Bimetallic Single‑Atom Catalysts for Water Splitting

Green hydrogen from water splitting has emerged as a critical energy vector with the potential to spearhead the global transition to a fossil fuel-independent society.The field of catalysis has been revolutionized by single-atom catalysts(SACs),which exhibit unique and intricate interactions between atomically dispersed metal atoms and their supports.Recently,bimetallic SACs(bimSACs)have garnered significant attention for leveraging the synergistic functions of two metal ions coordinated on appropriately designed supports.BimSACs offer an avenue for rich metal–metal and metal–support cooperativity,potentially addressing current limitations of SACs in effectively furnishing transformations which involve synchronous proton–electron exchanges,substrate activation with reversible redox cycles,simultaneous multi-electron transfer,regulation of spin states,tuning of electronic properties,and cyclic transition states with low activation energies.This review aims to encapsulate the growing advancements in bimSACs,with an emphasis on their pivotal role in hydrogen generation via water splitting.We subsequently delve into advanced experimental methodologies for the elaborate characterization of SACs,elucidate their electronic properties,and discuss their local coordination environment.Overall,we present comprehensive discussion on the deployment of bimSACs in both hydrogen evolution reaction and oxygen evolution reaction,the two half-reactions of the water electrolysis process.

Preparation of Ce-TiO_(2)-RGO catalyst and its application in the treatment of printing and dyeing wastewater

Ce-TiO_(2)-RGO composite photocatalyst was prepared by sol-gel method and ultrasonic treatment.The effect of Ce doping mass fraction on the degradation of textile printing and dyeing wastewater was studied.The catalysts were characterized by XRD,SEM,TEM,UV-vis and PL.The results showed that,Ce-TiO_(2)particles uniformly adsorbed on the GO surface,and the particle diameter of Ce-TiO_(2)was approximately 25-110 nm.After Ce doping,the absorption band edge of TiO_(2)-RGO composite photocatalyst was redshifted and the band gap was reduced.With the increase of Ce doping mass fraction,the PL intensity of Ce-TiO_(2)-RGO composite photocatalyst first decreased and then slightly increased,and the emission peak intensity of 6%Ce-TiO_(2)-RGO composite photocatalyst was the lowest at 410 nm and 470 nm.Taking textile printing and dyeing wastewater as the research object of degradation,the COD removal rate of 6%Ce-TiO_(2)-RGO reached the maximum of 82.21%at 180 min,and the COD value after degradation was 88.95 mg/L which was in line with the wastewater discharge standard.On the other hand,at 180 min,the degradation rate for textile printing and dyeing wastewater by 6%Ce-TiO_(2)-RGO also reached the maximum(99.21%).Therefore,the Ce-TiO_(2)-RGO composite photocatalyst showed great application potential in the treatment of textile dyeing wastewater.

Catalyst–Support Interaction in Polyaniline‑Supported Ni_(3)Fe Oxide to Boost Oxygen Evolution Activities for Rechargeable Zn‑Air Batteries

Catalyst–support interaction plays a crucial role in improving the catalytic activity of oxygen evolution reaction(OER).Here we modulate the catalyst–support interaction in polyaniline-supported Ni_(3)Fe oxide(Ni_(3)Fe oxide/PANI)with a robust hetero-interface,which significantly improves oxygen evolution activities with an overpotential of 270 mV at 10 mA cm^(-2)and specific activity of 2.08 mA cm_(ECSA)^(-2)at overpotential of 300 mV,3.84-fold that of Ni_(3)Fe oxide.It is revealed that the catalyst–support interaction between Ni_(3)Fe oxide and PANI support enhances the Ni–O covalency via the interfacial Ni–N bond,thus promoting the charge and mass transfer on Ni_(3)Fe oxide.Considering the excellent activity and stability,rechargeable Zn-air batteries with optimum Ni_(3)Fe oxide/PANI are assembled,delivering a low charge voltage of 1.95 V to cycle for 400 h at 10 mA cm^(-2).The regulation of the effect of catalyst–support interaction on catalytic activity provides new possibilities for the future design of highly efficient OER catalysts.

