Highly Conductive Cable‐Like Bicomponent Titania Photoanode Approaching Limitation of Electron and Hole Collection

Abstract

TiO 2 -based materials are cheap and stable choices for photoelectrochemical devices. However, the activity is still limited by the inefficient charge extraction. Here a highly conductive cable-like bicomponent titania photoanode, consisting of reduced anatase-coated TiO 2 -B nanowires, is proposed to simultaneously establish effective electron and hole transport channels separately, which meets the requirements of electronic dynamics for efficient water splitting. A synergistic effect of charge separation from the built-in electric field is demonstrated with this 1D TiO 2 -B/anatase heterojunction, in which a high electron collection efficiency of up to 97.1% at 0.6 V versus reversible hydrogen electrode is achieved. The efficient electron collection approaching the limitation is also attributed to the large electron conducting region in the photoanode. Moreover, the O-deficient amorphous layer is found to be more catalytic toward the oxygen evolution reaction through quantifying rate constants for charge recombination and charge transfer. It can reduce onset potential and suppress charge-carrier recombination simultaneously, prompting surface hole collection efficiency up to 95% at 0.6 V versus reversible hydrogen electrode.

Enhanced Charge Carrier Lifetime of TiS3 Photoanode by Introduction of S22− Vacancies for Efficient Photoelectrochemical Hydrogen Evolution

“…Based on the τ t and τ n , the electron diffusion length ( L n ) and electron collection efficiency (η col ) can be obtained via the equations: η col = 1 − τ t /τ n ; L n = L (τ n /τ t /2.35) 1/2 . [ 19,21 ] The L n of the TiS 3− x photoanode ranges from 45 to 60 µm in the potential range of 1.0–1.6 V RHE (Figure 4b), which is close to the NR thickness (50 µm). For the TiS 3− x photoanode, L n is increased to 78–110 nm in the same potential range due to a 20‐fold increase in electron conductivity.…”

“…To have a deeper insight into the influence of S 2 2− vacancies on the PEC performance under test condition, the charge dynamics at different applied potentials were investigated by the intensity‐modulated photocurrent spectroscopy (IMPS) and small perturbation transient photocurrent measurements. [ 19,20 ] The typical IMPS response and small perturbation transient photocurrent are shown in Figure S6a,b, Supporting Information. The details for the calculation of time constants are displayed in Supporting Information.…”

“…The good stability of the photoanode in the solution with Na 2 SO 3 as hole scavenger could stem from the fast oxidation of Na 2 SO 3 leaving little holes accumulating in the photoanodes. [ 19,23–25 ] The hydrogen evolution rate at 1.23 V RHE reaches a value of 0.25 mmol h −1 cm −2 , corresponding ≈100% faradaic efficiency for hydrogen evolution.…”

Efficient Photocatalytic Hydrogen Peroxide Generation Coupled with Selective Benzylamine Oxidation over Defective ZrS3 Nanobelts

“…The higher k t /(k t + k rec ) of ZrSS 2-x and ZrS 1-y S 2-x than that of ZrS 3 indicates a more e cient benzylamine oxidation for the defective ZrS 3 (Figure 4b). 37 The ZrSS 2-x exhibits a decreased k rec compared to ZrS 3 (Figure 4c and d), revealing that the more e cient benzylamine oxidation on ZrSS 2-x stems from the enhanced carrier lifetime induced by the S 2 2vacancies. The k rec of ZrS 1-y S 2-x was further decreased due to its e cient hole extraction induced by the large surface band bending.…”

“…34,35 In addition, the anion vacancies existing on the surface of n-type semiconductors can further improve its photocatalytic and photoelectrochemical performance by accelerating the kinetics of hole transfer on the surface. [36][37][38][39] The crystal structure analysis of ZrS 3 inspires us that the S 2 2and S 2-vacancies can be separately introduced into ZrS 3 by different methods (Schematic 1 and S1). annealing is expected to be an effective scheme to produce S 2 2vacancies in ZrS 3 .…”