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Understanding the characteristics of interfacial hydroxyl (OH) at the solid/liquid electrochemical interface is crucial for deciphering synergistic catalysis. However, it remains challenging to elucidate the influences of spatial distance between interfacial OH and neighboring reactants on reaction kinetics at the atomic level. Herein, we visualize the distance-dependent synergistic interaction in heterogeneous dual-site catalysis by using ex-situ infrared nanospectroscopy and in situ infrared spectroscopy techniques. These spectroscopic techniques achieve direct identification of the spatial distribution of synergistic species and reveal that OH facilitates the reactant deprotonation process depending on site distances in dual-site catalysts. Via modulating Ir–Co pair distances, we find that the dynamic equilibrium between generation and consumption of OH accounts for high-efficiency synergism at the optimized distance of 7.9 Å. At farther or shorter distances, spatial inaccessibility and resistance of OH with intermediates lead to OH accumulation, thereby diminishing the synergistic effect. Hence, a volcano-shaped curve has been established between the spatial distance and mass activity using formic acid oxidation as the probe reaction. This notion could also be extended to oxophilic metals, like Ir–Ru pairs, where volcano curves and dynamic equilibrium further evidence the universal significance of spatial distances.

Manipulation of the spin state holds great promise to improve the electrochemical activity of transition metal-based catalysts. However, the underlying relationship between the nonplanar metal coordination environment and spin states remains to be explored. Herein, we report the precise regulation of nonplanar Fe atomic d-orbital energy level into an irregular tetrahedral crystal field configuration by introducing P atoms. With the increase of P coordination number, the spin magnetic moment decreases linearly from 3.8 μB to 0.2 μB, and the high spin content decreases linearly from 31% to 5%. Significantly, a volcanic curve between the spin states of Fe-based catalysts (Fe–NxPy) and oxygen reduction reaction (ORR) activity has been unequivocally established based on the thermodynamic results. Thus, the Fe–N3P1catalyst with a 19% medium spin state experimentally exhibits the optimal reaction activity with a high half-wave potential of 0.92 V. These findings indicate that regulating electron spin moments through coordination engineering is a promising catalyst design strategy, providing important insights into spin catalysis.

Tailoring the local microenvironment of a single-atom active site is an effective pathway to promote electrocatalytic performance. Herein, we introduced a sulfur site to address the undesirable electron selectivity of a single-atom Fe-N4catalyst for oxygen reduction reaction (ORR). Comprehensive X-ray spectroscopic results, coupled with theoretical calculations, reveal that the introduction of a second-shell S site optimizes the local electron distribution of the Fe-N4moiety, enhancing its ORR activity. Furthermore, in situsynchrotron spectroscopy demonstrates that the presence of S in the Fe-N4moiety facilitates the breakage of the O-O bonding by reinforcing the adsorption of *OOH intermediates, accounting for enhanced ORR activity and four-electron selectivity. The well-designed catalyst exhibits satisfactory alkaline ORR activity, featuring a half-wave potential of 0.93 V versus reversible hydrogen electrode. Importantly, it effectively suppresses the yield of hydrogen peroxide to 4%, achieving a maximum power density of 241.1 mW cm-2in a Zn–air battery.

Manipulation of selectivity in the catalytic electrochemical carbon dioxide reduction reaction (eCO2RR) poses significant challenges due to inevitable structure reconstruction. One approach is to develop effective strategies for controlling reaction pathways to gain a deeper understanding of mechanisms in robust CO2RR systems. In this work, by precise introduction of 1,10-phenanthroline as a bidentate ligand modulator, the electronic property of the copper site was effectively regulated, thereby directing selectivity switch. By modification of [Cu3(btec)(OH)2]n, the use of [Cu2(btec)(phen)2]n·(H2O)nachieved the selectivity switch from ethylene (faradaic efficiency (FE) = 41%, FEC2+= 67%) to methane (FECH4= 69%). Various in situ spectroscopic characterizations revealed that [Cu2(btec)(phen)2]n·(H2O)npromoted the hydrogenation of *CO intermediates, leading to methane generation instead of dimerization to form C2+products. Acting as a delocalized p-conjugation scaffold, 1,10-phenanthroline in [Cu2(btec)(phen)2]n·(H2O)nhelps stabilize Cud+. This work presents a novel approach to regulate the coordination environment of active sites with the aim of selectively modulating the CO2RR.

