Nitrogen Reduction Reaction Activity Research Articles

Design of novel transition metal doped pyrazine-modified graphyne as highly effective electrocatalysts for nitrogen fixation

The production of ammonia consumes plenty of energy every year, so it is crucial to develop efficient and sustainable methods of electrocatalytic ammonia synthesis. Although some materials have shown high catalytic activity for nitrogen reduction reaction (NRR), searching for catalytic materials with excellent electrical properties is still a promising topic. Graphyne and its family are well suited as catalysts due to their high electrical conductivity and carrier mobility. In this paper, we have systematically studied the catalytic properties of transition metal atoms anchored on pyrazine-modified graphyne (pyGY) for NRR by density functional theory calculations. Through a series of scanning procedures, Nb, Mo and W-pyGYs are found to be excellent catalysts for electrocatalytic NRR with limiting potentials of − 0.43 V, − 0.36 V, and − 0.46 V, respectively. Moreover, solvation effects are considered and the lowering effect of solvent on the limiting potential is revealed. In addition, the mechanism of superior catalytic activity is explored from an electronic perspective. Finally, two descriptors related to electronegativity and valence electron number are selected to clarify the trend of NRR activity. The volcano diagram trends of NN bond length, Gibbs free energy change in the first hydrogenation step and limiting potential are revealed. This work provides a reliable method for screening efficient electrocatalytic nitrogen fixation catalysts.

Surface hydrophobic modification of MXene to promote the electrochemical conversion of N2 to NH3

Hydrophobic treatment of the catalyst surfaces can suppress the competitive hydrogen evolution reaction (HER) during the nitrogen reduction reaction (NRR). In this work, the surface of Ti3C2Tix MXene is modified by cetyltrimethylammonium bromide (CTAB) and trimethoxy (3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl) silane (FOTS) to increase the hydrophobicity of MXenes. The ammonia (NH3) production rate and faradaic efficiency (FE) are improved from 37.62 to 54.01 μg h−1 mg−1cat. and 5.5% to 18.1% at −0.7 V vs. RHE, respectively after surface modification. 15N isotopic labeling experiment confirms that nitrogen in produced ammonia originates from N2 in the electrolyte. The excellent NRR activity of surface hydrophobic MXenes is mainly due to surfactant molecules, which inhibit the entry of water molecules and the competitive HER, which have been verified by in situ FT-IR, DFT and molecular dynamics calculations. This strategy provides an ingenious method to design more active NRR electrocatalysts.

Surface modification of CeO2−x nanorods with Sn doping for enhanced nitrogen electroreduction

While the electrochemical nitrogen reduction reaction (NRR) represents a prospective blueprint for environmentally renewable ammonia generation, it has yet to overcome the limitations of weak activity and inferior selectivity. In this regard, surface modification tactic was constructed to markedly enhance the activity and selectivity via introducing Sn atoms into the surface of defective cerium oxide (denoted as Sn-CeO2−x) as the active and robust electrocatalyst for NRR under benign environment. The introduction of Sn atoms in CeO2−x can not only inhibit the HER activity of the catalyst but also modulate the electronic structure of ceria and optimize N-Ce interaction, thus enhancing NRR activity and selectivity. Outperforming all previous CeO2-based NRR catalysts, this catalyst has demonstrated an ammonia yield rate of 41.1 μg mgcat−1 h−1 and an exceptional Faradic efficiency of 35.3%. This work presents a viable approach for the development of advanced NRR electrocatalysts.

