High-Throughput Screening of Efficient Biatom Catalysts Based on Monolayer Carbon Nitride for the Nitric Oxide Reduction Reaction

Electronic Modulation of Doped MoS2 Nanosheets for Improved CO2 Sensing and Capture

Transition-metal dichalcogenides (TMDs) are widely used in the gas sensing field, owing to their high surface-to-volume ratio enabled by the two-dimensional (2D) structure, adjustable band gap, and high electron transfer. However, it is challenging for TMD materials to realize superior CO2 sensing, due to their weak CO2 adsorption capacity. Herein, we predict through density functional theory (DFT) calculations that rare earth metal doping is an effective strategy to boost the CO2 sensing capability of TMDs. As a proof-of-concept, we investigate and find that the introduction of rare earth metal atoms (La, Ce, Pr, or Nd) can induce lattice strain and modulate the electronic properties of MoS2. When negative charges are injected in rare earth metal doped MoS2 (R-MoS2), the 5d or 4f orbital of the rare earth metal atom in R-MoS2 can produce a stronger orbital hybridization with 2p orbitals of C and O in CO2. Therefore, the CO2 adsorption is significantly enhanced and the charge transfer is facilitated for negatively charged R-MoS2. Moreover, negatively charged R-MoS2 exhibits an excellent CO2 selectivity. Our results indicate that the rare earth metal doping and electronic modulation in 2D materials may provide a new pathway for CO2 sensing and capture.

Advancing electrocatalytic reactions through mapping key intermediates to active sites via descriptors

Descriptors play a crucial role in electrocatalysis as they can provide valuable insights into the electrochemical performance of energy conversion and storage processes. They allow for the understanding of different catalytic activities and enable the prediction of better catalysts without relying on the time-consuming trial-and-error approaches. Hence, this comprehensive review focuses on highlighting the significant advancements in commonly used descriptors for critical electrocatalytic reactions. First, the fundamental reaction processes and key intermediates involved in several electrocatalytic reactions are summarized. Subsequently, three types of descriptors are classified and introduced based on different reactions and catalysts. These include d-band center descriptors, readily accessible intrinsic property descriptors, and spin-related descriptors, all of which contribute to a profound understanding of catalytic behavior. Furthermore, multi-type descriptors that collectively determine the catalytic performance are also summarized. Finally, we discuss the future of descriptors, envisioning their potential to integrate multiple factors, broaden application scopes, and synergize with artificial intelligence for more efficient catalyst design and discovery.

A two-dimensional covalent organic framework with single-atom manganese for electrochemical NO reduction: a computational study

Covalent organic frameworks (COFs) exhibit great potential for electrocatalysis. Here, using DFT calculations and constant-potential modelling, we report the feasibility of a series of COFs toward NO reduction via regulating their central metal atoms and linking ligands. A COF with single-atom Mn is identified to possess superior activity while maintaining high NH3 selectivity.

Graphene-based iron single-atom catalysts for electrocatalytic nitric oxide reduction: a first-principles study

The electrocatalytic NO reduction reaction (NORR) emerges as an intriguing strategy to convert harmful NO into valuable NH3. Due to their unique intrinsic properties, graphene-based Fe single-atom catalysts (SACs) have gained considerable attention in electrocatalysis, while their potential for NORR and the underlying mechanism remain to be explored. Herein, using constant-potential density functional theory calculations, we systematically investigated the electrocatalytic NORR on the graphene-based Fe SACs. By changing the local coordination environment of Fe single atoms, 26 systems were constructed. Theoretical results show that, among these systems, the Fe SAC coordinated with four pyrrole N atoms and that co-coordinated with three pyridine N atoms and one O atom exhibit excellent NORR activity with low limiting potentials of -0.26 and -0.33 V, respectively, as well as have high selectivity toward NH3 by inhibiting the formation of byproducts, especially under applied potential. Furthermore, electronic structure analyses indicate that NO molecules can be effectively adsorbed and activated via the electron "donation-backdonation" mechanism. In particular, the d-band center of the Fe SACs was identified as an efficient catalytic activity descriptor for NORR. Our work could stimulate and guide the experimental exploration of graphene-based Fe SACs for efficient NORR toward NH3 under ambient conditions.

Transition metal small clusters anchored on biphenylene for effective electrocatalytic nitrogen reduction