Rational design of well-defined active sites is crucial for promoting sluggish oxygen reduction reactions. Herein, leveraging the surfactant-oriented and solvent–ligand effects, we develop a facile self-assembly strategy to construct a core–shell catalyst comprising a high-index Pt shell encapsulating a PtCu3intermetallic core with efficient oxygen-reduction performance. Without undergoing a high-temperature route, the ordered PtCu3is directly fabricated through the accelerated reduction of Cu2+, followed by the deposition of the remaining Pt precursor onto its surface, forming high-index steps oriented by the steric hindrance of surfactant. This approach results in a high half-wave potential of 0.911 V versus reversible hydrogen electrode, with negligible deactivation even after 15000-cycle operation. Operandospectroscopies identify that this core–shell catalyst facilitates the conversion of oxygen-involving intermediates and ensures antidissolution ability. Theoretical investigations rationalize that this improvement is attributed to reinforced electronic interactions around high-index Pt, stabilizing the binding strength of rate-determining OHadsspecies.

Electrocatalytic reduction of nitrate to ammonia (NO3RR) is gaining attention for low carbon emissions and environmental protection. However, low ammonia production rate and poor selectivity have remained major challenges in this multi-proton coupling process. Herein, we report a facile strategy toward a novel Fe-based hybrid structure composed of Fe single atoms and Fe3C atomic clusters that demonstrates outstanding performance for synergistic electrocatalytic NO3RR. By operandosynchrotron Fourier transform infrared spectroscopy and theoretical computation, we clarify that Fe single atoms serve as the active site for NO3RR, while Fe3C clusters facilitate H2O dissociation to provide protons (*H) for continued hydrogenation reactions. As a result, the Fe-based electrocatalyst exhibits ammonia Faradaic efficiency of nearly 100%, with a corresponding production rate of 24768 μg h–1cm–2at −0.4 V vs RHE, exceeding most reported metal-based catalysts. This research provides valuable guidance toward multi-step reactions.

Exploring the atomic interaction mechanisms of dense single-atom catalysts (SACs) is of great significance for their application in oxygen reduction reaction (ORR). However, the intrinsic mechanism of the site-distance effect on the catalytic performance has been largely ignored. Here, we demonstrate the site-distance effect of Fe–Rhx@NC catalysts in ORR theoretically and experimentally. Bader charge analysis reveals that the strong interaction between Fe and Rh atoms at a certain atomic distance (dFe–Rh) alters the catalytic electronic structure, facilitating the optimization of catalyst adsorption strength. Motivated by the theoretical calculations, we designed and synthesized the Fe–Rhx@NC catalysts through a spatial confinement strategy. The characterization results prove that the Fe–Rh2@NC has the optimal dFe–Rh, which improves its intrinsic ORR activity, providing a half wave potential of 0.91 V, higher than that of the commercial Pt/C (0.86 V). This study emphasizes the importance of determining the basic mechanism of the site-distance effect in dissimilar metal atoms catalysts, which is conducive to the design of efficient catalyst systems for practical applications.

The emerging metal nanocluster provides a platform for the investigation of structural features, unique properties, and structure–property correlation of nanomaterials at the atomic level. Construction of open sites on the surface of the metal nanocluster is a long-pursued but challenging goal. Herein, we realized the construction of “open organic sites” in a metal nanocluster for the first time. Specifically, we introduce the PNP (2,6-bis(diphenylphosphinomethyl)pyridine) pincer ligand in the synthesis of the gold nanocluster, enabling the construction of a structurally precise Au8(PNP)4nanocluster. The rigidity and the unique bonding mode of PNP lead to open nitrogen sites on the surface of the Au8(PNP)4nanocluster, which have been utilized as multifunctional sites in this work for efficient kinetic resolution and catalysis. The gold pincer nanocluster and the open nitrogen site-induced performance will be enlightening for the construction of multifunctional metal nanoclusters.

