Synergistic Catalysis over Iron‐Nitrogen Sites Anchored with Cobalt Phthalocyanine for Efficient CO2 Electroreduction

Simultaneously achieving high Faradaic efficiency, current density, and stability at low overpotentials is essential for industrial applications of electrochemical CO₂ reduction reaction (CO₂RR). However, great challenges still remain in this catalytic process. Herein, a synergistic catalysis strategy is presented to improve CO₂RR performance by anchoring Fe‐N sites with cobalt phthalocyanine (denoted as CoPc©Fe‐N‐C). The potential window of CO Faradaic efficiency above 90% is significantly broadened from 0.18 V over Fe‐N‐C alone to 0.71 V over CoPc©Fe‐N‐C while the onset potential of CO₂RR over both catalysts is as low as ?0.13 V versus reversible hydrogen electrode. What is more, the maximum CO current density is increased ten times with significantly enhanced stability. Density functional theory calculations suggest that anchored cobalt phthalocyanine promotes the CO desorption and suppresses the competitive hydrogen evolution reaction over Fe‐N sites, while the *COOH formation remains almost unchanged, thus demonstrating unprecedented synergistic effect toward CO₂RR.     

Abundant Ce3+ Ions in Au‐CeOx Nanosheets to Enhance CO2 Electroreduction Performance

The electroreduction of CO₂ to CO provides a potential way to solve the environmental problems caused by excess fossil fuel utilization. Loading transition metals on metal oxides is an efficient strategy for CO₂ electroreduction as well as for reducing metal usage. However, it needs a great potential to overcome the energy barrier to increase CO selectivity. This paper describes how 8.7 wt% gold nanoparticles (NPs) loaded on CeO_x nanosheets (NSs) with high Ce³⁺ concentration effectively decrease the overpotential for CO₂ electroreduction. The 3.6 nm gold NPs on CeO_x NSs containing 47.3% Ce³⁺ achieve CO faradaic efficiency of 90.1% at ?0.5 V in 0.1 m KHCO₃ solution. Furthermore, the CO₂ electroreduction activity shows a strong relationship with the fractions of Ce³⁺ on Au‐CeO_x NSs, which has never been reported. In situ surface‐enhanced infrared absorption spectroscopy shows that Au‐CeO_x NSs with high Ce³⁺ concentration promote CO₂ activation and *COOH formation. Theoretical calculations also indicate that the improved performance is attributed to the enhanced *COOH formation on Au‐CeO_x NSs with high Ce³⁺ fraction.     

Novel Bi-Doped Amorphous SnOx Nanoshells for Efficient Electrochemical CO2 Reduction into Formate at Low Overpotentials

Engineering novel Sn-based bimetallic materials could provide intriguing catalytic properties to boost the electrochemical CO₂ reduction. Herein, the first synthesis of homogeneous Sn_1−xBi_x alloy nanoparticles (x up to 0.20) with native Bi-doped amorphous SnO_x shells for efficient CO₂ reduction is reported. The Bi-SnO_x nanoshells boost the production of formate with high Faradaic efficiencies (>90%) over a wide potential window (−0.67 to −0.92 V vs RHE) with low overpotentials, outperforming current tin oxide catalysts. The state-of-the-art Bi-SnO_x nanoshells derived from Sn_0.80Bi_0.20 alloy nanoparticles exhibit a great partial current density of 74.6 mA cm⁻² and high Faradaic efficiency of 95.8%. The detailed electrocatalytic analyses and corresponding density functional theory calculations simultaneously reveal that the incorporation of Bi atoms into Sn species facilitates formate production by suppressing the formation of H₂ and CO.     

