Self-template-oriented synthesis of lead-free perovskite Cs_(3)Bi_(2)I_(9) nanosheets for boosting photocatalysis of CO_(2) reduction over Z-scheme heterojunction Cs_(3)Bi_(2)I_(9)/CeO_(2)

Lead halide perovskite (LHP) nanocrystals have been intensely studied as photocatalysts for artificial photosynthesis in recent years.However,the toxicity of lead in LHP seriously limits their potential for widespread applications.Herein,we first present the synthesis of 2D lead-free halide perovskite (Cs_(3)Bi_(2)I_(9)) nanosheets with self-template-oriented method,in which BiOI/Bi_(2)O_(2) nanosheets were used as the template and Bi ion source simultaneously.Through facile electrostatic self-assembly strategy,a Z-scheme heterojunction composed of Cs_(3)Bi_(2)I_(9)nanosheets and CeO_(2) nanosheets (Cs_(3)Bi_(2)I_(9)/CeO_(2)-3:1) was constructed as photocatalyst for the photo-reduction of CO_(2) coupled with the oxidation of H_(2)O.Due to the matching energy levels and the close interfacial contact between Cs_(3)Bi_(2)I_(9)and CeO_(2) nanosheets,the separation efficiency of the photogenerated carriers in Cs_(3)Bi_(2)I_(9)/CeO_(2)-3:1 composite was significantly improved.Consequently,the environment-friendly halide perovskite heterojunction Cs_(3)Bi_(2)I_(9)/CeO_(2)-3:1presents impressive photocatalytic activity for the reduction of CO_(2)to CH_(4)and CO with an electron consumption yield of 877.04μmol g^(-1),which is over 7 and 15 times higher than those of pristine Cs_(3)Bi_(2)I_(9)and CeO_(2)nanosheets,exceeding the yield of other reported bismuth-based perovskite for photocatalytic CO_(2)reduction.

Ligand-free CsPbBr_(3) with calliandra-like nanostructure for efficient artificial photosynthesis

The low-efficiency CO_(2) uptake capacity and insufficient photogenerated exciton dissociation of current metal halide perovskite(MHP)nanocrystals with end-capping ligands extremely restrict their application in the field of artificial photosynthesis.Herein,we demonstrate that ligand-free CsPbBr_(3) with calliandralike nanostructure(LF-CPB CL)can be synthesized easily through a ligand-free seed-assisted dissolutionrecrystallization growth process,exhibiting significantly enhanced CO_(2) uptake capacity.More specifically,the abundant surface bromine(Br)vacancies in ligand-free MHP materials are demonstrated to be beneficial to photogenerated carrier separation.The electron consumption rate of LF-CPB CL for photocatalytic CO_(2) reduction increases 7 and 20 times over those of traditional ligand-capping CsPbBr_(3)nanocrystal(L-CPB NC)and bulk CsPbBr_(3),respectively.Moreover,the absence of ligand hindrance can facilitate the interfacial electronic coupling between LF-CPB CL and tetra(4-carboxyphenyl)porphyrin iron(Ⅲ)chloride(Fe-TCPP)cocatalyst,bringing forth significantly accelerated interfacial charge separation.The LF-CPB CL/Fe-TCPP exhibits a total electron consumption rate of 145.6μmol g^(-1) h^(-1) for CO_(2)photoreduction coupled with water oxidation which is over 14 times higher than that of L-CPB NC/FeTCPP.

Lattice-matched in-situ construction of 2D/2D T-SrTiO_(3)/CsPbBr_(3) heterostructure for efficient photocatalysis of CO_(2) reduction

The elaborate regulation of heterostructure interface to accelerate the interfacial charge separation is one of practicable approaches to improve the photocatalytic CO_(2)reduction performance of halide perovskite(HP) materials. Herein, we report an in-situ growth strategy for the construction of 2D CsPbBr_(3)based heterostructure with perovskite oxide(SrTiO_(3)) nanosheet as substrate(CsPbBr_(3)/SrTiO_(3)). Lattice matching and matchable energy band structures between CsPbBr_(3)and SrTiO_(3)endow CsPbBr_(3)/SrTiO_(3)heterostructure with an efficient interfacial charge separation. Moreover, the interfacial charge transfer rate can be further accelerated by etching SrTiO_(3)with NH_(4)F to form flat surface capped with Ti-O bonds. The resultant 2D/2D T-SrTiO_(3)/CsPbBr_(3)heterostructure exhibits an impressive photocatalytic activity for CO_(2)conversion with a CO yield of 120.2 ± 4.9 μmol g^(-1)h^(-1)at the light intensity of 100 m W/cm^(2)and water as electron source, which is about 10 and 7 times higher than those of the pristine SrTiO_(3)and CsPbBr_(3)nanosheets, surpassing the reported halide perovskite-based photocatalysts under the same conditions.

