Fe 2 O 3 Porous Film with Single Grain Layer for Photoelectrochemical Water Oxidation: Reducing of Grain Boundary Effect

ACS Appl. Mater. Interfaces

Xiong

et al. 2016

153

106

In a photoelectrochemical (PEC) cell for water splitting, the critical issue is charge separation and transport, which is usually completed by designing semiconductor heterojunctions. TiO2 anatase-rutile mixed junctions could largely improve photocatalytic properties, but impairs PEC water splitting performance. We designed and prepared two types of TiO2 heterostructures with the anatase thin film and rutile nanowire phases organized in different sequences. The two types of heterostructures were used as PEC photoanodes for water splitting and demonstrated completely opposite results. Rutile nanowires on anatase film demonstrated enhanced photocurrent density and onset potential, whereas strong negative performance was obtained from anatase film on rutile nanowire structures. The mechanism was investigated by photoresponse, light absorption and reflectance, and electrochemical impedance spectra. This work revealed the significant role of phase sequence in performance gain of anatase-rutile TiO2 heterostructured PEC photoanodes.

Section: Introductionmentioning

confidence: 99%

Enhanced Photoelectrochemical Performance from Rationally Designed Anatase/Rutile TiO₂ Heterostructures

ACS Appl. Mater. Interfaces

Xiong

et al. 2016

153

106

“…However, this efficiency has been largely restrained by several key issues: a very short minority carrier lifetime (<10 ps), a short hole diffusion length (2–4 nm), and poor oxygen evolution reaction kinetics . The limitations can be circumvented by developing an optimized geometry nanostructure where the carrier transport distance is minimized, and/or employing some surface modification to catalyze or fasten the oxygen evolution process …”

Section: Introductionmentioning

confidence: 99%

Ultrathin Amorphous Ni(OH)₂ Nanosheets on Ultrathin α‐Fe₂O₃ Films for Improved Photoelectrochemical Water Oxidation

Liu

et al. 2016

Adv Materials Inter

Hematite (α‐Fe2O3) is a promising photoanode material for photoelectrochemical (PEC) water splitting, however, its performance is largely limited by the short hole diffusion length that requires the thin active layer and efficient catalysts. In this work, ultrathin α‐Fe2O3 films are fabricated using atomic layer deposition technology, and then ultrathin amorphous Ni(OH)2 nanosheets are decorated on α‐Fe2O3 films through a hydrothermal method. The microscopic morphology, phase, and composition are characterized by scanning electron microscopy, X‐ray diffraction, X‐ray photoelectron spectra, and high resolution transmission electron microscopy. The quantity of Ni(OH)2 is adjusted by controlling the growth time. The results show that the onset potential of the optimum thick Ni(OH)2/Fe2O3 films demonstrate a cathodical shift by 400 mV, and the photocurrent density at 1.23 V is enhanced from 0.21 to 0.37 mA cm−2 compared with the pristine ultrathin α‐Fe2O3 films. The Ni(OH)2/Fe2O3 films show the superior stability up to 20 h. The enhanced PEC performances are attributed to the amorphous Ni(OH)2 nanosheets that do not affect obviously the light utilization, maintain large specific area to the electrolyte, and store holes produced in Fe2O3 for oxidizing water efficiently in situ with fast regeneration of Ni2+.

“…The light harvesting characteristic of a semiconductor is a key factor in controlling its photoresponse ability, which is closely relevant to the morphology of materials [25,26]. higher than that of the pristine CuO, indicating that the 3D structure does not increase the light harvesting efficiency.…”

Section: Resultsmentioning

confidence: 99%

Enhancing photoelectrochemical activity with three-dimensional p-CuO/n-ZnO junction photocathodes

Liu

et al. 2016

Sci. China Mater.

Designing photoelectrodes with particular nanostructure and composition has been regarded as a promising approach to improve the photoelectrochemical (PEC) water splitting efficiency. We report the design and synthesis of a three-dimensional (3D) nanostructure with CuO nanocones as backbones and ZnO nanorods as branches, using a facile water bath reaction process together with the atomic layer deposition (ALD) technology. As utilized in photocathodes, the optimized CuO/ZnO nanostructure, 37 cycles of ALD ZnO seedlayer and 55 min of water bath reaction of ZnO nanorods, demonstrate highly improved PEC performance. The ratio of photo to dark current density for the 3D CuO/ZnO is 6.4, much higher than the value of 2.7 for the CuO electrode. The enhanced activity is attributed to the synergistic effects of effective carrier separation and collection, reduced charge recombination, and increased carrier lifetime in the CuO/ZnO heterojunction. This work demonstrates the feasibility of designing novel 3D nanostructures by ALD technology as efficient photoelectrodes.