Revealing the Kinetic Balance between Proton-Feeding and Hydrogenation in CO2 Electroreduction

Electrocatalytic reduction of CO₂ to high-value-added chemicals provides a feasible path for global carbon balance. Herein, the fabrication of Ni_NPx@Ni_SAy-NG (x,y = 1, 2, 3; NG = nitrogen-doped graphite) is reported, in which Ni single atom sites (Ni_SA) and Ni nanoparticles (Ni_NP) coexist. These Ni_NPx@Ni_SAy-NG presented a volcano-like trend for maximum CO Faradaic efficiency (FE_CO) with the highest point at Ni_NP2@Ni_SA2-NG in CO₂RR. Ni_NP2@Ni_SA2-NG exhibited ≈98% of maximum FE_CO and a large current density of −264 mA cm⁻² at −0.98 V (vs. RHE) in the flow cell. In situ experiment and density functional theory (DFT) calculations confirmed that the proper content of Ni_SA and Ni_NP balanced kinetic between proton-feeding and CO₂ hydrogenation. The Ni_NP in Ni_NP2@Ni_SA2-NG promoted the formation of H* and reduced the energy barrier of *CO₂ hydrogenation to *COOH, and CO desorption can be efficiently facilitated by Ni_SA sites, thereby resulting in enhanced CO₂RR performance.     

Alumina‐Supported CoFe Alloy Catalysts Derived from Layered‐Double‐Hydroxide Nanosheets for Efficient Photothermal CO2 Hydrogenation to Hydrocarbons

A series of novel CoFe‐based catalysts are successfully fabricated by hydrogen reduction of CoFeAl layered‐double‐hydroxide (LDH) nanosheets at 300–700 °C. The chemical composition and morphology of the reaction products (denoted herein as CoFe‐x) are highly dependent on the reduction temperature (x). CO₂ hydrogenation experiments are conducted on the CoFe‐x catalysts under UV–vis excitation. With increasing LDH‐nanosheet reduction temperature, the CoFe‐x catalysts show a progressive selectivity shift from CO to CH₄, and eventually to high‐value hydrocarbons (C₂₊). CoFe‐650 shows remarkable selectivity toward hydrocarbons (60% CH₄, 35% C₂₊). X‐ray absorption fine structure, high‐resolution transmission electron microscopy, Mössbauer spectroscopy, and density functional theory calculations demonstrate that alumina‐supported CoFe‐alloy nanoparticles are responsible for the high selectivity of CoFe‐650 for C₂₊ hydrocarbons, also allowing exploitation of photothermal effects. This study demonstrates a vibrant new catalyst platform for harnessing clean, abundant solar‐energy to produce valuable chemicals and fuels from CO₂.     

2D Metal Chalcogenides for IR Photodetection

Infrared (IR) photodetectors are finding diverse applications in imaging, information communication, military, etc. 2D metal chalcogenides (2DMCs) have attracted increasing interest in view of their unique structures and extraordinary physical properties. They have demonstrated outstanding IR detection performance including high responsivity and detectivity, high on/off ratio, fast response rate, stable room temperature operability, and good mechanical flexibility, which has opened up a new prospect in next‐generation IR photodetectors. This Review presents a comprehensive summary of recent progress in advanced IR photodetectors based on 2DMCs. The rationale of the photodetectors containing photocurrent generation mechanisms and performance parameters are briefly introduced. The device performances of 2DMCs‐based IR photodetectors are also systematically summarized, and some representative achievements are highlighted as well. Finally, conclusions and outlooks are delivered as a guideline for this thriving field.     

Metal‐Free Carbon Materials for CO2 Electrochemical Reduction

The rapid increase of the CO₂ concentration in the Earth's atmosphere has resulted in numerous environmental issues, such as global warming, ocean acidification, melting of the polar ice, rising sea level, and extinction of species. To search for suitable and capable catalytic systems for CO₂ conversion, electrochemical reduction of CO₂ (CO₂RR) holds great promise. Emerging heterogeneous carbon materials have been considered as promising metal‐free electrocatalysts for the CO₂RR, owing to their abundant natural resources, tailorable porous structures, resistance to acids and bases, high‐temperature stability, and environmental friendliness. They exhibit remarkable CO₂RR properties, including catalytic activity, long durability, and high selectivity. Here, various carbon materials (e.g., carbon fibers, carbon nanotubes, graphene, diamond, nanoporous carbon, and graphene dots) with heteroatom doping (e.g., N, S, and B) that can be used as metal‐free catalysts for the CO₂RR are highlighted. Recent advances regarding the identification of active sites for the CO₂RR and the pathway of reduction of CO₂ to the final product are comprehensively reviewed. Additionally, the emerging challenges and some perspectives on the development of heteroatom‐doped carbon materials as metal‐free electrocatalysts for the CO₂RR are included.     

