Electrochemical Fabrication of rGO-embedded Ag-TiO2 Nanoring/Nanotube Arrays for Plasmonic Solar Water Splitting

Plasmon-driven photocatalytic reaction based on gold microsphere array

Plasma-driven photocatalytic reactions have great research value in the fields of energy utilization, environmental pollution treatment and micro-nano information encryption. In most cases, the substrates used to study photocatalytic reactions are dispersed and disordered, which leads to poor signal reproducibility and makes it difficult to realize applications in the field of quantitative analysis. In this paper, two different sizes of polystyrene (PS) microspheres were used as templates to prepare gold microsphere arrays (Au MA) with homogeneous particle size and regular arrangement. The p-Aminothiophenol (PATP) was selected as the probe molecule to systematically investigate the photocatalytic reaction on Au MA, and the dependence of the photocatalytic reaction on the particle size of the spheres was discussed. It was found that the smaller size of Au MA has higher catalytic activity. In addition, using conventional gold films as a comparison, no significant photocatalytic reaction was found under the same experimental conditions. The reason is the existence of strong surface plasma "hot spots" in the interstices of the particles on the surface of the Au MA, which promotes the reaction. The above experimental results are of theoretical and practical significance for the in-depth study of the photocatalytic effect of micro-nano array catalytic substrates.

Directional Damping of Plasmons at Metal-Semiconductor Interfaces

ConspectusOver the past decade, it has been shown that surface plasmons can enhance photoelectric conversion in photovoltaics, photocatalysis, and other optoelectronic applications through their plasmonic absorption and damping processes. However, plasmonically enhanced devices have yet to routinely match or exceed the efficiencies of traditional semiconductor devices. The effect of plasmonic losses dissipates the absorbed photoenergy mostly into heat and that has hampered the realization of superior next-generation plasmonic optoelectronic devices. Several approaches are being explored to alleviate this situation, including using gain to compensate for the plasmonic losses, designing and synthesizing alternative low-loss plasmonic materials, and reducing activation barriers in plasmonic devices and physical thicknesses of photoabsorber layers to lower the plasmonic losses. A newly proposed plasmon-induced interfacial charge-transfer transition (PIICTT) mechanism has proven to be effective in minimizing energy loss during interfacial charge transfer. The PIICTT leads to a damping of metallic plasmonics by directly generating excitons at the plasmonic metal/semiconductor heteronanostructures. This novel concept has been proven to overcome some of the limitations of electron-transfer inefficiencies, renewing a focus on surface plasmon damping processes with the goal that the plasmonic excitation energies of metal nanoparticles can be more efficiently transferred to the adjacent semiconductor components in the absence and presence of an effective interlayer of carrier-selective blocking layer (CSBL). Several theoretical and experimental studies have concluded that efficient plasmon-induced ultrafast hot-carrier transfer was observed in plasmonic-metal/semiconductor heteronanostructures. The PIICTT mechanism may well be a general phenomenon at plasmonic metal/semiconductor, metal/molecule, semiconductor/semiconductor, and semiconductor/molecule heterointerfaces. Thus, the PIICTT presents a new opportunity to limit energy loss in plasmonic-metal nanostructures and increase device efficiencies based on plasmonic coupling. The nonradiative damping of surface plasmons can impact the energy flux direction and thereby provide a new process beyond light trapping, focusing, and hot carrier creation.In this Account, we draw much attention to the benefits of interfacial plasmonic coupling, highlighting recent pioneering discoveries in which plasmon-induced interfacial charge- and energy-transfer processes enable the generation of hot charge carriers near the plasmonic-metal/semiconductor interfaces. This process is likely to increase the photoelectric conversion efficiency, constituting "plasmonic enhancement". We also discuss recent advances in the dynamics of surface plasmon relaxation and highlight exciting new possibilities for plasmonic metals and their interactions with strongly attached semiconductors to provide directional energy fluxes. While this new research area comes on the heels of much elaborate research on both metal and semiconductor nanomaterials, it provides a subtle but important refinement in understanding the optoelectronic properties of materials with far-reaching consequences from fundamental interface science to technological applications. We hope that this Account will contribute to a more systematic description of interface-coupled plasmonics, both fundamentally and in terms of applications toward the design of plasmonic heterostructured devices.

Surface plasmon-driven photoelectrochemical water splitting of a Ag/TiO2 nanoplate photoanode

A silver/titanium dioxide nanoplate (Ag/TiO₂ NP) photoelectrode was designed and fabricated from vertically aligned TiO₂ nanoplates (NP) decorated with silver nanoparticles (NPs) through a simple hydrothermal synthesis and electrodeposition route. The electrodeposition times of Ag NPs on the TiO₂ NP were crucial for surface plasmon-driven photoelectrochemical (PEC) water splitting performance. The Ag/TiO₂ NP at the optimal deposition time of 5 min with a Ag element content of 0.53 wt% demonstrated a remarkably high photocurrent density of 0.35 mA cm⁻² at 1.23 V vs. RHE under AM 1.5G illumination, which was 5 fold higher than that of the pristine TiO₂ NP. It was clear that the enhanced light absorption properties and PEC performance for Ag/TiO₂ NP could be effectively adjusted by simply controlling the loading amounts of metallic Ag NPs (average size of 10–30 nm) at different electrodeposition times. The superior PEC performance of the Ag/TiO₂ NP photoanode was attributed to the synergistic effects of the plasmonic Ag NPs and the TiO₂ nanoplate. Interestingly, the plasmonic effect of Ag NPs not only increased the visible-light response (λ_max = 570 nm) of TiO₂ but also provided hot electrons to promote photocurrent generation and suppress charge recombination. Importantly, this study offers a potentially efficient strategy for the design and fabrication of a new type of TiO₂ hybrid nanostructure with a plasmonic enhancement for PEC water splitting.

