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Plasmon-Mediated Electrocatalysis for Sustainable Energy: From Electrochemical Conversion of Different Feedstocks to Fuel Cell Reactions Chi Hun Choi, Kyungwha Chung, Trang Thi Hong Nguyen, and Dong Ha Kim ACS Energy Lett., Just Accepted Manuscript • DOI: 10.1021/acsenergylett.8b00461 • Publication Date (Web): 15 May 2018 Downloaded from http://pubs.acs.org on May 15, 2018

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ACS Energy Letters

Plasmon-Mediated Electrocatalysis for Sustainable Energy: From Electrochemical Conversion of Different Feedstocks to Fuel Cell Reactions Chi Hun Choi, 1,† Kyungwha Chung,1,† Trang-T. H. Nguyen,2 and Dong Ha Kim1,* 1

Department of Chemistry and Nano Science, Division of Molecular and Life Sciences, College

of Natural Sciences, Ewha Womans University, 52, Ewhayeodae-gil, Seodaemun-gu, Seoul 03760, Korea 2

Department of Physics, Quy Nhon University, 170 An Duong Vuong, Quy Nhon, Binh Dinh,

Viet Nam †

These authors contributed equally to this work.

Corresponding Author *Email: [email protected]

ACS Paragon Plus Environment

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Abstract

The incorporation of plasmonic properties recently emerged as the advanced strategy for achieving high performance catalysis. The hot carriers and near-field enhancement induced by localized surface plasmon resonance (LSPR) excitation are the key parameters that are responsible for the enhanced performances. Thus, the logical combination of the plasmonic nanostructures and electrocatalytic materials can be an effective strategy for further widening the application of the plasmonic effect. Herein, this short review provides a concise overview of the fundamental principles of LSPR, the mechanism of plasmon-enhanced electrocatalysis, alternative design methods of plasmonic nanomaterials for various catalytic systems, and recent progress in plasmon-mediated electrocatalysis for the production of energy, including electrochemical conversion of different feedstock into fuels along with fuel cell catalysis. This review also shed light on the areas where major advancements are required to further improve the field of plasmon-mediated electrocatalysis to achieve a major paradigm shift towards the sustainable future.


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TOC GRAPHICS


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The continuous consumption of combustion energy has proven itself to be unsustainable due to the imminent exhaustion of the remaining fossil fuel reservoirs and detrimental environmental consequences. To resolve these critical issues, the development of technologies that can produce renewable fuels and chemicals from various renewable feedstocks is the utmost significant scientific challenge that the current society must overcome in order to achieve the sustainable future. The redox processes induced by electrocatalysts as the conversion platform recently showed many promising results as the alternative method that can produce value-added chemicals (e.g., hydrogen, hydrocarbons, oxygenates) from the simple, abundant feedstocks (e.g., water, carbon dioxide).1-5 Despite the extensive effort to create electrocatalytic materials with high turnover rate, the current outcome still lacks the demonstrative performance for the viable industrial applications. Hence, more fundamental understanding of the catalytic reaction, novel materials, and strategies that can outperform the current state-of-the-art catalysts are required to introduce the renewable energy technology at a global scale. The major progress was recently achieved with the development of plasmonic-mediated energy conversion technologies such as plasmon-mediated photochemical reactions,6-14 photovoltaics,15-17 and chemical synthesis.18 In particular, the strategic combination of electrocatalysis and plasmonic effect has emerged as a novel, breakthrough method for improving the overall electrocatalytic processes.19-22 This review discusses and provides the synopsis of recent research approaches, design methodologies, applications, and challenges of incorporating the plasmonic nanostructures and their influential factors especially for hot carriers and near-field enhancement mediated catalysis to increase the overall electrocatalytic performance in the field of energy production. The major difference between the photothermal catalytic pathways and this review is that most of the reactions presented in the published works