Oxygen vacancy modulation in interfacial engineering Fe3O4 over carbon nanofiber boosting ambient electrocatalytic N2 reduction

The oxygen vacancy modulation of interface-engineered Fe3O4 nanograins over carbon nanofiber (Fe@CNF) was achieved to improve electrocatalytic nitrogen reduction reaction (NRR) activity and stability via facile electrospinning and tuning thermal procedure. The optimal catalyst calcined at 800 ℃ (Fe@CNF-800) was endowed with abundant nanograin boundaries and optimized oxygen vacancy (Vo) concentration of iron oxides, thereby affording 37.1 μg h−1 mgcat.-1 (−0.2 V vs. reversible hydrogen electrode (RHE)) NH3 yield and rational Faraday efficiency (10.2%), with 13.6 times atomic activity enhancement compared to of that commercial Fe3O4. The interfacial effect of assembled nanograins in particles correlated with the formation of Vo and more intrinsic active sites, which is conducive to the trapping and activation of nitrogen (N2). The in-situ X-ray photoelectron spectroscopy (XPS) measurement revealed the real consumption of adsorbed oxygen when introducing N2 by the trapping effect of Vo. Density-Functional-Theory (DFT) calculation validates the promotive hydrogenation effect and elimination of hydrogen intermediate (H*) interacted with N2 transferring toward oxygen of the support. The optimal catalyst shows a lasting NRR activity at least 90 h, outperforming most reported Fe-based NRR catalysts.

Tuning electrocatalytic nitrogen reduction on supported nickel cluster via substrate phase engineering

Metal clusters supported on the substrate is promising nitrogen reduction reaction (NRR) electrocatalysts due to their diversity and tunable sizes. However, how to rationally select clusters depending on substrates to promote NRR performance is not elucidated yet. To address this problem, we systematically investigate the NRR activity of Nin (n = 4, 13) clusters anchored on H and T′-phases WTe2 substrates, which offer ‘uniform’ and ‘nonuniform’ surfaces, respectively. Based on density functional theory calculations, we find that Ni4@H-WTe2 exhibits the highest NRR activity with an ultralow overpotential of 0.24 V, which is superior to that of Ni13@H-WTe2. While for the T′ phase WTe2, a larger cluster Ni13@T′-WTe2 is preferred. These differences arise from the distorted interaction between clusters and H and T′-WTe2 surfaces. The ‘uniform surface’ possessing one type of Te atom tends to deform small clusters severely, while the ‘nonuniform surface’ offers a buckling surface that deforms large Ni13 sufficiently. With the phases engineered deformation of Nin, the NRR performance is modulated. Our work highlights a strategy to design efficient NRR electrocatalysts via matching substrate phase and cluster size.

Boosting photocatalytic nitrogen reduction reaction by Jahn-Teller effect

Compared with traditional the Haber-Bosch process, photocatalytic ammonia production has attracted a considerable attention due to its advantages of low energy consumption and sustainability. In this work, we mainly study the photocatalytic nitrogen reduction reaction (NRR) on MoO3·0.55H2O and α-MoO3. Structure analysis shows that compared to α-MoO6, the [MoO6] octahedrons in MoO3·0.55H2O obviously distort (Jahn-Teller distortion), leading to the formation of Lewis acid active sites that favors the adsorption and activation of N2. X-ray photoelectron spectroscopy (XPS) further confirms the formation of more Mo5+ as Lewis acid active sites in MoO3·0.55H2O. Transient photocurrent, photoluminescence and electrochemical impedance spectra (EIS) confirmed that MoO3·0.55H2O has a higher charge separation and transfer efficiency than α-MoO3. Density functional theory (DFT) calculation further confirmed that the N2 adsorption on MoO3·0.55H2O is more favorable thermodynamically than that on α-MoO3. As a result, under visible light irradiation (λ ≥ 400 nm) for 60 min, an ammonia production rate of 88.6 μmol·gcat-1 was achieved on MoO3·0.55H2O, which is about 4.6 times higher than that on α-MoO3. In comparison to other photocatalysts, MoO3·0.55H2O exhibits an excellent photocatalytic NRR activity under visible light irradiation without using sacrificial agent. This work offers a new fundamental understanding to photocatalytic NRR from the viewpoint of crystal fine structure, which benefits designing efficient photocatalysts.

