Elastic and Conductive Cross-linked Anion Exchange Membranes Based on Polyphenylene Oxide and Poly(vinyl alcohol) for H2 -O2 Fuel Cells.

A series of cross-linked AEMs (c-DQPPO/PVA) are synthesized by using rigid polyphenylene oxide and flexible poly(vinyl alcohol) as the backbones. Dual cations are grafted on the PPO backbone to improve the ion exchange capacity (IEC), while glutaraldehyde is introduced to enhance compatibility and reduce swelling ratio of AEMs. In addition to the enhanced mechanical properties resulting from the rigid-flexible cross-linked network, c-DQPPO/PVA AEMs also exhibit impressive ionic conductivity, which can be attributed to their high IEC, good hydrophilicity of PVA, and well-defined micro-morphology. Additionally, due to confined dimension behavior and ordered micro-morphology, c-DQPPO/PVA AEMs demonstrate excellent chemical stability. Specifically, c-DQPPO/PVA-7.5 exhibits a wet-state tensile strength of 12.5 MPa and an elongation at break of 53.0 % at 25 °C. Its OH- conductivity and swelling degree at 80 °C are measured to be 125.7 mS cm-1 and 8.2 %, respectively, with an IEC of 3.05 mmol g-1 . After 30 days in a 1 M NaOH solution at 80 °C, c-DQPPO/PVA-7.5 experiences degradation rates of 12.8 % for tensile strength, 27.4 % for elongation at break, 14.7 % for IEC, and 19.2 % for ion conductivity. With its excellent properties, c-DQPPO/PVA-7.5 exhibits a peak power density of 0.751 W cm-2 at 60 °C in an H2 -O2 fuel cell.

Promoting effect of amorphous support on ruthenium-based catalyst for electrochemical hydrogen evolution reaction.

Nano-network Ru with definite lattice defects on amorphous Co nanosheets is obtained for the first time. Amorphous Co support can promote the surface Ru to obtain special morphology and modified electronic structure, thus improving HER activity in alkaline solution. A current density of 10 mA cm-2 can be obtained only with an overpotential of 33.5 mV.

Preparation of Acidic Electrolyzed Water by a RuO2@TiO2 Electrode with High Selectivity for Chlorine Evolution and Its Sterilization Effect.

The food hygiene problems caused by bacterial biofilms in food processing equipment are directly related to human life safety and health. Therefore, it is of great strategic significance to study new food sterilization technology. An acidic electrolyzed water (AEW) disinfectant is an electrochemical sterilization technology which has the characteristics of wide adaptability, high efficiency, and environmental friendliness. However, since the sterilization efficiency of AEW for biofilms is not ideal, it is necessary to increase the available chlorine content (ACC) in AEW. A feasible method to increase the ACC is by increasing the chlorine evolution reaction (CER) selectivity of the electrode for AEW preparation. In this paper, the RuO2@TiO2 electrode was prepared by thermal decomposition combined with high-vacuum magnetron sputtering. Compared with the oxygen evolution reaction (OER) activity of an ordinary RuO2 electrode, the OER activity of the RuO2@TiO2 electrode is significantly reduced. However, the CER activity of the RuO2@TiO2 electrode is close to the OER activity of RuO2. The CER mechanism of the RuO2@TiO2 electrode is the second electron transfer, and the OER mechanism is the formation and transformation of OHads. The potential difference between the CER and OER of the RuO2@TiO2 electrode is 174 mV, which is 65 mV higher than that of the RuO2 electrode, so the selectivity of the CER of the RuO2@TiO2 electrode is remarkably improved. During the preparation of AEW, the ACC obtained with the RuO2@TiO2 electrode is 1.7 times that obtained with the RuO2 electrode. In the sterilization experiments on Escherichia coli and Bacillus subtilis biofilms, the logarithmic killing values of AEW prepared the by RuO2@TiO2 electrode are higher than those of AEW prepared by the RuO2 electrode.

The volcanic relationship between the HER activity and lattice constant of RuCo alloy nanofilms.

