Query: Enhancing photoelectrochemical water splitting by combining work

Candidate papers:

abstract: We herein demonstrate the unusual effectiveness of two strategies in combination to enhance photoelectrochemical water splitting. First, the work function adjustment via molybdenum (Mo) doping significantly reduces the interfacial energy loss and increases the open circuit photovoltage of bismuth vanadate (BiVO4) photoelectrochemical cells. Second, the creation and optimization of the heterojunction of boron (B) doping carbon nitride (C3N4) and Mo doping BiVO4 to enforce directional charge transfer, accomplished by work function adjustment via B doping for C3N4, substantially boost the charge separation of photo generated electron hole pairs at the B C3N4 and Mo BiVO4 interface. The synergy between the above efforts have significantly reduced the onset potential, and enhanced charge separation and optical properties of the BiVO4 based photoanode, culminating in achieving a record applied bias photon to current efficiency of 2.67% at 0.54 V vs. the reversible hydrogen electrode. This work sheds light on designing and fabricating the semiconductor structures for the next generation photoelectrodes. While photoelectrodes represent a promising solar to fuel conversion technology, material challenges limit performances. Here, authors improve the onset potential and charge separation of bismuth vanadate photoanode water splitting performances by work function tuning and heterojunction engineering.
author_names: Kai-Hang Ye

Haibo Li

Duan Huang

Shuang Xiao

Weitao Qiu

Mingyang Li

Yu-wen Hu

Wenjie Mai

Hongbing Ji

Shihe Yang
title: Enhancing photoelectrochemical water splitting by combining work function tuning and heterojunction engineering
venue: Nature Communications
year: 2019

abstract: Hydrogen is one alternative clean fuel for micro scale devices when generated by solar irradiation through water splitting. The photoelectrolysis of water has been intensively studied since the seminal work of Fujishima and Honda in 1972 where titania was used as an anode photocatalyst [1] While TiO2 is an attractive material because it is inexpensive and a well known catalyst for water dissociation, one of the major drawbacks that limits its practicality is that it only absorbs light in the UV region. Recent results of combining Au nanoparticles with TiO2 has been suggested to prevent electron hole recombination of the photoexcited titania hence enhancing its photoelectrochemical performance [2 3] In this study, three layers of TiO2 is electrosynthesized on ITO substrates using the generation of base method followed by annealing steps in between each deposited layer and a final heat treatment to ensure the anatase crystallinity of the deposits. [4] The thickness of the films was between 2 3 mm with a cracked morphology. Au nanoparticles were subsequently electrodeposited onto the electrogenerated TiO2 and pulsing conditions that affect the Au nanoparticle size and uniformity were investigated. Pulsed waveforms included a nucleation, growth and dissolution step. Results indicate that the first nucleation step is key in determining the size of the particles and the clumps formed as well as their density. Photoelectrochemical tests including step photoresponse analysis under different light sources, electrochemical impedance analysis and intensity modulated photocurrent spectroscopy techniques were employed to characterize the enhanced photoelectrochemical response of three different forms of the TiO2 Au composite: (1) TiO2 decorated with Au nanoparticles, TiO2/Au, (2) TiO2 with embedded Au
author_names: Jessy Elhajj
title: Electrosynthesis of TiO2 Au composites for water splitting applications and their photoelectrochemical characterization
year: 2008

abstract: Abstract Developing low cost but effective cocatalyst is of crucial importance for strongly enhancing the photoelectrodes performance in photoelectrochemical (PEC) water splitting. Herein, we firstly report a rational and low cost design of a ternary photocathode that Cu2O sandwiched by spatial noble metal free cocatalysts (NiS nanoparticles on the surface and Al nanoparticles on the bottom) to realize enhanced PEC performance. The integration of Al with surface plasmon resonance (SPR) effect and electron trapper NiS spatially loaded on the Cu2O nanocubes is indeed conducive to excite the hot electron hole pairs, boost the solar light absorption and elevate ultrafast spatial transfer and separation of photogenerated electrons and holes, resulting in remarkable photocurrent density of 5.16 mA/cm2 at 0 V vs. RHE, an eight fold enhancement than that of pristine Cu2O. The selection of noble metal free Al and NiS cocatalysts is superior substitute to noble metal Au and Pt from the comparison with our previous work. Therefore, this work could inspire ongoing interest in the design of highly efficient and cost effective hybrid photoelectrodes which is able to replace noble metals in practical applications of PEC water splitting.
author_names: Da Chen