Mo-based catalysts based on B-modified two-dimensional carbon-rich conjugate frameworks for efficient nitrogen reduction reaction

Under environmental conditions, electrochemical nitrogen reduction reaction (NRR), which has the advantages of low energy consumption, zero CO2 emissions, green and sustainability, is considered to be an alternative to the Haber-Bosch method for ammonia synthesis. However, the practical application of NRR is hindered by the poor N2 adsorption capacity, low NH3 synthesis efficiency, and poor selectivity of the catalyst. In this paper, from a theoretical point of view, we design a Mo-based catalyst with multiple active sites based on B-modified 2D CCFs. The B atom has a similar N2 activation mechanism to transition metal atoms in that their empty orbitals (sp3, d orbitals) can accept lone pairs of electrons of nitrogen and feedback electrons to the anti-bond orbitals of the NˆN bond. Moreover, the addition of the B atom leads to new orbital hybridization and charge distribution, which strengthens the N2 adsorption capacity and reduces the energy change, thereby improving the NRR catalytic activity. After a series of analyses, it is concluded that MoZr-BPc CCF catalyst has the best NRR activity with the minimum limiting potential of −0.36 V, the overpotential of 0.20 V, and FENRR of 100%, and it can well inhibit the HER extremely. The synergistic effect of non-metallic and metal atoms provides a new idea for the rational design of NRR electrocatalysts and lays a theoretical foundation for the widespread use of NRR in practical applications.

Hetero-phase zirconia encapsulated with Au nanoparticles for boosting electrocatalytic nitrogen reduction

Electrocatalytic nitrogen reduction reaction (NRR) is considered as an attractive approach for ammonia synthesis under mild conditions. A bottleneck of NRR is the exploration of efficient catalysts for accelerating reaction kinetics, among which heterogeneous structures possessing distinct atomic arrangement could modify electronic structure, and therefore altering their NRR activity. Here, we report a facile strategy for fabricating hetero-phase metal oxides derived from metal organic framework that are further integrated with Au nanoparticles as NRR catalysts. The phase composition of zirconia can be easily adjusted by simply changing the reaction temperature, where the monoclinic and tetragonal phases with the roughly close proportions have a distinct interface, leading to a strong interaction between Au and ZrO2. The enhanced interaction renders Au to be more electropositive and facilitates stronger binding to N2. As a result, a remarkable ammonia yield of 22.32 µg h−1 mgcat.−1 and a Faradaic efficiency of 31.92% can be achieved at low overpotential. This work is expected to pave the way for the design of heterogeneous structures and the exploration of hetero-phase nanostructures in boosting the electrocatalytic NRR.

Design of novel transition-metal-doped C4N4 as highly effective electrocatalysts for nitrogen fixation with a new intrinsic descriptor

Electrocatalytic nitrogen reduction reaction (NRR) is an efficient and green way to produce ammonia, which offers an alternative option to the conventional Haber-Bosch process. Unfortunately, the large-scale industrial application of NRR processes is still hindered by poor Faraday efficiency and high overpotential, which need to be overcome urgently. Herein, combined with density functional theory and particle swarm optimization algorithm for the nitrogen carbide monolayer structural search (CmN8-m, m = 1–7), the surprising discovery is that single transition metal-atom-doped C4N4 monolayers (TM@C4N4) could effectively accelerate nitrogen reduction reaction. TM@C4N4 (TM = 29 transition metals) as single-atom catalysts are evaluated via traditional multi-step screening method, and their structures, NRR activity, selectivity and solvation effect are investigated to evaluate their NRR performance. Through the screening steps, W@C4N4 possesses the highest activity for NRR with a very low limiting potential of −0.29 V. Moreover, an intrinsic descriptor φ is proposed with machine learning, which shortens the screening process and provides a new idea for finding efficient SACs. This work not only offers promising catalysts W@C4N4 for NRR process but also offers a new intrinsic and universal descriptor φ.

