Palladium‐Based Nanomaterials: A Platform to Produce Reactive Oxygen Species for Catalyzing Oxidation Reactions

Oxidation reactions by molecular oxygen (O₂) over palladium (Pd)‐based nanomaterials are a series of processes crucial to the synthesis of fine chemicals. In the past decades, investigations of related catalytic materials have mainly been focused on the synthesis of Pd‐based nanomaterials from the angle of tailoring their surface structures, compositions and supporting materials, in efforts to improve their activities in organic reactions. From the perspective of rational materials design, it is imperative to address the fundamental issues associated with catalyst performance, one of which should be oxygen activation by Pd‐based nanomaterials. Here, the fundamentals that account for the transformation from O₂ to reactive oxygen species over Pd, with a focus on singlet O₂ and its analogue, are introduced. Methods for detecting and differentiating species are also presented to facilitate future fundamental research. Key factors for tuning the oxygen activation efficiencies of catalytic materials are then outlined, and recent developments in Pd‐catalyzed oxygen‐related organic reactions are summarized in alignment with each key factor. To close, we discuss the challenges and opportunities for photocatalysis research at this unique intersection as well as the potential impact on other research fields.     

Separation of Ru(III), Rh(III) and Pd(II) from nitric acid solutions using ion-exchange resins bearing carboxylic betaine

To understand the adsorption properties of a styrene–divinylbenzene copolymer functionalized with N,N,N-trimethylglycine, AMP03, the adsorption behaviours for platinoid ions (Ru(III), Rh(III) and Pd(II)) were examined. Furthermore, we performed adsorption experiments using sample solutions by adding triethylamine, thiourea and N,N,N-trimethylglycine. Based on the adsorption data obtained in this study, we performed chromatographic experiments. The results indicated that all platinoid ions in the feed solution completely adsorbed on AMP03, and almost 80% of the adsorbed platinoid ions were recovered. These results show that AMP03 has the potential to recover Ru(III), Rh(III) and Pd(II) from high-level liquid waste.     

Recovery of deuterium from hydrogen–deuterium mixture using palladium

The applicability of palladium for the separation of hydrogen isotopes (hydrogen and deuterium) is evaluated systematically by generating isotherm data and conducting column experiments in a laboratory set-up. Effect of various parameters such as concentration of the isotopic mixture, particle size, eluent flow rate, etc. is studied experimentally. A fixed-bed chromatographic model is developed and validated using the experimental data. The model is further used to predict the performance of a multi-column configuration for large-scale separation. Chromatographic separation is thus found to be a promising technique to achieve the required purity and hence it may be clubbed with the existing systems (e.g. cryogenic distillation) to obtain enhanced performance.     

Facile surface modification of porous stainless steel substrate with TiO2 intermediate layer for fabrication of H2-permeable composite palladium membranes

The increasing demand in compact hydrogen separators greatly stimulated the investigation and utilization of composite palladium membranes. Porous stainless steel (PSS) tubes were chosen as substrate material in this study, and a novel process of carbon-assisted solid-state sintering was introduced to modify the PSS surface with a TiO₂ layer. A Pd/TiO₂/PSS membrane with a Pd thickness of 6 µm was successfully fabricated via electroless plating. Scanning electron microscopy (SEM), metallographic microscopy, X-ray diffraction and pore-size analyses were performed for material characterizations. As measured by H₂/N₂ single-gas testing, the fabricated Pd/TiO₂/PSS membrane is permeable and selective to hydrogen, and it was stable during a time-on-stream of 100 h under 450°C.     

