Direct Electrochemical Visualization of the Orthogonal Charge Separation in Anatase Nanotube Photoanodes for Water Splitting

Abstract

Photoelectrochemical (PEC) water splitting is an important and rapidly developing technology that produces H2 as a renewable resource, but local surface investigations remain a major challenge. Using scanning electrochemical cell microscopy (SECCM), the PEC catalytic effects of anatase TiO2-nanotube arrays grown on Ti felt are explored. The SECCM imaging is performed both perpendicular and parallel to the nanotube growth direction. In contrast to bulk cyclic voltammetry measurements, SECCM measures only the upper region of the nanotubes that remain in contact with the electrolyte, which provides a better understanding of the phenomena connected to the longitudinal charge transport. Despite the presence of regions with higher and lower photocurrent, the PEC reactivities of the nanotube tops and walls are roughly comparable with each other. The data support the model of orthogonal electron–hole separation. This model facilitates the photogenerated hole diffusion over the short distance to the electrolyte interface due to the sufficient transport of photoexcited electrons along the long axial direction of TiO2 nanotubes and is often applied to one-dimensional systems. Observed results were additionally supported by the nanotube decoration with photoelectrochemically deposited PbO2 particles.

The New Era of High-Throughput Nanoelectrochemistry

“…The results of this study underlined the suitability of CVD-grown coatings for practical photoelectrode production. The performance of TiO 2 nanotube structures was considered 302 against proposed models for photoinduced charge separation within this architecture. Photocatalytic activity was recorded at different parts of a nanotube surface, with data supporting the orthogonal electron–hole separation model.…”

The new era of high throughput nanoelectrochemistry

“…The results of this study underlined the suitability of CVD-grown coatings for practical photoelectrode production. The performance of TiO2 nanotube structures was considered, 303 against proposed models for photo-induced charge separation within this architecture. Photocatalytic activity was recorded at different parts of a nanotube surface, with data supporting the orthogonal electron-hole separation model.…”

Data-driven analysis of the local current distributions of 316L stainless steel corrosion in NaCl solution

“…The cell dimensions (micro-capillary pipette size) can range between tens of microns to tens of nm 33 . The versatility of the technique in terms of setup and polarisation modes (potentio/galvanostatic, potentiodynamic) has allowed studying a wide range of interfacial phenomena such as (photo)electrocatalysis [34][35][36] , electrodissolution [37][38][39][40] , electrodeposition 40,41 , other phase formation processes 42 , gas evolution reactions 43 , solid-electrolyte interphases 44 , and nanoimpact electrochemistry 38 from a different perspective, including a statistical and probabilistic approach 38,40,41 .…”