Nanoporous Au Thin Films on Si Photoelectrodes for Selective and Efficient Photoelectrochemical CO₂ Reduction

Abstract

An Si photoelectrode with a nanoporous Au thin film for highly selective and efficient photoelectrochemical (PEC) CO 2 reduction reaction (CO 2 RR) is presented. The nanoporous Au thin film is formed by electrochemical reduction of an anodized Au thin film. The electrochemical treatments of the Au thin film critically improve CO 2 reduction catalytic activity of Au catalysts and exhibit CO Faradaic efficiency of 96% at 480 mV of overpotential. To apply the electrochemical pretreatment of Au films for PEC CO 2 RR, a new Si photoelectrode design with mesh-type co-catalysts independently wired at the front and the back of the photoelectrode is demonstrated. Due to the superior CO 2 RR activity of the nanoporous Au mesh and high photovoltage from Si, the Si photoelectrode with the nanoporous Au thin film mesh shows conversion of CO 2 to CO with 91% Faradaic efficiency at positive potential than the CO 2 / CO equilibrium potential.

Morphological Characteristics of Au Films Deposited on Ti: A Combined SEM-AFM Study

“…Applications which demand high-porous Au film [48][49][50], require film deposited in glancing condition. In this sense, for example, nanoporous Au films take advantage of their enormous exposed surface area to enhance chemical, electrochemical, and photoelectrochemical reactions (such as photoelectrochemical CO 2 reduction [49], etc.…”

Electrochemically anodized one-dimensional semiconductors: a fruitful platform for solar energy conversion

“…Among diverse semiconductors, spatially ordered 1D nanostructures are especially suitable for PEC CO 2 reduction on account of their unique structural merits [148,[150][151][152]. For instance, Song and co-workers fabricated Si photoelectrode with nanoporous Au mesh as co-catalyst by electrochemical anodization for highly selective and efficient PEC CO 2 reduction under simulated solar light irradiation [146]. In this work, the authors evidenced that such anodized Si photoelectrode exhibited highly efficient selective CO 2 reduction performance to CO in aqueous solution.…”

Semiconductor‐Based Photoelectrochemical Conversion of Carbon Dioxide: Stepping Towards Artificial Photosynthesis

“…Suffering from easy aggregation and low coverage on the silicon electrode, decoration with particulate cocatalysts has inherent limitations. Instead of particulates, gold mesh‐type cocatalyst over a silicon photoelectrode was constructed; this exhibited excellent CO 2 reduction performance, with over 90 % CO FE and a reduction current of −2.94 mA cm −2 induced by the grain boundaries of nanoparticles on the gold surface …”