Plasmon-Driven Electrochemical Methanol Oxidation on Gold Nanohole Electrodes

Hot or Not? Reassessing Mechanisms of Photocurrent Generation in Plasmon-Enhanced Electrocatalysis

It is now widely accepted that certain effects arising from localised surface plasmon resonance, such as enhanced electromagnetic fields, hot carriers, and thermal effects, can facilitate electrocatalytic processes. This newly emerging field of research is commonly referred to as plasmon-enhanced electrocatalysis (PEEC) and is attracting increasing interest from the research community, particularly regarding harnessing the high energy of hot carriers. However, this has led to a lack of critical analysis in the literature, where the participation of hot carriers is routinely claimed due to their perceived desirability, while the contribution of other effects is often not sufficiently investigated. As a result, correctly differentiating between the possible mechanisms at play has become a key point of contention. In this review, we specifically focus on the mechanisms behind photocurrents observed in PEEC and critically evaluate the possibility of alternative sources of current enhancement in the reported PEEC systems. Furthermore, we present guidelines for the best experimental practices and methods to distinguish between the various enhancement mechanisms in PEEC.

Optrode-Assisted Multiparametric Near-Infrared Spectroscopy for the Analysis of Liquids

We demonstrate a sensing scheme for liquid analytes that integrates multiple optical fiber sensors in a near-infrared spectrometer. With a simple optofluidic method, a broadband radiation is encoded in a time-domain interferogram and distributed to different sensing units that interrogate the sample simultaneously; the spectral readout of each unit is extracted from its output signal by a Fourier transform routine. The proposed method allows performing a multiparametric analysis of liquid samples in a compact setup where the radiation source, measurement units, and spectral readout are all integrated in a robust telecom optical fiber. An experimental validation is provided by combining a plasmonic nanostructured fiber probe and a transmission cuvette in the setup and demonstrating the simultaneous measurement of the absorption spectrum and the refractive index of water-methanol solutions.

Directing Energy Flow in Core-Shell Nanostructures for Efficient Plasmon-Enhanced Electrocatalysis

Conjugating plasmonic metals with catalytically active materials with controlled configurations can harness their light energy harvesting ability in catalysis. Herein, we present a well-defined core-shell nanostructure composed of an octahedral Au nanocrystal core and a PdPt alloy shell as a bifunctional energy conversion platform for plasmon-enhanced electrocatalysis. The prepared Au@PdPt core-shell nanostructures exhibited significant enhancements in electrocatalytic activity for methanol oxidation and oxygen reduction reactions under visible-light irradiation. Our experimental and computational studies revealed that the electronic hybridization of Pd and Pt allows the alloy material to have a large imaginary dielectric function, which can efficiently induce the shell-biased distribution of plasmon energy upon illumination and, hence, its relaxation at the catalytically active region to promote electrocatalysis.

One-pot synthesis of core@shell PdAuPt nanodendrite@Pd nanosheets for boosted visible light-driven methanol electrooxidation

Herein, we developed a one-pot, surfactant-free approach to obtain a PdPtAu@Pd core@shell catalyst for the photocatalytic methanol oxidation reaction. By virtue of its dimensions, conjunction architecture and robust core@shell construction, 0D@2D PdPtAu@Pd exhibited a superior catalytic performance, with a mass activity 2.3- and 6.7-times higher than that of Pt/C and Pd/C catalysts, respectively.

In Situ Replacement Synthesis of Co@NCNT Encapsulated CoPt3 @Co2 P Heterojunction Boosting Methanol Oxidation and Hydrogen Evolution

Simultaneous boosting electrochemical methanol oxidation reaction (MOR) for direct methanol fuel cells and production of hydrogen is meaningful but challenging. Herein, a sea urchin-shaped cobalt-embedded N-doped carbon nanotubes (Co@NCNT) encapsulated CoPt₃ @Co₂ P heterojunction (CoPt₃ @Co₂ P/Co@NCNT) is fabricated. Theoretical calculations confirm that electrons at the interfaces transfer from CoPt₃ to Co₂ P, where electron hole region on CoPt₃ is beneficial to improving the MOR activity, whereas accumulation region on Co₂ P favors to the optimization of H₂ O and H* absorption energies for hydrogen evolution reaction (HER). Benefitting from its interfacial electronic reconfiguration, the CoPt₃ @Co₂ P/Co@NCNT heterojunction exhibits excellent electrocatalytic performances for MOR and HER, in which the mass activity (2981 mA mg_Pt ^-1 ) for MOR is 14.2 times than that of Pt/C (20%), and the smallest overpotentials only requires 19 mV to deliver a current density of 10 mA cm^-2 for HER. Moreover, the electrolyzer employing CoPt₃ @Co₂ P/Co@NCNT for anodic MOR and cathodic H₂ production only requires a low voltage of 1.43 V at 10 mA cm^-2 with impressive long-life cycling stability, which is obviously better than that of commercial Pt/C//RuO₂ . This study offers a novel strategy for other organics oxidation reaction coupled with HER catalyzed production of hydrogen.

Localized surface plasmon resonance for enhanced electrocatalysis

Electrocatalysis plays a vital role in energy conversion and storage in modern society. Localized surface plasmon resonance (LSPR) is a highly attractive approach to enhance the electrocatalytic activity and selectivity with solar energy. LSPR excitation can induce the transfer of hot electrons and holes, electromagnetic field enhancement, lattice heating, resonant energy transfer and scattering, in turn boosting a variety of electrocatalytic reactions. Although the LSPR-mediated electrocatalysis has been investigated, the underlying mechanism has not been well explained. Moreover, the efficiency is strongly dependent on the structure and composition of plasmonic metals. In this review, the currently proposed mechanisms for plasmon-mediated electrocatalysis are introduced and the preparation methods to design supported plasmonic nanostructures and related electrodes are summarized. In addition, we focus on the characterization strategies used for verifying and differentiating LSPR mechanisms involved at the electrochemical interface. Following that are highlights of representative examples of direct plasmonic metal-driven and indirect plasmon-enhanced electrocatalytic reactions. Finally, this review concludes with a discussion on the remaining challenges and future opportunities for coupling LSPR with electrocatalysis.