Jianqiang Wang

An Aqueous Rechargeable Formate‐Based Hydrogen Battery Driven by Heterogeneous Pd Catalysis

The formate-based rechargeable hydrogen battery (RHB) promises high reversible capacity to meet the need for safe, reliable, and sustainable H2 storage used in fuel cell applications. Described herein is an additive-free RHB which is based on repetitive cycles operated between aqueous formate dehydrogenation (discharging) and bicarbonate hydrogenation (charging). Key to this truly efficient and durable H2 handling system is the use of highly strained Pd nanoparticles anchored on graphite oxide nanosheets as a robust and efficient solid catalyst, which can facilitate both the discharging and charging processes in a reversible and highly facile manner. Up to six repeated discharging/charging cycles can be performed without noticeable degradation in the storage capacity.

Catalytic conversion of biomass-derived levulinic acid into γ-valerolactone using iridium nanoparticles supported on carbon nanotubes

A new method has been developed for the catalytic conversion of biomass-derived levulinic acid (LA) into gamma-valerolactone (GVL) with molecular hydrogen (H-2) using a series of heterogeneous noble metal catalysts. Excellent yields of the GVL were obtained under mild reaction conditions of 50 degrees C and 2 MPa of H-2 using iridium nanoparticles supported on carbon nanotubes (Ir/CNT). It is noteworthy that the reaction proceeded smoothly in the presence of formic acid (FA, co-produced with LA in equimolar amounts during the acid-mediated hydrolysis of lignocellulosic biomass). Furthermore, the FA remained intact, highlighting the practical advantages of this process for the convenient and cost-effective processing of a biomass-derived LA/FA solution. The method is effective for the simultaneous production of GVL and FA from a wide variety of renewable biomass resources

Research Progress on the Indirect Hydrogenation of Carbon Dioxide to Methanol

Methanol is a sustainable source of liquid fuels and one of the most useful organic chemicals. To date, most of the work in this area has focused on the direct hydrogenation of CO2 to methanol. However, this process requires high operating temperatures (200-250u2009°C), which limits the theoretical yield of methanol. Thus, it is desirable to find a new strategy for the efficient conversion of CO2 to methanol at relatively low reaction temperatures. This Minireview seeks to outline the recent advances on the indirect hydrogenation of CO2 to methanol. Much emphasis is placed on discussing specific systems, including hydrogenation of CO2 derivatives (organic carbonates, carbamates, formates, cyclic carbonates, etc.) and cascade reactions, with the aim of critically highlighting both the achievements and remaining challenges associated with this field.

Structural changes of Rh-Mn nanoparticles inside carbon nanotubes studied by X-ray absorption spectroscopy

Supported Rh-based catalysts such as Rh-Mn nanoparticles (NPs) have potential use in the synthesis of ethanol from syngas. The structure of Rh-Mn NPs in multi-walled carbon nanotubes under different atmospheres and temperatures was studied by X-ray absorption spectroscopy (XAS). TEM images showed that the NPs dispersed in the carbon nanotubes had a uniform size of 2 nm. XAS data revealed that the Rh-Mn NPs before reduction were composed of Rh2O3 clusters and mixed Mn oxide species. After reduction in a 10% H-2-90% He atmosphere, the mixed Mn oxides were converted into nearly pure MnO. In contrast, the Rh2O3 clusters were easily decomposed to metallic Rh clusters even under a He atmosphere at 250 degrees C. The Rh clusters remained in the metal state under the next reduction atmosphere, but their dispersion in the Rh-Mn NPs increased with increasing temperature. No significant Mn-Rh or Mn-O-Rh interaction in the reduced NPs was observed in the extended X-ray absorption fine structure analysis. The results showed that there was no interaction between the MnO particles and Rh clusters and the role of the Mn promoter was mainly to improve Rh dispersion

Size-control growth of thermally stable Au nanoparticles encapsulated within ordered mesoporous carbon framework

Simultaneously controlling the size of Au nanoparticles and immobilizing their location to specific active sites while hindering migration and sintering at elevated temperatures is a current challenge within materials chemistry. Typical methods require the use of protecting agents to control the properties of Au nanoparticles and therefore it is difficult to decouple the influence of the protecting agent and the support material. By functionalizing the internal surface area of mesoporous carbon supports with thiol groups and implementing a simple acid extraction step, we are able to design the resulting materials with precise control over the Au nanoparticle size without the need for the presence of any protecting group, whilst simultaneously confining the nanoparticles to within the internal porous network. Monodispersed Au nanoparticles in the absence of protecting agents were encapsulated into ordered mesoporous carbon at various loading levels via a coordination-assisted self-assembly approach. The X-ray diffractograms and transmission electron microscopy micrographs show that the particles have controlled and well-defined diameters between 3 and 18 nm at concentrations between 1.1 and 9.0 wt%. The Au nanoparticles are intercalated into the pore matrix to different degrees depending on the synthesis conditions and are stable after high temperature treatment at 600 °C. N2 adsorption-desorption isotherms show that the Au functionalized mesoporous carbon catalysts possess high surface areas (1269–1743 m2/g), large pore volumes (0.78–1.38 cm3/g) and interpenetrated, uniform bimodal mesopores with the primary larger mesopore lying in the range of 3.4–5.7 nm and the smaller secondary mesopore having a diameter close to 2 nm. X-ray absorption near extended spectroscopy analysis reveals changes to the electronic properties of the Au nanoparticles as a function of reduced particle size. The predominant factors that significantly determine the end Au nanoparticle size is both the thiol group concentration and subjecting the as-made materials to an additional concentrated sulfuric acid extraction step.