Bing Ni

Modifying Commercial Carbon with Trace Amounts of ZIF to Prepare Derivatives with Superior ORR Activities

Reducing costs while maintaining high activities and stabilities of oxygen reduction reaction (ORR) catalysts has long been pursued for applications to membrane fuel cells. Here, an absorption-reaction method is used to prepare a zeolitic imidazolate framework coated commercial carbon, and the pyrolysis of such material brings about impressive ORR activities and stabilities with large diffusion-limited current density, half-wave potential, and no obvious decay after 10 000 cyclic voltammetry cycles, which is even better than that of the commercial Pt/C catalysts. The absorption-reaction method is realized by simply soaking the commercial carbon black sequentially in Co(NO3 )2 and 2-methylimidazole solutions at ambient conditions. The detailed analysis on such carbon materials reveals that both Co and N are essential to activities, even the amount of N and Co species is very low. The reduction of raw materials and simplified handling procedures result in well-controlled costs in applications.

Porous Tetrametallic PtCuBiMn Nanosheets with a High Catalytic Activity and Methanol Tolerance Limit for Oxygen Reduction Reactions

Porous PtCuBiMn nanosheets are developed with a thickness of ≈3-4 nm. The specific and mass activities of these nanosheets are ten and seven times greater than that of commercial Pt/C catalyst, respectively. PtCuBiMn nanosheets demonstrate superior catalytic performance for the oxygen reduction reaction, as well as resistance to methanol cross-over effects, suggesting that it is a promising catalyst for direct methanol fuel cells.

Fullerene‐Like Nickel Oxysulfide Hollow Nanospheres as Bifunctional Electrocatalysts for Water Splitting

Fullerene-like nickel oxysulfide hollow nanospheres with ≈50 nm are constructed by in situ growth on the surface of nickel foam by taking advantage of solvothermal reaction. The as-prepared composite exhibits exhilaratingly high HER and OER performance in 1 m KOH, which opens up a very promising aspect for non-noble metal chalcogenides as bifunctional electrocatalysts.

Ultra-small Tetrametallic Pt-Pd-Rh-Ag Nanoframes with Tunable Behavior for Direct Formic Acid/Methanol Oxidation

Reversible tuning of ultra-small multimetallic Pt-Pd-Rh-Ag nanoframes is achieved. These nanoframes showed tunable and reversible modes for the oxidation of small organic molecules by simply inducing segregation with adsorbates, such as SO42- and OH- . This is the first example of reversible segregation under electrocatalytic conditions in atomic-sized electrocatalysts. These nanoframes also showed a controllable activity and good stability for the oxidation of small organic molecules.

Competitive Coordination Strategy to Finely Tune Pore Environment of Zirconium-Based Metal–Organic Frameworks

Metal-organic frameworks (MOFs) are a class of crystalline porous materials with reticular architectures. Precisely tuning pore environment of MOFs has drawn tremendous attention but remains a great challenge. In this work, we demonstrate a competitive coordination approach to synthesize a series of zirconium-metalloporphyrinic MOFs through introducing H2O and monocarboxylic acid as modulating reagents, in which well-ordered mesoporous channels could be observed clearly under conventional transmission electron microscopy. Owing to plenty of unsaturated Lewis acid catalytic sites exposed in the visualized mesoporous channels, these structures exhibit outstanding catalytic activity and excellent stability in the chemical fixation of carbon dioxide to cyclic carbonates. The zirconium-based MOFs with ordered channel structures are expected to pave the way to expand the potential applications of MOFs.

Ultrathin 2D Zirconium Metal-Organic Framework Nanosheets: Preparation and Application in Photocatalysis

Synthesizing ultrathin 2D metal-organic framework nanosheets in high yields has received increasing research interest but remains a great challenge. In this work, ultrathin zirconium-porphyrinic metal-organic framework (MOF) nanosheets with thickness down to ≈1.5 nm are synthesized through a pseudoassembly-disassembly strategy. Owing to the their unique properties originating from their ultrathin thickness and highly exposed active sites, the as-prepared ultrathin nanosheets exhibit far superior photocatalysis performance compared to the corresponding bulk MOF. This work highlights new opportunities in designing ultrathin MOF nanosheets and paves the way to expand the potential applications of MOFs.