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were conducted under the constant temperature. This review particularly focuses on two major criteria: (1) electrochemical conversion of different feedstock into fuels such as water splitting and CO2 reduction and (2) plasmon-mediated fuel cell chemistry (e.g., oxygen reduction reaction, alcohol oxidation reactions). The examples where the plasmonic nanostructures were excited with the low-intensity laser light source are particularly emphasized to elucidate the unprecedented activity, selectivity, and practicality of the plasmon-mediated electrocatalysis. The review first introduces the fundamental mechanisms in plasmon-mediated electrocatalysis, which involve localized surface plasmon resonance (LSPR) decays, plasmonic hot carrier enhanced electrocatalysis, and near-field enhancement. This is followed by a discussion of hot carrier and near-field enhancement mediated electrocatalysts with the strategically designed plasmonic nanomaterials and their incorporation in the electrocatalytic system for a variety of applications such as water-splitting reactions and CO2 reduction. Throughout the review, the crucial aspects of the plasmon-mediated electrocatalysts to amplify the reactivity and/or selectivity of the final product are spotlighted to spur future research in this particular field. Finally, a critical perspective and conclusion regarding the practicality of plasmon-mediated electrocatalysis, mechanistic hypothesis, and open questions in plasmonic electrocatalysis are provided to encompass the initial understanding, limitations, and possible opportunities for developing high-performance plasmon-mediated electrocatalysis. Mechanisms in plasmon-enhanced electrocatalysis. Surface plasmons (SPs) are the collective oscillation of surface charges confined to the interface between dielectric and metal. Upon the strong interaction between surface plasmons and the light of their plasmon frequency, the resonance leads to several consequences which can affect to the electrocatalytic performances. Once SPs are excited by the incident light, relaxation of plasmon energy arises via radiative or


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nonradiative decays. Recently, the non-radiative decay process has been extensively investigated and discussed in numerous articles,23-31 because energetic hot carriers can be generated via Landau damping. Thereafter, the energy relaxation of hot carriers occurs through electronphonon and phonon-phonon collision leading to the heat emission to the environment.23 Ultrafast dynamics of the nonradiative decay restrict the efficient use of hot electrons and holes. Thus, it is necessary to extract them within tens of femtoseconds. In this regard, Wu et al. suggested the plasmon-induced metal-to-semiconductor interfacial charge-transfer transition (PICTT) pathway which is more efficient than the conventional hot-electron transfer from the conduction band of metal to conduction band of semiconductor, or direct interfacial charge-transfer transition.32 PICTT pathway, which is a type of

chemical interface damping (CID),33 requires strong

coupling between the metal and the semiconductor or the adsorbates, and results in the broadening of plasmon band. As plasmon energy directly generate the excited electron in the conduction band of semiconductor, it does not involve the hot electron in metal side and the electron-electron scattering in the metal is less. The plasmonic effects in electrocatalysis can be summarized as following: (1) upon exposure to a light source (preferably a laser that corresponds to the plasmonic wavelength to maximize the plasmon-enhanced electrocatalysis) the plasmonic hot carriers can participate in the electrocatalytic reaction to increase the catalytic performance upon the light illumination. The plasmonic hot electrons can be injected from the metal nanoparticles into the other electrocatalytic materials, can strengthen the adsorption of active species, potentially enhance the surface charge heterogeneity and charge density, hence enhance the rate of reactions. On the other hand, the generated hot holes, usually left on the surface of plasmonic nanoparticles, induce oxidative chemical conversion that can either withdraw electrons from the hosting


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substrate or directly oxidize small molecules, usually electron donors. (2) The electromagnetic near-field enhancement can facilitate the interaction between the reactant molecules and the catalytic sites of the metal34 to induce stronger polarized electrostatic field, which thereby makes the reactant moieties more activated for catalytic reaction35 or increase quantum-mechanical tunneling of proton.34 (3) The non-radiative decay leads to the heat emission, which can be beneficial for the electrocatalytic reaction kinetics. Temperature increase can promote the decrease of the activation energy and the Gibbs free energy of the catalytic reaction and the increase of the mass transport and solubility of gases enabling the decrease in solution resistivity.36 However, it should be emphasized that this review particularly focuses on the hot carriers and near-field enhancement to differentiate our perspectives from previously reported reviews and photothermal-based results. The overall processes are simplified and shown in Scheme 1. In addition to those plasmonic effect upon the light illumination, plasmonic metals, such as gold, silver, copper also show intrinsic catalytic activities which will be further discussed in the next sections with detailed mechanism and synopsis of representative research outcomes.


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Scheme 1. The simplified representation of plasmon-mediated electrocatalysis. Upon light irradiation, the generated hot carriers and near-field enhancement can induce alternative reaction pathways and increase catalytic performances for a variety of plasmon-mediated electrocatalytic systems.


