Recent advances and perspectives in cobalt‐based heterogeneous catalysts for photocatalytic water splitting,CO_(2) reduction,and N_(2) fixation

Solar‐driven conversion of carbon dioxide,water and nitrogen into high value‐added fuels(e.g.H_(2),CO,CH_(4),CH_(3)OH,NH_(3) and so on)is regarded as an environmental‐friendly and ideal route for relieving the greenhouse gas effect and countering energy crisis,which is an attractive and challenging topic.Hence,various types of photocatalysts have been developed successively to meet the requirements of these photocatalysis.Among them,cobalt‐based heterogeneous catalysts emerge as one of the most promising photocatalysts that open up alluring vistas in the field of solar‐to‐fuels conversion,which can effectively enhance photocatalytic efficiency by extending light absorption range,promoting charge separation,providing active sites,and lowering reaction barrier.In this review,we first present the working principles of cobalt‐based heterogeneous catalysts for photocatalytic water splitting,CO_(2) reduction,and N_(2) fixation.Second,five efficient strategies including surface modification,morphology modulation,crystallinity controlling,crystal engineering and doping,are discussed for improving the photocatalytic performance with different types cobalt‐based catalysts(cobalt nanoparticles and single atom,oxides,sulfides,phosphides,MOFs,COFs,LDHs,carbide,and nitrides).Third,we outline the applications for the state‐of‐the‐art photocatalytic CO_(2) reduction and water splitting,and nitrogen fixation over cobalt‐based heterogeneous catalysts.Finally,the central challenges and possible improvements of cobalt‐based photocatalysis in the future are presented.The purpose of this review is to summarize the past experience and lessons,and provide reference for the further development of cobalt‐based photocatalysis technology.

Evaluation of the possible slip surface of a highly heterogeneous rock slope using dynamic reduction method

A new method, the dynamic reduction method(DRM) combined with the strain-softening method, was applied to evaluate the possible slip surface of a highly heterogeneous rock slope of the Dagangshan hydropower station in Southwest China.In DRM, only the strength of the failure elements is reduced and the softening reduction factor K is adopted to calculate the strength parameters. The simulation results calculated by DRM show that the further slip surface on the right slope of the Dagangshan hydropower station is limited in the middle part of the slope, while both SRM(strength reduction method) and LEM(limit equilibrium method) predict a failure surface which extends upper and longer. The observations and analysis from the three recorded sliding events indicate that the failure mode predicted by DRM is more likely the scenario.The results in this study illustrate that for highly heterogeneous slopes with geological discontinuities in different length scales, the proposed DRM can provide a reliable prediction of the location of the slip surface.

Cobalt‐N_(4) macrocyclic complexes for heterogeneous electrocatalysis of the CO_(2) reduction reaction

Metal-N_(4)(M-N_(4))macrocyclic complexes are interesting electrocatalysts due to their well-defined structures and rich molecular tuning.Among them,metal phthalocyanines have been widely studied for the carbon dioxide reduction reaction(CO_(2)RR)in heterogeneous systems and demonstrated good electrocatalytic performance.However,other complexes like metal corroles and metal porphyrins are much less explored,and often show inferior performances.In this study,three cobalt macrocyclic complexes,cobalt phthalocyanine,cobalt meso-tetraphenylporphyrin,and cobalt meso-triphenylcorrole(CoPc,CoTPP and CoTPC)are investigated in heterogeneous electrocatalysis of CO_(2)RR.Although CoPc/carbon nanotube(CNT)hybrid exhibits high electrocatalytic activity,CNT hybridization does not work for CoTPC and CoTPP that hold weak interactions with CNTs.By the drop-dry method with a high molecular loading of 5.4×10^(–7) mol cm^(–2),CoTPC and CoTPP could deliver appreciable electrode activities.Poly(4-vinylpyridine)(PVP)introduction is further demonstrated as a facile method to afford enhanced activities for CoTPP at low molecular loadings through enhancing molecule-substrate interactions.The partial current density of carbon monoxide for CoTPP+CNT/PVP is around 8 times higher than the sample without PVP at–0.67 V versus reversible hydrogen electrode.This work provides solutions to enhance the electrode activities of molecular electrocatalysts with weak substrate interactions in heterogeneous systems.

