Fumin Li

Unexpected catalytic activity of rhodium nanodendrites with nanosheet subunits for methanol electrooxidation in an alkaline medium

Nanocrystals of Rh, an important member of the noble metal catalyst family, have wide applications in heterogeneous catalytic reactions. Controlling the morphology of these noble metal nanocrystals has become an effective strategy for improving their catalytic activity and durability. In this work, well-defined Rh nanodendrites with very thin triangular branches as subunits are synthesized using a facile diethylene glycol reduction method, assisted by polyethyleneimine as a complex-forming agent and surfactant. For the first time, the methanol oxidation reaction (MOR) on Rh nanocrystals with a well-defined morphology is investigated using various electrochemical techniques in an alkaline medium. Unexpectedly, the as-prepared Rh nanodendrites, with ultrathin nanosheet subunits, exhibit superior electrocatalytic activity and durability during the MOR in an alkaline medium, indicating that Rh nanocrystals with specific morphology may be highly promising alternatives to Pt electrocatalysts in the MOR in an alkaline medium.

Sandwich-structured Au@polyallylamine@Pd nanostructures: tuning the electronic properties of the Pd shell for electrocatalysis

We report herein the synthesis of core–shell sandwich Au@polyallylamine@Pd nanostructures, in which the electronic structure of the Pd shell can be strongly tuned by the medial polyallylamine layers. The designed Au@polyallylamine@Pd nanostructures exhibit significantly improved electrocatalytic activity and stability for the formic acid oxidation reaction through the preferential dehydrogenation pathway.

Reduced graphene oxide supported platinum nanocubes composites: one-pot hydrothermal synthesis and enhanced catalytic activity

Reduced graphene oxide (rGO) supported platinum nanocubes (Pt-NCs) composites (Pt-NCs/rGO) were synthesized successfully by a water-based co-chemical reduction method, in which polyallylamine hydrochloride acted as a multi-functional molecule for the functionalization of graphene oxide, anchorage of Pt(II) precursor, and control of Pt crystal facets. The morphology, structure, composition, and catalytic property of Pt-NCs/rGO composites were characterized in detail by various spectroscopic techniques. Transmission electron microscopy images showed well-defined Pt-NCs with an average size of 9 nm uniformly distributed on the rGO surface. The as-prepared Pt-NCs/rGO composites had excellent colloidal stability in the aqueous solution, and exhibited superior catalytic activity towards the hydrogenation reduction of nitro groups compared to commercial Pt black. The improved catalytic activity originated from the abundant exposed Pt{100} facets of Pt-NCs, excellent dispersion of Pt-NCs on the rGO surface, and synergistic effect between Pt-NCs and rGO.

In situ bubble template-assisted synthesis of phosphonate-functionalized Rh nanodendrites and their catalytic application

The controllable synthesis of branched noble metal nanostructures has attracted significant attention as it provides excellent catalytic activity and durability to these metal nanostructures. In the present study, a facile and effective complexation–reduction strategy was developed for synthesizing Rh nanodendrites with hippocampus tail-like branches (Rh-NDHTs) using N2H4·H2O as a reductant and multiphosphonate molecule with small molecular weight as a complexant and functional agent. During the synthesis, the coordination interaction between multiphosphonate and RhCl3 as well as the hydrazine decomposition reaction (H2NNH2 = N2 + 2H2) catalyzed by the freshly formed Rh nanocrystals play important roles in the generation of Rh-NDHTs. Moreover, phosphonate functionalization of Rh-NDHTs was simultaneously achieved during the course of the synthesis, originating from the strong adsorption of multiphosphonate on the Rh surface. When used as a heterogeneous catalyst for the o-phenylenediamine oxidation reaction, the phosphonate-functionalized Rh-NDHTs exhibited enhanced catalytic efficiency and durability as compared to the commercially available Rh nanocrystals, attributing to their extraordinary morphological and interfacial properties.

Atoms diffusion-induced phase engineering of platinum-gold alloy nanocrystals with high electrocatalytic performance for the formic acid oxidation reaction

Bimetallic noble metal nanocrystals have been widely applied in many fields, which generally are synthesized by the wet-chemistry reduction method. This work presents a purposely designed atoms diffusion induced phase engineering of PtAu alloy nanocrystals on platy Au substrate (PtAu-on-Au nanostructures) through simple hydrothermal treatment. Benefitting from the synergistic effects of component and structure, PtAu-on-Au nanostructures remarkably enhance the dehydrogenation pathway of the formic acid oxidation reaction (FAOR), and thus exhibit much higher FAOR activity and durability compared with Pt nanocrystals on platy Au substrate (Pt-on-Au nanostructures) and commercial Pd black due to an excellent stability of platy Au substrate and a high oxidation resistance of PtAu alloy nanocrystals. The atoms diffusion-induced phase engineering demonstrated in this work builds a bridge between the traditional metallurgy and modern nanotechnologies, which also provides some useful insights in developing noble metals based alloyed nanostructures for the energy and environmental applications.

Interfacial proton enrichment enhances proton-coupled electrocatalytic reactions

Proton-coupled electrocatalytic reactions, such as the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) in acidic media, are very important half-reactions of fuel cells and water electrolysis. Aiming at increasing the interfacial proton concentration to improve the ORR/HER activity, we synthesize PdNi alloy nanostructures (PdNi-ANSs)–polyethyleneimine (PEI) inorganic–organic nanocomposites (PdNi-ANSs@PEI) by a PEI assisted cyanogel-reduction strategy. Various physical characterization techniques show that PdNi-ANSs are successfully functionalized by the PEI polymer during the synthesis of PdNi-ANSs@PEI because of the N–Pd interaction. Thanks to the increased interfacial proton concentration caused by the protonation of amine groups at PEI in acidic media, the molecular weight optimized PdNi-ANSs@PEI exhibit enhanced ORR/HER activity compared to PdNi-ANSs without PEI and commercial electrocatalysts, which indicates that the electrocatalytic activity of metal nanostructures can be remarkably improved by reasonable interface design.

From monometallic Au nanowires to trimetallic AuPtRh nanowires: interface control for the formic acid electrooxidation

Developing an easy-to-expand synthetic method for nanostructures is highly desired, which will help in investigating the effect of the type and content of the extended component on catalytic performance. Based on original Au nanowires (NWs), we design a two-step interface control strategy to synthesize a series of bimetallic AuPt NWs and trimetallic AuPtRh NWs for the formic acid oxidation reaction (FAOR). By controlling the proportion of Au and Pt, a Au/Pt interface can achieve a AuPt alloy structure, which makes Au6Pt1/C show a complete direct dehydrogenation pathway for the FAOR. The further design and fabrication of an advanced Au/Pt/Rh interface are proved to be more active than the Au/Pt interface for the FAOR. The mechanism analysis and experimental results demonstrate that Rh atoms on the Au/Pt/Rh interface can provide active hydroxyl species, so that the adsorption of formate and the desorption of generated hydrogen species are promoted at Pt atoms on the Au/Pt/Rh interface. Consequently, Au6Pt1Rh0.5/C electrocatalysts exhibit excellent mass activity (8.05 A mgPt−1) and specific activity (14.3 mA cm−2) for the FAOR, which exceed those of most of the reported Pt-based or Pd-based electrocatalysts.