Zhifeng Liu

Zhengang Guo

Weiguo Yan

Mengnan Ruan
title: Decorating Cu2O photocathode with noble metal free Al and NiS cocatalysts for efficient photoelectrochemical water splitting by light harvesting management and charge separation design
year: 2020

abstract: ABSTRACT In the present work, aluminum doped plate like tungsten oxide (WO 3 photoelectrodes were investigated by photoelectrochemical methods in order to evaluate the possibility of their application in water splitting. The aluminum doped plate like WO 3 films were prepared by hydrothermal method in nitric acid from a radio frequency (RF) magnetron sputtered aluminum tungsten layer on fluorine doped tin oxide (FTO) glass. The crystal structure, composition and morphology of pure and aluminum doped WO 3 were compared using x ray diffraction (XRD) x ray photoelectron spectroscopy (XPS) scanning electron microscopy (SEM) and transmission electron microscopy (TEM) The results indicate that aluminum can be doped into WO 3 plate like photoelectrodes by placing radio frequency magnetron sputtered aluminum tungsten films using a facile hydrothermal method. Plate like WO 3 films doped with 0.77 atom% aluminum showed photocurrent density of 1.14 mA/cm 2 at 1.2 V vs. Ag/AgCl, which was 1.3 times higher than that of the pure WO 3 (0.87 mA/cm 2 Incident photon to current efficiency (IPCE) measurements carried out on photoelectrochemical (PEC) cell with aluminum doped WO 3 plate like photoelectrodes as anodes demonstrated a significant increase of photoresponse in the intrinsic absorption range. Electrochemical impendence spectroscopy (EIS) showed that aluminum doped WO 3 possessed higher charge transfer rate and electrical conductivity than those of pristine WO 3 thus presented a better performance in photoelectrochemical properties.
author_names: Wenzhang Li

Faqi Zhan

Jie Li

Canjun Liu

Yanghui Yang

Yaomin Li

Qi-Yuan Chen
title: Enhancing photoelectrochemical water splitting by aluminum doped plate like WO3 electrodes
year: 2015

abstract: Abstract Photoelectrochemical solar water splitting is a promising method for harvesting clean and sustainable solar energy by the carbon emission free production of energy rich hydrogen. Various strategies such as nanostructuring, composite engineering, and multilayer formation have been adopted for energy efficient photoelectrode preparation, with the ultimate goal of enhancing the efficiency of energy harvesting and storage via the photoelectrochemical water splitting reaction. This review summarizes recent advances in the abovementioned strategies for fabricating water splitting photoelectrodes and outlines relationships between the structure, composition, and electrochemical properties of such photoelectrodes. Our aim is to help readers become cognizant of recent developments in the field, providing them with a distinct perspective for carrying out innovative work on photoelectrode preparation.
author_names: Edmund P Samuel

Bhavana N Joshi

Min Woo Kim

Mark T Swihart

Sam S Yoon
title: Morphology engineering of photoelectrodes for efficient photoelectrochemical water splitting
year: 2020

abstract: Solar water oxidation is considered as a promising method for efficient utilization of solar energy and bismuth vanadate (BiVO4 is a potential photoanode. Catalyst loading on BiVO4 is often used to tackle the limitations of charge recombination and sluggish kinetics. In this study, amorphous nickel oxide (NiOx is loaded onto Mo doped BiVO4 by photochemical metal organic deposition method. The resulting NiOx /Mo:BiVO4 photoanodes demonstrate a two fold improvement in photocurrent density (2.44 mA cm 2 at 1.23 V versus reversible hydrogen electrode (RHE) compared with the uncatalyzed samples. After NiOx modification the charge separation and charge transfer efficiencies improve significantly across the entire potential range. It is further elucidated by open circuit photovoltage (OCP) time resolved microwave conductivity (TRMC) and rapid scan voltammetry (RSV) measurements that NiOx modification induces larger band bending and promotes efficient charge transfer on the surface of BiVO4 This work provides insight into designing BiVO4 catalyst assemblies by using a simple surface modification route for efficient solar water oxidation.
author_names: Mengyuan Zhang

Rajini P Antony

Sing Yang Chiam

Fatwa Firdaus Abdi

Lydia Helena Wong
title: Understanding the Roles of NiOx in Enhancing the Photoelectrochemical Performance of BiVO4 Photoanodes for Solar Water Splitting.
venue: ChemSusChem
year: 2019

abstract: Abstract In photoelectrochemical (PEC) water splitting, the efficiency of an electrode is determined by light absorption and charge transformation between the electrode and electrolyte. Titanium (Ti) and molybdenum (Mo) doped tungsten sulfide (WS2) nanosheets were prepared via a relatively low temperature chemical vapor deposition (CVD) method and applied to enhance the light absorption of WS2 nanosheets as the water oxidation catalyst in the PEC water splitting process. Both Ti and Mo doping showed significant enhancement in photoelectrochemical performance of prepared WS2 nanosheets. The novel Ti doped WS2 photoanode exhibited a high photocurrent density of 10.44 mA/cm2 at 1.23 V versus the reversible hydrogen electrode (RHE) under standard AM 1.5 G illumination, which was >100% increase compared to that of the pristine WS2 photoanode. The maximum of applied bias photon to current efficiency (ABPE) of Ti doped WS2 photoanode was 2.84% that showed a 338% growth comparing to WS2 photoanode. The charge transfer resistance (Rct) of Ti doped WS2 nanosheets was 6.3 kO, which corresponds about two times less than pristine WS2 nanosheets. The high donor density of Ti doped WS2 nanosheets leads to improve electrical conductivity and confirms the lower Rct which enhancing the electrocatalytic activity and PEC performance. This work demonstrates the feasibility process for doping foreign element in the WS2 nanosheets as an excellent photoanode for PEC water splitting.
author_names: Ali Ahmadi

