Themed collection Single-Atom Catalysis

Zhiqun Lin, María Escudero-Escribano and Jun Li introduce the Journal of Materials Chemistry A themed issue on single-atom catalysis.

The versatility of MOFs is ideal for designing efficient CO2RR electrocatalysts, yet their poor stability and conductivity needs to be improved.

The direction and spatial distribution of charge transfer between a single atom and its support are key factors for SAC performance.

This perspective outlines recent advances, future opportunities and challenges in the research field of single-atom-based catalysts (SACs) in the photoelectrocatalytic (PEC) system.

Heterogeneous chemical reactions catalyzed over solid surfaces at operating temperatures are used to produce a vital part of energy, food, healthcare products, cleaner environments and chemicals.

Carbon monoxide and formic acid play a significant role in industrial processes and are exceedingly economical C₁ products in electrochemical CO₂ reduction reactions (ECR).

Scaffolds in the graphic indicate active sites of SACs. Ideal active sites come from a tenon-and-mortise structure and highlight that the most active SACs require various strategies to achieve synergy, building on a foundation of mutual promotion, restriction, and balance.

The significant structural effects of supported Ni catalysts from nanoparticles to single atoms on CO₂ hydrogenation were summarized.

The recent advances in the stability of SACs, including the selection of metals and supports, synthetic strategies, and the catalytic stability in electrocatalysis.

An overview of two types of SACs for the CO₂RR and the corresponding strategies to regulate the catalytic activity.

The unique structures of single-atom catalysts (SACs) endow them with widespread energy applications. This review summarized the achievements of multifarious synchrotron-radiation characterization methods in studying the local environments of SACs.

This review delivers an overview of non-noble metal-based single-atom catalysts (SACs) for CO₂RR and provides insights into mechanistic understanding from different aspects.

This perspective provides an overview and outlook of polyoxometalate-based single-atom catalysts with atomic-precision structures and wide-ranging functionalities, including isolated POM clusters, POM-based assemblies, and supported POM structures.

This review highlights several important electrocatalytic reactions performed over single-atomic synergistic structures, including SAC-nanoparticles (SAC-NPs), SAC-clusters (SACCs), dual-atom sites (DACs), and single-atomic alloys (SAAs).

Single-atom catalysts (SACs) have attracted wide interest from researchers, as they promisingly bridge the gap between homogeneous and heterogeneous catalysts.

The review highlights recent advances and remaining challenges in single atom catalysts for thermal- and electro-catalytic hydrogenation reactions.

Based on the “bifunctionality index”, which can be both measured and calculated, we elaborated a joint volcano plot for O₂ reduction and evolution. The plot shows how scaling relations limit the bifunctional performance of single-atom catalysts.

A single-atom Co-PTS-COPs@MWCNT catalyst was crafted via a simple yet robust pyrolysis-free approach for high-efficiency oxygen reduction.

Improved catalytic durability towards acidic oxygen reduction reaction is achieved by using a Pt-free and Fe-free single-atom catalyst based on Mn, Co and N co-doped carbon (MnCo–N–C), compared with a Co and N co-doped carbon (Co–N–C) catalyst.

The prepared SA-Fe-3DOMC catalyst with rich pore structure and densely accessible Fe–N₄ active was demonstrated to boost ORR catalytic performance and peak power density for Zn–air batteries.

Electrochemical deposition from an electrolyte containing Cu²⁺ loads Cu(0) nanoparticles (3.34 wt%) into a COF, making them resemble a single-site catalyst. This Cu@COF serves as an excellent heterogeneous catalyst for multi-fold Ullmann coupling reactions.

All-silica MFI zeolite was used as a support for the synthesis of promoter-free robust transition metal catalysts. Effects of different physical parameters and catalyst deactivation mechanism were studied for the ethane dehydrogenation reaction.

A systematic density functional theory study to investigate the stability of single-atom catalysts (SACs) over a series of O-terminated MXenes with the stoichiometry of M₂CO₂.

This work reports that via confining high density of 16 wt% single Mo atoms into the lattice of CoOOH nanosheets and simultaneously fabricating robust nanoframes of the nanosheets, an unprecedented large-current-density OER activity is achieved.

Single-atom catalysts, in particular the Fe–N–C family of materials, have emerged as a promising alternative to platinum group metals in fuel cells as catalysts for the oxygen reduction reaction.

Single atom alloys (SAAs) based on TM doped Ru(0001) were investigated for their nitrogen reduction activity using density functional modelling. V@Ru(0001) was found to exhibit a low negative limiting potential and the TOF of the V@Ru(0001) catalyst was shown to be high.

Compared to Ru single atom catalyst, hetero-RuM (M = Fe, Os, and Ir) double atom catalysts showed improved N₂RR activity with the help of d_xz and d_xy bonding orbital, caused by strain, dopant and configurational effects.

Single-atom catalyst of Cu₁@ZnO/GPET synthesized via hydrothermal method is shown to exhibit excellent photocatalytic activity towards the degradation of methylene blue solution due to high electron–hole separation efficiency.

Computational studies of structural and catalytic properties of single atom catalysts suggest they are attractive candidates for methane-to-methanol conversion.

The single-atom Co anchored on N-doped carbon supports with a multiscale porous structure has been successfully constructed for the epoxidation of cyclooctene with 95% yield of 1,2-epoxycycloheptane at 140 °C and 0.5 MPa O₂.

