Side-on Adsorption Research Articles

Iron Monomers or Trimers on Nitrogen-Doped Carbon: Which Is Better for the Electrocatalytic Nitrogen Reduction Reaction?

The electrocatalytic nitrogen reduction reaction (NRR) presents an alternative method for the Haber-Bosch process, and single-atom catalysts (SACs) to achieve efficient NRR have attracted considerable attention in the past decades. However, whether SACs are more suitable for NRR compared to atomic-cluster catalysts (ACCs) remains to be studied. Herein, we have successfully synthesized both the Fe monomers (Fe1) and trimers (Fe3) on nitrogen-doped carbon catalysts. Both the experiments and DFT calculations indicate that compared to the end-on adsorption of N2 on Fe1 catalysts, N2 activation is enhanced via the side-on adsorption on Fe3 catalysts, and the reaction follows the enzymatic pathway with a reduced free energy barrier for NRR. As a result, the Fe3 catalysts achieved better NRR performance (NH3 yield rate of 27.89 μg h-1 mg-1cat. and Faradaic efficiency of 45.13%) than Fe1 catalysts (10.98 μg h-1 mg-1cat. and 20.98%). Therefore, our research presents guidance to prepare more efficient NRR catalysts.

Pauling-type adsorption of O2 induced by S-scheme electric field for boosted photocatalytic H2O2 production

The effective adsorption of oxygen (O2) molecules over photocatalysts is a critical step in promoting the performance of photocatalytic H2O2 production. However, g-C3N4 usually features a Yeager-type (side-on) adsorption configuration of O2 molecules, which causes the breaking of O–O bonds and severely hinders the H2O2 production activity. Herein, we synthesized an oxygen-vacancy-rich TiO2–x/g-C3N4 step-scheme (S-scheme) heterojunction to regulate the oxygen adsorption configuration and improve the 2e– ORR selectivity of H2O2 production. In-situ X-ray photoelectron spectroscopy (in-situ XPS) and density functional theory (DFT) calculations reveal that the S-scheme heterojunction is formed between TiO2–x and g-C3N4. The difference between their Fermi levels leads to the electron flow from g-C3N4 to TiO2–x, which increases the electron-deficient sites in g-C3N4. As a result, the cleavage of O–O bonds on the surface of g-C3N4 is avoided and the oxygen adsorption configuration is tuned from Yeager-type to Pauling-type (end-on). Consequently, the photocatalytic H2O2 production rate is dramatically improved to 1780.3 μmol h–1, which is about 5 times higher than that of pristine g-C3N4. This work paves a new way to tailor the oxygen adsorption configuration by rationally designing S-scheme heterojunction photocatalysts.

Tip-like Fe-N4 Sites Induced Surface Microenvironments Regulation Boosts the Oxygen Reduction Reaction.

Single atom catalysts with defined local structures and favorable surface microenvironments are significant for overcoming slow kinetics and accelerating O2 electroreduction. Here, enriched tip-like FeN4 sites (T-Fe SAC) on spherical carbon surfaces were developed to investigate the change in surface microenvironments and catalysis behavior. Finite element method (FEM) simulations, together with experiments, indicate the strong local electric field of the tip-like FeN4 and the more denser interfacial water layer, thereby enhancing the kinetics of the proton-coupled electron transfer process. In situ spectroelectrochemical studies and the density functional theory (DFT) calculation results indicate the pathway transition on the tip-like FeN4 sites, promoting the dissociation of O-O bond via side-on adsorption model. The adsorbed OH* can be facilely released on the curved surface and accelerate the oxygen reduction reaction (ORR) kinetics. The obtained T-Fe SAC nanoreactor exhibits excellent ORR activities (E1/2 =0.91 V vs. RHE) and remarkable stability, exceeding those of flat FeN4 and Pt/C. This work clarified the in-depth insights into the origin of catalytic activity of tip-like FeN4 sites and held great promise in industrial catalysis, electrochemical energy storage, and many other fields.

