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Superbugs in groundwater are posing severe health risks through waterborne pathways. An emerging approach for green disinfection lies at photocatalysis, which levers the locally generated superoxide radical (·O2−) for neutralization. However, the spin-forbidden feature of O2 hinders the photocatalytic generation of active ·O2−, and thus greatly limited the disinfection efficiency, especially for real groundwater with a low dissolved oxygen (DO) concentration. Herein, we report a class of strained Mo4/3B2-xTz MBene (MB) with enhanced adsorption/activation of molecular O2 for photocatalytic disinfection, and find the strain induced spin polarization of In2S3/Mo4/3B2-xTz (IS/MB) can facilitate the spin-orbit hybridization of Mo sites and O2 to overcome the spin-forbidden of O2, which results in a 16.59-fold increase in ·O2− photocatalytic production in low DO condition (2.46 mg L-1). In particular, we demonstrate an In2S3/Mo4/3B2-xTz (50 mg)-based continuous-flow-disinfection system stably operates over 62 h and collects 37.2 L bacteria-free groundwater, which represents state-of-the-art photodisinfection materials for groundwater disinfection. Most importantly, the disinfection capacity of the continuous-flow-disinfection system is 25 times higher than that of commercial sodium hypochlorite (NaOCl), suggesting the practical potential for groundwater purification. Photocatalytic disinfection is a known pollution-free water treatment strategy. However, its efficiency is limited due to the spin-forbidden feature of O2, which hinders photocatalytic ·O2− formation and limits its disinfection efficiency. Here the authors produce a strained Mo4/3B2-xTz MBene that can increase ·O2− photocatalytic production, which results in high levels of photocatalytic disinfection. [ABSTRACT FROM AUTHOR]

The atomic-thick anticorrosion coating for copper (Cu) electrodes is essential for the miniaturisation in the semiconductor industry. Graphene has long been expected to be the ultimate anticorrosion material, however, its real anticorrosion performance is still under great controversy. Specifically, strong electronic couplings can limit the interfacial diffusion of corrosive molecules, whereas they can also promote the surficial galvanic corrosion. Here, we report the enhanced anticorrosion for Cu simply via a bilayer graphene coating, which provides protection for more than 5 years at room temperature and 1000 h at 200 °C. Such excellent anticorrosion is attributed to a nontrivial Janus-doping effect in bilayer graphene, where the heavily doped bottom layer forms a strong interaction with Cu to limit the interfacial diffusion, while the nearly charge neutral top layer behaves inertly to alleviate the galvanic corrosion. Our study will likely expand the application scenarios of Cu under various extreme operating conditions. Atomically thick anticorrosion coatings on Cu are desired for future applications, but still at its infancy. Here, the authors report a Janus-doping mechanism in bilayer graphene on Cu substrate that results in an enhanced anticorrosion performance. [ABSTRACT FROM AUTHOR]

Despite the extremely high hardness of recently proposed high-entropy carbides (HECs), the low fracture toughness limits their applications in harsh mechanical environment. Here, we introduce a metastability engineering strategy to achieve superhard HECs with enhanced toughness via in-situ metastable particles. This is realized by developing a (WTaNbZrTi)C HEC showing a solid solution matrix with uniformly dispersed in-situ tetragonal and monoclinic ZrO2 particles. Apart from a high hardness of 21.0 GPa, the HEC can obtain an enhanced fracture toughness of 5.89 MPa·m1/2, significantly exceeding the value predicted by rule of mixture and that of other reported HECs. The toughening effect is primarily attributed to the transformation of the metastable tetragonal ZrO2 particles under mechanical loading, which promotes crack tip shielding mechanisms including crack deflection, crack bridging and crack branching. The work demonstrates the concept of using in-situ metastable particles for toughening bulk high-entropy ceramics by taking advantage of their compositional flexibility. High-entropy carbides (HECs) with high hardness usually suffer from low fracture toughness. Here, the authors demonstrate a metastability engineering strategy for toughening superhard HECs by introducing in situ metastable ceramic particles, which are transformable under mechanical loading. [ABSTRACT FROM AUTHOR]

Electrochemical conversion of nitrate to ammonia offers an efficient approach to reducing nitrate pollutants and a potential technology for low-temperature and low-pressure ammonia synthesis. However, the process is limited by multiple competing reactions and NO3− adsorption on cathode surfaces. Here, we report a Fe/Cu diatomic catalyst on holey nitrogen-doped graphene which exhibits high catalytic activities and selectivity for ammonia production. The catalyst enables a maximum ammonia Faradaic efficiency of 92.51% (−0.3 V(RHE)) and a high NH3 yield rate of 1.08 mmol h−1 mg−1 (at − 0.5 V(RHE)). Computational and theoretical analysis reveals that a relatively strong interaction between NO3− and Fe/Cu promotes the adsorption and discharge of NO3− anions. Nitrogen-oxygen bonds are also shown to be weakened due to the existence of hetero-atomic dual sites which lowers the overall reaction barriers. The dual-site and hetero-atom strategy in this work provides a flexible design for further catalyst development and expands the electrocatalytic techniques for nitrate reduction and ammonia synthesis. Nitrate electroreduction to ammonia can decrease pollutants and produce high-value ammonia. Here, the authors design a Fe/Cu diatomic catalyst on nitrogen-doped graphene, which exhibits high catalytic activities of and selectivity for ammonia. [ABSTRACT FROM AUTHOR]