Targeted Modulation of Competitive Active Sites toward Nitrogen Fixation via Sulfur Vacancy Engineering Over MoS2

AbstractElectrocatalytic nitrogen reduction reaction (NRR) offers an environmentally benign and sustainable alternative for NH3 synthesis. However, developing NRR electrocatalysts with both high activity and selectivity remains a significant challenge. Guided by the density functional theory (DFT) calculations and further verified by the experiment, a modulated MoS2 with well‐controlled S vacancies (MoS2‐Vs) is prepared as an excellent electrocatalyst for NRR, where both the activity and selectivity of NRR mightily rely on the S‐vacancy concentration. The optimized catalyst (MoS2‐7H) in a suitable S‐vacancy concentration (17.5%) is empowered with an excellent NRR activity (NH3 yield rate: 66.74 µg h−1 mg−1 at −0.6 V) and selectivity (Faradic efficiency (FE): 14.68% at −0.5 V). Further mechanistic study reveals that the NRR performance is powerfully concentration‐dependent since its activity is enhanced due to the S‐vacancy‐strengthened N2 adsorption and reduced reaction energy barrier. Simultaneously, its selectivity is synchronously improved by the steadily enhanced NRR activity and inversely suppressed hydrogen evolution reaction through limiting H2 desorption kinetics, which sets it markedly apart from other reported defective MoS2‐based catalysts.

Electro- and Photocatalytic Conversion of N2 to NH3 by Chemically Modified Transition Metal Dichalcogenides, MoS2, and WS2

Electro- and photocatalytic reduction of N2 to NH3—the nitrogen reduction reaction (NRR)—is an environmentally- and energy-friendly alternative to the Haber-Bosch process for ammonia production. There is a great demand for the development of novel semiconductor-based electrocatalysts with high efficiency and stability for the direct conversion of inert substrates—including N2 to ammonia—using visible light irradiation under ambient conditions. Herein we report electro-, and photocatalytic NRR with transition metal dichalcogenides (TMDCs), viz MoS2 and WS2. Improved acid treatment of bulk TMDCs yields exfoliated TMDCs (exTMDCs) only a few layers thick with ∼10% S vacancies. Linear scan voltammograms on exMoS2 and exWS2 electrodes reveal significant NRR activity for exTMDC-modified electrodes, which is greatly enhanced by visible light illumination. Spectral measurements confirm ammonia as the main reaction product of electrocatalytic and photocatalytic NRR, and the absence of hydrazine byproduct. Femtosecond-resolved transient absorption studies provide direct evidence of interaction between photo-generated excitons/trions with N2 adsorbed at S vacancies. DFT calculations corroborate N2 binding to exMoS2 at S-vacancies, with substantial π-backbonding to activate dinitrogen. Our findings suggest that chemically functionalized exTMDC materials could fulfill the need for highly-desired, inexpensive catalysts for the sustainable production of NH3 using Sunlight under neutral pH conditions without appreciable competing production of H2.

Double transition metal atoms supported on defective borophene as efficient electrocatalysts for nitrogen reduction: a theoretical study

Electrocatalytic nitrogen reduction reaction (NRR) provides a promising approach for ammonia production under mild conditions. Developing high efficiency catalysts is the key and challenge for their practical application. Here, we employ density functional theory (DFT) to design a series of transition metal double-atom catalysts (DACs) with defective β12-borophene (DB-Hij) as the substrate, namely TM2@DB-Hij, where TM = Sc∼Zn, Zr∼Rh (expect Tc) and Hf∼Os. Two potential candidate catalysts Zr2@DB-H12 and Hf2@DB-H12 were selected based on three screening strategy. DFT calculation shows that on the two DACs, NRR starts from an end-on adsorption configuration of N2 and proceeds via the enzymatic mechanism. These two DACs not only exhibit excellent catalytic activity, with the limiting potentials of -0.28 and -0.39 V, respectively, but also effectively suppress the competing hydrogen evolution reaction (HER). Moreover, the effects of two substrates on the catalytic performance of TM2@DB-H12 were also investigated. The existence of Ag(111) substrate prepared in the experiment reduced the activity of the designed DACs, while the NRR activity was improved when graphene was used to replace Ag(111). The present study indicates that the substrates affect the electrocatalytic performance of catalysts to a certain extent, which should be considered in future research.