Tailoring local environment of oxygen vacancies by molybdenum doping on MnO2 for enhanced catalytic oxidation of VOCs

The microenvironment of oxygen vacancies plays an important role in metal oxide catalysts for VOCs catalytic oxidation. A simple strategy was provided to tailor the local environment of oxygen vacancies over MnO2 via Mo doping engineering to enhance its catalytic activity. The 0.3MoMnO2 with Mo/Mn quality ratio of 0.3 showed superior catalytic oxidation performance of benzene and anti-toxicity (H2O, SO2, and particulate matter). Its benzene oxidation rate at 190℃ was 1.95 × 10−4 mol/g/h, which was about three and two times higher than that of MnO2 and 0.9MoMnO2, respectively. The Mn-Ov-Mo sites were experimentally verified as the dominant active centers on 0.3MoMnO2. Through DFT calculation, Mo doping could enhance the oxygen adsorption on oxygen vacancies of MnO2. The remarkably well activity of Mn-Ov-Mo was rationally explained by the moderate oxygen adsorption energy to maintain a dynamic equilibrium of oxygen adsorption and desorption, which enhanced the oxygen activation, thereby promoting the benzene catalytic oxidation. However, excessive Mo doping induced the formation of Mo-Ov-Mo, and its side-on oxygen adsorption configuration was not conducive to oxygen transfer. This work broadens the understanding of the relationship between the local environment of oxygen vacancies and catalytic activities, which is beneficial for the rational design of efficient VOCs catalysts.

Electrocatalytic Urea Synthesis via C-N Coupling from CO2 and Nitrogenous Species.

ConspectusIndustrial urea synthesis consists of the Haber-Bosch process to produce ammonia and the subsequent Bosch-Meiser process to produce urea. Compared to the conventional energy-intensive urea synthetic protocol, electrocatalytic C-N coupling from CO2 and nitrogenous species emerges as a promising alternative to construct a C-N bond under ambient conditions and to realize the direct synthesis of high-value urea products via skipping the intermediate step of ammonia production. The main challenges for electrocatalytic C-N coupling lie in the intrinsic inertness of molecules and the competition with parallel side reactions. In this Account, we give an overview of our recent progress toward electrocatalytic C-N coupling from CO2 and nitrogenous species toward urea synthesis.To begin, we present the direct transformation of dinitrogen (N2) to the C-N bond by coelectrolysis, verifying the feasibility of direct urea synthesis from N2 and CO2 under ambient conditions. In contrast to the highly endothermic step of proton coupling in conventional N2 reduction, the N2 activation and construction of the C-N bond arise from a thermodynamic spontaneous reaction between CO (derived from CO2 reduction) and *N═N* (the asterisks represent the adsorption sites), and the crucial *NCON* species mediates the interconversion of N2, CO2, and urea. Based on theoretical guidance, the effect of N2 adsorption configurations on C-N coupling is investigated on the model catalysts with defined active site structure, revealing that the side-on adsorption rather than the end-on one favors C-N coupling and urea synthesis.Electrocatalytic C-N coupling of CO2 and nitrate (NO3-) is also an effective pathway to achieve direct urea synthesis. We summarize our progress in the C-N coupling of CO2 and NO3-, from the aspects of modulating intermediate species adsorption and reaction paths, monitoring irreversible and reversible reconstruction of active sites, and precisely constructing active sites to match activities and to boost the electrocatalytic urea synthesis. In each case, in situ electrochemical technologies and density functional theory (DFT) calculations are carried out to unveil the microscopic mechanisms for the promotion of C-N coupling and the enhancement of urea synthesis activity. In the last section, we put forward the limitations, challenges, and perspectives in these two coupling systems for further development of electrocatalytic urea synthesis.

Atomically Precise Dinuclear Ni2 Active Site-Modified MOF-Derived ZnO@NC Heterojunction toward High-Performance N2 Photofixation

The development of heterogeneous catalysts with atom-dispersed active sites is essential to facilitate nitrogen (N2) activation for the N2 reduction reaction (NRR). However, it remains a major challenge to tune the coordination configuration of the metal centers to further accelerate the activation kinetics. Herein, an atomically precise dinuclear Ni2 site-modified metal–organic framework (MOF)-derived ZnO@NC heterojunction (ZnO@NC-Ni2) was developed for effective N2 photofixation under mild conditions. Moreover, advanced structural characterization indicates that the most active N-coordinated bimetallic site configurations are Ni2–N6, where two Ni1–N4 moieties are shared with two N atoms. Theoretical calculations further demonstrate that the binuclear Ni2 active sites of ZnO@NC-Ni2 could adjust the N2 adsorption configuration as the side-on bridging adsorption mode (denoted as “*N≡N*”), while the single metal Ni1 sites of ZnO@NC-Ni1 tend to form a terminal adsorption configuration with N2 (“*N≡N” type). As a result, the unique electronic structure of binuclear Ni2 active sites in ZnO@NC-Ni2 tends to proceed as an associative alternating pathway, thereby decreasing the activation energy barrier of the reaction procedure and favoring the photocatalytic NRR. The present study provides a perspective to probe the relationship between the coordination architecture of earth-abundant metal active centers and NRR activities.

