The Role of an Inert Electrode Support in Plasmonic Electrocatalysis

Plasmonic nanostructures loaded onto catalytically inert conductive support materials are believed to be advantageous for maximizing photocatalytic effects in photoelectrochemical systems due to the increased efficiency of Schottky barrier-free architectures in collecting hot charge carriers. However, the systematic mechanistic investigation and description of the inert electrode support contribution to plasmonic electrocatalysis is missing. Herein, we systematically investigated the effect of the supporting electrode material on the observed photocatalytic enhancement by comparing photoelectrocatalytic properties of AuNPs supported on highly oriented pyrolytic graphite (HOPG) and on indium tin oxide (ITO) electrodes using electrocatalytic benzyl alcohol (BnOH) oxidation as a model system. Upon illumination, only ~(3 ± 1)% enhancement in catalytic current was recorded on the AuNP/ITO electrodes in contrast to ~(42 ± 6)% enhancement on AuNP/HOPG electrodes. Our results showed that the local heating due to light absorption by the electrode material itself independent of localized surface plasmon effects is the primary source of the observed significant photo-induced enhancement on the HOPG electrodes in comparison to the ITO electrodes. Moreover, we demonstrated that an increased interfacial charge transfer at elevated temperatures, and not faster substrate diffusion is the main source of the enhancement. This work highlights the importance of systematic evaluation of contributions of all parts, even if they are catalytically inert, to the light-induced facilitation of catalytic reactions in plasmonic systems

Role of an Inert Electrode Support in Plasmonic Electrocatalysis

Direct loading of plasmonic nanostructures onto catalytically inert conductive support materials leads to the Schottky barrier-free architecture of the photocatalytic system. Such systems have recently attracted the attention of the research community as they permit collection of hot carriers independent of their energy when additional charge separation strategies are used. However, a systematic mechanistic investigation and description of the contribution of an inert conductive support to plasmonic electrocatalysis is missing. Herein, we systematically investigated the effect of the supporting electrode material on the observed photoinduced enhancement by comparing the photoelectrocatalytic properties of AuNPs supported on highly oriented pyrolytic graphite (HOPG) and indium tin oxide (ITO) electrodes using electrocatalytic benzyl alcohol (BnOH) oxidation as a model system. Upon illumination, only similar to(3 +/- 1)% enhancement in catalytic current was recorded on the AuNP/ITO electrodes in contrast to similar to(42 +/- 6)% enhancement on AuNP/HOPG electrodes. Our results showed that the local heating due to light absorption by the electrode material itself independent of localized surface plasmon effects is the primary source of the observed significant photoinduced enhancement on the HOPG electrodes in comparison to the ITO electrodes. Moreover, we demonstrated that an increased interfacial charge transfer at elevated temperatures and not faster reactant diffusion as suggested previously is the main source of the thermal enhancement. This work highlights the importance of the systematic evaluation of contributions of all parts, even if they are catalytically inert, to the light-induced facilitation of catalytic reactions in plasmonic system

CFD Simulations for Performance Enhancement of a Solar Chimney Power Plant (SCPP) and Techno-Economic Feasibility for a 5 MW SCPP in an Indian Context

The use of solar energy for power generation using the innovative solar chimney concept has been explored by many researchers mostly with the help of analytical models as well as CFD simulations while experimental studies for a pilot and bench scale facilities have been carried out. The efficiencies of these chimneys, however, are less than 1% (~0.07% for 50 kW pilot plant similar to Manzanares plant in Spain). In the present study, an effort has been made to make modifications in the chimney design to improve the efficiency of the chimney in terms of power generation. CFD simulations have been carried out for this modified design and the efficiency is seen to improve to 0.12% for a 50 kW chimney. Furthermore, a techno-economic feasibility analysis has been carried out for a conventional 5 MW solar power plant which can be installed on the western part of India, which receives good solar irradiation throughout the year. Two cases with and without government subsidies have been considered. It is observed that a high rate of return (~20.4%) is obtained for a selling price of electricity of Rs 5 per kWh with government subsidy, while a rate of return of ~19% is obtained for Rs 10 per kWh without government subsidy

Automated Analysis of Nano-Impact Single-Entity Electrochemistry Signals Using Unsupervised Machine Learning and Template Matching