Improving Electrocatalytic Nitrogen Reduction Selectivity and Yield by Suppressing Hydrogen Evolution Reaction via Electronic Metal–Support Interaction

AbstractThe electrochemical nitrogen reduction reaction (NRR) has the potential to replace the Haber–Bosch process for ammonia synthesis under ambient conditions. However, the selectivity and yield of the NRR are impractical, owing to the preferential binding of the electrocatalyst to H and the consequential coverage of active sites. In this study, VO2, with N2 strongly adsorbed over H atoms, is used as a support to provide a N2 source to avoid the hydrogen evolution reaction. Mo, with a high NRR activity, is introduced as the active site to promote the NRR. Meanwhile, the electronic metal–support interaction between the support and Mo creates electron‐deficient sites, which weakens H adsorption and lowers the energy barrier of the first step, protonation, thereby kinetically enhancing the NRR activity. The average NH3 yield of Mo/VO2 is 190.1 µgNH3 mgcat.−1 h−1 and the Faradaic efficiency is 32.4% at −0.5 V versus reversible hydrogen electrode, which is 10.8 and 2.8 times greater than that of VO2, respectively.

Regulating the Coordination Environment of Single-Atom Catalysts Anchored on Thiophene Linked Porphyrin for an Efficient Nitrogen Reduction Reaction.

The electrochemical nitrogen reduction reaction (NRR) offers a promising strategy to resolve high energy consumption in the nitrogen industry. Recently, the regulation of the electronic structure of single-atom catalysts (SACs) by adjusting their coordination environment has emerged as a rather promising strategy to further enhance their electrocatalytic activity. Herein, we design novel SACs supported by thiophene-linked porphyrin (TM-N4/TP and TM-N4-xBx/TP, where TM = Sc to Au) as potential NRR catalysts using density functional theory calculations. Among these catalysts, TM-N4/TP (TM = Ti, Nb, Mo, Ta, W, and Re) and TM-N4/TP with a water bilayer (TM = Nb, Mo, W, and Re) show excellent activity (low limiting potential) but low selectivity. Encouragingly, we find that Mo-N3B/TP, Mo-N2B2-2/TP, W-N3B/TP, W-N2B2-2/TP, Re-N3B/TP, Re-N2B2-2/TP, and Re-N2B2-1/TP serve as the most efficient NRR electrocatalysts, as they present stability, superior activity, better selectivity with low limiting potentials (-0.18 ∼ -0.90 V), and high Faradaic efficiencies (>99.80%). Based on microkinetic modeling, kinetic analysis of the NRR is performed and shows that the Re-N2B2-1/TP catalyst is more efficient for NH3 formation. Additionally, multiple-level descriptors provide insight into the origin of NRR activity and enable fast prescreening among numerous candidates. This work provides a new perspective to design highly efficient catalysts for the NRR under ambient conditions.

P‐d Orbital Hybridization Engineered Single‐Atom Catalyst for Electrocatalytic Ammonia Synthesis

The rational design of metal single‐atom catalysts (SACs) for electrochemical nitrogen reduction reaction (NRR) is challenging. Two‐dimensional metal–organic frameworks (2DMOFs) is a unique class of promising SACs. Up to now, the roles of individual metals, coordination atoms, and their synergy effect on the electroanalytic performance remain unclear. Therefore, in this work, a series of 2DMOFs with different metals and coordinating atoms are systematically investigated as electrocatalysts for ammonia synthesis using density functional theory calculations. For a specific metal, a proper metal‐intermediate atoms p‐d orbital hybridization interaction strength is found to be a key indicator for their NRR catalytic activities. The hybridization interaction strength can be quantitatively described with the p−/d‐ band center energy difference (∆d‐p), which is found to be a sufficient descriptor for both the p‐d hybridization strength and the NRR performance. The maximum free energy change (ΔGmax) and ∆d‐p have a volcanic relationship with OsC4(Se)4 located at the apex of the volcanic curve, showing the best NRR performance. The asymmetrical coordination environment could regulate the band structure subtly in terms of band overlap and positions. This work may shed new light on the application of orbital engineering in electrocatalytic NRR activity and especially promotes the rational design for SACs.