Enhanced Interfacial Electron Transfer by Asymmetric Cu-Ov -In Sites on In2 O3 for Efficient Peroxymonosulfate Activation.

Enhancing the peroxymonosulfate (PMS) activation efficiency to generate more radicals is vital to promote the Fenton-like reaction activity, however, how to promote the PMS adsorption and accelerate the interfacial electron transfer to boost its activation kinetics remains a great challenge. Herein, we prepared Cu-doped defect-rich In2 O3 (Cu-In2 O3 /Ov ) catalysts containing asymmetric Cu-Ov -In sites for PMS activation in water purification. The intrinsic catalytic activity is that the side-on adsorption configuration of the O-O bond (Cu-O-O-In) at the Cu-Ov -In sites significantly stretches the O-O bond length. Meanwhile, the Cu-Ov -In sites increase the electron density near the Fermi energy level, promoting more and faster electron transfer to the O-O bond for generating more SO4 ⋅- and ⋅OH. The degradation rate constant of tetracycline achieved by Cu-In2 O3 /Ov is 31.8 times faster than In2 O3 /Ov , and it shows the possibility of membrane reactor for practical wastewater treatment.

Theoretical exploration of the nitrogen fixation mechanism of two-dimensional dual-metal TM1TM2@C9N4 electrocatalysts.

The electrochemical nitrogen reduction reaction (eNRR) to NH3 has become an alternative to traditional NH3 production techniques, while developing NRR catalysts with high activity and high selectivity is of great importance. In this study, we systematically investigated the potentiality of dual transition metal (TM) atom anchored electrocatalysts, TM1TM2@C9N4 (TM1, TM2 = 3(4)d TM atoms), for the NRR through the first principles high-throughput screening method. A total of 78 TM1TM2@C9N4 candidates were designed to evaluate their stability, catalytic activity, and selectivity for the NRR. Four TM1TM2@C9N4 candidates (TM1TM2 = NiRu, FeNi, TiNi, and NiZr) with an end-on N2 adsorption configuration, and two candidates (TM1TM2 = TiNi and TiFe) with a side-on adsorption configuration, were screened out with the advantage of suppressing the hydrogen evolution reaction (HER) and exhibiting high NRR activity. Moreover, the catalysts with end-on and side-on N2 adsorption configurations were determined to favor distal and consecutive reaction pathways, respectively, with favorable limiting potentials of only -0.33 V to -0.53 V. Detailed analysis showed that the N2 adsorption and activation are primarily ascribed to the strong back-donation interactions between the d-electrons of TM atoms and the anti-orbitals of an N2 molecule. Our findings pave a way for the rational design and rapid screening of highly active C9N4-based catalysts for the NRR.

First-principles study on the catalytic performance of transition metal atom-doped CrSe2 for the oxygen reduction reaction.

Since the oxygen reduction reaction (ORR) is the cathodic reaction of energy storage and conversion devices such as fuel cells and metal-air batteries, the search for catalysts with high-performance toward ORR has become the focus of attention. Transition metal dichalcogenides (TMDs) have the advantages of easy integration, inexpensive, harmless, good stability, and have vast application prospects in stabilizing the single atom. Hence, in this study, we investigated the feasibility of several 4d/5d single transition metals (TM = Rh, Pd, Ag, Ir, Pt, and Au) doped with CrSe2 for ORR electrocatalysis on the basis of density functional theory (DFT) calculations. Our results demonstrated that most of the TM-doped systems are stable, exhibiting metal conductivity, and can well activate the adsorbed O2. Interestingly, compared with end-on adsorption configuration, O2 is more likely to be adsorbed on the catalysts by a side-on adsorption configuration. Among all the candidate ORR catalysts, Pd-doped and Pt-doped CrSe2 have the best catalytic performance with a low overpotential of 0.43 and 0.50 V, respectively, making them good ORR candidate high performance catalysts. Our DFT work helps to understand the interaction between the O2 molecule and transition metal single atoms on CrSe2 supports and provides ideas for designing stable and efficient ORR catalysts.

Adsorption mechanism of the N2 and NRR intermediates on oxygen modified MnN4-graphene layers - a single atom catalysis perspective.