Nano-impact (NIE) (also referred to as collision) single-entity electrochemistry is an emerging technique that enables electrochemical investigation of individual entities, ranging from metal nanoparticles to single cells and biomolecules. To obtain meaningful information from NIE experiments, analysis and feature extraction on large datasets are necessary. Herein, a method is developed for the automated analysis of NIE data based on unsupervised machine learning and template matching approaches. Template matching not only facilitates downstream processing of the NIE data but also provides a more accurate analysis of the NIE signal characteristics and variations that are difficult to discern with conventional data analysis techniques, such as the height threshold method. The developed algorithm enables fast automated processing of large experimental datasets recorded with different systems, requiring minimal human intervention and thereby eliminating human bias in data analysis. As a result, it improves the standardization of data processing and NIE signal interpretation across various experiments and applications. Nano-impact (NIE) electrochemistry is an emerging technique for studying individual entities. Analyzing large NIE datasets, often with low signal-to-noise ratios, is challenging. Herein, an automated approach is introduced using unsupervised machine learning and template matching for accurate feature extraction from spike-shaped NIE signals. It improves data processing, accuracy and standardization, reducing human bias in signal interpretation across experiments.image (c) 2023 WILEY-VCH Gmb

Automated Analysis of Nano-Impact Single-Entity Electrochemistry Signals using Unsupervised Machine Learning and Template Matching

Nano-impact single-entity electrochemistry (NIE) is an emerging technique that enables electrochemical investigation of individual entities, ranging from metal nanoparticles to single cells and biomolecules. To extract meaningful information from NIE experiments, statistical analysis of large datasets is necessary. In this study, we developed a method for the automated analysis of NIE data based on unsupervised machine learning and template matching approaches. Template matching not only facilitates downstream processing of the NIE data but also provides a more accurate analysis of the NIE signal characteristics and variations that are difficult to discern with conventional data analysis techniques, such as the height threshold method. The developed algorithm enables fast automated processing of large experimental datasets recorded with different systems, requiring minimal human intervention and thereby eliminating human bias in data analysis. As a result, it improves the standardization of data processing and NIE signal interpretation across various experiments and applications

Single-Entity Protein Electrochemistry of Diffusion-Limited Enzymes

Single-entity electrochemistry has recently emerged as a promising method for label-free exploration of the catalytic functions of individual enzymes. However, skepticism within the scientific community regarding the applicability of the method for single enzyme measurements has arisen due to issues in the experimental data presented in the literature and limited theoretical modeling of such data. Here, we address these concerns through a thorough experimental investigation of two diffusion-limited enzymes, catalase and superoxide dismutase, employing a combination of protein film voltammetry and single-entity protein electrochemistry measurements. We then introduce a novel theoretical model for simulating the current responses, generated by the reduction of the product of the enzymatic reaction of single enzyme molecules at the electrode. This model is based on a combination of finite element simulations using COMSOL Multiphysics and random walk simulations. It incorporates the diffusion-limited enzymatic kinetics of the investigated enzymes and introduces a geometry that mimics the substrate diffusion channel of the enzyme. Our work demonstrates that the experimentally detected current signals align with the simulated current signals, affirming that they can be attributed to the catalytic activity of single enzymes detected via the product of the enzymatic reaction

Nano-Impact Single-Entity Electrochemistry Enables Plasmon-Enhanced Electrocatalysis

Plasmon-enhanced electrocatalysis (PEEC), based on a combination of localized surface plasmon resonance excitation and an electrochemical bias applied to a plasmonic material, can result in improved electrical-to-chemical energy conversion compared to conventional electrocatalysis. Here, we demonstrate the advantages of nano-impact single-entity electrochemistry (SEE) for investigating the intrinsic activity of plasmonic catalysts at the single-particle level using glucose electrooxidation and oxygen reduction on gold nanoparticles as model reactions. We show that in conventional ensemble measurements, plasmonic effects have minimal impact on photocurrents. We suggest that this is due to the continuous equilibration of the Fermi level (EF) of the deposited gold nanoparticles with the EF of the working electrode, leading to fast neutralization of hot carriers by the measuring circuit. The photocurrents detected in the ensemble measurements are primarily caused by photo-induced heating of the supporting electrode material. In SEE, the EF of suspended gold nanoparticles is unaffected by the working electrode potential. As a result, plasmonic effects are the dominant source of photocurrents under SEE experimental conditions