RuCo-ANFs with different proportions can be successfully prepared by magnetron sputtering, and their lattice constants can be adjusted accurately. In the RuCo-ANF, there is an obvious electronic interaction between Ru and Co, thus adjusting the ΔGH* on its surface. There is a volcanic relationship between the HER activity and the lattice constant of RuCo-ANF.

Plasma-Activated Acidic Electrolyzed Water: A New Food Disinfectant for Bacterial Suspension and Biofilm.

Food-borne diseases are widespread all over the world, and food safety has attracted much attention. This study is the first to use plasma to activate acidic electrolyzed water (AEW) to obtain a new disinfectant for food processing. The germicidal efficacy of plasma-activated acidic electrolyzed water (PA-AEW) on B. subtilis suspension and biofilm was investigated. Furthermore, the synergistic effect of different bactericidal factors was inferred by investigating the physicochemical parameters of PA-AEW and the influencing factors of bactericidal effect. The results demonstrate that PA-AEW is a highly effective and rapid disinfectant. The killing logarithm (KL) value of PA-AEW on B. subtilis suspension could reach 2.33 log10CFU/mL with a sterilization time of 10 s, which is significantly higher than that of AEW (KL = 0.58 log10CFU/mL) and plasma-activated water (PAW) (KL = 0.98 log10CFU/mL) (significant difference, p < 0.01). Moreover, the KL value of the B. subtilis biofilm of PA-AEW was 2.41 log10CFU/mL, better than that of PAW and AEW (significant difference, p < 0.01), indicating that PA-AEW has important application prospects in food processing. The synergistic effect should come from the interaction between reactive chlorine species (RCS) and reactive oxygen and nitrogen species (RONS) in PA-AEW.

A novel bifunctional catalyst for overall water electrolysis: nano IrxMn(1-x)Oy hybrids with L12-IrMn3 phase.

A nano IrxMn(1-x)Oy hybrid electrode with a L12-IrMn3 phase was used as a bifunctional catalyst with ultra-low iridium loading for overall water electrolysis in an acid solution for the first time. The HER activity of the IrxMn(1-x)Oy hybrid electrode not only exceeded that of IrO2, but also exceeded that of Pt/C. The OER activity of the IrxMn(1-x)Oy hybrid electrode also exceeded that of IrO2.

Conductivity and Stability Properties of Anion Exchange Membranes: Cation Effect and Backbone Effect.

The rise of heterocycle cations, a new class of stable cations, has fueled faster growth of research interest in heterocycle cation-attached anion exchange membranes (AEMs). However, once cations are grafted onto backbones, the effect of backbones on properties of AEMs must also be taken into account. In order to comprehensively study the influence of cations effect and backbones effect on AEMs performance, a series of AEMs were prepared by grafting spacer cations, heterocycles cations, and aromatic cations onto brominated poly(2,6-dimethyl-1,4-phenylene oxide) (BPPO) or poly(vinylbenzyl chloride) (PVB) backbones, respectively. Spacer cation [trimethylamine (TMA), N,N-dimethylethylamine (DMEA)]-attached AEMs showed general ion transportation and stability behaviors, but exhibited high cationic reaction efficiency. Heterocycle cation [1-methylpyrrolidine (MPY), 1-methylpiperidine (MPrD)]-attached AEMs showed excellent chemical stability, but their ion conduction properties were unimpressive. Aromatic cation [1-methylimidazole (MeIm), N,N-dimethylaniline (DMAni)]-attached AEMs exhibited superior ionic conductivity, while their poor cations stabilities hindered the application of the membranes. Besides, it was found that PVB-based AEMs had excellent backbone stability, but BPPO-based AEMs exhibited higher OH- conductivity and cation stability than those of the same cations grafted PVB-based AEMs due to their higher water uptake (WU). For example, the ionic conductivities (ICs) of BPPO-TMA and PVB-TMA at 80 °C were 53.1 and 38.3 mS cm-1 , and their WU was 152.3 and 95.1 %, respectively. After the stability test, the IC losses of BPPO-TMA and PVB-TMA were 21.4 and 32.2 %, respectively. The result demonstrated that the conductivity and stability properties of the AEMs could be enhanced by increasing the WU of the membranes. These findings allowed the matching of cations to the appropriate backbones and reasonable modification of the AEM structure. In addition, these results helped to fundamentally understand the influence of cation effect and backbone effect on AEM performance.