In the past decade, isolated single atoms have been successfully dispersed on various substrates, with their potential applications being intensively investigated in different reactions. While the essential target of research in single-atom catalysis is the precise synthesis of stable single-atom catalysts (SACs) with clear configurations and impressive catalytic performance, theoretical investigations have also played important roles in identifying active sites, revealing catalytic mechanisms, and establishing structure–activity relationships. Nevertheless, special attention should still be paid in theoretical works to the particularity of SACs. In this Perspective, we will summarize the theoretical progress made on the understanding of the rich phenomena in single-atom catalysis. We focus on the determination of local structures of SACs via comparison between experiments and simulations, the discovery of distinctive catalytic mechanisms induced by multiadsorption, synergetic effects, and dynamic evolutions, to name a few, the proposal of criteria for theoretically designing SACs, and the extension of original concepts of single-atom catalysis. We hope that this Perspective will inspire more in-depth thinking on future theoretical studies of SACs.

Development of high-efficiency and inexpensive oxygen evolution reaction (OER) catalysts is highly desirable for water electrolysis devices and rechargeable metal–air batteries. Herein, we report novel one-dimensional (1D) Fe-doped α-Ni(OH)2nanobelts as OER-active electrocatalysts. In-depth characterizations revealed that Fe atoms are incorporated into the lattice of Ni(OH)2, resulting in the strong electron interaction with active Ni sites. Moreover, a contraction of Ni–O bond distance induced by Fe is revealed by operandoX-ray absorption fine structure spectroscopy under OER working condition, which leads to a near-optimized adsorption of oxygen intermediates. Consequently, the Fe-doped α-Ni(OH)2nanobelts deliver significantly promoted OER activity in alkaline solutions with a low OER overpotential of 236 mV at 10 mA cm–2along with good stability. This work provides a strategy for developing efficiently non-noble metal catalysts, gives insights to the Fe doping effect and the dynamic evolution of disturbed atomic and electronic structure of Ni active sites.

Element doping strategy has been proven to be an efficient route to both activate the catalytic sites and optimize the electronic structure for transition metal dichalcogenides. However, the specific influence of element doping on the catalytic performance still remained obscure. Herein, we reveal the doping effect on the atomic and electronic structure of Se active sites during the electrocatalytic hydrogen evolution reaction (HER) through in situ X-ray adsorption spectroscopy. We reveal a dynamic structure evolution in Co-doped tungsten diselenide (Co-WSe2) nanosheets, which lead to the optimized electronic state of Se active sites and further promote H2production under HER. The theoretical calculations verified the rationality of the structural evolution and demonstrated the doping effect on the electronic structure of Se active sites, thus, resulting in a 140 mV decrease of overpotential at 10 mA/cm2for Co-WSe2nanosheets. This work provides a new understanding of the element doping effect on enhancing electrochemical performance.

The adsorption energies for single Ni atom on CuAl2O4(100) and (110) surfaces are −5.30 and −4.08 eV, respectively. The growth and aggregation of Ni can be effectively inhibited on the perfect CuAl2O4(100) surface. The adsorption of Ni on the spinel surface is accompanied by charge transfer. The interaction of Ni with CuAl2O4surface is stronger than with the γ-Al2O3(110) surface.