Photoreduction of CO_2 to methanol over Bi_2S_3/CdS photocatalyst under visible light irradiation

The Bi2S3,CdS and Bi2S3/CdS photocatalysts were prepared by direct reactions between their corresponding salt and thiourea in a hy- drothermal autoclave.The photocatalytic activities of these photocatalysts for reducing CO2 to CH3OH under visible light irradiation have been investigated.The results show that the photocatalytic activity and visible light response of Bi2S3 are higher than those of CdS.The Bi2S3 modification can enhance the photocatalytic activity and visible light response of CdS.The photocatalytic activity of Bi2S3/CdS hetero-junction photocatalyst was the highest and the highest yields of methanol was 613μmol/g when the weight proportion of Bi2S3 to CdS was 15%,which was about three times as large as that of CdS or two times of that of Bi2S3.

Photocatalytic reduction of carbon dioxide to methanol by Cu_2O/SiC nanocrystallite under visible light irradiation

The Cu2O/SiC photocatalyst was obtained from SiC nanoparticles （NPs） modified by Cu2O. Their photocatalytic activities for reducing CO2 to CH3OH under visible light irradiation have been investigated. The results indicated that besides a small quantity of 6H-SiC, SiC NPs mainly consisted of 3C-SiC. The band gaps of SiC and Cu2O were estimated to be about 1.95 and 2.23 eV from UV-Vis spectra, respectively. The Cu2O modification can enhance the photocatalytic performance of SiC NPs, and the largest yields of methanol on SiC, Cu2O and Cu2O/SiC photocatalysts under visible light irradiation were 153, 104 and 191μmol/g, respectively.

Enhanced electrocatalytic activity of iron amino porphyrins using a flow cell for reduction of CO_(2) to CO

The flexibility of molecular catalysts is highly coveted for the electrochemical reduction of carbon dioxide(CO_(2)) to carbon monoxide(CO) in both homogeneous and heterogeneous systems.While the electrocatalytic activity of molecular catalysts has been widely studied in H-cells;their less studied capabilities in more efficient flow cell reactors have the potential to rival that of heterogeneous catalysts.In this work,a comparative study of amino functionalized iron-tetraphenylporphyrins(amino-Fe-TPPs) immobilized onto carbonaceous materials in both H-cells and flow cells was conducted to selectively reduce CO_(2) to CO.In a flow cell set up operating in alkaline media,the resulting hybrid catalyst exhibits 87% faradaic efficiency(FE) with extraordinary current density(j) of 119 mA/cm^(2) and turnover frequency(TOF) of 14 s^(-1) at-1.0 V vs.RHE.This remarkable catalytic activity was achieved through thoughtful combination of molecular and flow cell design that provides an effective strategy for future immobilized heterogeneous approaches toward CO_(2) reduction reactions(CO_(2) RRs).

Doping [Ru(bpy)3]^(2+ )into metal-organic framework to facilitate the separation and reuse of noble-metal photosensitizer during CO2 photoreduction

It is desirable to develop highly efficient and sustainable catalytic systems for CO_(2) photoreduction using efficient heterogeneous photosensitizers(PSs);however,this remains a great challenge.In this study,we doped[Ru(bpy)3]^(2+) into UiO-metal-organic frameworks(MOFs)to facilitate the separation and reuse of noble metal PS.By simply adjusting the loading amount,a series of heterogeneous photoactive MOFs,namely,UiO-Ru-1,UiO-Ru-2,and UiO-Ru-3,were constructed to act as heterogeneous PSs to drive the efficient CO_(2) photoreduction under visible-light irradiation.Remarkably,UiO-Ru-2 exhibited the best photosensitizing ability among the prepared MOFs in sensitizing the iron quarterpyridine catalyst(C-l),and the CO yield reached as high as 171 mmol/g with ca.100%selectivity,which is a record value among all the MOF-based photocatalysts.This photoactive MOF can be recycled and reused three times without any obvious activity loss,signifying its good photochemical stability.Experimental investigations confirmed that the strong visible absorption,long-lived excited state,appropriate redox potential,good photocatalytic stability,and excellent collaboration with C-l were attributable to the superior catalytic activity.This work highlights an avenue for constructing heterogeneous PSs with excellent recyclability using MOF as the platform for efficient CO_(2) reduction.

