfer Hydrogenation of Nitroarenes to Arylamines.

Selective hydrogenation of nitroarenes to arylamines is a great challenge because of the complicated mechanism and competitive hydrogenation of reducible functional groups. Isolated single-atomic site catalysts, benefitting from their uniform and well-defined catalytic sites, are promising to achieve high activity and selectivity. Herein, we prepared an isolated iron single-atomic catalyst supported on ordered mesoporous nitrogen-doped carbon (Fe1/N-C). The as-prepared Fe1/N-C showed excellent activity and tolerance for functional groups in the transfer hydrogenation of nitroarenes over hydrazine hydrate. Density functional theory calculations revealed that the single atomically dispersed, partially positively charged Fe atoms and the lowered energy barrier collectively contribute to the superior hydrogenation performances for nitroarenes.

Copper atom-pair catalyst anchored on alloy nanowires for selective and efficient electrochemical reduction of CO2.

The electrochemical reduction of CO2 could play an important role in addressing climate-change issues and global energy demands as part of a carbon-neutral energy cycle. Single-atom catalysts can display outstanding electrocatalytic performance; however, given their single-site nature they are usually only amenable to reactions that involve single molecules. For processes that involve multiple molecules, improved catalytic properties could be achieved through the development of atomically dispersed catalysts with higher complexities. Here we report a catalyst that features two adjacent copper atoms, which we call an 'atom-pair catalyst', that work together to carry out the critical bimolecular step in CO2 reduction. The atom-pair catalyst features stable Cu10-Cu1x+ pair structures, with Cu1x+ adsorbing H2O and the neighbouring Cu10 adsorbing CO2, which thereby promotes CO2 activation. This results in a Faradaic efficiency for CO generation above 92%, with the competing hydrogen evolution reaction almost completely suppressed. Experimental characterization and density functional theory revealed that the adsorption configuration reduces the activation energy, which generates high selectivity, activity and stability under relatively low potentials.

Toward Bifunctional Overall Water Splitting Electrocatalyst: General Preparation of Transition Metal Phosphide Nanoparticles Decorated N-Doped Porous Carbon Spheres.

It is very important to explore novel synthesis strategies for constructing highly active and inexpensive electrocatalysts for water-splitting. In present work, a novel and efficient coordination-polymerization-pyrolysis (CPP) strategy was developed to prepare cobalt phosphide nanoparticles modified N-doped porous carbon spheres (CoP@NPCSs) hybrids as a powerful catalyst for overall water-splitting (OWS). It can be found that both the carbonization temperatures and the metal contents affect the electrocatalytic performances. As a result, a device assembled with CoP@NPCSs demonstrates low potential (1.643 V @ 10 mA·cm-2) and good stabilization for OWS. Besides, other transition metal phosphides (TMPs)-based materials also can be synthesized by the CPP approach, evidencing the generality of the CPP strategy. Here, we not only constructs a high-efficiency OWS catalyst, but also broadens the synthetic methodology of TMPs from nanoscale.

Ir/g-C3N4/Nitrogen-Doped Graphene Nanocomposites as Bifunctional Electrocatalysts for Overall Water Splitting in Acidic Electrolytes.

Nitrogen-doped graphene (NG) chemically coupled with graphitic carbon nitride (g-C3N4) may facilitate the kinetics of overall electrochemical water splitting. Herein, a facile strategy is adopted to synthesize monodispersed Ir nanoparticles on g-C3N4/NG layers. Benefiting from the synergistic effect between different components of the catalyst, the optimal Ir/g-C3N4/NG catalyst with a low content of Ir (5.9 wt %) exhibits highly active for electrochemical water splitting in acidic electrolyte. Specifically, as a hydrogen evolution reaction catalyst, the optimal Ir/g-C3N4/NG exhibits a Tafel slope of 22 mV·dec-1. The optimal catalyst requires an overpotential of 22 mV to reach the current density of 10 mA·cm-2, the value of which is superior to Ir/NG (32 mV) and 20 wt % Pt/C (28 mV) catalysts; as an oxygen evolution reaction catalyst, it also achieve the Tafel slope of only 72.8 mV·dec-1. At the overpotential of 300 mV, the mass activity of the optimal Ir/g-C3N4/NG catalyst is 2.8 times as large as that of 5.7 wt % Ir/NG catalyst. More significantly, as a bifunctional catalyst, the optimal Ir/g-C3N4/NG achieves a current density of 10 mA·cm-2 with a potential of only 1.56 V and displays good stability for overall water splitting. This work provides a new strategy to design highly efficient acidic catalysts for electrochemical overall water splitting.