The synthesis of ammonia via an electrochemical nitrogen reduction reaction (NRR, N2 + 6H+ + 6e- → 2NH3), which can weaken but not directly break an inert NN bond under mild conditions via multiple progressive protonation steps, has been proposed as one of the most attractive alternatives for the production of NH3. However, the development of appropriate catalyst materials is a major challenge in the application of NRRs. Recently, single- or multi-metal atoms anchored on two-dimensional (2D) substrates have been demonstrated as ideal candidates for facilitating NRRs. In this work, by applying spin-polarized density functional theory and ab initio molecular dynamic simulations, we systematically explored the performances of nine types of transition metal multi-atoms anchored on a recently developed 2D biphenylene (BPN) sheet in nitrogen reduction. Structural stability and NRR performance catalyzed by TMn (TM = V, Fe, Ni, Mo, Ru, Rh, W, Re, Ir; n = 1-4) clusters anchored on BPN sheets were systematically explored. After a strict six-step screening strategy, it was found that W2, Ru2 and Mo4 clusters loaded on BPN demonstrate superior potential for nitrogen reduction with extremely low onset potentials of -0.26, -0.36 and -0.17 V, respectively. Electronic structure analysis revealed that the enhanced ability of these multi-atom catalysts to effectively capture and reduce the N2 molecule can be attributed to bidirectional charge transfer between the d orbitals of transition metal atoms and molecular orbitals of the adsorbed N2 through a "donation-back donation" mechanism. Our findings highlight the value of BPN sheets as a substrate for designing multi-atom nitrogen reduction reaction catalysts.

High-Throughput Computational Design of 2D Ternary Chalcogenides for Sustainable Energy

Two-dimensional materials are considered to be promising for next-generation electronic and energy devices. However, the limited availability of 2D materials hinders their applications. Herein, we employed high-throughput computation to discover new 2D materials by cleaving the bulk and to investigate their electronic, thermoelectric, and optoelectronic properties. Using our database containing 810 structures of chalcogenides ABX3 (A or B = Al, Ga, In, Si, Ge, Sn, P, As, Sb, and Bi; X = S, Se, and Te), we identified 204 new 2D compounds promising for experimental preparation according to the exfoliation energy. Notably, 96 of them are more easily exfoliated than graphene, 52 compounds show higher Seebeck coefficients than Bi2Te3 at 300 K, and 20 compounds have power factors beyond 2 × 10-3 Wm-1 K-2 at 900 K. Also, 6 new compounds exhibit high theoretical photovoltaic efficiency exceeding 30%. Our findings expand the 2D materials family and provide new 2D compounds for sustainable thermoelectric and optoelectronic energy applications.

Single and double transition metal atoms doped graphdiyne for highly efficient electrocatalytic reduction of nitric oxide to ammonia

The electrocatalytic conversion of nitric oxide (NORR) to ammonia (NH3) represents a pivotal approach for sustainable energy transformation and efficient waste utilization. Designing highly effective catalysts to facilitate the conversion of NO into NH3 remains a formidable challenge. In this work, the density functional theory (DFT) is used to design NORR catalysts based on single and double transition metal (TM:Fe, Co, Ni and Cu) atoms supported by graphdiyne (TM@GDY). Among eight catalysts, the Cu2@GDY is selected as a the most stable NORR catalyst with high NH3 activity and selectivity. A pivotal discovery underscores that the NORR mechanism is thermodynamically constrained on single atom catalysts (SACs), while being governed by electrochemical processes on double atom catalysts (DACs), a distinction arising from the different d-band centers of these catalysts. Therefore, this work not only introduces an efficient NORR catalyst but also provides crucial insights into the fundamental parameters influencing NORR performance.

Fundamentals, rational catalyst design, and remaining challenges in electrochemical NOx reduction reaction

Nitrogen oxides (NOx) emissions carry pernicious consequences on air quality and human health, prompting an upsurge of interest in eliminating them from the atmosphere. The electrochemical NOx reduction reaction (NOxRR) is among the promising techniques for NOx removal and potential conversion into valuable chemical feedstock with high conversion efficiency while benefiting energy conservation. However, developing efficient and stable electrocatalysts for NOxRR remains an arduous challenge. This review provides a comprehensive survey of recent advancements in NOxRR, encompassing the underlying fundamentals of the reaction mechanism and rationale behind the design of electrocatalysts using computational modeling and experimental efforts. The potential utilization of NOxRR in a Zn-NOx battery is also explored as a proof of concept for concurrent NOx abatement, NH3 synthesis, and decarbonizing energy generation. Despite significant strides in this domain, several hurdles still need to be resolved in developing efficient and long-lasting electrocatalysts for NOx reduction. These possible means are necessary to augment the catalytic activity and electrocatalyst selectivity and surmount the challenges of catalyst deactivation and corrosion. Furthermore, sustained research and development of NOxRR could offer a promising solution to the urgent issue of NOx pollution, culminating in a cleaner and healthier environment.

Revealing the origin of activity in phthalocyanine-based dual-metal sites towards electrochemical nitric oxide reduction

Coordinated ligands play crucial roles in tuning the electrochemical nitrate reduction performance of phthalocyanine (Pc)-based dual atom catalysts. With the assistance of axial O ligands, fast NO to NH3 conversion can be realized on O-Ni2-Pc and O-Cu2-Pc. A 2-N product, N2O, can be synthesized on Co2-Pc, Cr2-Pc, O-Co2-Pc, and O-Fe2-Pc through N-N coupling with high NO coverage. ΔENO can be identified as a valid descriptor to support rational M2-Pc design.

