Understanding how light interacts with matter at the nanometre scale is a fundamental issue in optoelectronics and nanophotonics. In particular, many applications (such as bio-sensing, cancer therapy and all-optical signal processing) rely on surface-bound optical excitations in metallic nanoparticles. However, so far no experimental technique has been capable of imaging localized optical excitations with sufficient resolution to reveal their dramatic spatial variation over one single nanoparticle. Here, we present a novel method applied on silver nanotriangles, achieving such resolution by recording maps of plasmons in the near-infrared/visible/ultraviolet domain using electron beams instead of photons. This method relies on the detection of plasmons as resonance peaks in the energy-loss spectra of subnanometre electron beams rastered on nanoparticles of well-defined geometrical parameters. This represents a significant improvement in the spatial resolution with which plasmonic modes can be imaged, and provides a powerful tool in the development of nanometre-level optics.

Mapping surface plasmons on a single metallic nanoparticle

Understanding the structure-performance relationship of active sites at atomic scale

Molybdenum disulfide (MoS2) is a promising nonprecious catalyst for the hydrogen evolution reaction (HER) that has been extensively studied due to its excellent performance, but the lack of understanding of the factors that impact its catalytic activity hinders further design and enhancement of MoS2-based electrocatalysts. Here, by using novel porous (holey) metallic 1T phase MoS2 nanosheets synthesized by a liquid-ammonia-assisted lithiation route, we systematically investigated the contributions of crystal structure (phase), edges, and sulfur vacancies (S-vacancies) to the catalytic activity toward HER from five representative MoS2 nanosheet samples, including 2H and 1T phase, porous 2H and 1T phase, and sulfur-compensated porous 2H phase. Superior HER catalytic activity was achieved in the porous 1T phase MoS2 nanosheets that have even more edges and S-vacancies than conventional 1T phase MoS2. A comparative study revealed that the phase serves as the key role in determining the HER performance, as 1T phase MoS2 always outperforms the corresponding 2H phase MoS2 samples, and that both edges and S-vacancies also contribute significantly to the catalytic activity in porous MoS2 samples. Then, using combined defect characterization techniques of electron spin resonance spectroscopy and positron annihilation lifetime spectroscopy to quantify the S-vacancies, the contributions of each factor were individually elucidated. This study presents new insights and opens up new avenues for designing electrocatalysts based on MoS2 or other layered materials with enhanced HER performance.

(Invited) Contributions of Phase, Sulfur Vacancies, and Edges to the Hydrogen Evolution Reaction Catalytic Activity of Porous Molybdenum Disulfide Nanosheets

The effective separation of photogenerated carriers plays a vital role in photocatalytic reactions. In addition to the intrinsic driving force of photocatalysis, an external field generating an enh...

Recent Advances in Noncontact External-Field-Assisted Photocatalysis: From Fundamentals to Applications

FeCo/FeCoP encapsulated in N, Mn-codoped three-dimensional fluffy porous carbon nanostructures as highly efficient bifunctional electrocatalyst with multi-components synergistic catalysis for ultra-stable rechargeable Zn-air batteries.

Plasmonic nanomaterials coupled with catalytically active surfaces can provide unique opportunities for various catalysis applications, where surface plasmons produced upon proper light excitation can be adopted to drive and/or facilitate various chemical reactions. A brief introduction to the localized surface plasmon resonance and recent design and fabrication of highly efficient plasmonic nanostructures, including plasmonic metal nanostructures and metal/semiconductor heterostructures is given. Taking advantage of these plasmonic nanostructures, the following highlights summarize recent advances in plasmon-driven photochemical reactions (coupling reactions, O2 dissociation and oxidation reactions, H2 dissociation and hydrogenation reactions, N2 fixation and NH3 decomposition, and CO2 reduction) and plasmon-enhanced electrocatalytic reactions (hydrogen evolution reaction, oxygen reduction reaction, oxygen evolution reaction, alcohol oxidation reaction, and CO2 reduction). Theoretical and experimental approaches for understanding the underlying mechanism of surface plasmon are discussed. A proper discussion and perspective of the remaining challenges and future opportunities for plasmonic nanomaterials and plasmon-related chemistry in the field of energy conversion and storage is given in conclusion.