Design of molecular M[sbnd]N[sbnd]C dual-atom catalysts for nitrogen reduction starting from surface state analysis

Under electrocatalytic conditions, the state of a catalyst surface (e.g., adsorbate coverage) can be very different from a pristine form due to the existing conversion equilibrium between water and H- and O-containing adsorbates. Dismissing the analysis of the catalyst surface state under operating conditionsmay lead to misleading guidelines for experiments. Given that confirming the actual active site of the catalyst under operating conditions is indispensable to providing practical guidance for experiments, herein, we analyzed the relations between the Gibbs free energy and the potential of a new type of molecular metal-nitrogen-carbon (MNC) dual-atom catalysts (DACs) with a unique 5 N-coordination environment, by spin-polarized density functional theory (DFT) and surface Pourbaix diagram calculations. Analyzing the derived surface Pourbaix diagrams, we screened out three catalysts, N3-Ni-Ni-N2, N3-Co-Ni-N2, and N3-Ni-Co-N2, to further study the activity of nitrogen reduction reaction (NRR). The results display that N3-Co-Ni-N2 is a promising NRR catalyst with a relatively low ΔG of 0.49 eV and slow kinetics of the competing hydrogen evolution. This work proposes a new strategy to guide DAC experiments more precisely: the analysis of the surface occupancy state of the catalysts under electrochemical conditions should be performed before activity analysis.

Controllable Exfoliation of MOF-Derived Van Der Waals Superstructure into Ultrathin 2D B/N Co-Doped Porous Carbon Nanosheets: A Superior Catalyst for Ambient Ammonia Electrosynthesis.

The electrocatalytic nitrogen reduction reaction (NRR) to synthesize NH3 under ambient conditions is a promising alternative route to the conventional Haber-Bosch process, but it is still a great challenge to develop electrocatalysts' high Faraday efficiency and ammonia yield. Herein, a facile and efficient exfoliation strategy to synthesize ultrathin 2D boron and nitrogen co-doped porous carbon nanosheets (B/NC NS) via a metal-organic framework (MOF)-derived van der Waals superstructure, is reported. The results of experiments and theoretical calculations show that the doping of boron and nitrogen can modulate the electronic structure of the adjacent carbon atoms; which thus, promotes the competitive adsorption of nitrogen and reduces the energy required for ammonia synthesis. The B/NC NS exhibits excellent catalytic performance and stability in electrocatalytic NRR, with a yield rate of 153.4 µg·h-1 ·mg-1 cat and a Faraday efficiency of 33.1%, which is better than most of the reported NRR electrocatalysts. The ammonia yield of B/NC NS can maintain 92.7% of the initial NRR activity after 48h stability test. The authors' controllable exfoliation strategy using MOF-derived van der Waals superstructure can provide a new insight for the synthesis of other 2D materials.

Theoretical design toward highly efficient single-atom catalysts for nitrogen reduction by regulating the “acceptance-donation” mechanism

