Correlating Oxidation State and Surface Ligand Motifs with the Selectivity of CO2 Photoreduction to C2 Products

The design for non-Cu-based catalysts with the function of producing C₂₊ products requires systematic knowledge of the intrinsic connection between the surface state as well as the catalytic activity and selectivity. In this work, photochemical in situ spectral surface characterization techniques combined with the first principle calculations (DFT) were applied to investigate the relationships between the composition of surface states, coordinated motifs, and catalytic selectivity of a titanium oxynitride catalyst. When the catalyst mediates CO₂ photoreduction, C₂ product selectivity is positively correlated with the surface Ti²⁺/Ti³⁺ ratio and the surface oxidation state is regulated and controlled by coordinated motifs of N−Ti-O/V[O], which can reduce the potential dimerization energy barriers of *CO−CO* and promote spontaneous formation of the subsequent *CO−CH₂* intermediate. This phenomenon provides a new perspective for the design of heterogeneous catalysts for photoreduction of CO₂ into useful products.     

Redox Replacement of Silver on MOF-Derived Cu/C Nanoparticles on Gas Diffusion Electrodes for Electrocatalytic CO2 Reduction

Bimetallic tandem catalysts have emerged as a promising strategy to locally increase the CO flux during electrochemical CO₂ reduction, so as to maximize the rate of conversion to C−C-coupled products. Considering this, a novel Cu/C−Ag nanostructured catalyst has been prepared by a redox replacement process, in which the ratio of the two metals can be tuned by the replacement time. An optimum Cu/Ag composition with similarly sized particles showed the highest CO₂ conversion to C₂₊ products compared to non-Ag-modified gas-diffusion electrodes. Gas chromatography and in-situ Raman measurements in a CO₂ gas diffusion cell suggest the formation of top-bound linear adsorbed *CO followed by consumption of CO in the successive cascade steps, as evidenced by the increasingνC−H bands. These findings suggest that two mechanisms operate simultaneously towards the production of HCO₂H and C−C-coupled products on the Cu/Ag bimetallic surface.     

Carbon-Based Electron Buffer Layer on ZnOx−Fe5C2−Fe3O4 Boosts Ethanol Synthesis from CO2 Hydrogenation

The conversion of CO₂ into ethanol with renewable H₂ has attracted tremendous attention due to its integrated functions of carbon elimination and chemical synthesis, but remains challenging. The electronic properties of a catalyst are essential to determine the adsorption strength and configuration of the key intermediates, therefore altering the reaction network for targeted synthesis. Herein, we describe a catalytic system in which a carbon buffer layer is employed to tailor the electronic properties of the ternary ZnO_x−Fe₅C₂−Fe₃O₄, in which the electron-transfer pathway (ZnO_x→Fe species or carbon layer) ensures the appropriate adsorption strength of −CO* on the catalytic interface, facilitating C−C coupling between −CH_x* and −CO* for ethanol synthesis. Benefiting from this unique electron-transfer buffering effect, an extremely high ethanol yield of 366.6 g_EtOH kg_cat⁻¹ h⁻¹ (with CO of 10 vol % co-feeding) is achieved from CO₂ hydrogenation. This work provides a powerful electronic modulation strategy for catalyst design in terms of highly oriented synthesis.     

Wurtzite CuGaS2 with an In-Situ-Formed CuO Layer Photocatalyzes CO2 Conversion to Ethylene with High Selectivity

We present surface reconstruction-induced C−C coupling whereby CO₂ is converted into ethylene. The wurtzite phase of CuGaS_2. undergoes in situ surface reconstruction, leading to the formation of a thin CuO layer over the pristine catalyst, which facilitates selective conversion of CO₂ to ethylene (C₂H₄). Upon illumination, the catalyst efficiently converts CO₂ to C₂H₄ with 75.1 % selectivity (92.7 % selectivity in terms of R_electron) and a 20.6 μmol g⁻¹ h⁻¹ evolution rate. Subsequent spectroscopic and microscopic studies supported by theoretical analysis revealed operando-generated Cu²⁺, with the assistance of existing Cu⁺, functioning as an anchor for the generated *CO and thereby facilitating C−C coupling. This study demonstrates strain-induced in situ surface reconstruction leading to heterojunction formation, which finetunes the oxidation state of Cu and modulates the CO₂ reduction reaction pathway to selective formation of ethylene.     