Efficient and Robust Carbon Dioxide Electroreduction Enabled by Atomically Dispersed Snδ+ Sites

Electrocatalytic CO₂ reduction at considerably low overpotentials still remains a great challenge. Here, a positively charged single‐atom metal electrocatalyst to largely reduce the overpotentials is designed and hence CO₂ electroreduction performance is accelerated. Taking the metal Sn as an example, kilogram‐scale single‐atom Sn^δ+ on N‐doped graphene is first fabricated by a quick freeze–vacuum drying–calcination method. Synchrotron‐radiation X‐ray absorption fine structure and high‐angle annular dark‐field scanning transmission electron microscopy demonstrate the atomically dispersed Sn atoms are positively charged, which enables CO₂ activation and protonation to proceed spontaneously through stabilizing CO₂^??* and HCOO^?*, affirmed by in situ Fourier transform infrared spectra and Gibbs free energy calculations. Furthermore, N‐doping facilitates the rate‐limiting formate desorption step, verified by the decreased desorption energy from 2.16 to 1.01 eV and the elongated Sn? HCOO^? bond length. As an result, single‐atom Sn^δ+ on N‐doped graphene exhibits a very low onset overpotential down to 60 mV for formate production and shows a very large turnover frequency up to 11930 h^?1, while its electroreduction activity proceeds without deactivation even after 200 h. This work offers a new pathway for manipulating electrocatalytic performance.     

Economizing Production of Diverse 2D Layered Metal Hydroxides for Efficient Overall Water Splitting

2D layered metal hydroxides (LMH) are promising materials for electrochemical energy conversion and storage. Compared with exfoliation of bulk layered materials, wet chemistry synthesis of 2D LMH materials under mild conditions still remains a big challenge. Here, an “MgO‐mediated strategy” for mass production of various 2D LMH nanosheets is presented by hydrolyzing MgO in metal salt aqueous solutions at room temperature. Benefiting from this economical and scalable strategy, ultrathin LMH nanosheets (M = Ni, Fe, Co, NiFe, and NiCo) and their derivatives (e.g., metal oxides and sulfides) can be synthesized in high yields. More importantly, this strategy opens up opportunities to fabricate hierarchically structured LMH nanosheets, resulting in high‐performance electrocatalysts for the oxygen‐ and hydrogen‐evolution reactions to realize stable overall water splitting with a low cell voltage of 1.55 V at 10 mA cm⁻². This work provides a powerful platform for the synthesis and applications of 2D materials.     

One-Step Phase Separation for Core-Shell Carbon@Indium Oxide@Bismuth Microspheres with Enhanced Activity for CO2 Electroreduction to Formate

It is a substantial challenge to construct electrocatalysts with high activity, good selectivity, and long-term stability for electrocatalytic reduction of carbon dioxide to formic acid. Herein, bismuth and indium species are innovatively integrated into a uniform heterogeneous spherical structure by a neoteric quasi-microemulsion method, and a novel C@In₂O₃@Bi₅₀ core-shell structure is constructed through a subsequent one-step phase separation strategy due to melting point difference and Kirkendall effect with the nano-limiting effect of the carbon structure. This core-shell C@In₂O₃@Bi₅₀ catalyst can selectively reduce CO₂ to formate with high selectivity (≈90% faradaic efficiency), large partial current density (24.53 mA cm⁻² at −1.36 V), and long-term stability (up to 14.5 h), superior to most of the Bi-based catalysts. The hybrid Bi/In₂O₃ interfaces of core-shell C@In₂O₃@Bi will stabilize the key intermediate HCOO* and suppress CO poisoning, benefiting the CO₂RR selectivity and stability, while the internal cavity of core-shell structure will improve the reaction kinetics because of the large specific surface area and the enhancement of ion shuttle and electron transfer. Furthermore, the nano-limited domain effect of outmost carbon prevent active components from oxidation and agglomeration, helpful for stabilizing the catalyst. This work offers valuable insights into core-shell structure engineering to promote practical CO₂ conversion technology.     