Morteza Zargar Shoushtari
title: Enhancing the photoelectrochemical water splitting performance of WS2 nanosheets by doping titanium and molybdenum via a low temperature CVD method
venue: Journal of Electroanalytical Chemistry
year: 2019

abstract: In this work, we explored a facile, scalable and effective method for substantially enhancing photocurrent and incident photon to current efficiency of WO3 thin film photoanodes by a mild reduction treatment under low oxygen pressure. Experimental data from photoelectrochemical and electrochemical impedance spectroscopies have shown that such treatment can increase the charge carrier density on WO3 photoanode surfaces resulting in improvements in hole collection efficiency and reduction in charge recombination. Despite a much thinner layer of WO3 (about 500 nm) compared to those in other published studies, the electrodes exhibited an ultra high photocurrent density of 1.81 mA cm 2 at 1.23 V vs. RHE. This current density is one of the highest ones among WO3 based photoanodes described in literature. The proposed surface modulation approach offers an effective and scalable method to prepare high performance thin film photoanodes for photoelectrochemical water splitting.
author_names: Jiajie Cen

Qiyuan Wu

Danhua Yan

Wenrui Zhang

Yue Zhao

Xiao Tong

Mingzhao Liu

Alexander Orlov
title: New aspects of improving the performance of WO3 thin films for photoelectrochemical water splitting by tuning the ultrathin depletion region
year: 2019

abstract: Abstract Gallium nitride (GaN) is one of the ubiquitously known photoanode for photoelectrochemical water splitting (PEC WS) due to its tunable band gap and favorable band edge positions. However, the unavoidable surface defects in GaN induces surface Fermi level pinning and surface band bending which severely reduces its PEC conversion efficiency. Constructing heterostructure is the key to approaching better charge separation efficiency and light harvesting ability for PEC WS. Considering this, we have fabricated ternary heterostructure of GaN/ZnO/MWCNTs photoanode by combining metal organic chemical vapour deposition (MOCVD) hydrothermal and 'dip and dry' methods. FE SEM results showed the formation of 3D hierarchical honeycomb structure of ZnO on GaN thin film surface when MWCNTs are added into hydrothermal reaction. We investigate the advantage of ZnO honeycomb structure in enhancing the solar PEC WS performance of GaN photoanode. The synergy of incorporating MWCNTs has resulted into improvement in surface morphology, electron transportation and light harvesting capability. The as obtained ternary heterostructure exhibits photocurrent (Jph) of 3.02 mA/cm2 at 0 V versus Pt electrode under 1 sun light illumination which is about 2.58 times higher than that of pristine GaN photoanodes (Jph 1.14 mA/cm2)
author_names: Santosh S Patil

Muhammad Ali Johar

Mostafa Afifi Hassan

Deepak Rajaram Patil

Sang-Wan Ryu
title: Anchoring MWCNTs to 3D honeycomb ZnO/GaN heterostructures to enhancing photoelectrochemical water oxidation
year: 2018

abstract: Abstract Plasmonic metal nanoparticles containing photoanodes are known to exhibit stable photoelectrochemical (PEC) performance due to their optical and electronic properties. In this work, we report the application of plasmonic Bi nanoparticles supported over a g C3N4/Bi2S3 photoanode for PEC water splitting. Typical results indicated that g C3N4/Bi2S3/BiNPs ternary composite photoanode showed a high photo current density of 7.11 mA cm 2 at 1.23 V under solar irradiation, which was 5 and 10 times higher than g C3N4/Bi2S3 and g C3N4 photoanodes, respectively. Further, the composite electrode also demonstrated superior solar to hydrogen efficiency and long term stability. It was concluded that Bi nanoparticles play a major role in enhancing the PEC performance for hydrogen evolution reaction. Thus, g C3N4/Bi2S3/BiNPs has superior PEC performance and proved to work as an alternative to noble metal based photo electrodes for solar water splitting reactions.
author_names: Palyam Subramanyam

Bhagat Ram Meena

Duvvuri Suryakala

Melepurath Deepa

Ch Subrahmanyam
title: Plasmonic nanometal decorated photoanodes for efficient photoelectrochemical water splitting
year: 2020