Selective Photocatalytic Reduction of CO2 to CO Mediated by Silver Single Atoms Anchored on Tubular Carbon Nitride

Artificial photosynthesis is a promising strategy for converting carbon dioxide (CO₂) and water (H₂O) into fuels and value-added chemical products. However, photocatalysts usually suffered from low activity and product selectivity due to the sluggish dynamic transfer of photoexcited charge carriers. Herein, we describe anchoring of Ag single atoms on hollow porous polygonal C₃N₄ nanotubes (PCN) to form the photocatalyst Ag₁@PCN with Ag−N₃ coordination for CO₂ photoreduction using H₂O as the reductant. The as-synthesized Ag₁@PCN exhibits a high CO production rate of 0.32 μmol h⁻¹ (mass of catalyst: 2 mg), a high selectivity (>94 %), and an excellent stability in the long term. Experiments and density functional theory (DFT) reveal that the strong metal–support interactions (Ag−N₃) favor *CO₂ adsorption, *COOH generation and desorption, and accelerate dynamic transfer of photoexcited charge carriers between C₃N₄ and Ag single atoms, thereby accounting for the enhanced CO₂ photoreduction activity with a high CO selectivity. This work provides a deep insight into the important role of strong metal–support interactions in enhancing the photoactivity and CO selectivity of CO₂ photoreduction.     

Electrochemical and in-situ X-ray diffraction studies of Ti3C2Tx MXene in ionic liquid electrolyte

2D titanium carbide (Ti₃C₂T_x MXene) showed good capacitance in both organic and neat ionic liquid electrolytes, but its charge storage mechanism is still not fully understood. Here, electrochemical characteristics of Ti₃C₂T_x electrode were studied in neat EMI-TFSI electrolyte. A capacitive behavior was observed within a large electrochemical potential range (from − 1.5 to 1.5 V vs. Ag). Intercalation and de-intercalation of EMI⁺ cations and/or TFSI⁻ anions were investigated by in-situ X-ray diffraction. Interlayer spacing of Ti₃C₂T_x flakes decreases during positive polarization, which can be ascribed to either electrostatic attraction effect between intercalated TFSI⁻ anions and positively charged Ti₃C₂T_x nanosheets or steric effect caused by de-intercalation of EMI⁺ cations. The expansion of interlayer spacing when polarized to negative potentials is explained by steric effect of cation intercalation.     

Solar-Driven CO2 Conversion via Optimized Photothermal Catalysis in a Lotus Pod Structure

Photothermal CO₂ reduction is one of the most promising routes to efficiently utilize solar energy for fuel production at high rates. However, this reaction is currently limited by underdeveloped catalysts with low photothermal conversion efficiency, insufficient exposure of active sites, low active material loading, and high material cost. Herein, we report a potassium-modified carbon-supported cobalt (K⁺−Co−C) catalyst mimicking the structure of a lotus pod that addresses these challenges. As a result of the designed lotus-pod structure which features an efficient photothermal C substrate with hierarchical pores, an intimate Co/C interface with covalent bonding, and exposed Co catalytic sites with optimized CO binding strength, the K⁺−Co−C catalyst shows a record-high photothermal CO₂ hydrogenation rate of 758 mmol g_cat⁻¹ h⁻¹ (2871 mmol g_Co⁻¹ h⁻¹) with a 99.8 % selectivity for CO, three orders of magnitude higher than typical photochemical CO₂ reduction reactions. We further demonstrate with this catalyst effective CO₂ conversion under natural sunlight one hour before sunset during the winter season, putting forward an important step towards practical solar fuel production.     