As potential alternatives to Pt-based catalysts for oxygen reduction reaction (ORR), iron (Fe)-based single-atomic site catalysts (SACs) have shown superior performances compared with others. For Fe SACs, the effect of directly coordinating N atoms has received intensive discussion, yet by contrast, the effect of secondary coordinating atoms has been left largely unexplored. Here, we developed a route to tuning externally doped N around Fe SACs to boost ORR activity. Density functional theory (DFT) calculations established the four different models for FeN4for ORR, indicating that the FeN4-PR-GN (pyrrolic-N for the first coordination shell and graphitic-N for the second coordination shell) can effectively improve the ORR performance. On the basis of theoretical calculations, we developed a two-step strategy including interior encapsulation and surface adsorption, which helped to regulate the different external coordination N of Fe SACs. The best-performing catalyst, FeN4-PR-GN, displays excellent ORR performances in alkaline electrolytes; in particular, the catalyst gives a half-wave potential of 0.92 V (vs.RHE) and high stability, which is much better than those of commercial Pt/C. Our work here not only demonstrates an efficient catalyst to boost ORR performances, but also develops a facile strategy for the preparation of SACs for advanced fuel cells.

A series of novel 2-Ar-1,2,3-triazole derivatives were designed and synthesized based on our previously discovered active compound 6dagainst Rhizoctonia solani. Most of these compounds exhibited good antifungal activity against R. solaniat a concentration of 25 μg/mL. Based on the results of biological activity, we established a three-dimensional quantitative structure–activity relationship (3D-QSAR) model that guided the synthesis of compound 7y. Compound 7yexhibited superior activity against R. solani(EC50= 0.47 μg/mL) compared to the positive controls hymexazol (EC50= 12.80 μg/mL) and tebuconazole (EC50= 0.87 μg/mL). Furthermore, compound 7ydemonstrated better protective activity than the aforementioned two commercial fungicides in both detached leaf assays and greenhouse experiments, achieving 56.21% and 65.75% protective efficacy, respectively, at a concentration of 100 μg/mL. The ergosterol content was determined and molecular docking was performed to explore the mechanism of these active molecules. DFT calculation and MEP analysis were performed to illustrate the results of this study. These results suggest that compound 7ycould serve as a novel 2-Ar-1,2,3-triazole lead compound for controlling R. solani.

Proton-exchange-membrane fuel cells (PEMFCs) are attractive next-generation power sources for use in vehicles and other applications1, with development efforts focusing on improving the catalyst system of the fuel cell. One problem is catalyst poisoning by impurity gases such as carbon monoxide (CO), which typically comprises about one per cent of hydrogen fuel2–4. A possible solution is on-board hydrogen purification, which involves preferential oxidation of CO in hydrogen (PROX)3–7. However, this approach is challenging8–15because the catalyst needs to be active and selective towards CO oxidation over a broad range of low temperatures so that CO is efficiently removed (to below 50 parts per million) during continuous PEMFC operation (at about 353 kelvin) and, in the case of automotive fuel cells, during frequent cold-start periods. Here we show that atomically dispersed iron hydroxide, selectively deposited on silica-supported platinum (Pt) nanoparticles, enables complete and 100 per cent selective CO removal through the PROX reaction over the broad temperature range of 198 to 380 kelvin. We find that the mass-specific activity of this system is about 30 times higher than that of more conventional catalysts consisting of Pt on iron oxide supports. In situ X-ray absorption fine-structure measurements reveal that most of the iron hydroxide exists as Fe1(OH)xclusters anchored on the Pt nanoparticles, with density functional theory calculations indicating that Fe1(OH)x–Pt single interfacial sites can readily react with CO and facilitate oxygen activation. These findings suggest that in addition to strategies that target oxide-supported precious-metal nanoparticles or isolated metal atoms, the deposition of isolated transition-metal complexes offers new ways of designing highly active metal catalysts.

Two-dimensional (2D) materials with the vertical intrinsic electric fields show great promise in inhibiting the recombination of photogenerated carriers and widening light absorption region for the photocatalytic applications. For the first time, we investigated the potential feasibility of the experimentally attainable 2D M2X3(M = Al, Ga, In; X = S, Se, Te) family featuring out-of-plane ferroelectricity used in photocatalytic water splitting. By using first-principles calculations, all the nine members of 2D M2X3are verified to be available photocatalysts for overall water splitting. The predicted solar-to-hydrogen efficiency of Al2Te3, Ga2Se3, Ga2Te3, In2S3, In2Se3, and In2Te3are larger than 10%. Excitingly, In2Te3is manifested to be an infrared-light driven photocatalyst, and its solar-to-hydrogen efficiency limit using the full solar spectrum even reaches up to 32.1%, which breaks the conventional theoretical efficiency limit.