Interfacial engineering of heterogeneous molecular electrocatalysts using ionic liquids towards efficient hydrogen peroxide production

Efficient and selective oxygen reduction reaction(ORR)electrocatalysts are critical to realizing decentralized H_(2)O_(2)production and utilization.Here we demonstrate a facile interfacial engineering strategy using a hydrophobic ionic liquid(IL,i.e.,[BMIM][NTF2])to boost the performance of a nitrogen coordinated single atom cobalt catalyst(i.e.),cobalt phthalocyanine(CoPc)supported on carbon nanotubes(CNTs).We find a strong correlation between the ORR performance of CoPc/CNT and the thickness of its IL coatings.Detailed characterization revealed that a higher O_(2)solubility(2.12×10^(−3)mol/L)in the IL compared to aqueous electrolytes provides a local O2 enriched surface layer near active catalytic sites,enhancing the ORR thermodynamics.Further,the hydrophobic IL can efficiently repel the as‐synthesized H_(2)O_(2)molecules from the catalyst surface,preventing their fast decomposition to H_(2)O,resulting in improved H_(2)O_(2)selectivity.Compared to CoPc/CNT without IL coatings,the catalyst with an optimal~8 nm IL coating can deliver a nearly 4 times higher mass specific kinetic current density and 12.5%higher H2O2 selectivity up to 92%.In a two‐electrode electrolyzer test,the optimal catalyst exhibits an enhanced productivity of 3.71 molH2O2 gcat^(–1)h^(–1),and robust stability.This IL‐based interfacial engineering strategy may also be extended to many other electrochemical reactions by carefully tailoring the thickness and hydrophobicity of IL coatings.

Cobalt-based heterogeneous catalysts for photocatalytic carbon dioxide reduction

Solar light-driven CO_(2)reduction to high value-added chemicals has considered as an outstanding way to solve energy crisis and climate warming.Recently,various photocatalysts have been developed to achieve this reaction.Among them,cobaltbased heterogeneous catalysts have attracted great interest because of their promising performance,product selectivity and stability.Herein,we systematically summarize the research progress of various cobalt-based heterogeneous catalysts for the photoreduction of CO_(2),such as single-atom cobalt,and cobalt-based oxides,nitrides,sulfi des,phosphides,metal-organic frameworks and covalent-organic frameworks.Meanwhile,the advantages and structure-activity relationship of these catalysts in photocatalytic CO_(2)reduction reaction are discussed.Finally,the challenges and prospects for constructing cobaltbased heterogeneous catalysts with high effi ciency are highlighted.

Study on the Mechanism of Heterogeneous Catalysis (2) <br>—The Relative Catalytic Activities of Fe, Co, Ni, Cu, Ag and SiO2 in the Carbon Catalyzed Gasification Reaction

This is a validation article. The experimental results such as the relative catalytic activities of Fe, Co, Ni, Cu, Ag and SiO2 poisoning in the carbothermic reduction iron oxide show that the Electron Cyclic Donate-Accept Catalytic Mechanism-ECDAM or Electron Obital Deformation-Recovery cycle Catalysis Mechanism-EODRM are credible, and the Chemical Reaction Model Catalytic Cyclic Mechanism-CRMM such as the Oxygen Transfer Mechanism-OTT that is long and wide spread in the literature is completely unreliable. Because the Fe, Co, Ni, Cu, Ag were unlikely to react cyclic oxidation—reduction reaction with the carbon in the carbon reduction reaction tank.