In the present work the adsorption of N2 and the nitrogen reduction reaction (NRR) intermediates have been investigated on oxygen modified MnNxOy (x + y = 4, x ≠ 0)/graphene layers through periodic density functional theory calculations. Various number of oxygen atoms substitute nitrogen atoms within the MnNxOy, with their effect on the layer stability, chemical bonding and N2 adsorption being explored. As the oxygen amount increases in the porphyrin unit, Mn-O interactions weaken with reference to that of Mn-N, bonding orbitals become less populated while the antibonding orbitals between Mn-N-O atoms become partially occupied, as evidenced by the Crystal orbital Hamiltonian population (COHP) and integrated crystal orbital bond index (ICOBI) analyses. During N2 adsorption on the different layers, the substitution of two and three nitrogen atoms by oxygen leads to the longest NN molecular bond length. Two main orientations for the N2 molecules sorption have been investigated: side-on and end-on which are perpendicular and parallel to the surface normal, respectively. When the interaction of N2 with MnNO3 layer is considered, d-band center variation of the Mn with reference to the pre-adsorbed state is more obvious after side-on adsorption configuration. For the selected layers based on initial N2 adsorption energies, the adsorption energies of nitrogen reduction reaction intermediates follow a trend based on the number of oxygen atoms in the porphyrin units. Charge density difference (CDD) maps and partial density of states (PDOS) analysis reveal that the interaction of N2 with oxygen modified layers takes place through electron acception-donation mechanism between the partially occupied Mn-d orbitals and the 2p orbitals of the N2 molecule. DDEC6-derived bond orders and atomic charges support the PDOS and adsorption/formation energy trends, and further clarify the bonding strengths of the atoms in the porphyrin units, as well as the Mn-N2 interactions in the adsorbed systems.

Plasma-Assisted Dinitrogen Activation via Dual Platinum Cluster Catalysis: A Strategy for Ammonia Synthesis under Mild Conditions

Plasma-Assisted Dinitrogen Activation via Dual Platinum Cluster Catalysis: A Strategy for Ammonia Synthesis under Mild Conditions

Concentrate and degrade PFOA with a photo-regenerable composite of In-doped TNTs@AC

“Concentrate-and-degrade” is an effective strategy to promote mass transfer and degradation of pollutants in photocatalytic systems, yet suitable and cost-effective photocatalysts are required to practice the new concept. In this study, we doped a post-transition metal of Indium (In) on a novel composite adsorptive photocatalyst, activated carbon-supported titanate nanotubes (TNTs@AC), to effectively degrade perfluorooctanoic acid (PFOA). In/TNTs@AC exhibited both excellent PFOA adsorption (>99% in 30 min) and photodegradation (>99% in 4 h) under optimal conditions (25 °C, pH 7, 1 atm, 1 g/L catalyst, 0.1 mg/L PFOA, 254 nm). The heterojunction structure of the composite facilitated a cooperative adsorption mode of PFOA, i.e., binding of the carboxylic head group of PFOA to the metal oxide and attachment of the hydrophobic tail to AC. The resulting side-on adsorption mode facilitates the electron (e‒) transfer from the carboxylic head to the photogenerated hole (h+), which was the major oxidant verified by scavenger tests. Furthermore, the presence of In enables direct electron transfer and facilitates the subsequent stepwise defluorination. Finally, In/TNTs@AC was amenable to repeated uses in four consecutive adsorption-photodegradation runs. The findings showed that adsorptive photocatalysts can be prepared by hybridization of carbon and photoactive semiconductors and the enabled “concentrate-and-degrade” strategy is promising for the removal and degradation of trace levels of PFOA from polluted waters.

Rational Synthesis of Polymeric Nitrogen N8– with Ultraviolet Irradiation and Its Oxygen Reduction Reaction Mechanism Study with In Situ Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy

Polynitrogen (PN) deposited on multiwalled carbon nanotubes was synthesized by cyclic voltammetry with ultraviolet (UV) irradiation. Compared to the sample formed without UV, a larger amount of N8– was synthesized and was found to distribute more uniformly on the MWNTs with 254 nm UV irradiation, indicating that the production of more azide (N3)0 radicals as the precursors for synthesis of N8– by photoexcitation of azide (N3–) ions is a rate-limiting step for PN synthesis. An oxygen reduction reaction kinetics study indicated a four-electron reaction pathway on N8–, whereas a two-electron process occurs on N3–. Analysis by in situ shell-isolated nanoparticle-enhanced Raman spectroscopy revealed that the side-on and end-on O2 adsorption occurred at N8– and N3–, respectively, confirming the electron transfer process. A full direct-methanol fuel cell study shows that methanol crossover typically reduces the current density of Pt/C by ∼40% but has very little effect on the performance of the PN-MWNT catalyst after testing for 120 h. Moreover, the power density from the PN-MWNT cathode is at least twice that from a Pt/C cathode.

