Co2FeO4@rGO composite: Towards trifunctional water splitting in alkaline media

Development of efficient, low cost and multifunctional electrocatalysts for water splitting to harvest hydrogen fuels is a challenging task, but the combination of carbon materials with transition metal-based compounds is providing a unique and attractive strategy. Herein, composite systems based on cobalt ferrite oxide-reduced graphene oxide (Co₂FeO₄) @(rGO) using simultaneous hydrothermal and chemical reduction methods have been prepared. The proposed study eliminates one step associated with the conversion of GO into rGO as it uses direct GO during the synthesis of cobalt ferrite oxide, consequently rGO based hybrid system is achieved in-situ significantly, the optimized Co₂FeO₄@rGO composite has revealed an outstanding multifunctional applications related to both oxygen evolution reaction (OER) and hydrogen counterpart (HER). Various metal oxidation states and oxygen vacancies at the surface of Co₂FeO₄@rGO composites guided the multifunctional surface properties. The optimized Co₂FeO₄@rGO composite presents excellent multifunctional properties with onset potential of 0.60 V for ORR, an overpotential of 240 mV at a 20 mAcm^?2 for OER and 320 mV at a 10 mAcm^?2 for HER respectively. Results revealed that these multifunctional properties of the optimized Co₂FeO₄@ rGO composite are associated with high electrical conductivity, high density of active sites, crystal defects, oxygen vacancies, and favorable electronic structure arisinng from the substitution of Fe for Co atoms in binary spinel oxide phase. These surface features synergistically uplifted the electrocatalytic properties of Co₂FeO₄@rGO composites. The multifunctional properties of the Co₂FeO₄@ rGO composite could be of high interest for its use in a wide range of applications in sustainable and renewable energy fields.     

High performance H2 sensor based on rGO-wrapped SnO2–Pd porous hollow spheres

Hydrogen (H₂) sensors based on metal oxide semiconductors (MOS) are promising for many applications such as a rocket propellant, industrial gas and the safety of storage. However, poor selectivity at low analyte concentrations, and independent response on high humidity limit the practical applications. Herein, we designed rGO-wrapped SnO₂–Pd porous hollow spheres composite (SnO₂–Pd@rGO) for high performance H₂ sensor. The porous hollow structure was from the carbon sphere template. The rGO wrapping was via self-assembly of GO on SnO₂-based spheres with subsequent thermal reduction in H₂ ambient. This sensor exhibited excellently selective H₂ sensing performances at 390 °C, linear response over a broad concentration range (0.1–1000 ppm) with recovery time of only 3 s, a high response of ～8 to 0.1 ppm H₂ in a minute, and acceptable stability under high humidity conditions (e. g. 80%). The calculated detection limit of 16.5 ppb opened up the possibility of trace H₂ monitoring. Furthermore, this sensor demonstrated certain response to H₂ at the minimum concentration of 50 ppm at 130 °C. These performances mainly benefited from the special hollow porous structure with abundant heterojunctions, the catalysis of the doped-PdO_x, the relative hydrophobic surface from rGO, and the deoxygenation after H₂ reduction.     

3-Dimensional flower-like clusters of CoNiP nanofoils in-situ grown on randomly-dispersed rGO-Nanosheets with superior electrocatalysis for hydrogen evolution reactions

It has been being an interesting challenge to develop novel electrocatalysts with advantageous nanostructures and thereby-improved catalytic performance for hydrogen evolution reaction (HER) over the past years. Herein, we report on the flower-like clusters of CoNiP nanofoils thickly grown on the randomly-interconnected reduced graphene oxide (rGO) nanosheets (CoNiP-NF/rGO) of 3-dimensional framework architecture, which has been successfully achieved via an optimized solvothermal process with Ni-doped ZIF-67 (Ni-ZIF-67) dodecahedral particles as the precursor and graphene oxide (GO) nanosheets as the substrate for the in-situ growth of flower-like CoNi-hydroxides nanofoils, as well as a following topotactic transformation in a controlled phosphorization. Benefiting from its distinctly advantageous nanostructures featured with extremely high specific surface area, enriched catalytic active sites and enhanced electronic transportation, the as-prepared CoNiP-NF/rGO exhibits an excellent electrocatalytic performance of HER with an onset overpotential of 33 mV, an overpotential of 82 mV at 10 mA cm⁻², a Tafel slope of 37 mV dec⁻¹ and a high chemical stability in acidic solutions. Such an advantageous nanostructure and its positive influences on the electrocatalytic performance are useful for the preparation of other nonprecious metal electrocatalysts.     

Effect of annealing temperature and graphene concentrations on photovoltaic and NIR-detector applications of PbS/rGO nanocomposites

The effect of annealing temperature on photovoltaic and near-infrared (NIR) detector applications of PbS nanoparticles (NPs) and PbS/graphene nanocomposites was investigated. The products were synthesized by a simple co-precipitation method and graphene oxide (GO) sheets were used as graphene source. Several characterization techniques were used to show transfer of the GO into reduced graphene oxide (rGO) during the synthesis process. In addition, the effect of graphene concentrations on morphology, structure, photovoltaic, and detector parameters of the samples were studied. Transmission electron microscope (TEM) images showed that, the PbS NPs were agglomerated, while, the PbS/rGO nanocomposites were dispersed completely after annealing under H₂/Ar gas atmosphere. UV–visible spectrometer showed an absorption peak for all samples in the near infrared red (NIR) region of the electromagnetic spectrum. The results indicated that, photocurrent intensity, responsivity of the samples to an NIR source, and solar-cell efficiency were affected by annealing of samples and graphene concentrations.     