TiO_(2)-based photocatalysts for CO_(2) reduction and solar fuel generation

Solar-driven CO_(2) reduction is an efficient way to convert sustainable solar energy and massive CO_(2) to renewable solar fuels,such as CH_(4),HCOOH,HCHO,and CH_(3)OH,etc.Up to now,significant research efforts have been devoted to exploring the reaction path and developing the photocatalysts.In heterogeneous photocatalysis,among the semiconductor-based photocatalysts,titania(TiO_(2)),as an inexpensive and practically sustainable metal oxides,remains the most extensively studied photocatalyst over the past decades.In this review,we summarize the most recent advances in the solar-driven CO_(2) reduction using TiO_(2)-based photocatalysts,which include the fabrication of heterojunction,surface functional modification,band structure engineering,and morphology design,aiming to improve the CO_(2) conversion efficiency and selectivity to the desired product.Additionally,photoelectrochemical and photothermal approaches are introduced and the fundamental principles to activate and enhance the performance of TiO_(2) for the specific reaction are discussed.The exploration of the solar-driven approaches and discussion on the underlying mechanism allow the comprehensive understanding of CO_(2) photoreduction,that can lead to a rational design and synthesis of TiO_(2)-based photocatalysts.

Structural and interfacial engineering of well‐defined metal‐organic ensembles for electrocatalytic carbon dioxide reduction

Electrochemical carbon dioxide reduction(CO_(2)RR)has been generally regarded as green technologies that can convert renewable energy such as sunlight and wind into fuels and valuable chemicals.However,the large‐scale implementation of CO_(2)RR is severely hindered by the lack of high‐performance CO_(2)RR electrocatalysts.Heterogeneous molecular catalysts and metal‐organic framework with well‐defined structure and high tunability of the metal centers and ligands show great promise for CO_(2)RR in terms of both fundamental understanding and practical application.Here,structural and interfacial engineering of these well‐defined metal‐organic ensembles is summarized.This review starts from the fundamental electrochemistry of CO_(2)RR and its evaluation criteria,and then moves to the heterogeneous molecular catalysts and metal‐organic framework with emphasis on the engineering of metal centers and ligands,their interaction with supports,as well as in situ reconstruction of metal‐organic ensembles.Summary and outlook are present in the end,with the hope to inspire and provoke more genuine thinking on the design and fabrication of efficient CO_(2)RR electrocatalysts.

Degradation study on tin- and bismuth-based gas-diffusion electrodes during electrochemical CO_(2) reduction in highly alkaline media

This work investigated the degradation of tin – based gas-diffusion electrodes (GDE) and also a promising Bi2O3 GDE in electrochemical CO_(2) reduction in highly alkaline media which has not been studied before. The contributions of the electrode wetting (or flooding, if excessively) and catalyst leaching on the degradation were analyzed. Therefore, electrochemical impedance spectroscopy was used to monitor the wetted surface area of the GDE in combination with post-mortem analysis of the penetration depth by visualizing the electrolyte’s cation in the GDE cross-section. Furthermore, to reveal a possible degradation of the electrocatalyst, its distribution was mapped in the GDEs cross-section after operation while the catholyte was additionally analyzed via ICP-MS. The results clearly demonstrate that the SnO_(2) catalyst dissolves in the reaction zone inside the GDE and might be partially redeposited near the GDEs surface. Since the redeposition process occurs only partially a steady loss of catalyst was observed impeding a clear distinction of the two degradation phenomena. Nevertheless, the deterioration of the electrode performance measured as faraday efficiency (FE) of the parasitic hydrogen evolution reaction (HER) qualitatively correlates with the differential double layer capacitance (Cdl). A significant difference of the rate of increase for the hydrogen FE and Cdl can be ascribed to the superposition of both above-mentioned degradation mechanisms. The demonstrated instability of SnO_(2) contrasts with the behavior of Bi2O3 GDE which is stabilized during CO_(2) conversion by redeposition of the diluted dissolved species as metallic Bi which is active for the CO_(2) reduction reaction.