Trimetallic PtCoFe Alloy Monolayer Superlattices as Bifunctional Oxygen‐Reduction and Ethanol‐Oxidation Electrocatalysts

A synthesis strategy for the preparation of trimetallic PtCoFe alloy nanoparticle superlattices is reported. Trimetallic PtCoFe alloy monolayer array of nanoparticle superlattices with a large density of high index facets and platinum-rich surface are successfully prepared by coreduction of metal precursors in formamide solvent. The concentration of cetyl trimethyl ammonium bromide plays a vital role for the formation of a monolayer array of nanoparticle superlattices, while the size of nanoparticles is determined by NaI. The prepared monolayer array of nanoparticle superlattices is the superior catalyst for oxygen reduction reaction as well as for ethanol oxidation owing to their specific structural and compositional characteristics.

The formation of (NiFe)S2 pyrite mesocrystals as efficient pre-catalysts for water oxidation

Designing intricate structures and searching for functional materials has attracted wide interest in nanoscience. Herein we have fabricated (NiFe)S2 pyrite mesocrystals in the form of nearly-single crystalline porous cubes, and studied their self-optimization to realize efficient activity toward water oxidation under electrochemical conditions. The growth mechanism of the mesocrystals was a non-classical mechanism, which was initiated by the formation of a large quantity of small nickel sulfide clusters, followed by the aggregation and transformation of these small clusters in an oriented manner. When these mesocrystals were tested for water oxidation under electrocatalytic conditions, the materials served as pre-catalysts and immediately self-optimized to form amorphous S-doped metal (oxy)hydroxides, which are the real catalytically active materials. As a result, the observed overpotential to reach a current density of 10 mA cm−2 on glassy carbon electrodes was less than 260 mV. The growth mechanism studied here may provide opportunities for constructing intricate sulfide structures, and the self-optimization process during water oxidation can inspire new thoughts on electrocatalysis.

Surface Oxidation of AuNi Heterodimers to Achieve High Activities toward Hydrogen/Oxygen Evolution and Oxygen Reduction Reactions

Although much attention has been paid to the exploration of highly active electrocatalysts, especially catalysts for hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), the development of multifunctional catalysts remains a challenge. Here, we utilize AuNi heterodimers as the starting materials to achieve high activities toward HER, OER and ORR. The HER and ORR activities in an alkali environment are similar to those of Pt catalysts, and the OER activity is very high and better than that of commercial IrO2 . Both the experimental and calculated results suggest that the surface oxidation under oxidative conditions is the main reason for the different activities. The NiO/Ni interface which exists in the as-synthesized heterodimers contributes to high HER activity, the Ni(OH)2 -Ni-Au interface and the surface Ni(OH)2 obtained in electrochemical conditons gives rise to promising ORR and OER activities, respectively. As a comparison, a Au@Ni core-shell structure is also synthesized and examined. The core-shell structure shows lower activities for HER and OER than the heterodimers, and reduces O2 selectively to H2 O2 . The work here allows for the development of a method to design multifunctional catalysts via the partial oxidation of a metal surface to create different active centers.

Mesoporous ZrO2 Nanoframes for Biomass Upgrading

The rational design and preparation of a high-performance catalyst for biomass upgrading are of great significance and remain a great challenge. In this work, mesoporous ZrO2 nanoframe, hollow ring, sphere, and core-shell nanostructures have been developed through a surfactant-free route for upgrading biomass acids into liquid alkane fuels. The obtained ZrO2 nanostructures possess well-defined hollow features, high surface areas, and mesopores. The diversity of the resultant ZrO2 nanostructures should arise from the discrepant hydrolysis of two different ligands in zirconocene dichloride (Cp2ZrCl2) as the zirconium precursor. The time-dependent experiments indicate that Ostwald ripening and salt-crystal-template formation mechanisms should account for hollow spheres and nanoframes, respectively. Impressively, compared with the hollow sphere, commercial nanoparticle, and the ever-reported typical results, the ZrO2 nanoframe-promoted Ni catalyst exhibits greatly enhanced catalytic activity in the upgrading of biomass acids to liquid alkane fuels, which should be ascribed to the hollow feature, large active surface area, highly dispersed Ni, and strong metal-support interactions arising from the structural advantages of nanoframes. The nanoframes also possess excellent solvothermal and thermal stability. Our findings here can be expected to offer new perspectives in material chemistry and ZrO2-based catalytic and other applications.