Titanium Carbide (Ti3C2Tx) MXene Ornamented with Palladium Nanoparticles for Electrochemical CO Oxidation

Titanium carbide (Ti₃C₂T_x) MXene possesses various unique physicochemical and catalytic properties. However, the electrochemical CO oxidation performance is not yet addressed experimentally. Herein, Ti₃C₂T_x (T_X=OH, O, and F) ordered and exfoliated two-dimensional nanosheets ornamented with semi-spherical palladium nanoparticles (2.5 Wt. %) with an average diameter of (10±1 nm) (denoted as Pd/Ti₃C₂T_x) is rationally designed for the electrochemical CO oxidation. The fabrication process is based on the selective chemical etching of Ti₃AlC₂ and delamination under sonication to form Ti₃C₂Tx nanosheets that are used as a substrate and reducing agent for supporting in situ growth of Pd nanoparticles via impregnation with Pd salt. Interestingly, Pd-free Ti₃C₂T_x displayed inferior CO oxidation activity, while Pd/Ti₃C₂T_x enhanced the CO oxidation activity substantially. This is attributed to the combination of outstanding physicochemical properties of Ti₃C₂T_x and the catalytic merits of Pd nanoparticles.     

Toward Understanding the Enhanced Pseudocapacitive Storage in 3D SnS/MXene Architectures Enabled by Engineered Surface Reactions

The optimization of three-dimensional (3D) MXene-based electrodes with desired electrochemical performances is highly demanded. Here, a precursor-guided strategy is reported for fabricating the 3D SnS/MXene architecture with tiny SnS nanocrystals (≈5 nm in size) covalently decorated on the wrinkled Ti₃C₂T_x nanosheets through Ti−S bonds (denoted as SnS/Ti₃C₂T_x-O). The formation of Ti−S bonds between SnS and Ti₃C₂T_x was confirmed by extended X-ray absorption fine structure (EXAFS). Rather than bulky SnS plates decorated on Ti₃C₂T_x (SnS/Ti₃C₂T_x-H) by one-step hydrothermal sulfidation followed by post annealing, this SnS/Ti₃C₂T_x-O presents size-dependent structural and dynamic properties. The as-formed 3D hierarchical structure can provide short ion-diffusion pathways and electron transport distances because of the more accessible surface sites. In addition, benefiting from the tiny SnS nanocrystals that can effectively improve Na⁺ diffusion and suppress structural variation upon charge/discharge processes, the as-obtained SnS/Ti₃C₂T_x-O can generate pseudocapacitance-dominated storage behavior enabled by engineered surface reactions. As predicted, this electrode exhibits an enhanced Na storage capacity of 565 mAh g⁻¹ at 0.1 A g⁻¹ after 75 cycles, outperforming SnS/Ti₃C₂T_x-H (336 mAh g⁻¹), SnS (212 mAh g⁻¹), and Ti₃C₂T_x (104 mAh g⁻¹) electrodes.     

Enhanced Electrochemical Reduction of CO2 to CO on Ag/SnO2 by a Synergistic Effect of Morphology and Structural Defects

Silver (Ag)-based materials are considered to be promising materials for electrochemical reduction of CO₂ to produce CO, but the selectivity and efficiency of traditional polycrystalline Ag materials are insufficient; there still exists a great challenge to explore novel modified Ag based materials. Herein, a nanocomposite of Ag and SnO₂ (Ag/SnO₂) for efficient reduction of CO₂ to CO is reported. HRTEM and XRD patterns clearly demonstrated the lattice destruction of Ag and the amorphous SnO₂ in the Ag/SnO₂ nanocomposite. Electrochemical tests indicated the nanocomposite containing 15% SnO₂ possesses highest catalytic selectivity featured by a CO faradaic efficiency (FE) of 99.2% at −0.9 V versus reversible hydrogen electrode (vs RHE) and FE>90% for the CO product at a wide potential range from −0.8 V to −1.4 V vs RHE. Experimental characterization and analysis showed that the high catalytic performance is attributed to not only the branched morphology of Ag/SnO₂ nanocomposites (NCs), which endows the maximum exposure of active sites, but also the special adsorption capacity of abundant defect sites in the crystal for *COOH (the key intermediate of CO formation), which improves the intrinsic activity of the catalyst. But equally important, the existed SnO₂ also plays an important role in inhibiting hydrogen evolution reaction (HER) and anchoring defect sites. This work demonstrates the use of crystal defect engineering and synergy in composite to improve the efficiency of electrocatalytic CO₂ reduction reaction (CO₂RR).     