Activity and Selectivity of Bimetallic Catalysts Based on SBA-15 for Nitrate Reduction in Water

Nitrate from the application of nitrogen-based fertilizers in intensive agriculture is a notorious waste product, though it lacks cost-effective solutions for its removal from potential drinking water resources. Catalytic reduction appears to be a promising technique for converting nitrates to benign nitrogen gas. Mesoporous silica SBA-15 is a frequently used catalyst support that has large surface areas and highly ordered nanopores. In this work, mesoporous silica SBA-15 bimetallic catalysts for nitrate reduction were investigated. The catalyst was optimized for the selection of promoter metal (Sn and Cu), noble metal (Pd and Pt) and loading ratios of these metals at different temperatures and reduction conditions. The catalysts prepared were characterized by FT-IR, N2 physisorption, XRD, SEM, and ICP. All catalysts showed the presence of cylindrical mesoporous channels and uniform pore structures that remained even after metals loading. In the presence of a CO2 buffer, the catalysts 4Pd-1Cu/SBA-15 and 1Pt-1Cu/SBA-15 reduced at 100?C under H2 and 1Pd-1Cu/SBA-15 reduced at 200°C under H2 demonstrated very high nitrate conversion. Furthermore, the forementioned Pd catalysts had higher N2 selectivity (88% - 87%) compared to Pt catalyst (80%). Nitrate conversion by the 4Pd-1Cu/SBA-15 catalyst was significantly decreased to 81% in the absence of CO2.

Recent progress in C-N coupling for electrochemical CO_(2) reduction with inorganic nitrogenous species in aqueous solution

The electrocatalytic CO_(2) reduction in aqueous solution mainly involves bond cleavage and formation between C,H and O,and it is highly desirable to expand the bond formation reaction of C with other atoms to obtain novel and valuable chemicals.The electrochemical synthesis of N-containing organic chemicals in electrocatalytic CO_(2) reduction via introducing N sources is an effective strategy to expand the product scope,since chemicals con-taining C–N bonds(e.g.amides and amines)are important reactants/products for medicine,agriculture and in-dustry.This article focuses on the research progress of C–N coupling from CO_(2) and inorganic nitrogenous species in aqueous solution.Firstly,the reaction pathways related to the reaction intermediates for urea,formamide,acetamide,methylamine and ethylamine are highlighted.Then,the electrocatalytic performance of different catalysts for these several N-containing products are summarized and classified.Finally,the challenges and op-portunities are analyzed,aiming to provide general insights into future research directions for electrocatalytic C–N coupling.

V_(2)O_(3)/VN electrocatalysts with coherent heterogeneous interfaces for selecting low-energy nitrogen reduction pathways

Electrochemical nitrogen reduction reaction(NRR)is a sustainable alterna-tive to the Haber-Bosch process for ammonia(NH3)production.However,the significant uphill energy in the multistep NRR pathway is a bottleneck for favorable serial reactions.To overcome this challenge,we designed a vanadium oxide/nitride(V_(2)O_(3)/VN)hybrid electrocatalyst in which V_(2)O_(3)and VN coex-ist coherently at the heterogeneous interface.Since single-phase V_(2)O_(3)and VN exhibit different surface catalytic kinetics for NRR,the V_(2)O_(3)/VN hybrid elec-trocatalyst can provide alternating reaction pathways,selecting a lower energy pathway for each material in the serial NRR pathway.As a result,the ammo-nia yield of the V_(2)O_(3)/VN hybrid electrocatalyst was 219.6µg h^(-1)cm^(-2),and the Faradaic efficiency was 18.9%,which is much higher than that of single-phase VN,V_(2)O_(3),and VNxOy solid solution catalysts without heterointerfaces.Density functional theory calculations confirmed that the composition of these hybrid electrocatalysts allows NRR to proceed from a multistep reduction reaction to a low-energy reaction pathway through the migration and adsorption of interme-diate species.Therefore,the design of metal oxide/nitride hybrids with coherent heterointerfaces provides a novel strategy for synthesizing highly efficient elec-trochemical catalysts that induce steps favorable for the efficient low-energy progression of NRR.