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Design of plasmonic nanomaterials for catalyst systems. The activity and kinetics are the key parameters that must be considered to guide a new catalyst design. The active site and defect engineering strategies to increase the number of catalytic sites (e.g., doping, oxygen vacancy) and intrinsic activity of each catalytic sites (e.g., surface engineering and facet controls) are simultaneously employed to increase the overall catalytic turnover rate.2,

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On top of these

commonly accepted approaches to increase the catalytic performances, the incorporation of plasmonic metal nanostructures can deliver additional push to drive the catalytic conversion rate even further to achieve the active catalytic system due to the aforementioned plasmonic properties and intrinsic catalytic sites provided by the plasmonic nanostructures. The plasmonicmediated electrocatalysis is heavily focused on the generation of the hot carriers and near-field enhancement that can participate in modulating the thermodynamics of the catalytic systems. The incorporation of plasmonic nanoparticles can decrease the overpotential and activation energy of the catalytic systems by increasing the electron density and by providing catalytic active sites based on their facets or compositions that are specific for the product of interest, respectively. The increased electron density can deliver the electrons to the anti-bonding orbitals of the adsorbates to increase the probability of making reactive intermediates, which inherently increase the quantum yield, Faradaic efficiency for a particular product, and current density. Along with the increase in charge density, the surface and facet of these nanomaterials have different functionalities and provide favorable catalytic active sites for a various redox processes. The morphological control over these nanostructured plasmonic materials allowed the dynamic control over the selectivity and reactivity as well. This section summarizes the notable examples of each plasmonic metal nanostructures in photocatalysis and thermocatalysis where the similar


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strategies can be borrowed to incorporate these materials into the electrocatalytic systems to construct a synergistic, well-designed plasmon-mediated electrocatalyst. Noble metal-based plasmonic catalysts. Gold (Au) and silver (Ag) nanostructures have been extensively investigated due to their strong, easily-tunable plasmonic resonance and adsorption capability in the UV-Vis-NIR region, the major constituent of the solar flux. Such LSPR characteristics can be changed depending on their size, shape, and composition to tailor these materials into the desired catalytic reactions. This characteristic allows these nanomaterials to function as the nano-antenna in the semiconductor photocatalytic systems where they can harvest and convert light energy into electrons that can participate in the redox reactions. Recently, along with their exceptional light harvesting capability, many researchers reported that these noble metals exhibit unprecedented, innate catalytic capabilities that are desirable in designing the advanced electrocatalytic system. Au is chemically inert, coinage metal with high electrical conductivity and was often considered as inactive in the field of catalysis. Usually, in several studies on photocatalyst systems, Au was only recognized as an efficient, light absorbing material (antenna) in the antenna-reactor system to promote many photoconversion reactions when composited with the highly catalytic materials (reactor), such as TiO2,38-41 Pt,42-43 and Pd.44 However, the researchers realized that the nano-sized Au itself can serve as an additional catalytic platform along with the exceptional photophysical characteristics with respect to the different sizes and shapes, emerging Au as the distinguishable component for inducing a variety of catalytic reactions. The synthesis of Au nanostructures with various shapes are intensively well investigated in the past several decades.

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Especially, the anisotropic Au nanostructures such as

Au nanorods and nanobipyramids have multiple facets with large surface area and the absorption


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bands in visible-near infrared (NIR) region of the light. This phenomenon allows the excitation of localized surface plasmonic resonance through a wide range of solar spectrum. Another significant aspect to consider is that the catalytic activity on Au is sensitive to the crystal facets. Au(111) surface can be high activity sites for oxidation, while Au(100) is ideal for the reduction reaction involving bond breaking, respectively.49 The high selectivity of the facets allows dynamic and careful modification of reaction systems depending on the catalytic reaction of interest.50 Especially, Au provides high selectivity toward CO generation by CO2 reduction reaction (CO2RR), which is favorable for the conversion of greenhouse gas into valuable chemicals.51 Ag is also a very promising material for the plasmonic electrocatalyst due to the wider energy for intraband transitions24 and high extinction cross-section.52 Its catalytic properties have been extensively studied in CO2RR due to the high selectivity toward CO as the reduction product. Hoshi et al. revealed that stepped Ag(110) showed higher current density then flat Ag(111) and Ag(100) in CO2RR which is similar with the cases for Pt.53 Meanwhile, Liu et al. showed by density functional theory (DFT) simulations that higher CO2 reduction catalytic activity can be obtained on Ag(100) and Ag(110) than Ag(111) and suggested the triangular Ag nanoplate as an optimized structure because of its highly active edge sites for CO evolution.54 In the case of oxygen reduction reaction (ORR), Ag nanospheres showed higher catalytic activity than Ag cubes due to the high contents of Ag(111) facets over Ag(100) where oxygenated intermediates bind strongly to poison Ag catalysts’ surfaces.55 Copper-based plasmonic catalysts. Copper (Cu) has been widely utilized as the highly conducting metal in the field of electronics applications. Recently, Cu has been extensively investigated as the potential catalyst for the multiple applications to generate renewable, value-