Synthesis of 2D Metal Chalcogenide Thin Films through the Process Involving Solution‐Phase Deposition

2D metal chalcogenide thin films have recently attracted considerable attention owing to their unique physicochemical properties and great potential in a variety of applications. Synthesis of large‐area 2D metal chalcogenide thin films in controllable ways remains a key challenge in this research field. Recently, the solution‐based synthesis of 2D metal chalcogenide thin films has emerged as an alternative approach to vacuum‐based synthesis because it is relatively simple and easy to scale up for high‐throughput production. In addition, solution‐based thin films open new opportunities that cannot be achieved from vacuum‐based thin films. Here, a comprehensive summary regarding the basic structures and properties of different types of 2D metal chalcogenides, the mechanistic details of the chemical reactions in the synthesis of the metal chalcogenide thin films, recent successes in the synthesis by different reaction approaches, and the applications and potential uses is provided. In the last perspective section, the technical challenges to be overcome and the future research directions in the solution‐based synthesis of 2D metal chalcogenides are discussed.     

Phase-Inversion Induced 3D Electrode for Direct Acidic Electroreduction CO2 to Formic acid

Direct electrochemical CO₂ reduction to formic acid (FA) instead of formate is a challenging task due to the high acidity of FA and competitive hydrogen evolution reaction. Herein, 3D porous electrode (TDPE) is prepared by a simple phase inversion method, which can electrochemically reduce CO₂ to FA in acidic conditions. Owing to interconnected channels, high porosity, and appropriate wettability, TDPE not only improves mass transport, but also realizes pH gradient to build higher local pH micro-environment under acidic conditions for CO₂ reduction compared with planar electrode and gas diffusion electrode. Kinetic isotopic effect experiments demonstrate that the proton transfer becomes the rate-determining step at the pH of 1.8; however, not significant in neutral solution, suggesting that the proton is aiding the overall kinetics. Maximum FA Faradaic efficiency of 89.2% has been reached at pH 2.7 in a flow cell, generating FA concentration of 0.1 m . Integrating catalyst and gas–liquid partition layer into a single electrode structure by phase inversion method paves a facile avenue for direct production of FA by electrochemical CO₂ reduction.     

Heterostructures Based on 2D Materials: A Versatile Platform for Efficient Catalysis

The unique structural and electronic properties of 2D materials, including the metal and metal‐free ones, have prompted intense exploration in the search for new catalysts. The construction of different heterostructures based on 2D materials offers great opportunities for boosting the catalytic activity in electo(photo)chemical reactions. Particularly, the merits resulting from the synergism of the constituent components and the fascinating properties at the interface are tremendously interesting. This scenario has now become the state‐of‐the‐art point in the development of active catalysts for assisting energy conversion reactions including water splitting and CO₂ reduction. Here, starting from the theoretical background of the fundamental concepts, the progressive developments in the design and applications of heterostructures based on 2D materials are traced. Furthermore, a personal perspective on the exploration of 2D heterostructures for further potential application in catalysis is offered.     

Potential Link between Cu Surface and Selective CO2 Electroreduction: Perspective on Future Electrocatalyst Designs