Nano-impact single-entity electrochemistry enables plasmon-enhanced electrocatalysis

Plasmon-enhanced electrocatalysis (PEEC) based on a combination of localized surface plasmon resonance excitation and electrochemical bias applied to plasmonic material can result in improved electrical-to-chemical energy conversion compared to conventional electrocatalysis. Here, we demonstrate the advantages of nano-impact single-entity electrochemistry (SEE) for investigating the intrinsic activity of plasmonic catalysts at the single-particle level using glucose electrooxidation on gold nanoparticles as a model reaction. We show that in conventional ensemble measurements, plasmonic effects have minimal impact on photocurrent because the Fermi level of the deposited gold nanoparticles continuously equilibrates with the working electrode potential, leading to fast neutralization of hot carriers by the measuring circuit. The photocurrents detected in these measurements are caused by photo-induced heating of carbon-based electrodes. In SEE, the Fermi level of diffused gold nanoparticles is unaffected by the working electrode potential. As a result, plasmonic effects are the dominant source of photocurrents in SEE

Phosphorus-Induced One-Step Synthesis of NiCo₂S₄ Electrode Material for Efficient Hydrazine-Assisted Hydrogen Production

Rational control of the reaction parameters is highly important for synthesizing active electrocatalysts. NiCo2S4 is an excellent spinel-based electrocatalyst that is usually prepared through a two-step synthesis. Herein, a one-step hydrothermal route is reported to synthesize P-incorporated NiCo2S4. We discovered that the inclusion of P caused formation of the NiCo2S4 phase in a single step. Computational studies were performed to comprehend the mechanism of phase formation and to examine the energetics of lattice formation. Upon incorporation of the optimum amount of P, the stability of the NiCo2S4 lattice was found to increase steadily. In addition, the Bader charges on both the metal atoms Co and Ni in NiCo2S4 and P-incorporated NiCo2S4 were compared. The results show that replacing S with the optimal amount of P leads to a reduction in charge on both metal atoms, which can contribute to a more stable lattice formation. Further, the electrochemical performance of the as-synthesized materials was evaluated. Among the as-synthesized nickel cobalt sulfides, P-incorporated NiCo2S4 exhibits excellent activity toward hydrazine oxidation with an onset potential of 0.15 V vs RHE without the assistance of electrochemically active substrates like Ni or Co foam. In addition to the facile synthesis method, P-incorporated NiCo2S4 requires a very low cell voltage of 0.24 V to attain a current density of 10 mA cm–2 for hydrazine-assisted hydrogen production in a two-electrode cell. The free energy profile of the stepwise HzOR has been investigated in detail. The computational results suggested that HzOR on P-incorporated NiCo2S4 was more feasible than HzOR on NiCo2S4, and these findings corroborate the experimental evidence

A Highly Efficient UV–Vis–NIR Active Ln³⁺-Doped BiPO₄/BiVO₄ Nanocomposite for Photocatalysis Application

In this Article, we report the synthesis of Ln³⁺ (Yb³⁺, Tm³⁺)-doped BiPO₄/BiVO₄ nanocomposite photocatalyst that shows efficient photocatalytic activity under UV–visible–near-infrared (UV–vis–NIR) illumination. Incorporation of upconverting Ln³⁺ ion pairs in BiPO₄ nanocrystals resulted in strong emission in the visible region upon excitation with a NIR laser (980 nm). A composite of BiPO₄ nanocrystals and vanadate was prepared by the addition of vanadate source to BiPO₄ nanocrystals. In the nanocomposite, the strong blue emission from Tm³⁺ ions via upconversion is nonradiatively transferred to BiVO₄, resulting in the production of excitons. This in turn generates reactive oxygen species and efficiently degrades methylene blue dye in aqueous medium. The nanocomposite also shows high photocatalytic activity both under the visible region (0.010 min^–1) and under the full solar spectrum (0.047 min^–1). The results suggest that the photocatalytic activity of the nanocomposite under both NIR as well as full solar irradiation is better compared to other reported nanocomposite photocatalysts. The choice of BiPO₄ as the matrix for Ln³⁺ ions has been discussed in detail, as it plays an important role in the superior NIR photocatalytic activity of the nanocomposite photocatalyst