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added chemicals from the various feedstocks.56-58 Especially for CO2 reduction (CO2RR), Cu has been explored for its superb catalytic performances for generating simple to complex hydrocarbons. On top of the versatile catalytic abilities, Cu itself can also exhibit intense LSPR mode in its nanostructured forms. Unfortunately, the utilization of copper as the platform for LSPR enhancement has been limited and seldom reported due to its susceptibility to oxygen and water to form Cu2O or CuO under ambient condition. The Van Duyne’s group showed the oxidedependent LSPR extinction of Cu nanoparticle arrays to show the importance of eliminating the oxide layer for realizing LSPR characteristics. After the etching of native oxide layer with glacial acetic acid, the LSPR of Cu significantly increase distinctively with the corresponding LSPR wavelength of ~650 nm.59 The notable utilization of Cu LSPR mode in plasmon-mediated thermocatalysis was demonstrated by the Linic’s group that the efficient realization of propylene epoxidation through Cu nanoparticles was achieved under visible light irradiation at a mild temperature.60 The underlying mechanism for such enhancement in this particular reaction was that the generated hot electrons reduced the native oxide layer, Cux+ (x = 1 or 2) to Cu0, to maintain the plasmonic and highly reactive Cu0 surface for the propylene epoxidation. These aforementioned results suggest that LSPR excitation of Cu nanoparticles contributes to the catalytic enhancement where Cu nanoparticles can provide an ideal site for propylene epoxidation. The enhancement of electrocatalysis with plasmonic Cu nanoparticles only was seldom reported due to the instability of Cu materials that they not only suffer from the change in the oxidation states but also undergo dissolution and re-deposition to form dendritic structures during the electrocatalytic process.61 These phenomena inherently decrease and alter the plasmonic properties that the alternative strategies must be considered to encompass the


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plasmonic and catalytic aspects of copper. To overcome such drawbacks, the strategies used to protect the water/air unstable materials like metal phosphides and perovskite quantum dots can be borrowed to the protect plasmonic copper nanoparticles. Especially, the encapsulation of Cu nanoparticle with a thin shell through passivation or atomic layer deposition

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(e.g., carbon,

Al2O3, SiO2) or molecular passivation64 could be considered to increase the stability of copperbased materials and minimize the alteration in morphology to maintain a specific plasmonic resonance wavelength for optimizing the catalytic process under the light illumination. Other plasmonic nanocomposites (aluminum based plasmonic catalysts). The practical application of the localized surface plasmon resonance (LSPR) effect on the catalysis is currently limited by the ever rising price of the coinage metals, modest activity, and low scalability. Discovering the alternative metal nanostructures that can exhibit/support similar LSPR effect with highly tunable nature in both morphologies and corresponding LSPR wavelengths is the utmost importance in this plasmon-mediated catalysis field. Recently, aluminum (Al) nanostructures demonstrated the remarkable LSPR properties that encompass deep UV to visible/NIR regions of the optical spectrum.65-66 Aluminum, similar to copper, depends heavily on the presence of its native oxide layer on the surface of the nanomaterials for tuning the LSPR wavelength. The Halas’s group successfully demonstrated that differentiating the surface composition ratio between the pure Al metal and Al2O3 can effectively shift the LSPR wavelength from deep UV to the visible light range.65 Being the most abundant metal element on the earth’s crust, the successful demonstration of the LSPR effect with Al nanoparticles (sphere),67-68 nanodiscs,69-71 nanorods,72-73 and other nanostructures74-75 paved the alternative pathway for incorporating LSPR effect into many different applications, especially in the field of photocatalysis for organic degradation,76 CO2 reduction (water-gas shift),77 and H2 dissociation.78