Electrocatalysts Derived from Copper Complexes Transform CO into C2+ Products Effectively in a Flow Cell

Electrochemical reactors that electrolytically convert CO₂ into higher-value chemicals and fuels often pass a concentrated hydroxide electrolyte across the cathode. This strongly alkaline medium converts the majority of CO₂ into unreactive HCO₃⁻ and CO₃²⁻ byproducts rather than into CO₂ reduction reaction (CO2RR) products. The electrolysis of CO (instead of CO₂) does not suffer from this undesirable reaction chemistry because CO does not react with OH⁻. Moreover, CO can be more readily reduced into products containing two or more carbon atoms (i. e., C₂₊ products) compared to CO₂. We demonstrate here that an electrocatalyst layer derived from copper phthalocyanine ( CuPc ) mediates this conversion effectively in a flow cell. This catalyst achieved a 25 % higher selectivity for acetate formation at 200 mA/cm² than a known state-of-art oxide-derived Cu catalyst tested in the same flow cell. A gas diffusion electrode coated with CuPc electrolyzed CO into C₂₊ products at high rates of product formation (i. e., current densities ≥200 mA/cm²), and at high faradaic efficiencies for C₂₊ production (FE_C2+; >70 % at 200 mA/cm²). While operando Raman spectroscopy did not reveal evidence of structural changes to the copper molecular complex, X-ray photoelectron spectroscopy suggests that the catalyst undergoes conversion to a metallic copper species during catalysis. Notwithstanding, the ligand environment about the metal still impacts catalysis, which we demonstrated through the study of a homologous CuPc bearing ethoxy substituents. These findings reveal new strategies for using metal complexes for the formation of carbon-neutral chemicals and fuels at industrially relevant conditions.     

In Situ Reconstruction of a Hierarchical Sn-Cu/SnOx Core/Shell Catalyst for High-Performance CO2 Electroreduction

The electrochemical CO₂ reduction reaction (CO₂RR) to give C₁ (formate and CO) products is one of the most techno-economically achievable strategies for alleviating CO₂ emissions. Now, it is demonstrated that the SnO_x shell in Sn_2.7Cu catalyst with a hierarchical Sn-Cu core can be reconstructed in situ under cathodic potentials of CO₂RR. The resulting Sn_2.7Cu catalyst achieves a high current density of 406.7±14.4 mA cm⁻² with C₁ Faradaic efficiency of 98.0±0.9 % at −0.70 V vs. RHE, and remains stable at 243.1±19.2 mA cm⁻² with a C₁ Faradaic efficiency of 99.0±0.5 % for 40 h at −0.55 V vs. RHE. DFT calculations indicate that the reconstructed Sn/SnO_x interface facilitates formic acid production by optimizing binding of the reaction intermediate HCOO* while promotes Faradaic efficiency of C₁ products by suppressing the competitive hydrogen evolution reaction, resulting in high Faradaic efficiency, current density, and stability of CO₂RR at low overpotentials.     

Cu Atomic Chain Supported on Graphene Nanoribbon for Effective Conversion of CO2 to Ethanol

Cu catalysts are well-known for their good performance in CO₂ conversion. Compared to CO and CH₄ production, C₂ products have higher volumetric energy densities and are more valuable in industrial applications. In this work, we screened the catalytic ability of C₂ production on several 1D Cu atomic chain structures and find that Cu edge-decorated zigzag graphene nanoribbons (Cu−ZGNR) are capable of catalyzing CO₂ conversion to ethanol, and CH₃CH₂OH is the main C₂ product with a maximum free energy change of 0.60 eV. The planar tetracoordinate carbon structures in Cu-ZGNR provide unique chemical bonding features for catalytic reaction on the Cu atoms. Detailed mechanism analyses with transition states search show that CO* dimerization is favored against CHO* formation in the reaction. By adjusting the CO* coverage, the selectivity of the C₂ product can be enhanced owing to less pronounced steric effects for COCHO*, which is feasible under experimental conditions. This study expands the catalyst family for C₂ products from CO₂ based on nano carbon structures with new features.     

