Semi Transparent Three-Dimensional Macroporous Quaternary Oxynitride Photoanodes for Photoelectrochemical Water Oxidation

Abstract

Semi transparent three-dimensional macroporous (3DM) photoanodes based on quaternary oxynitrides have the potential to simultaneously realize superior light harvesting and efficient charge transfer in a tandem photoelectrochemical (PEC) cell. A 3DM CaTaO 2 N photoanode was prepared for the first time on a GaN/Al 2 O 3 substrate via a chemical route, and it exhibits a high transmittance of >60% in the wide solar spectrum and a photoresponse onset at −0.3 V versus the reversible hydrogen electrode (V RHE ) under simulated solar illumination. In particular, a plateau photocurrent density of 0.21 mA cm −2 was achieved at a low potential of 0.4 V RHE , which was 1.6-fold and more than 50fold higher than a two-dimensional macroporous (2DM) CaTaO 2 N/GaN/Al 2 O 3 photoanode and a conventional particlebased CaTaO 2 N/GaN/Al 2 O 3 photoanode, respectively. The bicontinuous, interconnected pore structure within this 3DM film can improve charge carrier separation and collection by reducing the average diffusion distance for minority carriers toward the electrolyte. Optical measurements and simulations verified the enhanced sunlight harvesting in the 3DM photoanode, which was ascribed to the concentrated distribution of the electric field and multiple scattering. This study provides guidance for future synthesis of highly efficient semitransparent 3DM quaternary oxynitride-based photoanodes for a tandem PEC device.

Hierarchically Periodic Macroporous CdS–ZnO Heterojunctions with Multiple Quantum Well-like Band Alignments for Efficient Photocatalytic Hydrogen Evolution without a Cocatalyst

“…The photocatalytic H 2 evolution with CdS is anticipated to improve by constructing hierarchically periodic macroporous (HPM) structures with open interconnections. The reasons for this are three-folds: (1) unlike bulk photocatalysts, the presence of macropores allows photons to penetrate the interior and crash with its skeleton; 7 (2) the carriers that successfully reach the semiconductor surface will participate in the photocatalytic reaction. 8 Macropore walls are usually composed of several nanograins.…”

Cation‐Doped SrTaO2N Prepared through a Flux Method for Visible‐Light‐Driven Water Splitting

“…Using highly crystalline porous LaTiO 2 N photoanode, photocurrent density above 4 mA cm −2 was reported at 1.23 V vs. RHE (Reversible hydrogen electrode) under simulated solar irradiation with an onset potential of 0.3 V vs. RHE which is lower than the commonly studied Ta 3 N 5 photoanode [19] . Their unique flexibility and visible‐light responsibility also motivated researchers to perform the overall water splitting in particulate Z‐scheme systems [20–24] or as semi‐transparent photoanodes in tandem photoelectrochemical cells [25,26] …”

“…[19] Their unique flexibility and visible-light respon-sibility also motivated researchers to perform the overall water splitting in particulate Z-scheme systems [20][21][22][23][24] or as semitransparent photoanodes in tandem photoelectrochemical cells. [25,26] Among various ABO 2 N-type semiconductors, SrTaO 2 N has attracted great attention due to its various unique physical and chemical properties, such as its band structure, [27] photophysical properties, [28,29] and ferroelectricity. [30] SrTaO 2 N is also a promising material for visible-light-driven photocatalytic water splitting due to its narrow band gap (~2.1 eV).…”

Synergistic effect of Nd doping and plasmonic Au nanoparticles on BiFeO3thin film photoanodes for enhancing photoelectrochemical performance

“…1 For photoelectrochemical (PEC) technology, the key lies in the photoelectrode material. 2,3 As a ferroelectric material with spontaneous polarization, BiFeO 3 (BFO) has been regarded as a new type of photoelectrode material in recent years. 4,5 However, BFO itself has relatively low charge mobility and a high electron-hole recombination rate, resulting in poor PEC performance.…”