Boosting Oxygen Evolution Reaction Performance on NiFe‑Based Catalysts Through d‑Orbital Hybridization

Anion-exchange membrane water electrolyzers(AEMWEs)for green hydrogen production have received intensive attention due to their feasibility of using earth-abundant NiFe-based catalysts.By introducing a third metal into NiFe-based catalysts to construct asymmetrical M-NiFe units,the d-orbital and electronic structures can be adjusted,which is an important strategy to achieve sufficient oxygen evolution reaction(OER)performance in AEMWEs.Herein,the ternary NiFeM(M:La,Mo)catalysts featured with distinct M-NiFe units and varying d-orbitals are reported in this work.Experimental and theoretical calculation results reveal that the doping of La leads to optimized hybridization between d orbital in NiFeM and 2p in oxygen,resulting in enhanced adsorption strength of oxygen intermediates,and reduced rate-determining step energy barrier,which is responsible for the enhanced OER performance.More critically,the obtained NiFeLa catalyst only requires 1.58 V to reach 1 A cm^(−2) in an anion exchange membrane electrolyzer and demonstrates excellent long-term stability of up to 600 h.

High Fe‑Loading Single‑Atom Catalyst Boosts ROS Production by Density Effect for Efficient Antibacterial Therapy

The current single-atom catalysts(SACs)for medicine still suffer from the limited active site density.Here,we develop a synthetic method capable of increasing both the metal loading and mass-specific activity of SACs by exchanging zinc with iron.The constructed iron SACs(h^(3)-FNC)with a high metal loading of 6.27 wt%and an optimized adjacent Fe distance of~4 A exhibit excellent oxidase-like catalytic performance without significant activity decay after being stored for six months and promising antibacterial effects.Attractively,a“density effect”has been found at a high-enough metal doping amount,at which individual active sites become close enough to interact with each other and alter the electronic structure,resulting in significantly boosted intrinsic activity of single-atomic iron sites in h^(3)-FNCs by 2.3 times compared to low-and medium-loading SACs.Consequently,the overall catalytic activity of h^(3)-FNC is highly improved,with mass activity and metal mass-specific activity that are,respectively,66 and 315 times higher than those of commercial Pt/C.In addition,h^(3)-FNCs demonstrate efficiently enhanced capability in catalyzing oxygen reduction into superoxide anion(O_(2)·^(−))and glutathione(GSH)depletion.Both in vitro and in vivo assays demonstrate the superior antibacterial efficacy of h^(3)-FNCs in promoting wound healing.This work presents an intriguing activity-enhancement effect in catalysts and exhibits impressive therapeutic efficacy in combating bacterial infections.

Preparation of Co/S co-doped carbon catalysts for excellent methylene blue degradation

S and Co co-doped carbon catalysts were prepared via pyrolysis of MOF-71 and thiourea mixtures at 800℃at a mass ratio of MOF-71 to thiourea of 1:0.1 to effectively activate peroxymonosulfate(PMS)for methylene blue(MB)degradation.The effects of two different mixing routes were identified on the MB degradation performance.Particularly,the catalyst obtained by the alcohol solvent evaporation(MOF-AEP)mixing route could degrade 95.60%MB(50 mg/L)within 4 min(degradation rate:K=0.78 min^(-1)),which was faster than that derived from the direct grinding method(MOF-DGP,80.97%,K=0.39 min^(-1)).X-ray photoelectron spectroscopy revealed that the Co-S content of MOF-AEP(43.39at%)was less than that of MOF-DGP(54.73at%),and the proportion of C-S-C in MOF-AEP(13.56at%)was higher than that of MOF-DGP(10.67at%).Density functional theory calculations revealed that the adsorption energy of Co for PMS was -2.94 eV when sulfur was doped as C-S-C on the carbon skeleton,which was higher than that when sulfur was doped next to cobalt in the form of Co-S bond(-2.86 eV).Thus,the C-S-C sites might provide more contributions to activate PMS compared with Co-S.Furthermore,the degradation parameters,including pH and MOF-AEP dosage,were investigated.Finally,radical quenching experiments and electron paramagnetic resonance(EPR)measurements revealed that ^(1)O_(2)might be the primary catalytic species,whereas·O~(2-)might be the secondary one in degrading MB.

rGO/CdS@HAP复合微球的光催化活性增强机理

为提升CdS基复合材料的光催化活性和稳定性,运用水热法在CdS@HAP(羟基磷灰石)微球表面包覆rGO(还原氧化石墨烯)并制备rGO/CdS@HAP光催化材料,利用XRD(X射线衍射)、SEM(扫描电子显微镜)、UV-vis(紫外-可见吸收光谱)等手段分析材料的晶体结构和理化性质,结合MB(亚甲基蓝)的光催化降解实验探讨rGO/CdS@HAP的光催化活性增强机理。结果表明:rGO/CdS@HAP具有中空微球结构,直径4—5μm,rGO以薄纱状均匀包裹在CdS@HAP表面;rGO/CdS@HAP具有优异的可见光吸收能力,在可见光辐射120 min后对MB的去除率高达94%,在光催化循环实验中表现出优异的光催化活性和稳定性。机理分析证实,由CdS和HAP构建的Ⅰ型异质结带隙较窄,有助于提升复合材料对可见光的吸收和利用,rGO在CdS@HAP表面的包覆提升载流子分离效率的同时为光生空穴提供高速的传输路径,有效抑制CdS的光腐蚀,从而实现rGO/CdS@HAP光催化活性和稳定性的显著增强。