Electrochemical reduction of carbon dioxide (CO₂RR) product distribution has been identified to be dependent on various surface factors, including the Cu facet, morphology, chemical states, doping, etc., which can alter the binding strength of key intermediates such as *CO and *OCCO during reduction. Therefore, in-depth knowledge of the Cu catalyst surface and identification of the active species under reaction conditions aid in designing efficient Cu-based electrocatalysts. This progress report categorizes various Cu-based electrocatalysts into four main groups, namely metallic Cu, Cu alloys, Cu compounds (Cu + non-metal), and supported Cu-based catalysts (Cu supported by carbon, metal oxides, or polymers). The detailed mechanisms for the selective CO₂RR are presented, followed by recent relevant developments on the synthetic procedures for preparing Cu and Cu-based nanoparticles. Herein, the potential link between the Cu surface and CO₂RR performance is highlighted, especially in terms of the chemical states, but other significant factors such as defective sites and roughened morphology of catalysts are equally considered during the discussion of current studies of CO₂RR with Cu-based electrocatalysts to fully understand the origin of the significant enhancement toward C₂ formation. This report concludes by providing suggestions for future designs of highly selective and stable Cu-based electrocatalysts for CO₂RR.     

2D Early Transition Metal Carbides (MXenes) for Catalysis

MXenes, a bourgeoning class of 2D transition metal carbides, are of considerable interest in catalysis due to their rich surface chemistry, tunable electronic structures, and thermal stability. Here, recent conceptual advances in applying MXenes and their nanocomposites in (photo)electrocatalysis and conventional heterogeneous catalysis are highlighted. In addition, the nature of active sites in the MXene‐based catalysts are discussed and the significance and challenges in the future development of catalysts using MXenes as the platforms are summarized.     

Scalable Synthesis of Holey Deficient 2D Co/NiO Single-Crystal Nanomeshes via Topological Transformation for Efficient Photocatalytic CO2 Reduction

Preparation of holey, single-crystal, 2D nanomaterials containing in-plane nanosized pores is very appealing for the environment and energy-related applications. Herein, an in situ topological transformation is showcased of 2D layered double hydroxides (LDHs) allows scalable synthesis of holey, single-crystal 2D transition metal oxides (TMOs) nanomesh of ultrathin thickness. As-synthesized 2D Co/NiO-2 nanomesh delivers superior photocatalytic CO₂-syngas conversion efficiency (i.e., V_CO of 32460 µmol h⁻¹ g⁻¹ CO and $V_{{\mathrm{H}}_2}$ of 17840 µmol h⁻¹ g⁻¹ H₂), with V_CO about 7.08 and 2.53 times that of NiO and 2D Co/NiO-1 nanomesh containing larger pore size, respectively. As revealed in high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), the high performance of Co/NiO-2 nanomesh primarily originates from the edge sites of nanopores, which carry more defect structures (e.g., atomic steps or vacancies) than basal plane for CO₂ adsorption, and from its single-crystal structure adept at charge transport. Theoretical calculation shows the topological transformation from 2D hydroxide to holey 2D oxide can be achieved, probably since the trace Co dopant induces a lattice distortion and thus a sharp decrease of the dehydration energy of hydroxide precursor. The findings can advance the design of intriguing holey 2D materials with well-defined geometric and electronic properties.     

Promoted Photocharge Separation in 2D Lateral Epitaxial Heterostructure for Visible-Light-Driven CO2 Photoreduction

Photocarrier recombination remains a big barrier for the improvement of solar energy conversion efficiency. For 2D materials, construction of heterostructures represents an efficient strategy to promote photoexcited carrier separation via an internal electric field at the heterointerface. However, due to the difficulty in seeking two components with suitable crystal lattice mismatch, most of the current 2D heterostructures are vertical heterostructures and the exploration of 2D lateral heterostructures is scarce and limited. Here, lateral epitaxial heterostructures of BiOCl @ Bi₂O₃ at the atomic level are fabricated via sonicating-assisted etching of Cl in BiOCl. This unique lateral heterostructure expedites photoexcited charge separation and transportation through the internal electric field induced by chemical bonding at the lateral interface. As a result, the lateral BiOCl @ Bi₂O₃ heterostructure demonstrates superior CO₂ photoreduction properties with a CO yield rate of about 30 µmol g⁻¹ h⁻¹ under visible light illumination. The strategy to fabricate lateral epitaxial heterostructures in this work is expected to provide inspiration for preparing other 2D lateral heterostructures used in optoelectronic devices, energy conversion, and storage fields.