微弧氧化电解液中加入Al_2O_3胶体对AZ91D复合陶瓷层性能的影响

在硅酸盐体系中加入Al_2O_3胶体对AZ91D镁合金进行微弧氧化,研究了Al_2O_3胶体的加入时间和加入量对陶瓷层组成、结构以及耐蚀性的影响。结果表明,在微弧氧化后期6 min(约为总氧化时间的3/5)时加入Al_2O_3胶体生成的复合陶瓷层耐蚀性最好;随Al_2O_3胶体用量的增加,陶瓷层的腐蚀速度明显减小,但当用量约超过电解液总容量的20%时,对陶瓷层的耐蚀性能提高不明显。     

Nanofiber‐Based Hydrocolloid from Colloid Electrospinning Toward Next Generation Wound Dressing

Nanofiber‐based hydrocolloid scaffold is prepared by colloid electrospinning of thermoplastic polyurethane (TPU)/sodium carboxymethyl cellulose (S.CMC) in tetrahydrofuran (THF)/dimethylformamide (DMF). The most suitable process of electrospinning for successful formation of fibers is investigated by controlling the concentration of polymeric solution and co‐solvent ratio. In order to accomplish high wettability, the amount of colloid (S.CMC) and the co‐solvent ratio (THF/DMF), which affects the morphology of fibers, are adjusted. Finally, the open wound healing effect is confirmed using nanofiber‐hydrocolloid from in vivo animal studies. A detailed study of the wound healing process is also demonstrated for the first time.

     

化学镀钯拖缸现象的电化学研究

目的 用电化学的方法探究化学镀钯出现拖缸现象的原因 方法 通过开路电位方法探测化学镀钯的引发过程,利用线性扫描伏安法测量极化曲线。在测量阳极极化曲线时不加入钯盐;在测量阴极极化曲线时,不加入次亚磷酸钠。分别求得次亚磷酸钠的起始氧化的电位(EO)、钯离子的起始还原电位(ER)随温度变化的关系曲线,以及甘氨酸浓度对EO和ER的影响,并且采用化学镀实验,研究钯层厚度变化与甘氨酸浓度的关系。结果 发现第1次使用和多次使用的化学镀钯液对引发钯沉积的快慢存在差异,即存在拖缸现象。在镀钯过程中,温度越高,镀液活性越强,越不容易出现拖缸现象,同时稳定性也会下降。在电化学实验中发现,EO随着温度的升高而负移,ER随着温度的升高而正移,二者的差值|ΔE|总体上随着温度的升高而减小。ΔE可以反映镀液的稳定性和衡量化学镀钯引发的难易程度。ΔE<0意味着镀液稳定,化学镀钯需要在催化剂表面引发。当|ΔE|≤0.73 V时,化学镀钯可以正常引发。当|ΔE| >0.73 V时,引发过程存在拖缸现象。甘氨酸的浓度可以影响ΔE。当甘氨酸的质量浓度接近10 g/L时,拖缸现象不明显,无甘氨酸或者其质量浓度大于20 g/L时,容易出现拖缸现象。结论 ΔE的值与化学镀钯液的稳定性和拖缸现象是否发生有关。     

微生物固定化吸附剂吸附Pd(II)的研究

微生物法在吸附处理重金属污染和回收贵金属方面具有广阔的发展前景。利用载体A固定化大肠杆菌开发了一种高效微生物固定化吸附剂,研究其对Pd(II)的吸附特性,构建其对Pd(II)的动态吸附模型,并开展了循环再生实验。结果表明,吸附柱的穿透时间和耗竭时间与大肠杆菌的浓度、微生物固定化吸附剂的填充量成正相关,与溶液流速成负相关;载体A:粘结剂:大肠杆菌的质量比为4:1:3,固定化吸附剂添加量为15 g、溶液流速3 mL/min时,吸附柱对Pd(II)有较好的吸附效率,穿透时间和耗竭时间分别为60 min和360 min;使用2 mol/L的HCl对负载Pd(II)后吸附剂进行解吸处理,解吸率达到99.32%;吸附-解吸循环5次后,固定化吸附剂对Pd(II)的吸附量基本保持不变。     

N510与D2EHDTPA对钯的协同萃取

用 2 -羟基 -5 -仲辛基 -二苯甲酮肟 (N5 1 0 )与二 -(2 -乙基己基 )二硫代磷酸 (D2 EHDTPA)的氯仿溶液 ,从高氯酸介质中对钯的协同萃取进行了研究。采用斜率法确定了萃合物的组成为 :L· Pd· A,协萃反应平衡常数为 lg K1 2 =1 .67,协同萃取配合物生成常数为 β1 2 =3 .3 0。同时计算了协同萃取反应的热力学函数值。