MoS_2 Nanosheet Arrays Rooted on Hollow rGO Spheres as Bifunctional Hydrogen Evolution Catalyst and Supercapacitor Electrode

MoS_2 has attracted attention as a promising hydrogen evolution reaction(HER) catalyst and a supercapacitor electrode material. However, its catalytic activity and capacitive performance are still hindered by its aggregation and poor intrinsic conductivity. Here, hollow rGO sphere-supported ultrathin MoS_2 nanosheet arrays(hrGO@MoS_2) are constructed via a dual-template approach and employed as bifunctional HER catalyst and supercapacitor electrode material. Because of the expanded interlayer spacing in MoS_2 nanosheets and more exposed electroactive S–Mo–S edges, the constructed h-rGO@MoS_2 architectures exhibit enhanced HER performance. Furthermore, benefiting from the synergistic effect of the improved conductivity and boosted specific surface areas(144.9 m^2 g^(-1), ca. 4.6-times that of pristine MoS_2), the h-rGO@MoS_2 architecture shows a high specific capacitance(238 F g^(-1) at a current density of 0.5 A g^(-1)), excellent rate capacitance, and remarkable cycle stability. Our synthesis method may be extended to construct other vertically aligned hollow architectures,which may serve both as efficient HER catalysts and supercapacitor electrodes.

铝二次电池用RGO-S电极材料制备与性能研究

以氧化石墨烯与硫代硫酸钠为原料,通过一步水热法,制备还原氧化石墨烯-硫(RGO-S)电极,通过XRD、XPS、SEM、TEM、恒流充放电测试等手段对电极进行分析。结果如下:在RGO-S中硫元素主要为单质,单质硫与还原氧化石墨烯之间主要是以物理吸附的方式结合,主要以S2p3形态存在,小部分以S2p1形态存在。硫元素含量越高,初次充放电容量越高,循环性能越差。硫碳质量比为3:7的RGO-S复合材料具有最优性能,经过120次的充放电循环后放电容量回复到92%左右,在高倍率电流密度下放电容量保持在58.83mAh/g。

Pt-Re/rGO bimetallic catalyst for highly selective hydrogenation of cinnamaldehyde to cinnamylalcohol

In the present work, a series of Pt-based catalysts, alloyed with a second metal, i.e., Re, Sn, Er, La, and Y, and supported on activated carbon, ordered mesoporous carbon, N-doped mesoporous carbon or reduced graphene oxide(rGO), have been developed for selective hydrogenation of cinnamaldehyde to cinnamylalcohol. Re and rGO were proved to be the most favorable metal dopant and catalyst support, respectively. Pt_(50) Re_(50)/rGO showed the highest cinnamylalcohol selectivity of 89% with 94% conversion of cinnamaldehyde at the reaction conditions of 120 °C, 2.0 MPaH_2 and 4 h.

CuCr_2O_4@rGO Nanocomposites as High-Performance Cathode Catalyst for Rechargeable Lithium–Oxygen Batteries

Rechargeable lithium–oxygen batteries have been considered as a promising energy storage technology because of their ultra-high theoretical energy densities which are comparable to gasoline. In order to improve the electrochemical properties of lithium–oxygen batteries(LOBs), especially the cycling performance, a high-efficiency cathode catalyst is the most important component.Hence, we aim to demonstrate that CuCr_2O_4@rGO(CCO@rGO) nanocomposites, which are synthesized using a facile hydrothermal method and followed by a series of calcination processes, are an effective cathode catalyst. The obtained CCO@rGO nanocomposites which served as the cathode catalyst of the LOBs exhibited an outstanding cycling performance for over 100 cycles with a fixed capacity of 1000 mAh g^(-1) at a current density of 200 mA g^(-1). The enhanced properties were attributed to the synergistic effect between the high catalytic efficiency of the spinel-structured CCO nanoparticles, the high specific surface area, and high conductivity of the rGO.

