Ag Catalyst Formaldehyde To Produce Hydrogen

As one of widely acceptable clean sources, hydrogen energy have been considered to intrinsically possess more distinct advantages than traditional fossil fuels. More specifically, it could supply more high thermal efficiency, while no any environmentally harmful by-product has been produced. Furthermore, the significant application of hydrogen, proton exchange membrane fuel cells, has attracted considerable attention in recent years. However, note that the major hurdle for its practical application is how to supply H2continually and steadily without high energy consumption or carbon monoxide. Unfortunately, the present hydrogen production technologies cannot fully satisfy these conditions. For example, the steam reforming of methane requires extremely high temperature and yields destructive by-products such as CO, which may degrade the fuel-cell components. Other methods to produce hydrogen such as water electrolysis and fermentative hydrogen production are also facing the same problems of high cost, low purity, and discontinuities. Recently, there are many researches on the hydrogen generation by hydrolyzing the chemical hydrides. Although this process has many merits compared with other methods for providing pure hydrogen at room temperature, the high costs are the significant barriers for its mass application. Hence, it is highly desirable to develop a low-cost as well as high efficient hydrogen generation procedure.Formaldehyde, as one of indoor volatile organic compounds, exists extensively in modern building materials and household products, can frequently cause cancer and other sickness. Meanwhile, formaldehyde in waste waters also presents a particularly difficult problem in commercial water purification, such as phenolic resin production and construction materials. At this stage, the photocatalytic degradation of formaldehyde with the help of semiconductor materials was the major method to reduce formaldehyde pollutio. However, the catalytic procedures available to date generally focus on the oxidation of HCHO gas in the indoor air with very low concentrations, while industrial waste water usually contains high concentrations of formaldehyde. Thereby, the reported methods cannot satisfy fully the criteria of adaptability for their practical utilizations in industrial waste water, especially for formaldehyde with high concentrations. Some nano metallic materials such as Ag and Cu could catalyze the formaldehyde in alkaline aqueous solution to convert into hydrogen quantitatively at room temperature. This reaction has two major benefits:the resulting gas was pure hydrogen, excluding CO or CO2, the reaction conditions were very mild and have a stable hydrogen production rate; the hydrogen can be detected immediately both in high and low concentrations of HCHO, as the adding of formaldehyde into the alkaline aqueous solutions with catalyst; hence, this reaction can be used to degrade large scale of formaldehyde pollutions, turning waste into wealth; it also can be selected as probe reaction to detect formaldehyde. However, using metal nanoparticles as the catalyst in a reaction has an intrinsic defect:these nanoparticles inevitably tend to agglomerate into large particles, which greatly reduce the catalytic performances as a result of the active site decrease. Thereby, it is highly desirable to develop a simple and effective strategy to prevent agglomeration, decrease the mass of noble metal, and improve the catalytic performance.These supported Ag/γ-Al2O3catalysts exhibit much higher catalytic activities compared with the normal Ag particles. By further optimizing the reaction parameters such as temperature, catalyst amounts, oxygen, formaldehyde concentrations, and NaOH concentrations, the hydrogen generation rate over Ag/γ-Al2O3catalyst has been maintained for hours. we demonstrate a simple and efficient process for generating hydrogen from the formaldehyde (HCHO) aqueous solution catalyzed by Ag nanoparticles dispersed on high specific surface area γ-Al2O3at room temperature. Moreover, this Ag/γ-Al2O3catalyst exhibits much higher capability and stability for hydrogen production than the unsupported Ag nanoparticles. By further optimizing the structure, component, and amounts of Ag/γ-Al2O3catalysts as well as reaction parameters such as reaction atmosphere, formaldehyde concentrations, and NaOH concentrations, the hydrogen generation rate could be greatly increased and maintained for ten hours without any decay. It may provide a general and favorable strategy for the fabrication of highly reactive and stable metal catalytst for the hydrogen production from organic aldehyde...