基于可变价NiFe-LDH/rGO对磷酸根离子的特异性电控分离

磷是一种不可再生资源。为解决现有磷污染以及磷资源流失等问题,通过油浴与热化学还原相结合的方法,成功制备出一种NiFe-LDH/rGO电活性杂化膜材料。使用电化学方法,在氧化还原电位的控制下,Ni、Fe(Ⅱ/Ⅲ)双金属发生核外电子的跃迁,高价态的Ni、Fe(Ⅲ)与\mathrm{P}{\mathrm{O}}_{\mathrm{4}}^{\mathrm{3}-}发生内球络合作用,实现\mathrm{P}{\mathrm{O}}_{\mathrm{4}}^{\mathrm{3}-}的选择性置入-置出。实验获得270 mg·g^-1的高\mathrm{P}{\mathrm{O}}_{\mathrm{4}}^{\mathrm{3}-}吸附容量及85%以上的再生效率。此外,该杂化膜材料在共存离子存在的复杂水体中,对\mathrm{P}{\mathrm{O}}_{\mathrm{4}}^{\mathrm{3}-}具有优异的选择性,为磷石膏渗滤液以及各种含磷废水污染等问题的解决提供有效的理论技术支撑,具有广阔的应用前景。     

功能化还原氧化石墨烯/天然橡胶导热复合材料的性能研究

采用2-巯基苯并咪唑(防老剂MB,以下简称MB)对氧化石墨烯(GO)进行还原及功能化,同时与采用抗坏血酸(VC)对GO进行还原对比,分别制得MB还原氧化石墨烯(rGO-MB)和VC还原氧化石墨烯(rGO-VC),并采用胶乳共混法制备rGO-MB/NR和rGO-VC/NR复合材料,对其性能进行研究。结果表明:MB成功还原了GO,MB接枝到了GO上;与rGO-VC/NR复合材料相比,rGO-MB/NR复合材料具有较低的Payne效应和较高的结合胶含量,拉伸强度和导热性能均明显提高。     

rGO-Sb2Se3薄膜电化学共沉积制备及光电化学性能

采用恒电位沉积法,在二元Sb-GO溶液体系中得到rGO-Sb预制层,在此过程中,GO被有效还原成rGO,并与Sb形成化学键。随后通过将预制层进行二段硒化热处理,快速去除多余的Se制备出rGO-Sb₂Se₃光阴极薄膜。通过XRD、SEM、Raman、XPS、UV-vis及PEC等手段对薄膜样品进行表征以及光电化学性能测试。结果表明:负载rGO使得rGO-Sb₂Se₃在700 nm以内的可见光区域的光吸收系数显著提升。rGO优良的导电性能及较高的载流子迁移率,可以快速转移电荷,抑制载流子的复合,因此光电化学性能以及光稳定性大大提高,光电流密度增大至接近Sb₂Se₃单相的2倍(?0.20 mA/cm²)。又因为rGO-Sb₂Se₃导带位置(?0.74 V vs.RHE)远负于析氢电位(0 V vs.RHE),故可作为一种新型光还原产氢的阴极,具备广阔的应用前景。     

The Investigation of Reduced Graphene Oxide/P3HT Composite Films for Ammonia Detection

In this paper, single reduced graphene oxide (rGO) and rGO/Poly (3-hexylthiophene) (P3HT) composite films were prepared by the spray process, which were deposited on the interdigitated transducers for preparing the resistive ammonia (NH₃) sensor. The morphology of sensitive films was characterized by scanning electron microscopy (SEM). The gas-sensing properties of GO/P3HT film sensor were tested and analyzed. The results showed that rGO/P3HT composite film sensor exhibited better sensing properties and restorability than that rGO film sensor, which maybe was ascribed to π-π interaction between rGO and P3HT and the superior surface morphology of composite films.     

基于rGO/g-C3N4纳米材料电化学传感器制备及其在日落黄检测中的应用

目的 开发一种简单、高灵敏度的电化学传感器, 用于定量测定商业食品中日落黄(sunset yellow, SY)的含量。方法 以氧化石墨烯(graphene oxide, GO)、石墨相氮化碳(g-C3N4)为原料, 水热还原制备复合材料(rGO/g-C3N4)。通过滴涂法将所制备的复合物溶液滴到工作电极上, 制备传感器。结果 在最优实验条件下, 用差分脉冲伏安法(differential pulse voltammetry, DPV)对不同质量浓度(20~120 mg/L)的SY进行检测, 线性方程为△I=0.06864C+0.06205, 检出限为0.125 mg/L。本传感器特异性和稳定性良好, 在实际样品检测中, 回收率为97.8%~101.2%。结论 rGO/g-C3N4复合纳米材料制备的传感器能够实现对SY的快速、灵敏检测, 且该方法操作简单、成本低, 在食品工业、安全检测等领域有巨大的应用前景。