原位生长FeCo/rGo纳米复合材料的电磁波吸收性能研究

利用化学开发高性能吸波材料是解决电磁污染问题和实现军事装备雷达隐身的有效手段。基于化学原位生长策略,以金属离子Fe^(2+)和Co^(2+)为原料,采用一步水热法制备FeCo/rGo复合材料,并对其形貌、结构以及吸波性能进行测试和分析。结果表明,当FeCo和氧化石墨烯的复合比为1∶0.5在厚度1.9 mm时有效吸收带宽达到5.5 GHz,其最小反射损耗达到-54.14 dB。复合比为1∶1时则实现了1.3 mm,4.5 GHz有效吸收带宽的吸波性能,这表明FeCo/rGo磁性材料有望成为一种极具应用价值的电磁吸波材料。

MoS2-rGO hybrid architecture as durable support for cathode catalyst in proton exchange membrane fuel cells

Carbon black is utilized as a conventional electrocatalyst support material for proton exchange membrane fuel cells. However, this support is prone to corrosion under oxidative and harsh environments, thus limiting the durability of the fuel cells. Meanwhile, carbon corrosion would also weaken the linkage between Pt and the support material, which causes Pt agglomeration, and consequently, deterioration of the cell performance. To overcome the drawbacks of a Pt/C electrocatalyst, a hybrid support material comprising molybdenum disulfide and reduced graphene oxide is proposed and synthesized in this study to exploit the graphitic nature of graphene and the availability of the exposed edges of MoS2. TEM results show the uniform dispersion of Pt nanoparticles over the MoS2-rGO surface. Electrochemical measurements indicate higher ECSA retention and better ORR activity after 10000 potential cycles for Pt/MoS2-rGO as compared to Pt/C, demonstrating the improved durability for this hybrid support material.

Direct electrospinning method for the construction of Z-scheme TiO_2/g-C_3N_4/RGO ternary heterojunction photocatalysts with remarkably ameliorated photocatalytic performance

A series of Z-scheme TiO2/g-C3N4/RGO ternary heterojunction photocatalysts are successfully constructed via a direct electrospinning technique coupled with an annealing process for the first time. They are investigated comprehensively in terms of crystal structure, morphology, composition, specific surface area, photoelectrochemical properties, photodegradation performance, etc. Compared with binary TiO2/g-C3N4 and single-component photocatalysts, ternary heterojunction photocatalysts show the best photodegradation performance for RhB under stimulated sunlight. This can be attributed to the enlarged specific surface area (111.41 m2/g), the formation of Z-scheme heterojunction, and the high separation migration efficiency of photoexcited charge carriers. A potential Z-scheme mechanism for ternary heterojunction photocatalysts is proposed to elucidate the remarkably ameliorated photocatalytic performance based on active species trapping experiments, PL detection test of hydroxyl radicals, and photoelectrochemical properties.

RGO(还原氧化石墨烯)二三事

在科技高速发展的今天,新型复合材料的发现发展受到了广泛的关注与重视。本文通过小型可穿戴传感器与RGO(还原氧化石墨烯)的对话,对新型材料RGO的制备、应用和发展展开了具体的描述。

Rational design of hollow oxygen deficiency-enriched NiFe_(2)O_(4)@N/rGO as bifunctional electrocatalysts for overall water splitting

Bimetallic metal organic framework(MOF)as a precursor to prepare catalysts with bifunctional catalytic activity of oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)attracts more and more attention.Herein,hollow oxygen deficiency-enriched NiFe_(2)O_(4) is synthesized by pyrolytic FeNi bimetallic MOF.The defects of rGO during carbonization can act as nucleation sites for FeNi particles.After nucleation and N doping,the FeNi particles were served as catalysts for the deposition of dissolved carbon in the defects of the N/rGO.These deposited carbon,like a bridge,connect N/rGO and hollow oxygen deficiency-enriched NiFe_(2)O_(4) together,which giving full play to the advantages of N/rGO in fast electron transfer,thereby improving its catalytic activity.The resultant NiFe_(2)O_(4)@N/rGO-800 exhibits a low overpotential of 252 mV at 20 mA cm^(-2) for OER and 157 mV at 10 mA cm^(-2) for HER in 1 M KOH,respectively.When used as bifunctional electrodes for overall water splitting,it also shows low cell voltage of 1.60 V and 1.67 V at 10 and 20 mA cm^(-2),respectively.