Enhanced Carbon Monoxide Electroreduction to >1 A cm−2 C2+ Products Using Copper Catalysts Dispersed on MgAl Layered Double Hydroxide Nanosheet House-of-Cards Scaffolds

Cu catalysts are most apt for reducing CO₍₂₎ to multi-carbon products in aqueous electrolytes. To enhance the product yield, we can increase the overpotential and the catalyst mass loading. However, these approaches can cause inadequate mass transport of CO₍₂₎ to the catalytic sites, which will then lead to H₂ evolution dominating the product selectivity. Herein, we use a MgAl LDH nanosheet ‘house-of-cards’ scaffold to disperse CuO-derived Cu (OD-Cu). With this support-catalyst design, at −0.7 V_RHE, CO could be reduced to C₂₊ products with a current density (j_C2+) of −1251 mA cm⁻². This is 14× that of the j_C2+ shown by unsupported OD-Cu. The current densities of C₂₊ alcohols and C₂H₄ were also high at −369 and −816 mA cm⁻² respectively. We propose that the porosity of the LDH nanosheet scaffold enhances CO diffusion through the Cu sites. The CO reduction rate can thus be increased, while minimizing H₂ evolution, even when high catalyst loadings and large overpotentials are used.     

Pt immobilized spontaneously on porous MXene/MAX hybrid monolith for hydrogen evolution reaction

Designing efficient electrocatalysts with low Pt loadings for hydrogen evolution reaction(HER) is urgently required for renewable and sustainable energy conversion.Here,we report a strategy that Pt nanoparticulates are spontaneously immobilized on porous MXene/MAX monolith as HER catalysts by utilizing the redox reaction between Ti_3C_2T_x MXene and [PtCl_4]~2 in H_2 PtCl_6 aqueous solution.By taking advantage of homogeneously distributed Pt nanoparticulates on highly electrically conductive porous Ti_3C_2T_x/Ti_3AlC_2 monolith,the as-prepared electrocatalysts show high catalytic performance for hydrogen evolution.Specifically,the binder-free electrocatalysts have Pt loadings as low as 8.9 μg/cm~2,with low overpotential of 43 mV at a curre nt density of 10 mA/cm~2 and low Tafel slope that three times lower than porous Ti_3C_2T_x/Ti_3AlC_2 without Pt loading.This strategy offers a new approach to constructing ultra-low Pt-loading HER catalysts on the basis of in situ redox reaction between noble metal ions and MXenes.     

Ag Doped Au44 Nanoclusters for Electrocatalytic Conversion of CO2 to CO

A novel Ag doped Au₄₄(C₁₀H₉)₂₈ nanocluster (C₁₀H₁₀=1-ethynyl-2,4-dimethylbenzene) was synthesized, that is, Ag_4+xAu_40-x(C₁₀H₉)₂₈ (x≤6), where four Ag positions located in the surface staple of the cluster have been determined, while six Au/Ag co-occupying positions have been found in the metal core of the cluster. The electronic configuration of Au₄₄(C₁₀H₉)₂₈ cluster is significantly disturbed by doping Ag atoms, hence promoting the electron transport capability. For the two-electron conversion reaction of CO₂ to CO in electrochemical reduction of CO₂, Ag doped Ag_4+xAu_40-x(C₁₀H₉)₂₈ catalyst exhibited higher effective activity and long-term stability than its counterpart Au₄₄(C₁₀H₉)₂₈ catalyst.     

FeMn、FeMnNa和FeMnK催化剂上合成气制低碳烯烃的比较

研究了钠、钾助剂对FeMn 合成低碳烯烃催化剂结构及性能的影响. 低温N₂吸附、X射线光电子能谱（XPS）、X射线衍射（XRD）、H₂程序升温还原（H₂-TPR）、CO/CO₂程序升温脱附（CO/CO₂-TPD）、Mössbauer 谱和CO+H₂反应的研究结果表明,增加Mn助剂含量促进了活性相的分散和低碳烯烃的生成,而过多锰助剂在催化剂表面的富集则降低了费托合成反应的CO转化率;钾助剂和钠助剂的加入均抑制了催化剂的还原并且促进了CO₂和CO的吸附. 比较还原后（H₂/CO摩尔比为20）和反应后（H₂/CO摩尔比为3.5）催化剂的体相结构可以发现,在FeMn、FeMnNa和FeMnK催化剂中,由于钾助剂的碱性和CO吸附能力较强,因此体相中FeC_x的含量相对较高;而活性测试结果表明,FeMnNa催化剂拥有最好的CO转化率（96.2%）和低碳烯烃选择性（30.5%,摩尔分数）.     