The chemical interrogation of individual atomic adsorbates on a surface significantly contributes to understanding the atomic-scale processes behind on-surface reactions. However, it remains highly challenging for current imaging or spectroscopic methods to achieve such a high chemical spatial resolution. Here we show that single oxygen adatoms on a boron monolayer (i.e., borophene) can be identified and mapped via ultrahigh vacuum tip-enhanced Raman spectroscopy (UHV-TERS) with ~4.8 Å spatial resolution and single bond (B–O) sensitivity. With this capability, we realize the atomically defined, chemically homogeneous, and thermally reversible oxidation of borophene via atomic oxygen in UHV. Furthermore, we reveal the propensity of borophene towards molecular oxygen activation at room temperature and phase-dependent chemical properties. In addition to offering atomic-level insights into the oxidation of borophene, this work demonstrates UHV-TERS as a powerful tool to probe the local chemistry of surface adsorbates in the atomic regime with widespread utilities in heterogeneous catalysis, on-surface molecular engineering, and low-dimensional materials. Here, the authors report the use of ultrahigh vacuum tip-enhanced Raman spectroscopy to characterize the oxidation processes of monolayer borophene with atomic-scale resolution and single-bond sensitivity, demonstrating the potential of the technique for probing the local chemistry of surface adsorbates on low-dimensional materials. [ABSTRACT FROM AUTHOR]

Electrochemical oxygen reduction could proceed via either 4e−-pathway toward maximum chemical-to-electric energy conversion or 2e−-pathway toward onsite H2O2 production. Bulk Pt catalysts are known as the best monometallic materials catalyzing O2-to-H2O conversion, however, controversies on the reduction product selectivity are noted for atomic dispersed Pt catalysts. Here, we prepare a series of carbon supported Pt single atom catalyst with varied neighboring dopants and Pt site densities to investigate the local coordination environment effect on branching oxygen reduction pathway. Manipulation of 2e− or 4e− reduction pathways is demonstrated through modification of the Pt coordination environment from Pt-C to Pt-N-C and Pt-S-C, giving rise to a controlled H2O2 selectivity from 23.3% to 81.4% and a turnover frequency ratio of H2O2/H2O from 0.30 to 2.67 at 0.4 V versus reversible hydrogen electrode. Energetic analysis suggests both 2e− and 4e− pathways share a common intermediate of *OOH, Pt-C motif favors its dissociative reduction while Pt-S and Pt-N motifs prefer its direct protonation into H2O2. By taking the Pt-N-C catalyst as a stereotype, we further demonstrate that the maximum H2O2 selectivity can be manipulated from 70 to 20% with increasing Pt site density, providing hints for regulating the stepwise oxygen reduction in different application scenarios. Controlling O2 reduction pathways can help optimize catalytic activity and product selectivity. Here the authors report facile manipulation of 2e‒ /4e‒ pathways on Pt-coordinated motifs by varying the Pt site density or the coordination environment. [ABSTRACT FROM AUTHOR]

Single-atom catalysts (SACs) have been applied in many fields due to their superior catalytic performance. Because of the unique properties of the single-atom-site, using the single atoms as catalysts to synthesize SACs is promising. In this work, we have successfully achieved Co1 SAC using Pt1 atoms as catalysts. More importantly, this synthesis strategy can be extended to achieve Fe and Ni SACs as well. X-ray absorption spectroscopy (XAS) results demonstrate that the achieved Fe, Co, and Ni SACs are in a M1-pyrrolic N4 (M= Fe, Co, and Ni) structure. Density functional theory (DFT) studies show that the Co(Cp)2 dissociation is enhanced by Pt1 atoms, thus leading to the formation of Co1 atoms instead of nanoparticles. These SACs are also evaluated under hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), and the nature of active sites under HER are unveiled by the operando XAS studies. These new findings extend the application fields of SACs to catalytic fabrication methodology, which is promising for the rational design of advanced SACs. Synthesizing single-atom catalysts through a general method presents a great challenge. Here the authors report that Fe, Co and Ni single-atom catalysts can be obtained using pre-located isolated Pt atoms as the catalyst and identify the role of Pt single atoms in the synthesis process. [ABSTRACT FROM AUTHOR]

