构筑Bi纳米粒子负载BiOCl纳米片欧姆结用于光催化CO_(2)还原

煤炭、石油和天然气等能源的不断增长消耗,不仅导致不可再生能源逐渐枯竭,还使大气中的CO_(2)浓度显著上升,引发严重的能源危机和气候问题。因此,我们必须开发清洁、可持续的能源转换技术,以应对不断增长的能源需求和日益严重的环境危机。受到自然界光合作用的启发,光催化CO_(2)转化利用太阳能驱动,可以将CO_(2)和水转化为高附加值的化学品。经过多年的发展,人工光合作用已被认为是一种绿色、经济、可持续的方法,有望助力实现国家的碳中和发展目标。然而,现有的光催化剂存在着载流子分离效率低和活性位点不足的问题,从而导致CO_(2)光还原效率较低。为了应对这些科学问题,研究人员发现将金属纳米粒子负载到半导体材料上形成欧姆结,可以产生内建电场,有助于光生电子和空穴的分离。因此,本研究通过溶剂热法在BiOCl纳米片表面负载Bi纳米粒子,构建了Bi/BiOCl欧姆结光催化剂。通过X射线衍射(XRD)、X射线光电子能谱(XPS)和透射电子显微镜(TEM)分析了光催化剂的成分和微观结构。利用紫外-可见漫反射光谱(UV-Vis DRS)研究了催化剂的光吸收性能。通过瞬态光电流响应测试、电化学阻抗谱(EIS)和电子自旋共振谱(ESR)研究了光生电子和空穴的分离能力。由于Bi纳米粒子与BiOCl的功函数不同,二者形成的欧姆结具有优异的电荷转移特性,可以显著提高光生载流子的利用效率。此外,Bi纳米粒子还可以作为助催化剂,促进惰性CO_(2)分子的活化。光催化测试结果显示,经过300 W氙灯照射4 h后,具有最佳活性的复合材料(Bi/BiOCl-2)将CO_(2)还原为CO(34.31μmol·g^(-1))和CH_(4)(1.57μmol·g^(-1))的速率分别是BiOCl纳米片的2.55倍和4.76倍。同位素示踪实验证实,产物是CO_(2)和水分子经过光催化反应得到的。此外,根据原位傅里叶变换红外光谱(in situ FTIR)结果,发现在CO_(2)还原过程中形成了^(*)CHO、^(*)CH_(3)O、b-CO_(3)^(2-)、m-CO_(3)^(2-)、HCO_(3)^(-)、HCOOH、^(*)COOH和HCOO^(-)等中间体,并进一步提出了可能的光催化CO_(2)还原机制。经过25 h的CO_(2)光还,原反应后,CO和CH_(4)产量持续增加,同时结合XRD、XPS和TEM结果表明,制备的Bi/BiOCl-2材料具有良好的结构稳定性。这项研究为高效CO_(2)光还原催化剂的构建提供了有益的参考。

Oxygen defect modulating the charge behavior in titanium dioxide for boosting photocatalytic nitrogen fixation performance

Extremely high-temperature and high-pressure requirement of Haber-Bosch process motivates the search for a sustainable ammonia synthesis approach under mild conditions.Photocatalytic technology is a potential solution to convert N2 to ammonia.However,the poor light absorption and low charge carrier separation efficiency in conventional semiconductors are bottlenecks for the application of this technology.Herein,a facile synthesis of anatase TiO_(2)nanosheets with an abundance of surface oxygen vacancies(TiO_(2)-OV)via the calcination treatment was reported.Photocatalytic experiments of the prepared anatase TiO_(2)samples showed that TiO_(2)-OV nanosheets exhibited remarkably increased ammonia yield for solar-driven N2 fixation in pure water,without adding any sacrificial agents.EPR,XPS,XRD,UV-Vis DRS,TEM,Raman,and PL techniques were employed to systematically explore the possible enhanced mechanism.Studies revealed that the introduced surface oxygen vacancies significantly extended the light absorption capability in the visible region,decreased the adsorption and activation barriers of inert N2,and improved the separation and transfer efficiency of the photogenerated electronhole pairs.Thus,a high rate of ammonia evolution in TiO_(2)-OV was realized.This work offers a promising and sustainable approach for the efficient artificial photosynthesis of ammonia.

Paper-derived cobalt and nitrogen co-doped carbon nanotube@porous carbon as a nonprecious metal electrocatalyst for the oxygen reduction reaction

The oxygen reduction reaction(ORR)is a vitally important process in fuel cells.The development of high‐performance and low‐cost ORR electrocatalysts with outstanding stability is essential for the commercialization of the electrochemical energy technology.Herein,we report a facile synthesis of cobalt(Co)and nitrogen(N)co‐doped carbon nanotube@porous carbon(Co/N/CNT@PC‐800)electrocatalyst through a one‐step pyrolysis of waste paper,dicyandiamide,and cobalt(II)acetylacetonate.The surface of the hierarchical porous carbon supported a large number of carbon nanotubes(CNTs),which were derived from dicyandiamide through the catalysis of Co.The addition of Co resulted in the formation of a hierarchical micro/mesoporous structure,which was beneficial for the exposure of active sites and rapid transportation of ORR‐relevant species(O2,H+,OH?,and H2O).The doped N and Co formed more active sites to enhance the ORR activity of the electrocatalyst.The Co/N/CNT@PC‐800 material exhibited optimal ORR performance with an onset potential of 0.005 V vs.Ag/AgCl and a half‐wave potential of?0.173 V vs.Ag/AgCl.Meanwhile,the electrocatalyst showed an excellent methanol tolerance and a long‐term operational durability than that of Pt/C,as well as a quasi‐four‐electron reaction pathway.The low‐cost and simple synthesis approach makes the Co/N/CNT@PC‐800 a prospective electrocatalyst for the ORR.Furthermore,this work provides an alternative approach for exploring the use of biomass‐derived electrocatalysts for renewable energy applications.