Photocatalytic Oxidative Coupling of Methane over Au1Ag Single-Atom Alloy Modified ZnO with Oxygen and Water Vapor: Synergy of Gold and Silver

C−H dissociation and C−C coupling are two key steps in converting CH₄ into multi-carbon compounds. Here we report a synergy of Au and Ag to greatly promote C₂H₆ formation over Au₁Ag single-atom alloy nanoparticles (Au₁Ag NPs)-modified ZnO catalyst via photocatalytic oxidative coupling of methane (POCM) with O₂ and H₂O. Atomically dispersed Au in Au₁Ag NPs effectively promotes the dissociation of O₂ and H₂O into *OOH, promoting C−H activation of CH₄ on the photogenerated O⁻ to form *CH₃. Electron-deficient Au single atoms, as hopping ladders, also facilitate the migration of electron donor *CH₃ from ZnO to Au₁Ag NPs. Finally, *CH₃ coupling can readily occur on Ag atoms of Au₁Ag NPs. An excellent C₂H₆ yield of 14.0 mmol g⁻¹ h⁻¹ with a selectivity of 79 % and an apparent quantum yield of 14.6 % at 350 nm is obtained via POCM with O₂ and H₂O, which is at least two times that of the photocatalytic system. The bimetallic synergistic strategy offers guidance for future catalyst design for POCM with O₂ and H₂O.     

Cu/CdCO3 catalysts for efficient electrochemical CO2 reduction over the wide potential window

High efficiency and low-cost catalyst-driven electrocatalytic CO₂ reduction to CO production are of great significance for energy storage and development. The severe competitive hydrogen evolution reaction occurs at large negative potential window limits the achievement of the target product from CO₂ at high efficiency. Here, we successfully prepared Cu_x/CdCO₃ composite catalyst rich in interfaces, in which achieved high CO Faraday efficiency exceeded 90% in a wide potential window of 700 mV and highest value up to 97.9% at −0.90 V vs. RHE. The excellent performance can be ascribed to the positive contribution of Cu_x/CdCO₃, which maintains a suitable high local pH value during electrochemical reduction, thus inhibiting the competitive hydrogen evolution reaction. Moreover, the compact structure between Cu and CdCO₃ ensures fast electron transfer both inside catalysts and interface, thus speeding up the reaction kinetics of CO₂ to CO conversion. Theoretically calculations further prove that the combination of Cu and CdCO₃ provides the well-defined electronic structure for intermediates adsorption, significantly reducing the reaction barrier for the formation of CO. This work provides new insights into the design of efficient electrochemical CO₂ reduction catalysts for inhibiting hydrogen evolution by adjusting the local pH effect.     

Platinum-Tin/Tin Oxide/CNT Catalysts for High-Performance Electrocatalytic Ethanol Oxidation

Ethanol is a promising liquid clean energy source in the energy conversion field. However, the self-poisoning caused by the strongly adsorbed reaction intermediates (typically, CO) is a critical problem in ethanol oxidation reaction. To address this issue, we proposed a joint use of two strategies, alloying of Pt with other metals and building Pt/metal-oxide interfaces, to achieve high-performance electrocatalytic ethanol oxidation. For this, a well-designed synthetic route combining wet impregnation with a two-step thermal treatment process was established to construct PtSn/SnO_x interfaces on carbon nanotubes. Using this route, the alloying of Pt−Sn and formation of PtSn−SnO_x interfaces can simultaneously be achieved, and the coverage of SnO_x thin films on PtSn alloy nanoparticles can be facilely tuned by the strong interaction between Pt and SnO_x. The results revealed that the partial coverage of SnO_x species not only retained the active sites, but also enhanced the CO anti-poisoning ability of the catalyst. Consequently, the H−PtSn/SnO_x/CNT-2 catalyst with an optimized PtSn−SnO_x interface showed significantly improved performances toward the ethanol oxidation reaction (825 mA mg_Pt⁻¹). This study provides deep insights into the structure-performance relationship of PtSn/metal oxide composite catalysts, which would be helpful for the future design and fabrication of high-performance Pt-based ethanol oxidation reaction catalysts.