Recent Advances in Plasmonic Nanostructures for Enhanced Photocatalysis and Electrocatalysis.

Oxygen evolution reaction (OER) in acidic media usually requires a catalyst with high content of noble Ir or Ru, becoming a bottleneck for the electrochemical water splitting. To address this issue, here we report the fabrication of a RuO2/(Co,Mn)3O4 nanocomposite with low Ru loading (2.51 wt%) as a highly efficient OER catalyst in acidic media (0.5 M H2SO4). Spectroscopic and theoretical studies demonstrate that the introduction of Mn in Co3O4 results in redistribution of electrons and the generation of electron-rich Ru species of the RuO2/(Co,Mn)3O4 catalyst. With modulated electronic properties, the adsorption of O on RuO2/(Co,Mn)3O4 is weakened and the rate determining step, formation of OOH*, of the OER process is therefore accelerated. At such a low Ru loading, RuO2/(Co,Mn)3O4 exhibits superior acidic OER activity (η =270 mV at 10 mA/cm2) and long‐term stability to the benchmark RuO2 catalyst. This work provides a new strategy for the design of cost-effective acidic OER electrocatalysts for energy conversion applications.

Low Ru loading RuO2/(Co,Mn)3O4 nanocomposite with modulated electronic structure for efficient oxygen evolution reaction in acid

Magnetic field-enhanced electrocatalysis has recently emerged as an advanced strategy with great application prospects for highly efficient energy conversion and storage. Directly or indirectly, th...

Recent Advances in Magnetic Field-Enhanced Electrocatalysis

Co-based bimetallic metal-organic frameworks (MOFs) have emerged as a kind of promising electrocatalyst for oxygen evolution reaction (OER). However, most of present works for Co-based bimetallic MOFs are still in try-and-wrong stage, while the OER performance trend and the underlying structure-function relationship remain unclear. To address this challenge, Co-based MOFs on carbon cloth (CC) (CoM MOFs/CC, M = Zn, Ni, and Cu) are prepared through a room-temperature method, and their structure and OER performance are compared systematically. Based on the results of overpotential and Tafel slope, the order of OER activity is ordered in the decreasing sequence: CoZn MOF > CoNi MOF > CoCu MOF > Co MOF. Spectroscopic studies clearly show that the better OER performance of CoM MOFs results from the higher oxidation state of Co, which is related to the choice of second metal. Theoretical calculations indicate that CoZn MOFs possess strengthened adsorption for O-containing intermediate, and lower energy barrier towards OER. This study figures out the effect of second metal on the OER performance of Co-based bimetallic MOFs and suggests that tuning the electronic structure of the metal site can be an effective strategy for other MOFs-based OER catalysts.

Understanding the Effect of Second Metal on CoM (M = Ni, Cu, Zn) Metal-Organic Frameworks for Electrocatalytic Oxygen Evolution Reaction.

Plasmonics has emerged as a promising methodology to promote chemical reactions and has become a field of intense research effort. Ag nanoparticles (NPs) as plasmonic catalysts have been extensively studied because of their remarkable optical properties. This review analyzes the emergence and development of localized surface plasmon resonance (LSPR) in organic chemistry, mainly focusing on the discovery of novel reactions with new mechanisms on Ag NPs. Initially, the basics of LSPR and LSPR-promoted photocatalytic mechanisms are illustrated. Then, the recent advances in plasmonic nanosilver-mediated photocatalysis in organic transformations are highlighted with an emphasis on the related reaction mechanisms. Finally, a proper perspective on the remaining challenges and future directions in the field of LSPR-promoted organic transformations is proposed.

Yuanyuan Zhang

Papers

Recent Advances in Plasmonic Nanostructures for Enhanced Photocatalysis and Electrocatalysis.

Low Ru loading RuO2/(Co,Mn)3O4 nanocomposite with modulated electronic structure for efficient oxygen evolution reaction in acid

Recent Advances in Magnetic Field-Enhanced Electrocatalysis

Understanding the Effect of Second Metal on CoM (M = Ni, Cu, Zn) Metal-Organic Frameworks for Electrocatalytic Oxygen Evolution Reaction.

Recent Advances in Plasmon-Promoted Organic Transformations Using Silver-Based Catalysts.