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These significant advancements in catalysis are attributed to the two major advantages of incorporating aluminum plasmonic nanostructures: (1) photo-generated hot electron transfer to the adsorbed substrates or photothermal effect to generate reactive intermediates and (2) antenna functionality for enhanced light absorption for antenna-reactor photocatalyst. Despite these exemplary works, more facile, mass-producible synthesis protocols of aluminum LSPR nanoparticles would contribute significantly to this field because the overall procedure requires inert atmosphere and water-free organic solvents to generate high purity materials. Also, the inherent activity of aluminum nanoparticles is not as much investigated when compared to other coinage metals, which suggests more research opportunities for this particular field. Shape refinement for optimization of catalytic performances. One of the strategies to increase the overall performance of the catalytic system is through incorporation with the novel metal nanostructures such as metal-tipped plasmonic nanostructures,79-81 and structures (e.g., porous or needle-like structures) that have high selective and/or electrochemical surface areas. For example, three-dimensional interconnected nanoporous Ag (np-Ag) demonstrated 92% Faradaic efficiency for CO2RR to CO.82 The np-Ag catalyst provides a 150 times larger electrochemical surface area (ECSA) and 20 times higher intrinsic high activity compared with polycrystalline Ag. This immense enhancement of intrinsic activity was enabled by high curvature (step sites) of np-Ag, which stabilized CO2•− intermediates. Sargent group also demonstrated enhanced of CO2 electroreduction by using highly curved metal needle tips.83 Nanometer-sized Au tips exhibit electric field concentrated at the tip due to the electrostatic repulsion of free electrons to generate electrostatic field gradient as shown in Figure 1a and b, respectively. The induced electric field increases the concentration of cations (K+) at the tip region of electrode. The accumulated potassium ions bind to the neighboring CO2 molecules through non-covalent interaction, which decrease the


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thermodynamic barrier by increasing the concentration of CO2 molecules at the active sites. As sharp tips of plasmonic nanostructures are well-known as hot spots, there will be strongly confined electromagnetic field at high curved regions, and hot carriers can be generated, affecting the electrocatalytic reactions.

Figure 1. (a) Schematic of np-Ag with stepped sites, (b) scanning electron microscopic image of np-Ag (scale bar, 500 nm) and (c) high-resolution transmission electron microscopic image of np-Ag (scale bar, 2 nm). (d) Tafel plots obtained from polycrystalline Ag and np-Ag. (e) simulated electron density distribution on the tip of electrodes. Arrows indicate electrostatic field distribution (scale bar, 5 nm), (f) computed surface K+ density and current density distributions on the Au tip. (g) a schematic demonstrating field-induced reagent concentration effect for enhancing CO2RR. (h) linear sweep voltammetry curves on Au needles, rods, and particles at scan rate of 10 mV s-1. (i) the corresponding SEM images of Au needle (top), Au rods (middle), and Au particles (bottom) (a-d: reproduced with permission from ref 82. Copyright 2014 Springer Nature. e-i: reproduced with permission from ref 83. Copyright 2016 Springer Nature.)


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Various electrocatalytic processes with plasmonic enhancement. The electrocatalysis and electrochemical conversion emerged as one of the most promising technologies to generate renewable fuels, evidenced by the significant increase in the number of publications in the past decade. However, only recently, the researchers discovered that the incorporation of plasmonic nanoparticles can manipulate the electrocatalytic performances through the LSPR effect. The key parameters of electrocatalysts such as current density, onset and overpotential, Faradaic efficiencies, and/or turnover number and frequencies are compared before and after the incorporation of plasmonic nanoparticles to elucidate the effect of plasmon-mediated electrocatalysis. Also, since we are considering the light input (usually laser) and plasmonic effect, the quantum yield will be also mentioned to elucidate the contribution of the light to enhance the overall catalytic performances. This section of the review pinpoints such unprecedented activities and quintessential examples of plasmon-mediated electrocatalytic energy conversion reactions, including electrochemical conversion of different feedstock into fuels and fuel cell electrocatalysis, and underlying mechanisms to elucidate the incorporated methodologies to optimize the electrocatalytic performances. Also, this section provides the possible strategies borrowed from photocatalysis and thermocatalysis to incorporate plasmonic nanostructures for the challenging reactions like CO2RR to induce intermediate generations, catalytic dynamics and other important criteria such as light power for energy production.