Engineering Coordination Environment of Cobalt Center in Molecular Catalysts for Improved Photocatalytic CO_(2) Reduction

The creation of effective and inexpensive catalysts is essential for photocatalytic CO_(2) reduction.Homogeneous molecular catalysts,possessing definite crystal structures,are desirable to study the relationship between catalytic performance and coordination microenvironment around catalytic center.In this report,we elaborately developed three Co(II)-based molecular catalysts with different coordination microenvironments for CO_(2) reduction,named[CoN_(3)O]ClO_(4),[CoN_(4)]ClO_(4),and[CoN_(3)S]ClO_(4),respectively.The optimal[CoN_(3)O]ClO_(4) photocatalyst has a maximum TON of 5652 in photocatalytic reduced CO_(2) reduction,which is 1.28 and 1.65 times greater than that of[CoN_(4)]ClO_(4) and[CoN_(3)S]ClO_(4),respectively.The high electronegativity of oxygen in L1(N,N-bis(2-pyridylmethyl)-N-(2-hydroxybenzyl)amine)provides the Co(II)catalytic centers with low reduction potentials and a more stable*COOH intermediate,which facilitates the CO_(2)-to-CO conversion and accounts for the high photocatalytic activity of[CoN_(3)O]ClO_(4).This work provides researchers new insights in development of catalysts for photocatalytic CO_(2) reduction.

Diatomic Pd catalyst with conjugated backbone for synergistic electrochemical CO_(2)reduction

Double-site catalysts have attracted widespread attention in the field of electrocatalysis due to their high metal loading,adjustable active centres,and electronic valence states.However,the development of bimetallic sites catalysts that coordinate with definite atoms is still in the exploratory stage.Here,we designed and synthesized a bimetallic palladium complex(BPB-Pd_(2))with conjugated backbone.The supported BPB-Pd_(2)was applied to electrochemical CO_(2)reduction reaction(CO_(2)RR)for the first time.The as-obtained BPB-Pd_(2)gives an exceptional Faradaic efficiency of CO(FECO)of 94.4%at−0.80 V vs.reversible hydrogen electrode(RHE),which is significantly superior to monoatomic palladium catalyst(BPB-Pd1).The density functional theory(DFT)calculations revealed that the essential reason for the outstanding activity of BPB-Pd_(2)toward CO_(2)RR was that the electronic effect between diatomic palladium reduces the free energy change for CO_(2)RR process.Thus,BPB-Pd_(2)exhibits moderate free energy change to form COOH*intermediate,which was beneficial for the generation of CO in CO_(2)RR.

Surface iodine and pyrenyl-graphdiyne co-modified Bi catalysts for highly efficient CO_(2) electroreduction in acidic electrolyte

CO_(2) electroreduction to formic acid/formate would contribute to alleviating the energy and climate crisis.This work reports a Bi-based catalyst derived from the in-situ electroreduction of Bi_(2)O_(2)CO_(3) modified with iodine and pyrenyl-graphdiyne(PGDY)on the surface for efficient electroreduction of CO_(2) in acidic electrolyte,with a high partial current density of 98.71 mA·cm^(-2) and high Faradaic efficiency(FE)>90%over the potential range from^(-1).2 to-1.5 V vs.reversible hydrogen electrode(RHE),as well as the long-term operational stability over 240 h without degradation in H-type cell.Experimental results and density function theory calculations show that the synergistic effect of surface iodine and PGDY is responsible for this active and extremely stable process of CO_(2) electroreduction via lowering the energy barriers for formation of*OCHO intermediate,suppressing the competitive HER by enhancing the concentration of both K+and CO_(2) at reaction interface,as well as preventing the dissolution and re-deposition of active Bi atoms on surface during catalytic reaction.This work provides new insight into designing highly active and stable electrocatalysts for CO_(2) reduction.

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.

Enhancing photocatalytic performance of metal-organic frameworks for CO_(2) reduction by a bimetallic strategy

Metal-organic frameworks(MOFs) as a type of crystalline heterogeneous catalysts have shown potential application in photocatalytic CO_(2)reduction.However,MOF catalysts with high efficiency and selectivity are still in pursuit.Herein,by a bimetallic strategy,the catalytic performance of a Co-MOF for photocatalytic CO_(2)reduction was enhanced.Specifically,the Co-MOF based on 4,5-dicarboxylic acid(H;IDC) and4,4’-bipydine(4,4’-bpy) can catalyze CO;reduction to CO,with high efficiency but relatively low selectivity.After replacement of 2/3 Co(Ⅱ) with Ni(Ⅱ) within Co-MOF,the resulted isostructural Co_(1)Ni_(2)-MOF not only retains high efficiency for photocatalytic CO_(2)reduction,but also shows enhanced CO selectivity.The CO evolution rate reaches 1160 μmol g^(-1)h^(-1)and the CO selectivity reaches as high as 94.6%.The enhanced photocatalytic CO_(2)reduction performance is supported by theoretical calculation results.This case demonstrates that bimetallic strategy is an effective mean to optimize the catalytic performance of MOF catalysts for photochemical CO_(2)reduction.