Ordered Porous Nitrogen-Doped Carbon Matrix with Atomically Dispersed Cobalt Sites as an Efficient Catalyst for Dehydrogenation and Transfer Hydrogenation of N-Heterocycles.

Single-atom catalysts (SACs) have been explored widely as potential substitutes for homogeneous catalysts. Isolated cobalt single-atom sites were stabilized on an ordered porous nitrogen-doped carbon matrix (ISAS-Co/OPNC). ISAS-Co/OPNC is a highly efficient catalyst for acceptorless dehydrogenation of N-heterocycles to release H2 . ISAS-Co/OPNC also exhibits excellent catalytic activity for the reverse transfer hydrogenation (or hydrogenation) of N-heterocycles to store H2 , using formic acid or external hydrogen as a hydrogen source. The catalytic performance of ISAS-Co/OPNC in both reactions surpasses previously reported homogeneous and heterogeneous precious-metal catalysts. The reaction mechanisms are systematically investigated using first-principles calculations and it is suggested that the Eley-Rideal mechanism is dominant.

Quantitative Study of Charge Carrier Dynamics in Well-Defined WO3 Nanowires and Nanosheets: Insight into the Crystal Facet Effect in Photocatalysis.

Photocatalysts with different morphologies and specific exposed facets usually exhibit distinguished activities. Previous researches have focused on revealing the essence of the facet effect in photocatalysis; however, quantitative analyses on the differences of carrier dynamic between different facets are scarce. Herein, we successfully synthesized WO3 nanosheets and nanowires with dominant exposed facets of {001} and {110}, respectively. The lower hole effective mass on {110} (0.94 m0) than on {001} (1.28 m0) calculated by density functional theory leads to the higher hole mobility on {110} (4.92 cm2 V-1 s-1) than on {001} (3.14 cm2 V-1 s-1). Combined with the Einstein equation and the lifetime of the hole, the calculated hole diffusion length on {110} (74.8 nm) is larger than on {001} (53.4 nm). Overall, the lower hole effective mass, higher hole mobility, and greater hole diffusion length on {110} collectively result in a photocatalytic activity on benzyl alcohol oxidation 2.46 times as high as that on {001}.

Single Tungsten Atoms Supported on MOF-Derived N-Doped Carbon for Robust Electrochemical Hydrogen Evolution.

Tungsten-based catalysts are promising candidates to generate hydrogen effectively. In this work, a single-W-atom catalyst supported on metal-organic framework (MOF)-derived N-doped carbon (W-SAC) for efficient electrochemical hydrogen evolution reaction (HER), with high activity and excellent stability is reported. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption fine structure (XAFS) spectroscopy analysis indicate the atomic dispersion of the W species, and reveal that the W1 N1 C3 moiety may be the favored local structure for the W species. The W-SAC exhibits a low overpotential of 85 mV at a current density of 10 mA cm-2 and a small Tafel slope of 53 mV dec-1 , in 0.1 m KOH solution. The HER activity of the W-SAC is almost equal to that of commercial Pt/C. Density functional theory (DFT) calculation suggests that the unique structure of the W1 N1 C3 moiety plays an important role in enhancing the HER performance. This work gives new insights into the investigation of efficient and practical W-based HER catalysts.

A Bimetallic Zn/Fe Polyphthalocyanine-Derived Single-Atom Fe-N4 Catalytic Site:A Superior Trifunctional Catalyst for Overall Water Splitting and Zn-Air Batteries.

Developing an efficient single-atom material (SAM) synthesis and exploring the energy-related catalytic reaction are important but still challenging. A polymerization-pyrolysis-evaporation (PPE) strategy was developed to synthesize N-doped porous carbon (NPC) with anchored atomically dispersed Fe-N4 catalytic sites. This material was derived from predesigned bimetallic Zn/Fe polyphthalocyanine. Experiments and calculations demonstrate the formed Fe-N4 site exhibits superior trifunctional electrocatalytic performance for oxygen reduction, oxygen evolution, and hydrogen evolution reactions. In overall water splitting and rechargeable Zn-air battery devices containing the Fe-N4 SAs/NPC catalyst, it exhibits high efficiency and extraordinary stability. This current PPE method is a general strategy for preparing M SAs/NPC (M=Co, Ni, Mn), bringing new perspectives for designing various SAMs for catalytic application.