A hybrid nanostructure Ag/TiO₂ photoelectrode for PEC water splitting with a remarkable high photocurrent density, 0.35 mA cm⁻² (5 fold higher than that of the pristine TiO₂ photoeletrode) was fabricated by a facile one-pot hydrothermal and electrodeposition method.

Investigation of the local photothermal effects by fabricating CQDs/Au/TiO2 photoelectrode in PEC water splitting system

The high efficiency of photoanode material is great significant for photoelectrochemical (PEC) water splitting. Herein, CQDs/Au/TiO2 nanorods array composite photoanode was constructed with special attention to local photothermal effects. The...

The CO2 photoconversion over reduced graphene oxide based on Ag/TiO2 photocatalyst in an advanced meso-scale continuous-flow photochemical reactor

This study aims at examining the use of an advanced meso-scale continuous-flow photochemical reactor for the photocatalytic conversion of CO₂ with water into fuel over TiO₂ (P25), Ag/TiO₂, and Ag/TiO₂/RGO catalysts. The silver loaded photocatalysts were prepared by one-step process via hydrothermal method. The prepared photocatalysts were characterized by various characterization techniques in order to identify the morphological, chemical, physical, and optical properties. The photocatalytic activity of the as-prepared catalysts was firstly examined by the photoelectrochemical (PEC) measurements and secondly by the photocatalytic reduction of CO₂ in the proposed setup. Liquid products were analyzed using gas chromatography-mass spectrometry (GC-MS) and total organic carbon (TOC) techniques. It was found that the ternary composite revealed an outstanding performance towards CO₂ photocatalytic reduction, where its selectivity was directed towards methanol production. The incorporation of graphene nanosheets enhanced the photocatalytic reduction of CO₂ by 3.3 and 9.4 times compared with Ag/TiO₂ and bare TiO₂, respectively, using the proposed photochemical reactor in a continuous mode. This study sheds the light on a novel type of a photocatalytic reactor where CO₂ conversion over Ag/TiO₂/RGO ternary composite was evaluated. A meso-scale continuous-flow photochemical reactor.

Challenges and prospects about the graphene role in the design of photoelectrodes for sunlight-driven water splitting

Graphene and its derivatives have emerged as potential materials for several technological applications including sunlight-driven water splitting reactions. This review critically addresses the latest achievements concerning the use of graphene as a player in the design of hybrid-photoelectrodes for photoelectrochemical cells. Insights about the charge carrier dynamics of graphene-based photocatalysts which include metal oxides and non-metal oxide semiconductors are also discussed. The concepts underpinning the continued progress in the field of graphene/photoelectrodes, including different graphene structures, architecture as well as the possible mechanisms for hydrogen and oxygen reactions are also presented. Despite several reports having demonstrated the potential of graphene-based photocatalysts, the achieved performance remains far from the targeted benchmark efficiency for commercial application. This review also highlights the challenges and opportunities related to graphene application in photoelectrochemical cells for future directions in the field.

MXene-Derived Defect-Rich TiO2@rGO as High-Rate Anodes for Full Na Ion Batteries and Capacitors

Sodium ion batteries and capacitors have demonstrated their potential applications for next-generation low-cost energy storage devices. These devices's rate ability is determined by the fast sodium ion storage behavior in electrode materials. Herein, a defective TiO2@reduced graphene oxide (M-TiO2@rGO) self-supporting foam electrode is constructed via a facile MXene decomposition and graphene oxide self-assembling process. The employment of the MXene parent phase exhibits distinctive advantages, enabling defect engineering, nanoengineering, and fluorine-doped metal oxides. As a result, the M-TiO2@rGO electrode shows a pseudocapacitance-dominated hybrid sodium storage mechanism. The pseudocapacitance-dominated process leads to high capacity, remarkable rate ability, and superior cycling performance. Significantly, an M-TiO2@rGO//Na3V2(PO4)3 sodium full cell and an M-TiO2@rGO//HPAC sodium ion capacitor are fabricated to demonstrate the promising application of M-TiO2@rGO. The sodium ion battery presents a capacity of 177.1 mAh g-1 at 500 mA g-1 and capacity retention of 74% after 200 cycles. The sodium ion capacitor delivers a maximum energy density of 101.2 Wh kg-1 and a maximum power density of 10,103.7 W kg-1. At 1.0 A g-1, it displays an energy retention of 84.7% after 10,000 cycles.