Single-atom catalysts (SACs) show great potential for driving electrochemical nitrogen reduction reaction (NRR). However, the lack of physico-chemical understanding of the ambiguous activation mechanism impedes the development of electrocatalysts. In this work, using first principles calculations, we tuned NRR activity and elucidated regulation mechanism of N2 activation by constructing SACs based on defective Ti2CO2 and Ti2NO2 MXenes. Interestingly, Mo@Ti2CO2-v and W@Ti2CO2-v show excellent NRR activity and selectivity with low limiting potentials of –0.27 and –0.27 V at the first hydrogenation (*N2→*NNH) and the last hydrogenation (*NH2→*NH3) steps via distal pathway, respectively. The intrinsic activity tendency can be related to adsorption energy of intermediate *NNH (ΔE(*NNH)). Furthermore, electronic structure analysis demonstrates that number of unpaired electrons in d orbitals (Nun-d) determines occupation of d orbitals, thus regulating the “acceptance-donation” mechanism. Particularly, transition metals with Nun-d of 5 and 4 show moderate “acceptance-donation” interaction, thus achieving encouraging NRR performance. Moreover, ΔE(*NNH) and Nun-d can be considered as promising descriptors for screening and designing effective SACs. Finally, our investigation not only contributes to discovery of novel SACs toward NRR, but also provides insightful guidance for other electrochemical reactions with high bond-order molecules and multi-electron steps, such as ORR and CO2RR.

A High-Throughput Screening toward Efficient Nitrogen Fixation: Transition Metal Single-Atom Catalysts Anchored on an Emerging π-π Conjugated Graphitic Carbon Nitride (g-C10N3) Substrate with Dirac Dispersion.

TM-Nx is becoming a comforting catalytic center for sustainable and green ammonia synthesis under ambient conditions, resulting in increasing interest in single-atom catalysts (SACs) for the electrochemical nitrogen reduction reaction (NRR). However, given the poor activity and unsatisfactory selectivity of existing catalysts, it remains a long-standing challenge to design efficient catalysts for nitrogen fixation. Currently, the two-dimensional (2D) graphitic carbon-nitride substrate provides abundant and evenly distributed holes for stably supporting transition-metal atoms, which presents a fascinating prospect for overcoming this challenge and promoting single-atom NRR. An emerging holey graphitic carbon-nitride skeleton with a C10N3 stoichiometric ratio (g-C10N3) from a supercell of graphene is constructed, which provides outstanding electric conductivity for achieving high-efficiency NRR due to the Dirac band dispersion. Herein, a high-throughput first-principles calculation is carried out to evaluate the feasibility of π-d conjugated SACs resulting from a single TM atom anchored on g-C10N3 (TM = Sc-Au) for NRR. We find that W metal embedded in g-C10N3 (W@g-C10N3) can compromise the ability to adsorb the key target reaction species (N2H and NH2), hence acquiring an optimal NRR behavior among 27 TM-candidates. Our calculations demonstrate that W@g-C10N3 shows a well-suppressed HER ability and, impressively, a low energy cost of -0.46 V. Additionally, all-around descriptors are proposed to uncover the fundamental mechanism of NRR activity, among which a 3D volcano plot (limiting potential, screening strategy, and electron origin) uncovers the NRR activity trend, achieving a quick and high-efficiency prescreening for numerous candidates. Overall, the strategy of the structure- and activity-based TM-Nx-containing unit design will offer useful insight for further theoretical and experimental attempts.

Newly designed photocatalyst of Fe4 single clusters on g-C6N6 for nitrogen reduction reaction

The current industrial synthesis of ammonia proceeds through Haber–Bosch process, in which the adsorbed N2 are directly dissociated, and the reaction is limited by Brønsted–Evans–Polanyi (BEP) relation. In this work, the catalytic properties of Fe4 clusters fixed on g-C6N6 for nitrogen reduction reaction (NRR) are explored by first-principle calculations. The studies on the structural stability, adsorption capacity for N2 and the change of Gibbs free energy proves that Fe4 cluster catalyst exhibits excellent catalytic activity and high selectivity for NRR. The “acceptance-donation” interaction between Fe4@g-C6N6 and N atoms presented by PDOS and Bader charge analysis will facilitate the breaking of NN bonds. The 100 % Faraday efficiency further proves the high NRR selectivity. The results provide an effective strategy for designing high-performance electrochemical NRR catalysts.