Heterogeneous molecular catalysts for electrocatalytic CO2 reduction

This review provides an overview of the literature regarding heterogeneous molecular catalysts for electrochemical CO2 reduction (ECR).Fundamental aspects of the science,including aggregation,electrochemical rate laws,and electrode-catalyst electronic coupling,are discussed to provide a solid foundation on which to design experiments and interpret results.Mechanistic aspects of ECR are presented based on electrokinetic and spectroscopic measurements as well as density functional theory (DFT) calculations.Consensus is improving for electrokinetic measurements,but the redox state of the metal center under reaction conditions and DFT reaction pathways lack agreement in the literature.Concerning the tunable aspects of the molecular catalyst,the impacts of the metal center,ligand substituents,and electrode support on the activity and selectivity toward ECR are presented with an emphasis on those studies that controlled for aggregation and minimized mass-transport limitations.Extended three-dimensional (3D) structures such as polymers,metal-organic frameworks (MOFs),and covalent-organic frameworks (COFs) are discussed as highly tunable architectures that begin to mimic the catalytic pockets of enzyme active sites.To achieve the full potential of these catalysts,design principles must emerge based on a combination of deconvoluting measurements to extract intrinsic catalyst properties and more reliable theoretical calculations to predict reaction pathways.

A Convenient Heterogeneous Reduction of Knoevenagel Product by Hantzsch Ester and Its Development into Reductive Alkylation of Malononitrile

Poor solubility of Hantzsch ester is used as indicator in the reduction of methylidene malononitrile.The Knoevenagel reaction is integrated to develop a reductive alkylation of malononitrile with aryl and aliphatic aldehyde as the carbonyl substrate.

可再生能源技术创新的减排效应:空间溢出与门槛特征

可再生能源技术创新是实现绿色低碳发展的重要动力。基于2003—2020年我国30个省份的面板数据,构建固定效应模型分析可再生能源技术创新对碳排放的影响及区域异质性,采用空间杜宾模型探究其空间溢出效应,并通过门槛回归模型检验可再生能源技术创新对碳排放的非线性影响。研究发现:就全国而言,可再生能源技术创新显著抑制碳排放;分区域来看,可再生能源技术创新的碳减排效应在东部地区显著,但在中部、西部及东北地区不显著;空间上,可再生能源技术创新不仅降低本地区的碳排放,同时促进邻近地区的碳减排;可再生能源技术创新对碳排放存在人口规模、研发投入、环境规制的门槛效应,较高的人口规模和研发投入、较低的环境规制可以强化可再生能源技术创新对碳减排的促进作用。

绿色金融改革创新试验区的碳减排效应——基于空间溢出效应与城市异质性的视角

实施绿色金融试点政策是我国自下而上完善绿色金融体系的重要举措,对于地区产业低碳转型和发展新质生产力具有重要意义。本文利用2010—2019年283个地级市的平衡面板数据,以绿色金融试点政策为切入点,采用双重差分模型和空间计量方法系统评估了实施绿色金融试点政策的碳减排效应。研究发现,绿色金融试点政策的实施显著降低了试点城市的工业碳排放总量和工业碳强度,且政策效果具有持续性和稳健性。绿色金融试点政策具有显著的空间溢出效应,即本地绿色金融试点政策的实施会对空间关联地区的碳减排产生积极影响,但施策过程中需防范污染产业转移风险。进一步研究发现,绿色金融试点政策的碳减排效应在不同区域和不同试点城市中呈现异质性。影响机制分析结果表明,绿色金融试点政策主要通过发展绿色信贷、优化能源消费结构和提升能源利用效率等方式促进地区碳减排。本文研究为我国完善绿色金融体系和实现“双碳”目标提供了实证参考。