Activating dual atomic electrocatalysts for the nitric oxide reduction reaction through the P/S element

The development of efficient atomic electrocatalysts to resolve the activity and selectivity issues of the nitric oxide reduction reaction (NORR) has increasingly received more attention but is still challenging. The current research on the dual atomic NORR electrocatalyst is exclusively focused on TM atoms. Herein, we propose a novel mechanism of introducing a P/S element, which takes advantage of finite orbitals to active the transition metal (TM) atoms of dual atomic electrocatalysts for NORR. The finite orbitals can hinder the capture of the lone pair electrons of NO but modulate the electronic configurations of the neighboring TM and thus the "donation-backdonation" mechanism can be realized. Through large-scale first-principles calculations, the catalytic performance of a series of P/S-TM biatoms supported by the monolayer CN (P/S-TM@CN) is evaluated. According to a "four-step" screening strategy, P-Cu@CN and S-Ni@CN are successfully screened as promising catalysts with outstanding activity and high selectivity for direct NO-to-NH₃ conversion. Moreover, we identify Δε_d-p as a valid descriptor to evaluate the adsorption of NO on such catalysts, allowing for reducing the number of catalytic candidates. Our work thus provides a new direction for the rational design of dual atomic electrocatalysts.

Role of transition metal d-orbitals in single-atom catalysts for nitric oxide electroreduction to ammonia

Recently, surging interests exist in direct electrochemical ammonia (NH₃) synthesis from nitric oxide (NO) due to the dual benefit of NH₃ synthesis and NO removal. However, designing highly efficient catalysts is still challenging. Based on density functional theory, the best ten candidates of transition-metal atoms (TMs) embedded in phosphorus carbide (PC) monolayer is screened out as highly active catalysts for direct NO-to-NH₃ electroreduction. The employment of machine learning-aided theoretical calculations helps to identify the critical role of TM-d orbitals in regulating NO activation. A V-shape tuning rule of TM-d orbitals for the Gibbs free energy change of NO or limiting potentials is further revealed as the design principle of TM embedded PC (TM-PC) for NO-to-NH₃ electroreduction. Moreover, after employing effective screening strategies including surface stability, selectivity, the kinetic barrier of potential-determining step, and thermal stability comprehensively studied for the ten TM-PC candidates, only Pt embedded PC monolayer has been identified as the most promising direct NO-to-NH₃ electroreduction with high feasibility and catalytic performance. This work not only offers a promising catalyst but also sheds light on the active origin and design principle of PC-based single-atom catalysts for NO-to-NH₃ conversion.

Beyond Purification: Highly Efficient and Selective Conversion of NO into Ammonia by Coupling Continuous Absorption and Photoreduction under Ambient Conditions

Although the selective catalytic reduction technology has been confirmed to be effective for nitrogen oxide (NO_x) removal, green and sustainable NO_x re-utilization under ambient conditions is still a great challenge. Herein, we develop an on-site system by coupling the continuous chemical absorption and photocatalytic reduction of NO in simulated flue gas (C_NO = 500 ppm, GHSV = 18,000 h^-1), which accomplishes an exceptional NO conversion into value-added ammonia with competitive conversion efficiency (89.05 ± 0.71%), ammonia production selectivity (95.58 ± 0.95%), and ammonia recovery efficiency (>90%) under ambient conditions. The anti-poisoning capacities, including the resistance against factors of H₂O, SO₂, and alkali/alkaline/heavy metals, are also achieved, which presents strong environmental practicability for treating NO_x in flue gas. In addition, the critical roles of corresponding chemical absorption and catalytic reduction components are also revealed by in situ characterizations. The emerging strategy herein not only achieves a milestone efficiency for sustainable NO purification but also opens a new route for contaminant resourcing in the near future of carbon neutrality.

The β-PdBi2 monolayer for efficient electrocatalytic NO reduction to NH3: a computational study

β-PdBi2 was proposed as a novel NORR catalyst for NH3 synthesis with high efficiency and high selectivity, and its catalytic activity can be enhanced by a tensile strain.

Electrochemical Reduction of Nitric Oxide with 1.7% Solar-to-Ammonia Efficiency Over Nanostructured Core-Shell Catalyst at Low Overpotentials

Transition metals have been recognized as excellent and efficient catalysts for the electrochemical nitric oxide reduction reaction (NORR) to value-added chemicals. In this work, a class of core-shell electrocatalysts that utilize nickel nanoparticles in the core and nitrogen-doped porous carbon architecture in the shell (Ni@NC) for the efficient electroreduction of NO to ammonia (NH3 ) is reported. In Ni@NC, the NC prevents the dissolution of Ni nanoparticles and ensures the long-term stability of the catalyst. The Ni nanoparticles involve in the catalytic reduction of NO to NH3 during electrolysis. As a result, the Ni@NC achieves a faradaic efficiency (FE) of 72.3% at 0.16 VRHE . The full-cell electrolyzer is constructed by coupling Ni@NC as cathode for NORR and RuO2 as an anode for oxygen evolution reaction (OER), which delivers a stable performance over 20 cycles at 1.5 V. While integrating this setup with a PV-electrolyzer cell, and it demonstrates an appreciable FE of >50%. Thus, the results exemplify that the core-shell catalyst based electrolyzer is a promising approach for the stable NO to NH3 electroconversion.