As a 100% atom-economy process, direct oxidation of methane into methanol remains as a grand challenge due to the dilemma between activation of methane and over-oxidation of methanol. Here, we report that water enabled mild oxidation of methane into methanol with >99% selectivity over Au single atoms on black phosphorus (Au1/BP) nanosheets under light irradiation. The mass activity of Au1/BP nanosheets reached 113.5 μmol gcatal−1 in water pressured with 33 bar of mixed gas (CH4:O2 = 10:1) at 90 °C under light irradiation (1.2 W), while the activation energy was 43.4 kJ mol−1. Mechanistic studies revealed that water assisted the activation of O2 to generate reactive hydroxyl groups and •OH radicals under light irradiation. Hydroxyl groups reacted with methane at Au single atoms to form water and CH3* species, followed by oxidation of CH3* via •OH radicals into methanol. Considering the recycling of water during the whole process, we can also regard water as a catalyst. It is important but challenging to oxidize methane by O2 into methanol under ambient conditions. Here, the authors achieved mild oxidation of methane into methanol over Au single atoms on black phosphorus nanosheets with the help of water under light irradiation. [ABSTRACT FROM AUTHOR]

Despite tremendous importance in catalysis, the design of oxide-metal interface has been hampered by the limited understanding of the nature of interfacial sites and the oxide-metal interaction (OMI). Through construction of well-defined Cu2O/Pt, Cu2O/Ag and Cu2O/Au interfaces, we find that Cu2O nanostructures (NSs) on Pt exhibit much lower thermal stability than on Ag and Au, although they show the same structure. The activities of these interfaces are compared for CO oxidation and follow the order of Cu2O/Pt > Cu2O/Au > Cu2O/Ag. OMI is found to determine the activity and stability of supported Cu2O NSs, which could be described by the formation energy of interfacial oxygen vacancy. Further, electronic interaction between Cu+ and metal substrates is found center to OMI, where the d band center could be used as a key descriptor. Our study provides insight for OMI and for the development of Cu-based catalysts for low temperature oxidation reactions. The design of oxide-metal interface for heterogeneous catalysis has been hampered by the limited fundamental understanding. Here, the authors demonstrate that the activities of cuprous oxide nanostructures for CO oxidation can be tuned via the oxide-metal (Cu2O/M, M = Pt, Ag, Au) interaction. [ABSTRACT FROM AUTHOR]

Building upon the d-band reactivity theory in surface chemistry and catalysis, we develop a Bayesian learning approach to probing chemisorption processes at atomically tailored metal sites. With representative species, e.g., *O and *OH, Bayesian models trained with ab initio adsorption properties of transition metals predict site reactivity at a diverse range of intermetallics and near-surface alloys while naturally providing uncertainty quantification from posterior sampling. More importantly, this conceptual framework sheds light on the orbitalwise nature of chemical bonding at adsorption sites with d-states characteristics ranging from bulk-like semi-elliptic bands to free-atom-like discrete energy levels, bridging the complexity of electronic descriptors for the prediction of novel catalytic materials. Developing a generalizable model to describe adsorption processes at metal surfaces can be extremely challenging due to complex phenomena involved. Here the authors introduce a Bayesian learning approach based on ab initio data and the d-band model to capture the essential physics of adsorbate–substrate interactions. [ABSTRACT FROM AUTHOR]

Understanding the nature of active sites is crucial in heterogeneous catalysis, and dynamic changes of catalyst structures during reaction turnover have brought into focus the dynamic nature of active sites. However, much less is known on how the structural dynamics couples with elementary reactions. Here we report an anomalous decrease in reaction free energies and barriers on dynamical sub-nanometer Au clusters. We calculate temperature dependence of free energies using ab initio molecular dynamics, and find significant entropic effects due to solid-to-liquid phase transitions of the Au clusters induced by adsorption of different states along the reaction coordinate. This finding demonstrates that catalyst dynamics can play an important role in catalyst activity. Understanding the dynamic evolution of the catalysts' structure under reaction conditions is crucial in heterogeneous catalysis. Here the authors use ab initio molecular dynamics simulations to show an anomalous decrease in reaction free energies and barriers on dynamical sub-nanometer Au clusters supported on MgO(001). [ABSTRACT FROM AUTHOR]

The rational design of heterogeneous catalysts relies on the efficient survey of mechanisms by density functional theory (DFT). However, massive reaction networks cannot be sampled effectively as they grow exponentially with the size of reactants. Here we present a statistical principal component analysis and regression applied to the DFT thermochemical data of 71 C 1 –C 2 species on 12 close-packed metal surfaces. Adsorption is controlled by covalent (d -band center) and ionic terms (reduction potential), modulated by conjugation and conformational contributions. All formation energies can be reproduced from only three key intermediates (predictors) calculated with DFT. The results agree with accurate experimental measurements having error bars comparable to those of DFT. The procedure can be extended to single-atom and near-surface alloys reducing the number of explicit DFT calculation needed by a factor of 20, thus paving the way for a rapid and accurate survey of whole reaction networks on multimetallic surfaces. Assessing catalytic mechanisms using DFT calculations greatly aids catalyst design, but is impractical for large molecules. Here the authors develop a statistical learning-based thermochemical model for estimating adsorption of organics onto metals, retaining DFT accuracy while reducing the number of calculations by a factor of 20. [ABSTRACT FROM AUTHOR]