Ammonia Oxidation Enhanced by Photopotential Generated by Plasmonic Excitation of a Bimetallic Electrocatalyst

Abstract

We study how visible light influences the activity of an electrocatalyst composed of Au and Pt nanoparticles. The bimetallic composition imparts a dual functionality: the Pt component catalyzes the electrochemical oxidation of ammonia to liberate hydrogen and the Au component absorbs visible light by the excitation of localized surface plasmon resonances. Under visible-light excitation, this catalyst exhibits enhanced electrochemical ammonia oxidation kinetics, outperforming previously reported electrochemical schemes. We trace the enhancement to a photochemical potential resulting from electron-hole carriers generated in the electrocatalyst by plasmonic excitation. The photopotential responsible for enhanced kinetics scales linearly with the light intensitya general design principle for eliciting superlative photoelectrochemical performance from catalysts comprised of plasmonic metals or hybrids. We also determine a photochemical conversion coefficient.

Light-Induced Voltages in Catalysis by Plasmonic Nanostructures

“…These include the reduction of CO 2 to hydrocarbons, 2,4,47,48 alcohol oxidation, 2,37 water oxidation to H 2 O 2 , 47 electrochemical H 2 evolution, 3 electrochemical CH 3 OH oxidation, 16 and electrochemical NH 3 oxidation. 49 The potentials on the photocharged NPs play an important energetic role in these reactions, understanding of which will guide strategies for harnessing solar energy.…”

“…Thus, light-induced potentials appear to be effective means for enhancing the kinetics of electrochemical reactions and amplifying the activities of electrocatalysts. This principle has been found to be operative in electrochemical oxidation reactions as well, including NH 3 oxidation on Au−Pt NPs 49 and methanol oxidation on Pd−Ag nanostructures, 16 where an The influence of the photopotential on the energetics of a reaction can be made quantitative, as recently described by Yu and Jain. 4 The known relationship between the kinetic and thermodynamic parameters of a reaction is…”

“…4 This simple intensity scaling, which serves as a signature that a photopotential influences the energetics of a reaction, also extends to electrochemical reactions. 3,49 Using data on the photoenhanced HER from Wilson and Jain, 3 we plot RT ln(| j light |), where the current density, j light , is a proxy for the reaction rate, as a function of the light intensity at a fixed applied overpotential (Figure 4A). Regardless of the applied overpotential, the trend is linear.…”

“…NH 3 oxidation on bimetallic Au−Pt NP catalysts under LSPR excitation shows the same signature. 49 Subtracting RT ln(|j light |) at a given I from RT ln(| j dark |), i.e., the intercept of the plot, yields the chemical potential contributed by light excitation at that intensity (Figure 4B). At the lowest overpotential and a light intensity of 2.55 W cm −2 , this contribution was determined in the HER study to be 2.5 kJ mol −1 or 26 meV, which is reflected in the ca.…”

Plasmon-enhanced catalysis and mechanism study by singleparticle spectroscopy

“…基于金属 纳米颗粒的SPR效应, 可有效扩展半导体光催化材料 的光吸收范围, 同时提高载流子分离效率. 在众多金 图 4 (a) 在黑暗和光照条件下测得的氨氧化峰值电流密度 和峰值电势(左); 激光强度与峰电流密度的关系(右) [41] . (b) SPR增强Pd x Ag合金纳米管催化甲醇氧化示意图 [42] .…”