Strong coupled spinel oxide with N-rGO for high-efficiency ORR/OER bifunctional electrocatalyst of Zn-air batteries

The high cost,scarcity,and poor stability of precious-metal-based catalysts have hindered their extensive application in energy conversion and storage.This stimulates the search for earth-abundant alternatives to replace noble metal electrocatalysts.Hence,in this study,we investigate a novel and low-cost bifunctional electrocatalyst consisting of ZnCoMnO_(4) anchored on nitrogen-doped graphene oxide(ZnCoMnO_(4)/N-rGO).Benefiting from the strong Co-N interaction in ZnCoMnO_(4) and the coupled conductive N-rGO,the catalysts exhibit high electrocatalytic activity.Moreover,density functional theory calculations support the dominant role of the strong Co-N electronic interaction,which leads to ZnCoMnO_(4)/N-rGO having more favorable binding energies with O2 and H_(2) O,resulting in fast reaction kinetics.The obtained ZnCoMnO_(4)/N-rGO electrocatalyst exhibits superb bifunctional activity,with a half-wave potential of 0.83 V for the oxygen reduction reaction and a low onset potential of 1.57 V for the oxygen evolution reaction in 0.1 M KOH solution.Furthermore,a Zn-air battery driven by the ZnCoMnO_(4)/N-rGO catalyst shows remarkable discharge/charge performance,with a power density of 138.52 mW cm^(-2) and longterm cycling stability for 48 h.This work provides a promising multifunctional electrocatalyst based on non-noble metals for the storage and conversion of renewable energy.

CdS/rGO复合气凝胶的自组装合成及光催化降解盐酸四环素性能

以L-赖氨酸为还原剂和交联剂,采用一步水热法制备嵌入CdS纳米薄片(CdS NSs)的三维CdS/还原氧化石墨烯(CdS/rGO)复合气凝胶。结果表明:CdS/rGO复合气凝胶大的比表面积BET(Brunauer-Emmett-Teller,BET)和海绵状性质可增强对污染物的吸附,且其质量轻可漂浮在水面上可增强对光的吸收,同时rGO的引入促进了光生电荷的分离,使该复合气凝胶的光催化性能得到明显提升。在可见光照射下,CdS/rGO复合气凝胶可以在45 min内将盐酸四环素(tetracycline hydrochloride,TC)完全降解,1.5 h后几乎所有TC都已经矿化。此外,CdS/rGO复合气凝胶还显示出高稳定性并且容易从反应体系中分离出来,进行回收循环使用。经过5次循环使用后,CdS/rGO复合气凝胶的光催化活性没有明显降低。

NiFe_(2)O_(4)/rGO电极材料的制备及电催化HMF氧化性能研究

利用五羟甲基糠醛(HMF)电合成的2,5-呋喃二甲酸(FDCA)具有与对苯二甲酸相似的结构和性质,为开发可降解性塑料、减少白色污染提供可能。利用CO_(2)激光成功合成了NiFe_(2)O_(4)/rGO电极材料,其微观形貌呈纳米颗粒镶嵌的氧化石墨烯结构。原位拉曼光谱表明,与Fe_(5)O_(12)/rGO电极材料相比,在HMF电催化氧化过程中NiFe_(2)O_(4)/rGO表面重构为NiOOH和FeOOH物种,证实了Ni的加入使材料更易发生表面重构。表面重构的NiFe_(2)O_(4)/rGO电极材料在100 mA·cm^(-2)时过电位降低至26 mV,且较制氧反应(OER)过电位降低约182 mV。表面重构后的电极材料拥有更大的比表面积,促进了反应物与电极材料的接触。反应物的转化率、目标产物的选择性及法拉第效率分别为99.8%、99.3%和87.6%。本研究为元素加入促进催化材料表面重构进而提高HMF的电催化氧化活性提供了有效途径。

Amorphous CoSnO_3@rGO nanocomposite as an efficient cathode catalyst for long-life Li-O_2 batteries

An amorphous CoSnO3@rGO nanocomposite fabricated using a surfactant‐assisted assembly method combined with thermal treatment served as a catalyst for non‐aqueous lithium‐oxygen(Li‐O2)batteries.In contrast to the specific surface area of the bare CoSnO3 nanoboxes(104.3 m2 g–1),the specific surface area of the CoSnO3@rGO nanocomposite increased to approximately 195.8 m2 g–1 and the electronic conductivity also improved.The increased specific surface area provided more space for the deposition of Li2O2,while the improved electronic conductivity accelerated the decomposition of Li2O2.Compared to bare CoSnO3,the overpotential reduced by approximately 20 and 60 mV at current densities of 100 and 500 mA g?1 when CoSnO3@rGO was used as the catalyst.A Li‐O2 battery using a CoSnO3@rGO nanocomposite as the cathode catalyst cycled indicated a superior cyclic stability of approximately 130 cycles at a current density of 200 mA g–1 with a limited capacity of 1000 mAh g–1,which is 25 cycles more than that of the bare amorphous CoSnO3 nanoboxes.