Query: Efficiency of Solar water Splitting Using Semiconductor Electrodes

Candidate papers:

abstract: Abstract Reliable measurement of the photoconversion efficiency for semiconductor electrodes is essential to the assessment of electrode performance. In this paper, the influence of the choice of light source on measured photoconversion efficiencies for semiconductor photoelectrodes is examined. Measurements of efficiency performed under xenon lamp and solar illumination are compared with efficiencies calculated by integrating the incident photon conversion efficiency (IPCE) over the lamp and solar spectra. It is shown that use of a xenon lamp as the light source can lead to a large overestimate of the photoconversion efficiency, relative to that obtained under standard AM1.5 solar illumination. The overestimate is greater when a water filter is fitted to the xenon lamp, and when a wide band gap semiconductor such as TiO2 is used as the photoelectrode. Achievable photoconversion efficiencies using rutile TiO2 are calculated taking into account the losses due to imperfect absorption, reflection and charge carrier recombination; these calculated efficiencies agree with the measurements to within experimental uncertainties. It is demonstrated that many photoconversion efficiencies presented in the literature are overestimated. It is concluded that reliable estimation of efficiency under standard conditions is best obtained by measuring the IPCE as a function of wavelength, and integrating over the AM1.5 solar spectrum, or by measuring under sunlight with a similar zenith angle to that of the AM1.5 spectrum.
author_names: Anthony B Murphy

Piers R F Barnes

Lakshman K Randeniya

Ian C Plumb

Ian E Grey

Michael D Horne

Julie Glasscock
title: Efficiency of solar water splitting using semiconductor electrodes
year: 2006

abstract: Starting from the classical GaInP/GaAs tandem photoelectrochemical water splitting device, higher solar to hydrogen efficiencies can be pursued by extending photon absorption to longer wavelengths. We incorporate strain balanced GaInAs/GaAsP quantum wells into the bottom GaAs junction, to increase the range of photon absorption. The inclusion of 1.34 eV quantum wells in the depletion region of the bottom cell extends the absorption edge to 930 nm. With a corresponding increase in the thickness of the top cell for current matching, the light limiting photocurrent increases by >8% The estimated solar to hydrogen efficiency is 13.6 0.5% and we show a pathway to further improvement. With the semiconductor device remaining on the growth substrate, this quantum well architecture may enable improved stability and durability of the photoelectrochemical electrodes.
author_names: Myles A Steiner

Collin Barraugh

Chase W Aldridge

Isabel Barraza Alvarez

Daniel J Friedman

Nicholas J Ekins-Daukes

Todd G Deutsch

James L Young
title: Photoelectrochemical water splitting using strain balanced multiple quantum well photovoltaic cells
year: 2019

abstract: Photoelectrochemical water splitting directly converts solar energy to chemical energy stored in hydrogen, a high energy density fuel. Although water splitting using semiconductor photoelectrodes has been studied for more than 40 years, it has only recently been demonstrated using dye sensitized electrodes. The quantum yield for water splitting in these dye based systems has, so far, been very low because the charge recombination reaction is faster than the catalytic four electron oxidation of water to oxygen. We show here that the quantum yield is more than doubled by incorporating an electron transfer mediator that is mimetic of the tyrosine histidine mediator in Photosystem II. The mediator molecule is covalently bound to the water oxidation catalyst, a colloidal iridium oxide particle, and is coadsorbed onto a porous titanium dioxide electrode with a Ruthenium polypyridyl sensitizer. As in the natural photosynthetic system, this molecule mediates electron transfer between a relatively slow metal oxide catalyst that oxidizes water on the millisecond timescale and a dye molecule that is oxidized in a fast light induced electron transfer reaction. The presence of the mediator molecule in the system results in photoelectrochemical water splitting with an internal quantum efficiency of approximately 2.3% using blue light.
author_names: Yixin Zhao