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Heterogeneous solid catalysts based on atomically dispersed Pd species are the most applicable catalysts in selective alkyne hydrogenation. However, the understanding of their structure–activity relationship remains ambiguous due to lack of structural analysis tools available and a unified synthetic system to obtain comparable Pd-based catalysts. Herein, we reported a convenient method to obtain Pd nanoclusters and Pd single atoms loaded on a nitrogen-doped carbon support (marked as Pd-NC@NC and Pd-SA@NC, respectively) in a uniform procedure and explored their structure–activity relationship in phenylacetylene hydrogenation. By the application of various kinds of characterization methods, we legibly illustrated the structures of Pd-NC@NC and Pd-SA@NC and found that Pd-NC@NC exhibited much higher mass activity than Pd-SA@NC (6.70 vs 0.33 mmol g–1h–1) in phenylacetylene semi-hydrogenation. Theoretical calculations revealed that the different abilities of Pd nanoclusters and Pd1-N4sites to adsorb reactants caused by steric hindrance were most likely to contribute to their different catalytic performances. This established structure–activity relationship provides guidelines for rationally designing metal catalysts for selective alkyne hydrogenation.

Electroreduction of CO2into useful fuels, especially if driven by renewable energy, represents a potentially ‘clean’ strategy for replacing fossil feedstocks and dealing with increasing CO2emissions and their adverse effects on climate. The critical bottleneck lies in activating CO2into the CO2•−radical anion or other intermediates that can be converted further, as the activation usually requires impractically high overpotentials. Recently, electrocatalysts based on oxide-derived metal nanostructures have been shown to enable CO2reduction at low overpotentials. However, it remains unclear how the electrocatalytic activity of these metals is influenced by their native oxides, mainly because microstructural features such as interfaces and defects influence CO2reduction activity yet are difficult to control. To evaluate the role of the two different catalytic sites, here we fabricate two kinds of four-atom-thick layers: pure cobalt metal, and co-existing domains of cobalt metal and cobalt oxide. Cobalt mainly produces formate (HCOO−) during CO2electroreduction; we find that surface cobalt atoms of the atomically thin layers have higher intrinsic activity and selectivity towards formate production, at lower overpotentials, than do surface cobalt atoms on bulk samples. Partial oxidation of the atomic layers further increases their intrinsic activity, allowing us to realize stable current densities of about 10 milliamperes per square centimetre over 40 hours, with approximately 90 per cent formate selectivity at an overpotential of only 0.24 volts, which outperforms previously reported metal or metal oxide electrodes evaluated under comparable conditions. The correct morphology and oxidation state can thus transform a material from one considered nearly non-catalytic for the CO2electroreduction reaction into an active catalyst. These findings point to new opportunities for manipulating and improving the CO2electroreduction properties of metal systems, especially once the influence of both the atomic-scale structure and the presence of oxide are mechanistically better understood.

Hydrogen adsorption structures and energetics on the (100), (110), (111), (210), (211), (310), and (321) iron surfaces up to saturation have been computed using spin-polarized density functional theory and ab initio thermodynamics. The computed hydrogen desorption temperatures and energies on the (100), (110), (111), and (211) surfaces as well as the Fe–H binding energies on the (110) and (111) surfaces agree well with the available experimental data. At typical hydrogen reduction temperature (675 K), the mainly exposed (110) and (310) facets represent the active surfaces, as supported by the transmission electron microscopy study. Our results offer an example of investigating and understanding surface structures and active facets of heterogeneous catalysts under experimental conditions.