MOFs derived FeNi_(3) nanoparticles decorated hollow N-doped carbon rod for high-performance oxygen evolution reaction

The sluggish electrochemical oxygen evolution reaction(OER) is a crucial process for clean energy conversion technology.The preparation of non-precious electrocatalysts with high performance for OER is still a main challenge.Herein,we report a FeNi_(3) nanoparticles incorporated on N-doped hollow carbon rod with extraordinary performance toward OER by in situ annealing the Ni-doped Fe based metal-organic frameworks(MOFs) precursors.Meanwhile,the pristine N atoms of MOFs doped into carbon frameworks can enhance the electrical conductivity,boost electron mass transport and electron transfer,and construct more active sites.Furthermore,constructing the Fe-Ni alloy structure can facilitate the formation of O-O bond,optimize the free energy for intermediate adsorption and improve OER performance.The as-prepared Fe-Ni bimetal decorated hollow N-doped nanocarbon hybrid structure possesses superior OER performance,which is surpass commercial IrO_(2) at a overpotential of only 340 mV to achieve the current density of 10 mA cm^(-2),as well as a small Tafel slope of 86.67 mV dec^(-1) in alkaline electrolyte.The Fe-Ni alloy/hollow N-doped nanocarbon hybrid structure shining the bright future for obtaining earth-abundant and superior efficient anode OER electrocatalyst.

Synchronous activation of Ag nanoparticles and BiOBr for boosting solar-driven CO_(2)reduction

Artificial photosynthesis of valuable chemicals from CO_(2)is a potential way to achieve sustainable carbon cycle.The CO_(2)conversion activity is still inhibited by the sluggish charge kinetics and poor CO_(2)activation.Herein,Ag nanoparticles coupled Bi OBr have been constructed by in-situ photoreduction strategy.The crafting of interface between Ag nanoparticles and Bi OBr nanosheets,achieving an ultra-fast charge transfer.The Bi OBr semiconductor excited electrons and plasmonic Ag nanoparticles generated high-energy hot electrons synchronous accelerates the C=O double bond activation.Thus,the optimized Ag/BiOBr-2 heterostructure shows excellent CO_(2)photoreduction activity with CO production of 133.75 and 6.83μmol/g under 5 h of 300 W Xe lamp and visible light(λ>400 nm)irradiation,which is 1.51 and 2.81 folds versus the pristine Bi OBr,respectively.The mechanism of CO_(2)photoreduction was in-depth understood through in-situ FT-IR spectrum and density functional theory calculations.This study provides some new perspectives into efficient photocatalytic CO_(2)reduction.

Crafting of plasmonic Au nanoparticles coupled ultrathin BiOBr nanosheets heterostructure: steering charge transfer for efficient CO_(2) photoreduction

Integrating semiconductor photocatalysts with outstanding visible light absorption and fast surface/interface charge transfer kinetics is still an enormous challenge for efficient CO_(2)photoreduction.In this work,the Au nanoparticles have been coupled with ultrathin BiOBr nanosheets,the formed heterostructure(Au/BiOBr)pos-sesses a localized surface plasmon resonance(LSPR)and enhances the visible light absorption ability,as well as forms a fast charge transport channel on the interface between Au and BiOBr.Thus,the heterostructure photo-catalyst exhibits higher photocatalytic CO_(2)to CO performance(135.3/16.43μmol g^(-1))than that of BiOBr(89.0/6.46μmol g^(-1))under 300 W Xe lamp and visible light(λ>400 nm)irradiation for 5 h,respectively.Finally,the in situ FT-IR spectroscopy revealed CO_(2)photoreduction process and found that the*COOH is the key intermediate for CO_(2)to CO.This work provides an effective method to construct multielectron transfer scheme for efficient photocatalytic CO_(2)reduction.

In-Situ Synthesis of CQDs/BiOBr Material via Mechanical Ball Milling with Enhanced Photocatalytic Performances

Designing simple, efficient, and environmentally friendly methods to construct high-efficient photocatalysts is an important strategy to promote the further development of the field of photocatalysis. Herein, flower-like carbon quantum dots(CQDs)/Bi OBr composite photocatalysts have been prepared via in-situ synthesis by mechanical ball milling in the existence of ionic liquid. The CQDs/Bi OBr composites exhibit higher photo-degradation performance for tetracycline(TC) than Bi OBr monomer and the commercial Bi_(2)O_(3) under visible light irradiation. For comparison, the different Br sources and synthetic methods are chosen to prepare Bi OBr and CQDs/Bi OBr composites. Photocatalysts prepared by ball milling and ionic liquid present significantly enhanced photocatalytic performance for removing TC. In addition, the introduction of CQDs could distinctly enhance the photocatalytic performances of pure Bi OBr. The reason is that CQDs as electron acceptor effectively separate electrons and holes and inhibit their recombination. The intermediates during photocatalytic degradation were tested using liquid chromatography-mass spectrometry(LC-MS) and possible degradation pathways were given. During degradation, ·OH, O_(2)^(·-)and h^(+) were identified to be the main active species based on electron spin resonance(ESR) spectra and free radical trapping experiments. A possible mechanism of CQDs/Bi OBr with enhanced photocatalytic performances was further proposed.