Nanostructured RuO2-Co3O4@RuCo-EO with low Ru loading as a high-efficiency electrochemical oxygen evolution catalyst.

Electrochemical water splitting technology is considered to be the most reliable method for converting renewable energy such as wind and solar energy into hydrogen. Here, a nanostructured RuO2/Co3O4-RuCo-EO electrode is designed via magnetron sputtering combined with electrochemical oxidation for the oxygen evolution reaction (OER) in an alkaline medium. The optimized RuO2/Co3O4-RuCo-EO electrode with a Ru loading of 0.064 mg cm-2 exhibits excellent electrocatalytic performance with a low overpotential of 220 mV at the current density of 10 mA cm-2 and a low Tafel slope of 59.9 mV dec-1 for the OER. Compared with RuO2 prepared by thermal decomposition, its overpotential is reduced by 82 mV. Meanwhile, compared with RuO2 prepared by magnetron sputtering, the overpotential is also reduced by 74 mV. Furthermore, compared with the RuO2/Ru with core-shell structure (η = 244 mV), the overpotential is still decreased by 24 mV. Therefore, the RuO2/Co3O4-RuCo-EO electrode has excellent OER activity. There are two reasons for the improvement of the OER activity. On the one hand, the core-shell structure is conducive to electron transport, and on the other hand, the addition of Co adjusts the electronic structure of Ru.

AuIr alloy with arbitrarily adjustable lattice parameters as a highly efficient electrocatalyst for the oxygen reduction reaction.

AuIr alloy nanoparticles were successfully prepared without using surfactants for the first time despite Au and Ir being immiscible according to phase diagrams. The lattice parameters of the AuIr alloy can be adjusted arbitrarily. The oxygen reduction reaction (ORR) activity of Au5Ir5 alloy is better than that of Au or Ir, and the oxygen evolution reaction (OER) activity of the Au5Ir5 alloy is as good as that of Ir in alkaline solution.

A nano AuTiO2-x composite with electrochemical characteristics of under-potential deposition of H (H-UPD) as a highly efficient electrocatalyst for hydrogen evolution.

An obvious H-UPD for a nano AuTiO2-x composite has been found for the first time in terms of the electrochemical characteristics of the Au composite. The electronic effect between Au and TiO2 and the oxygen vacancy defect would change the adsorption energy of H and HER activity. The HER activity of the AuTiO2-x electrode is 6.44 times that of the Au electrode.

Effect of platinum electrode materials and electrolysis processes on the preparation of acidic electrolyzed oxidizing water and slightly acidic electrolyzed water.

Electrolyzed oxidizing water (EOW) can be divided into acidic electrolyzed oxidizing water (AEOW) and slightly acidic electrolyzed water (SAEW). AEOW has the characteristics of low pH (pH < 2.7) and high oxidation-reduction potential (ORP > 1100 mV). SAEW is slightly acidic (pH = 5-6) and has an ORP of 700-900 mV. AEOW and SAEW both have a certain amount of active chlorine content (ACC), so they have the characteristics of broad spectrum, rapidity and high efficiency of sterilization. At present, there is little systematic research on AEOW and SAEW preparation. However, it is very important to study the preparation process, including electrode material and electrolytic process. First, the effects of Pt electrodes with different thermal decomposition temperatures on AEOW's pH, ORP and ACC values were investigated in detail. Next, for the SAEW preparation, the process is based on the preparation of AEOW by ion-exchange membrane electrolysis, reasonably mixing the electrolyzed cathode and anode solution. The effects of technological conditions such as electrolysis time, current density and electrolyte concentration have been systematically studied, and it is expected to get SAEW with a pH value slightly less than 7, a higher ORP value and a certain amount of ACC.

Pt skin on AuCu intermetallic substrate: a strategy to maximize Pt utilization for fuel cells.