John R Swierk

Jackson D Megiatto

Benjamin D Sherman

W Justin Youngblood

Dong-Dong Qin

Deanna M Lentz

Ana L Moore

Thomas A Moore

Devens Gust

Thomas E Mallouk
title: Improving the efficiency of water splitting in dye sensitized solar cells by using a biomimetic electron transfer mediator
venue: Proceedings of the National Academy of Sciences
year: 2012

abstract: Photoelectrochemical water splitting has been demonstrated as a promising way to efficiently split water. Currently, solar to hydrogen conversion efficiency using state of the art material combinations in PEC system is in the order of 7% Fabrication of nanostructured materials with unique morphologies and compositions is an important factor to fully utilize the possibilities in this field. We will present different strategies for the preparation of nanostructured metal oxide thin films by using electrodeposition and wet chemistry techniques. Focus will be given on the preparation of ZnO and CuO thin films where intermediate phases like Zn(OH)8Cl2.H2O and CuX (X=Br, Cl) were electrodeposited. Wet chemistry synthesis techniques will be also explored for the preparation of nanostructured WO3 and a Fe2O3 thin films. Especially, the hot pyrolysis technique for the preparation of colloidal W and Fe/Fe oxide nanoparticles will be shown. Spin coating of W and Fe/Fe oxide NPs onto optically conductive substrates and subsequent heat treatment of the obtained films was found to be a convenient way for the preparation of nanostructured WO3 and a Fe2O3 thin films.
author_names: Saim Emin

Matjaz Valant
title: Photoelectrochemical Water Splitting Studies with nanostructured n and p type semiconductor electrodes
year: 2017

abstract: Cu2O is a typical p type semiconductor that can efficiently absorb visible light and has a high absorption coefficient due to its narrow forbidden band. Thus, it finds potential applications in solar energy conversion and photocatalysis. However, Cu2O photocathodes suffer from a major issue of chemical stability and sluggish proton reduction for splitting water using sunlight. We present here a facile method of coating a thin MoS2 layer onto Cu2O to significantly improve its stability and proton reduction efficiency. MoS2 coating on top of Cu2O is achieved by spin coating a [Mo3S7(S2CNEt2)3]I precursor combined with a thermal annealing process to obtain the optimal stoichiometry. MoS2 thin films synthesized using this method show good prospects as both a protection layer and an electrocatalyst for hydrogen evolution reactions (HER) due to excellent stability and high electrocatalytic activity. The proton reduction performance of spin coated MoS2/FTO electrodes is studied to determine the optimal synthesis conditions using various derivatives of MoS2 precursors. Our study suggests that the rate limiting kinetic step of MoS2 synthesized in this method is the desorption of adsorbed hydrogen atoms to form molecular hydrogen, and that nanocrystalline MoS2 with copiously exposed S edges are more active for HER. Photoelectrochemical measurements demonstrate the highest activity for 3 layered <40 nm thick) MoS2/Cu2O photocathode fabricated at 450 degC with a photocurrent density of ~6.5 mA cm 2 at 0.2 V vs. RHE. Additionally, the MoS2 coating helps minimize the dark current of the Cu2O photocathode.
author_names: Pravin S Shinde

Patricia R Fontenot

James P Donahue

Joseph Waters

Patrick Kung

Louis E McNamara

Nathan I Hammer

Arunava Gupta

Shanlin Pan
title: Synthesis of MoS2 from [Mo3S7(S2CNEt2)3]I for enhancing photoelectrochemical performance and stability of Cu2O photocathode toward efficient solar water splitting
year: 2018

abstract: Abstract Storing solar energy via a chemical fuel of hydrogen from water splitting represents a clean alternative for petroleum fuel. Thus, it is highly desirable for the production of hydrogen using environment friendly and cost effective methods. Most photoelectrodes used for this conversion are semiconductor materials whose band gaps match the UV and visible radiation of solar energy. However, further improvement in electrodes performance may be possible by improving photoabsorption efficiency in near infrared region. This report represents our attempt to utilize IR photons for water splitting, and thus, spectral convertors were incorporated within the hematite nanorods (NRs) grown directly on a FTO glass. The results demonstrate that incorporation of spectral convertors within the hematite NRs leads to higher efficiency and performance in solar water splitting, because the convertors enable harvesting more photons both at UV and IR regions than conventional hematite.
author_names: Timur Sh Atabaev