Acetate-assistant efficient cation-exchange of halide perovskite nanocrystals to boost the photocatalytic CO_(2) reduction

The judicious implantation of active metal cations into the surface of semiconductor nanocrystal(NC)through cation-exchange is one of the facile and viable strategies to enhance the activity of catalysts for photocatalytic CO_(2)reduction,by shortening the transfer pathway of photogenerated carriers and increasing the active sites simultaneously.However,cation-exchange is hard to achieve for halide perovskite NCs owing to the stable octahedron of[PbX6]4−with strong interaction between halogen and lead.Herein,we report a facile method to overcome this obstacle by replacing partial Br−with acetate(Ac−)to generate CsPbBr_(3) NC(coded as CsPbBr_(3−x)Ac_(x)).A small amount of Ac−instead of Br−does not change the crystal structure of halide perovskite.Owing to the weaker interaction between acetate and lead in comparison with bromide,the corresponding octahedron structure containing acetate in CsPbBr_(3−x)Ac_(x) can be easily opened to realize efficient cation-exchange with Ni^(2+) ions.The resulting high loading amount of Ni^(2+) as active site endows CsPbBr_(3−x)Ac_(x) with an improved performance for photocatalytic CO_(2)reduction under visible light irradiation,exhibiting a significantly increased CO yield of 44.09μmol·g^(−1)·h^(−1),which is over 8 and 3 times higher than those of traditional pristine CsPbBr_(3) and nickel doped CsPbBr_(3) NC,respectively.This work provides a critical solution for the efficient metal doping of low-cost halide perovskite NCs to enhance their photocatalytic activity,promoting their practical applications in the field of photocatalysis.

Structural regulation of single-atomic site catalysts for enhanced electrocatalytic CO_(2)reduction

Electrocatalytic CO_(2)reduction reaction(CO_(2)RR)is considered an efficient way to convert CO_(2)into high-value-added chemicals,and thus is of significant social and economic value.Metal single-atomic site catalysts(SASCs)generally have excellent selectivity because of their 100%atomic utilization and uniform structure of active sites,and thus promise a broad range of applications.However,SASCs still face challenges such as low intrinsic activity and low density of active sites.Precise regulation of the microstructures of SASCs is an effective method to improve their CO_(2)RR performance and to obtain deep reduction products.In this article,we systematically summarize the current research status of SASCs developed for highly efficient catalysis of CO_(2)RR,discuss the various structural regulation methods for enhanced activity and selectivity of SASCs for CO_(2)RR,and review the application of in-situ characterization technologies in the SASC-catalyzed CO_(2)RR.We then discuss the problems yet to be solved in this area,and propose the future directions of the research on the design and application of SASCs for CO_(2)RR.

In-situ growth of PbI_(2) on ligand-free FAPbBr_(3) nanocrystals to significantly ameliorate the stability of CO_(2) photoreduction

Excellent optical properties involving strong visible light response and superior carrier transport endow metal halide perovskites(MHP)with a fascinating prospect in the field of photocatalysis.Nevertheless,the poor stability of MHP nanocrystals(NCs)in water-contained system,especially without the protection of long alkyl chain ligands,severely restricts their photocatalytic performance.In this context,we report an effortless strategy for the generation of ligand-free MHP NCs based photocatalyst with high water tolerance,by coating PbI_(2)on the surface of ligand-free formamidinium lead bromide(FAPb Br_(3))NCs via the facile procedure of in-situ conversion with the aid of ZnI_(2).Under the protection of PbI_(2)layer,the resultant FAPb Br_(3)/PbI_(2)composite exhibits significantly ameliorated stability in an artificial photosynthesis system with CO_(2)and H_(2)O vapor as feedstocks.Moreover,the formation of compact PbI_(2)layer can accelerate the separation of photogenerated carriers in FAPbBr_(3)NCs,bringing forth a remarkable improvement of CO_(2)photoreduction efficiency with an impressive electron consumption yield of 2053μmol/g in the absence of organic sacrificial agents,which is 7-fold over that of pristine FAPb Br_(3)NCs.