The dependence on Pt catalysts has been a major issue of proton-exchange membrane (PEM) fuel cells. Strategies to maximize the Pt utilization in catalysts include two main approaches: to put Pt atoms only at the catalyst surface and to further enhance the surface-specific catalytic activity (SA) of Pt. Thus far there has been no practical design that combines these two features into one single catalyst. Here we report a combined computational and experimental study on the design and implementation of Pt-skin catalysts with significantly improved SA toward the oxygen reduction reaction (ORR). Through screening, using density functional theory (DFT) calculations, a Pt-skin structure on AuCu(111) substrate, consisting of 1.5 monolayers of Pt, is found to have an appropriately weakened oxygen affinity, in comparison to that on Pt(111), which would be ideal for ORR catalysis. Such a structure is then realized by substituting the Cu atoms in three surface layers of AuCu intermetallic nanoparticles (AuCu iNPs) with Pt. The resulting Pt-skinned catalyst (denoted as Pt(S)AuCu iNPs) has been characterized in depth using synchrotron XRD, XPS, HRTEM, and HAADF-STEM/EDX, such that the Pt-skin structure is unambiguously identified. The thickness of the Pt skin was determined to be less than two atomic layers. Finally the catalytic activity of Pt(S)AuCu iNPs toward the ORR was measured via rotating disk electrode (RDE) voltammetry through which it was established that the SA was more than 2 times that of a commercial Pt/C catalyst. Taking into account the ultralow Pt loading in Pt(S)AuCu iNPs, the mass-specific catalytic activity (MA) was determined to be 0.56 A/mg(Pt)@0.9 V, a value that is well beyond the DOE 2017 target for ORR catalysts (0.44 A/mg(Pt)@0.9 V). These findings provide a strategic design and a realizable approach to high-performance and Pt-efficient catalysts for fuel cells.

Activating Ag by even more inert Au: a peculiar effect on electrocatalysis toward oxygen reduction in alkaline media.

Combined computational and experimental studies reveal a noble, non-d-band effect on Ag activation and electrocatalysis: upon coating Ag onto the even more inert Au surface, the catalytic activity toward the oxygen reduction reaction in alkaline media can be improved by about half an order of magnitude in comparison to the usual Ag surface.

[Sterilizing effect and mechanism of electrolyzed water].

OBJECTIVE: To study the sterilizing effect and mechanism of electrolyzed-oxidizing water (EOW) and electrolyzed-reductive water (ERW) for Bacillus subtilis var. niger (ATCC9372) and Escherichia coli (8099). METHODS: The generations of EOW and ERW were made in the ion membrane electrolysis cell. The sterilization manner was the suspension quantitative germicidal test. RESULTS: The killing rate of EOW for Bacillus subtilis var. niger was 99.59% in 30 minutes and the killing logarithm value was 2.38 log cfu/ml; the killing rate of ERW for Bacillus subtilis var. niger was 94.62% in 60 minutes and the killing logarithm value was 1.27 log cfu/ml; the killing rate of ERW for Escherichia coli was 100% in 30 minutes and the killing logarithm value was 8.26 log cfu/ml. When the available chlorine content (ACC) value in EOW was 74.90 mg/L and killing time was 30 minutes, the killing rate for Bacillus subtilis var. niger was 99.89% and the killing logarithm value was 2.67 log cfu/ml. When the ACC value was 6.82 mg/L, the killing rate for Bacillus subtilis var. niger was 83.30% and the killing logarithm value was 0. 78 log cfu/ml under the same time. When the oxidizing-reductive potential (ORP) and pH values of EOW were 1138 mV and 2.24 respectively, the killing rate for Bacillus subtilis var. niger was 99.99%. When the ORP and pH values of EOW were 883 mV and 5. 43 respectively, the killing rate of Bacillus subtilis var. niger was 99.73%. When the ORP value of ERW is -918 mV, the sterilizing rate for Bacillus subtilis var. niger was 94.62%; when the ORP value is -155 mV, the sterilizing ratio was only 40.19%. CONCLUSION: It indicates that the sterilizing mechanism of EOW is mainly chemical processes (ACC), while the physical factors are auxiliary. The sterilizing mechanism of ERW is physics sterilizing that the mainly factor is ORP.