Palladium-based single atom catalysts for high-performance electrochemical production of hydrogen peroxide

Electrochemical two-electron oxygen reduction reaction (2e-ORR) offers a green route for production of hydrogen peroxide (H2O2). However, it remains a key challenge to design and develop the catalysts possessing both high activity and selectivity. Herein, we design ten Palladium-based single atom catalysts (Pd-based SACs) and report the underlying mechanisms of the activity and selectivity for 2e-ORR to produce H2O2. The intermediate of *OOH is used as a descriptor to describe the catalytic activity of 2e−/4e− ORR through a volcano diagram due to a linear scaling relationship between *OOH and *O (or *OH). We find that a defect graphene binding with one Pd single atom (C4Pd), which is thermodynamically favorable, exhibits an ultralow overpotential (0.044 V) for production of H2O2. In particular, this catalyst displays excellent activity and selectivity for H2O2 in a faintly acid or neutral electrolyte instead of alkaline. Furthermore, the Pd atomic clusters binding on defect graphene (C4Pdx, x = 2, 3, 4, 5) exhibit poor performance for production of H2O2 than that of C4Pd. The computational results reveal that the side-on adsorption configurations of O2 molecule and *H constitute the limiting factors for the selectivity of H2O2. These findings offer new insights for interpreting the mechanisms of 2e-ORR and pave the way for future designs and developments of excellent catalysts for the direct synthesis of H2O2.

Rich B active centers in Penta-B2C as high-performance photocatalyst for nitrogen reduction

The photocatalytic nitrogen reduction reaction (NRR) has mild reaction conditions and only requires sunlight energy as a driving force to replace the traditional ammonia synthesis method. We herein investigate the catalytic activity and selectivity on Penta-B2C for NRR by using density functional theory calculations. Penta-B2C is a semiconductor with an indirect bandgap (2.328 eV) and is kinetically stable based on molecular dynamic simulations. The optical absorption spectrum of Penta-B2C is achieved in the ultraviolet and visible range. Effective light absorption is more conducive to generate photo-excited electrons and improving photocatalytic performances. Rich B atoms as activation sites in Penta-B2C facilitate capturing N2. The activated N2 molecule prefers the side-on adsorption configuration on Penta-B2C, which facilitates the subsequent reduction reaction. Among considered NRR mechanisms on Penta-B2C, the best pathway prefers the enzymatic mechanism, only required a low onset potential of 0.23 V. The hydrogen evolution reaction is inhibited when the hydrogen adsorption concentration is increased or N2 molecules first occupy the adsorption sites. Our results indicate Penta-B2C is a highly reactive and selective photocatalyst for NRR. Our work provides theoretical insights into the experiments and has guiding significance to synthesize efficient NRR photocatalysts.

Theoretical insights into bimetallic atoms supported on PC6 as highly efficient electrocatalysts for N2 electroreduction to NH3

Electrochemical N2 reduction under mild conditions has been regarded as a promising alternative to the conventional Haber-Bosch process. In the electrochemical reaction, a highly efficient catalyst plays an important role. Herein, we studied a series of bimetallic atoms catalysts, namely, two transition metal atoms doped on the PC6 monolayer (TM2@PC6, TM = Cr, Mn, Fe, Co. Ni, Mo, Ru, Rh, W, and Ir), to examine the electrocatalytic performance for nitrogen reduction reaction by employing the density functional theory computations. Co2@PC6 is screened out to be the best candidate for the N2 reduction, which has high Faradaic efficiency and lowest limiting potential of −0.28 V, followed by Mo2@PC6, and Fe2@PC6 with limiting potentials of −0.46, and −0.50 V, respectively. These predicted candidates have comparable or even better NRR catalytic activity than the other common two-dimensional materials. The N2H* formation is the potential-determining step for these catalysts. N2 with side-on adsorption configuration (occurred only for Co2@PC6) has the best NRR performance. This work not only provides the potential NRR catalyst but also gives insight into the mechanism to advance the development of efficient NRR catalysts.