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Water splitting reaction. Hydrogen is widely recognized as the renewable and environmentally friendly energy source owing to its high energy density and benign combustion byproducts.84-88 The clean electricity generation through hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) in fuel cell facilitated the general acknowledgement of hydrogen as the future energy carrier as well.2,

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Despite intensive research efforts, the industrial scale

application is still limited by the sluggish reaction rate due to the insufficient activity of the known electrocatalytic materials except for the scarce noble metals such as Pt, Pd, and Rh.90-92 To complicate this process even further, the coupled reaction of water oxidation to oxygen (OER) requires four holes to oxidize water to oxygen molecules, which inherently requires a significant overpotential to drive this reaction. This oxidative half reaction process becomes the critical bottleneck on top of the insufficient activities observed for the HER. Some earthabundant materials like MoS2 showed some promising possibility to replace the noble metals for HER performances; however, such materials still require more intensive research outcomes to exceed the reactivity of the noble metals. Thus, it is necessary to develop the effective strategies for improving the catalytic activity of these materials by increasing both the intrinsic activity and the number of active sites of the electrocatalysts.


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Figure 2. Expected mechanism of the plasmon enhanced activity toward HER: (a) Schematic Au-MoS2 and energy level diagram illuminating hot electrons injection and change of MoS2 Fermi level. (b) Different plausible hot electrons transfer pathways likely to occur during SPR: (I) forming an electron-hole pair, (II) recombination with the hole in the metal; (III) injection into the CB of semiconductor; (IV) direct electrochemical reduction of water on Au rods and (V) being transferred to the electron-deficient Au, returning to its ground state. (c) Schematic electron transfer pathways likely to occur during SPR for HER catalysis in the composite of Ndoped porous carbon (PNC) and Au nanoparticles. The dashed line (black) indicates the Fermi level of Au nanoparticles. (d) Schematic representation of generating reactive high valence state of Ni through Au nanoparticle incorporation. The dashed line (black) indicates the Fermi level of Au nanoparticles. (e) the electron spin resonance spectrum of Ni(OH)2, Ni(OH)2-Au, and Ni(OH)2-Au under illumination to show the generation of high valence NiIII state. (a-b: Reprinted with permission from ref 93. c: Reprinted with permission from ref 94. Copyright 2018 by the Royal Society of Chemistry. d-e: Reprinted with permission from ref 95.)


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One of the virtuous strategies is the introduction of both light and plasmonic nanomaterials to the electrocatalytic systems for the water-splitting reaction.21, 96-100 As a creative method for increasing the HER performance, the Chen’s group recently demonstrated a noble composite electrocatalytic system of plasmonic Au nanorods and chemically exfoliated molybdenum disulfide (ce-MoS2) nanosheets for the hydrogen evolution reaction (HER) to show that hot electrons generated through LSPR can dramatically increase the overall catalytic performance.93 The heterojunction between the AuNR and ce-MoS2 was simply made by mixing these materials together under sonication. The introduced Au nanorods exhibited two essential criteria that Au nanorods not only functioned as effective light harnessing materials (808 nm laser light source) but also converted the photons into the hot electrons through the means of LSPR decay. The induced hot electrons were then transferred to the conduction band of the MoS2 nanosheets through the Fermi level alignment and low Schottky barrier between Au and MoS2, resulting in the higher charge density of ce-MoS2 electrocatalyst. The transferred hot electrons acted as a boost for the electrocatalytic platform (ce-MoS2) for more competent hydrogen evolution. The summary of this complex process is shown in Figure 2a and b. It should be noted that the hot electrons can also directly participate in the hydrogen evolution reaction. However, due to the low reactivity of Au towards HER and low Schottky barrier between Au and ce-MoS2, the generated hot electrons were most likely injected to the conduction band of ce-


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MoS2, and the amount of hydrogen generated through the direct conversion at the gold surface was negligible. This simple strategy of constructing composite of plasmonic nanostructure with efficient HER catalyst like ce-MoS2 exhibited a significant advancement compared to the previous reports in HER performance that about three-fold increase in current and high turnover rate of 8.76 s-1 were observed under 808 nm laser irradiation, the LSPR maximum wavelength for the synthesized AuNR. The overpotential was also further decreased from 300 to 120 mV in the presence of ethanol, a hole scavenger, showing the dynamic electrocatalytic performance of the overall composite. The Zhang’s group also reported a similar research accomplishment by forming the composite nanomaterials with Au nanoparticles (

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