Optically modulated dual-mode memristor arrays based on core-shell CsPbBr_(3)@graphdiyne nanocrystals for fully memristive neuromorphic computing hardware

Artificial synapses and neurons are crucial milestones for neuromorphic computing hardware,and memristors with resistive and threshold switching characteristics are regarded as the most promising candidates for the construction of hardware neural networks.However,most of the memristors can only operate in one mode,that is,resistive switching or threshold switching,and distinct memristors are required to construct fully memristive neuromorphic computing hardware,making it more complex for the fabrication and integration of the hardware.Herein,we propose a flexible dual-mode memristor array based on core–shell CsPbBr3@graphdiyne nanocrystals,which features a 100%transition yield,small cycle-to-cycle and device-to-device variability,excellent flexibility,and environmental stability.Based on this dual-mode memristor,homo-material-based fully memristive neuromorphic computing hardware—a power-free artificial nociceptive signal processing system and a spiking neural network—are constructed for the first time.Our dual-mode memristors greatly simplify the fabrication and integration of fully memristive neuromorphic systems.

Low-loading gold in situ doped with sulfur by biomolecule-assisted approach for promoted electrochemical carbon dioxide reduction

For electrochemical carbon dioxide reduction(CO_(2)RR),CO_(2)-to-CO conversion is considered an ideal route towards carbon neutrality for practical applications.Gold(Au)is known as a promising catalyst with high selectivity for CO;however,it suffers from high cost and low mass-specific activity.In this study,we design and prepare a catalyst featuring uniform S-doped Au nanoparticles on N-doped carbon support(denoted as S-Au/NC)by an in situ synthesis strategy using biomolecules.The S-Au/NC displays high activity and selectivity for CO in CO_(2)RR with a Au loading as low as 0.4 wt.%.The Faradaic efficiency of CO(FECO)for S-Au/NC is above 95%at−0.75 V(vs.RHE);by contrast,the FECO of Au/NC(without S)is only 58%.The Tafel slope is 77.4 mV·dec−1,revealing a favorable kinetics process.Furthermore,S-Au/NC exhibits an excellent long-term stability for CO_(2)RR.Density functional theory(DFT)calculations reveal that the S dopant can boost the activity by reducing the free energy change of the potential-limiting step(formation of the*COOH intermediate).This work not only demonstrates a model catalyst featuring significantly reduced use of noble metals,but also establishes an in situ synthesis strategy for preparing high-performance catalysts.

Iron sites on defective BiOBr nanosheets:Tailoring the molecular oxygen activation for enhanced photocatalytic organic synthesis

Sunlight-driven activation of molecular oxygen(O_(2))for organic oxidation reactions offers an appealing strategy to cut down the reliance on fossil fuels in chemical industry,yet it remains a great challenge to simultaneously tailor the charge kinetics and promote reactant chemisorption on semiconductor catalysts for enhanced photocatalytic performance.Herein,we report iron sites immobilized on defective BiOBr nanosheets as an efficient and selective photocatalyst for activation of O_(2) to singlet oxygen(^(1)O_(2)).These Fe^(3+) species anchored by oxygen vacancies can not only facilitate the separation and migration of photogenerated charge carrier,but also serve as active sites for effective adsorption of 02.Moreover,low-temperature phosphorescence spectra combined with X-ray photoelectron spectroscopy(XPS)and electronic paramagnetic resonance(EPR)spectra under illumination reveal that the Fe species can boost the quantum yield of excited triplet state and accelerate the energy transfer from excited triplet state to adsorbed O2 via a chemical loop of Fe^(3+)/Fe^(2+),thereby achieving highly efficient and selective generation of ^(1)O_(2).As a result,the versatile iron sites on defective BiOBr nanosheets contributes to near-unity conversion rate and selectivity in both aerobic oxidative coupling of amines to imines and sulfoxidation of organic sulfides.This work highlights the significant role of metal sites anchored on semiconductors in regulating the charge/energy transfer during the heterogeneous photocatalytic process,and provides a new angle for designing high-performance photocatalysts.

石墨炔修饰超薄Bi_(2)O_(2)CO_(3)纳米片高效电催化CO_(2)还原制备甲酸

电催化还原CO_(2)被认为是一种清洁且有潜力的CO_(2)转换方式,可实现CO_(2)向高附加值化学产品的转化.目前,提高大电流密度下特定产物的选择性是实现其工业应用的关键.本文在超薄Bi_(2)O_(2)CO_(3)(BOC)二维纳米片表面原位修饰了石墨炔(GDY),获得复合材料BOC@GDY,并对其电催化CO2还原为甲酸反应性能进行了研究.结果表明,GDY的引入明显提高了催化剂的活性和选择性.原位X射线吸收谱和原位拉曼结果证实,在BOC@GDY中,BOC向金属铋的转变更加容易,从而能够提供更多的催化位点.此外,相比BOC,BOC@GDY显著提升了材料对CO_(2)的吸附,并且展现出更好的电子传输能力,促进了电催化还原CO_(2)反应的进行.GDY对电催化CO_(2)还原为甲酸的促进作用也适用于其他金属,例如Sn和In,具有一定的普适性.