Hong Ha Thi Vu

Muhammad Ajmal

Hyung Kook Kim

Yoon-Hwae Hwang
title: Dual mode spectral convertors as a simple approach for the enhancement of hematite's solar water splitting efficiency
year: 2015

abstract: One of the principal challenges for solar driven hydrogen production via water splitting is to improve the solar to hydrogen conversion efficiency. We have employed combinatorial chemistry using a materials inkjet printer, and selected CuBi2O4 as a promising p type material. The steady state photocurrent corresponding to water reduction for a 280 nm film at 0.2 V (RHE) was about 0.12 mA cm 2, significantly lower than that attainable for a 2 eV band gap semiconductor. We have applied intensity modulated photocurrent spectroscopy (IMPS) to distinguish between the photoelectrochemical processes involved and to determine the associated time constants, in order to gain insight into the loss processes responsible for the low efficiency. The charge separation efficiency reaches up to 0.66 at sufficiently negative potential, however, the recombination rate constant is larger than that corresponding to electron transfer to the solution. This results in a relative charge transfer efficiency of 0.2 0.4, explaining t.
author_names: Ingrid Rodriguez-Gutierrez

Rodrigo Garcia-Rodriguez

Manuel Rodriguez-Perez

Alberto Vega-Poot

Geonel Rodriguez Gattorno

Bruce A Parkinson

Gerko Oskam
title: Charge Transfer and Recombination Dynamics at Inkjet Printed CuBi2O4 Electrodes for Photoelectrochemical Water Splitting
year: 2018

abstract: Oxide photoelectrochemistry has been under continuous development over the last half century. These decades have witnessed the use of electrodes of different nature (from single crystals to nanoparticulate films) new electrode materials (including ternary and multinary transition metal oxides) and different strategies for improving their efficiency and stability (e.g. doping or protective layers) Although the very high initial expectations for using oxide electrodes in solar energy conversion were not fully met, substantial efforts have been devoted to reach an in depth understanding of the processes limiting their functioning, providing firm bases for further developments. In this article, we review our main contributions in this field; in particular, we focus on the water photooxidation (i.e. oxygen evolution reaction) water photoreduction (i.e. hydrogen evolution reaction) and full water splitting processes (in a tandem cell) with binary and ternary oxides, including metal hydroxides as co catalysts. We emphasize the importance of modeling and obtaining mechanistic insights and we conclude with a reflection on the main issues to be tackled in this field, which in our opinion should experience major advances in the coming years.
author_names: Damian Monllor-Satoca

Maria Isabel Diez-Garcia

Teresa Lana-Villarreal

Roberto Gomez
title: Photoelectrocatalytic production of solar fuels with semiconductor oxides: materials, activity and modeling.
venue: Chemical communications
year: 2020

abstract: We study the photoelectrochemical (PEC) solar water splitting assisted with synthesized nanostructures. Si nanowires decorated with silver dendrite nanostructures have been synthesized using metal assisted wet chemical etching of (100) Si wafer. Etching has been carried out in an aqueous solution consisting of 5M HF and 0.02M AgNO3. Investigations showed that such type of semiconductor nanostructures act as efficient working electrodes for the splitting of normal water in PEC method. An enhancement in the photon to current conversion efficiency and solar to hydrogen evolution was observed for obtaining a practical source of clean and renewable fuel.
author_names: Uday Dadwal

Neha Ranjan

Rupinder Singh
title: Silicon nanostructures induced photoelectrochemical solar water splitting for energy applications
year: 2016

abstract: Solar water splitting via multi junction semiconductor photoelectrochemical cells provides direct conversion of solar energy to stored chemical energy as hydrogen bonds. Economical hydrogen production demands high conversion efficiency to reduce balance of systems costs. For sufficient photovoltage, water splitting efficiency is proportional to the device photocurrent, which can be tuned by judicious selection and integration of optimal semiconductor bandgaps. Here, we demonstrate highly efficient, immersed water splitting electrodes enabled by inverted metamorphic epitaxy and a transparent graded buffer that allows the bandgap of each junction to be independently varied. Voltage losses at the electrolyte interface are reduced by 0.55 V over traditional, uniformly p doped photocathodes by using a buried p n junction. Advanced on sun benchmarking, spectrally corrected and validated with incident photon to current efficiency, yields over 16% solar to hydrogen efficiency with GaInP/GaInAs tandem absorbers, representing a 60% improvement over the classical, high efficiency tandem III V device. Solar water splitting efficiency can be enhanced by careful bandgap selection in multi junction semiconductor structures. Young et al. demonstrate a route that allows independent bandgap tuning of each junction in an immersed water splitting device, enabling a solar to hydrogen efficiency of over 16%
author_names: James L Young

Myles A Steiner

Henning Doscher

John A Turner

Todd G Deutsch
title: Direct solar to hydrogen conversion via inverted metamorphic multi junction semiconductor architectures
year: 2017