Embedding Ag single atoms onto densely arrayed Cu nanopyramids could optimize the *CO adsorption strength toward direct propanediol production via a one-step concerted *CO trimerization mechanism.

Single-atom catalysts on supported silicomolybdic acid for CO₂ electroreduction.

A simple and effective plasma-activated strategy is employed to synthesize a MOF-based single-atom copper catalyst, which contains abundant low-coordinated copper sites for high-performance CO₂ electroreduction to CH₄.

The NiN₄–Cl SAs/N–C electrocatalyst consisting of NiN₄–Cl active sites with axial Ni–Cl coordination was synthesized. The axial Cl-coordination modulates the electronic configuration of Ni–N₄ sites and enhances the interaction of Ni–H efficiently.

The proposed new non-noble-metal Mo₁/PMASAC is potentially more efficient and more selective than the current best Mo/BN and FeN₃/embedded graphene SAC, and the preferred mechanism is an enzymatic pathway.

SnO₂ supported single metal atoms offer unique bifunctional catalyst materials for electrochemical synthesis of hydrogen peroxide via 2e-ORR and 2e-WOR.

Layer-by-layer redispersion of high-loading carbon-supported metal nanoparticles into small clusters and single atoms via cyclic alternating exposure to C₂H₂ and HCl atmospheres.

A hierarchically porous N/C-network containing atomically dispersed Cl–FeN₄ nuclei as superior ORR electrocatalysts in an alkaline environment.

By taking advantage of the unique advantages of Eu³⁺ single atom catalysis and the II-type heterojunction in the field of photocatalytic reduction, a Eu³⁺ single atom doped CdS/InVO₄ II-type heterojunction was successfully constructed.

Atomically dispersed Ni sites are coupled with sub-5 nm Pd nanocrystals embedded in carbon frameworks to form a bifunctional catalyst, which could serve as a highly efficient catalyst for the ORR, OER, and Zn–air batteries.

Anchoring Au atoms on WO₃/TiO₂ nanotubes by a simple two-step electrochemical approach significantly improved the photocatalytic degradation of toluene, due to the enhanced transfer and separation of photogenerated carriers and adsorption.

By first-principles calculations, the singly dispersed bimetallic site, Pd₁Co₄/CoO_x SCC, is proposed to exhibit superior charge buffer capacity towards thermal dinitrogen hydrogenation based on a superimposed evaluation strategy.

As a novel electrocatalyst for acetylene semihydrogenation, single-atom nickel dispersed N-doped carbon exhibits a high acetylene conversion of 97.4%, which are attributed to weak π-adsorption of ethylene on individual Ni sites.

A Pd nanoparticle@Ni single-atomic catalyst (SAC) was developed for electrocatalytic ethanol oxidation. The Pd nanoparticles served as catalytic sites of ethanol, and the produced CO species adsorbed on Pd were electrochemically oxidized by Ni SAC.

A MnO_x-assisted strategy is proposed to improve the oxygen reduction activity and stability of Fe–N–C single-atom catalysts (SACs) by regulating the electron structure and reducing the side effects of the Fenton reaction.

Copper- and nitrogen-doped carbonaceous materials, obtained by a simple synthetic procedure are highly efficient and fast catalysts for the oxygen reduction reaction. It is shown, that Cu(I) containing materials perform with faster reaction kinetics.

In situ TEM observation and DFT calculation provide an atomic-scale understanding of the electrocatalysis mechanism of single-atom catalysts in an Na–O₂ nanobattery, where single-atomic Co sites facilitate the formation/decomposition of Na₂O₂.

A self-powered dual hydrogen production system constructed by combining a Zn–H₂ battery and an overall hydrazine splitting unit with Rh single atoms supported on oxygen-functionalized Ti₃C₂O_x bifunctional catalyst achieves a promising H₂ generation rate of 45.77 mmol h⁻¹.

In-doping induces electronic modifications in TiO₂ leading to an increase in the CO2 photoreduction selectivity towards CH₄.

A new graphdiyne-based manganese atomic catalyst (Mn_SA/GDY) was reported for efficient electrocatalytic nitrogen reduction to ammonia. It achieves a high ammonia yield rate and Faradaic efficiency at ambient temperatures and pressures.

We developed a TiO₂-supported single-atom Mo catalyst (Mo₁/TiO₂) where single Mo atoms paired with the neighboring surface Ti atoms function as Mo–Ti acid–base dual sites, realizing the decomposition of ABS at ∼225 °C.

Ir modification of FeNC catalysts improves the durability of the catalysts, but causes electronic changes that are disadvantageous for the activity.

Densely populated single-atom Fe–N_x-embedded carbon nanosheets (SAs-Fe/N-CNSs) synthesized by a Zn/g-C₃N₄-mediated dual-template strategy with excellent performance on ORRs and Zn–air batteries.

An advanced strategy for practical application of Pt-SA catalysts.

Platinum is atomically dispersed within P-doped C₃N₄ forming Pt–N/P/Cl coordination interactions, and exhibits markedly enhanced electrocatalytic activity towards the hydrogen evolution reaction in acidic media, as compared to the P-free counterpart.

The catalytic conversion of NO and CO into N₂ and CO₂ mediated by gas-phase rhodium-aluminum oxides (RhAlO_0–3 and RhAl₂O_1–4) has been identified. The polarized Rh–Al bond in the reactive systems is required to catalyze NO reduction by CO.