Acrolein hydrogenation via allyl alcohol, propanal, and enol into propanol on the Ni(111) surface has been investigated using the spin-polarized periodic density functional theory method. On the basis of the computed adsorption energies and effective hydrogenation barriers, acrolein hydrogenation into propanal and allyl alcohol obeys the Langmuir–Hinshelwood mechanism and propanal formation is more favored kinetically and thermodynamically than allyl alcohol formation. Hydrogenation of propanal and allyl alcohol should follow the Eley–Rideal mechanism. The adsorption energies of acrolein, allyl alcohol, and propanal along with the partial hydrogenation selectivity on Ni, Au, Ag, and Pt catalysts have been compared and discussed.

Spin-polarized density functional theory calculations have been performed to investigate formic acid dehydrogenation into carbon dioxide and hydrogen (HCO2H → CO2+ H2) on Ni(111). It is found that formic acid prefers the O (OC) atop adsorption on nickel surface and the H (H–O) atom bridging two neighboring nickel atoms, and formate prefers the bidentate adsorption with O atop on nickel surface. The computed stretching frequencies for deuterated formic acid (DCO2H) and deuterated formate (DCO2) on Ni(111) agree well with the experimentally observed IR spectra. Formic acid dehydrogenation into surface formate and hydrogen atom (HCO2H → HCO2+ H) has barrier of 0.41 eV and is exothermic by 0.35 eV. Formate dehydrogenation into carbon dioxide and hydrogen atom (HCO2→ CO2+ H) has an effective barrier of about 1.0 eV and is the rate-determining step. Our computed adsorption configurations and energetic data for formic acid dehydrogenation on Ni(111) are very close to the reported results for Pt(111), but in sharp contrast to the previously reported results for Pd(111). Our recalculated adsorption configurations and energetic data for formic acid dehydrogenation on Pd(111) are similar to those on Ni(111) and Pt(111), demonstrating the high similarities of these metals. These computed data show that Pd-catalyzed formic acid dehydrogenation has the lowest effective barrier (0.76 eV), followed by Ni (1.03 eV) and Pt (1.56 eV).

To develop high-performance and low-cost catalysts for electrochemical nitrogen reduction reaction (eNRR) in producing ammonia, a promising alternative to the Haber–Bosch process continues to be a substantial challenge. Herein, by using density functional theory calculations, single-atom-supported pristine and nitrogen-doped (N-doped) graphdiyne (GDY) monolayer-catalyzed eNRR were investigated to realize high performance via rational design. Candidate catalysts include 10 different transition-metal (M = Cr, Mn, Fe, Co, Ni, Cu, Mo, W, Re, and Ru) single-atom-anchored GDY monolayers (M1/GDY) and three different types of N-doped (sp2-N and sp-N) GDY monolayers (M1/Nn-GDY, n= 1–3), with 40 single-atom catalysts (SACs). Both Mo1/N3-GDY and W1/N3-GDY were screened out with rather low theoretical onset potentials of merely −0.36 and −0.41 V, respectively. Further investigation of the exemplar Mo1/N3-GDY system shows that it has high selectivity, stability, and activity toward ammonia. The synergy effect between single-atom Mo and the confined flexibility substrate gives rise to self-adjustment of the coordination microenvironment of Mo1/N3-GDY, that is, this doped first coordination sphere sp-N is confined, yet shows steric flexibility, and transfers into sp2-N without Mo-N bond formation when single-atom Mo is anchored. Therefore, the system regulates adsorption pattern and strength of N2and intermediates, and finally boosts the performance. This work provides a new idea of using a confined flexibility substrate to construct SACs for efficient synthesis of ammonia at ambient conditions.

A surface oxygen-injection strategy is proposed to synergistically modulate the electronic structure of the SnS2nanosheets, thereby regulating the oxophilicity of the catalyst surface.The surface oxygen doping facilitates the CO2activation and enhances the affinity for HCOO* species.The oxygen-injection SnS2nanosheets exhibit a remarkable Faradaic efficiency of 91.6% for carbonaceous products with a current density of 24.1 mA cm−2at -0.9 V vs RHE.