Orientation and Conformation of Proteins at the Air-Water Interface Determined from Integrative Molecular Dynamics Simulations and Sum Frequency Generation Spectroscopy.

Understanding the assembly of proteins at the air-water interface (AWI) informs the formation of protein films, emulsion properties, and protein aggregation. Determination of protein conformation and orientation at an interface is difficult to resolve with a single experimental or simulation technique alone. To date, the interfacial structure of even one of the most widely studied proteins, lysozyme, at the AWI remains unresolved. In this study, molecular dynamics (MD) simulations are used to determine if the protein adopts a side-on, head-on, or axial orientation at the AWI with two different forcefields, GROMOS-53a6 + SPC/E and a99SB-disp + TIP4P-D. Vibrational sum frequency generation (SFG) spectroscopy experiments and spectral SFG calculations validate consistency between the structure determined from MD and experiments. Overall, we show with strong agreement that lysozyme adopts an axial conformation at pH 7. Further, we provide molecular-level insight as to how pH influences the binding domains of lysozyme resulting in side-on adsorption near the isoelectric point of the lysozyme.

Enhanced photocatalytic degradation of perfluorooctanoic acid using carbon-modified bismuth phosphate composite: Effectiveness, material synergy and roles of carbon

Per- and polyfluoroalkyl substances (PFAS) such as perfluorooctanoic acid (PFOA) are recalcitrant to conventional wastewater treatment processes. In search for a more effective technology, we prepared a carbon sphere (CS) modified bismuth phosphate composite photocatalyst (BiOHP/CS) through a hydrothermal process. BiOHP/CS was able to adsorb > 99% of PFOA in 2 h (dosage = 1.0 g/L, initial PFOA = 200 µg/L, pH = 7.0), and subsequently, in situ decompose adsorbed PFOA nearly completely in 4 h of UV irradiation. The PFOA degradation rate was ~18 times greater than that by neat BiOHP. Advanced spectroscopic analyses and density functional theory calculations revealed that the carbon modification not only enhances the PFOA adsorption capacity, but also facilitates a side-on adsorption configuration of PFOA on the photoactive sites. While only the head carboxylate group was involved in PFOA adsorption on neat BiOHP, both the CF2/CF3 entities and the head carboxylate group participated in adsorption of PFOA on BiOHP/CS, which facilitates the subsequent photocatalytic cleavage of the CF bonds. Photoluminescence emission analysis and density of states calculations confirmed the CS-facilitated side-on adsorption mode and CS-enhanced separation of electrons and holes. In addition, the CS modification facilitates activation of PFOA by changing the electron distribution of the C-F bond, and enhances the stability and reusability of BiOHP by preventing photo-corrosion of the composite material. Overall, the findings provide important insights into the roles of carbonaceous modification and adsorption configurations in enhanced photocatalytic destruction of PFOA, which may guide future design and fabrication of environment-friendly adsorptive photocatalysts.

MoS2-Supported Fe2 Clusters Catalyzing Nitrogen Reduction Reaction to Produce Ammonia

Synergistic interactions within metal clusters help to improve the catalytic activity of individual metal atoms and contribute to advance the understanding of mechanisms in multisite catalysis. Herein, the MoS2-supported Fe2 cluster was chosen as the catalyst for nitrogen reduction reaction (NRR) to produce ammonia. First-principles calculations reveal that the Fe2/MoS2 exhibits high catalytic activity for electrochemical NRR and sheds light on the enzymatic mechanism which bears a low overpotential of 0.21 V. Compared with a single Fe atom on MoS2, the presence of a vicinal Fe atom (i.e., Fe2/MoS2) enables side-on adsorption of N2, which is propitious to effective N–N bond activation. Whereas the Fe3/MoS2 catalyst, simply with one more Fe atom involved, reduces electron depletion among Fe atoms and hence represses N2 adsorption. The origin of reasonable NRR catalysis of Fe2/MoS2 is further unveiled by natural charge population and projected crystal orbital Hamilton population (pCOHP) analyses. This investigation provides an effective strategy for designing active catalysts with low cost and multisite synergy catalysis.

Dimeric Fe Sites Effectively Activate Oxygen Molecule

In the November issue of Chem, Xiong and coworkers report the method of fine-tuning Fe atom numbers in Fe clusters coordinated to N on C. Compared with mono- and tri-iron centers, the di-iron center exhibited higher electrocatalytic activity for oxygen reduction reaction because it promoted side-on adsorption of O2.