Query: Photoelectrochemical devices for solar water splitting materials and challenges

Candidate papers:

abstract: It is widely accepted within the community that to achieve a sustainable society with an energy mix primarily based on solar energy we need an efficient strategy to convert and store sunlight into chemical fuels. A photoelectrochemical (PEC) device would therefore play a key role in offering the possibility of carbon neutral solar fuel production through artificial photosynthesis. The past five years have seen a surge in the development of promising semiconductor materials. In addition, low cost earth abundant co catalysts are ubiquitous in their employment in water splitting cells due to the sluggish kinetics of the oxygen evolution reaction (OER) This review commences with a fundamental understanding of semiconductor properties and charge transfer processes in a PEC device. We then describe various configurations of PEC devices, including single light absorber cells and multi light absorber devices (PEC, PV PEC and PV/electrolyser tandem cell) Recent progress on both photoelectrode materials (light absorbers) and electrocatalysts is summarized, and important factors which dominate photoelectrode performance, including light absorption, charge separation and transport, surface chemical reaction rate and the stability of the photoanode, are discussed. Controlling semiconductor properties is the primary concern in developing materials for solar water splitting. Accordingly, strategies to address the challenges for materials development in this area, such as the adoption of smart architectures, innovative device configuration design, co catalyst loading, and surface protection layer deposition, are outlined throughout the text, to deliver a highly efficient and stable PEC device for water splitting.
author_names: Chaoran Jiang

Savio J A Moniz

Aiqin Wang

Tao Zhang

Junwang Tang
title: Photoelectrochemical devices for solar water splitting materials and challenges.
venue: Chemical Society reviews
year: 2017

abstract: Photoelectrochemical water splitting (PEC) offers a promising path for sustainable generation of hydrogen fuel. However, improving solar fuel water splitting efficiency facing tremendous challenges, due to the energy loss related to fast recombination of the photogenerated charge carriers, electrode degradation, as well as limited light harvesting. This review focuses on the brief introduction of basic fundamental of PEC water splitting and the concept of various types of water splitting approaches. Numerous engineering strategies for the investgating of the higher efficiency of the PEC, including charge separation, light harvesting, and co catalysts doping, have been discussed. Moreover, recent remarkable progress and developments for PEC water splitting with some promising materials are discussed. Recent advanced applications of PEC are also reviewed. Finally, the review concludes with a summary and future outlook of this hot field.
author_names: Bandar Y Alfaifi

Habib Ullah

Sulaiman Yahya Alfaifi

Asif Ali Tahir

Tapas K Mallick
title: Photoelectrochemical solar water splitting: From basic principles to advanced devices
year: 2018

abstract: Photoelectrochemical (PEC) water splitting is a promising route for solar energy conversion to hydrogen. It produces clean hydrogen that can be used for refueling fuel cell electric vehicles or serve as a feedstock for the production of drop in liquid fuels by CO2 hydrogenation or ammonia via the Haber Bosch process. The greatest challenges towards PEC solar water splitting technology lay in the selection and optimization of stable photocatalytic materials for water photo oxidation, and the design of scalable PEC devices that produce hydrogen at a competitive cost. Iron oxide (a Fe2O3, hematite) is one of few materials meeting the basic selection criteria for stable photoanodes, but its poor charge transport properties and fast recombination present challenges for efficient charge separation and collection. We explore innovative solutions to these challenges using ultrathin (20 30 nm) films on specular back reflectors. This optical design traps the light in otherwise nearly translucent ultrathin films, amplifying the intensity close to the surface wherein photogenerated charge carriers can reach the surface and split water before recombination takes place.1 This is the enabling key towards the development of high efficiency epilayers whose properties can be tailored by material design at the atomic scale.2 Our recent efforts to uncover the design rules of these photoanodes will be presented. On the other end of the spectrum we explore innovative device architectures and operation schemes for scalable and competitive PEC solar water splitting technology. These include power and optical management schemes for optimizing the hydrogen and power outputs of PEC PV tandem cells,3 and separating the hydrogen production from the oxygen production for safe operation and on site hydrogen production.4
author_names: Avner Rothschild
title: Photoelectrochemical water splitting for solar energy conversion and storage
year: 2017

abstract: In order to be economically competitive with simple "brute force" (i.e. PV electrolyzer) strategies or the production of promising solar fuels, like H2, from fossil fuels, a practical photoelectrochemical device must optimize cost, longevity, and performance. A promising approach that meets these requirements is the combination of stable and inexpensive oxide semiconductor electrodes in a tandem photoelectrochemical device. In this article, we give an overview of the field including an examination of the potential solar to fuel conversion efficiency expected in a device with realistic losses. We next discuss recent advances with increasing the performance of promising semiconductor electrode materials and highlight how these advances have led to state of the art solar to chemical efficiencies in the 2 3% range in real devices. Challenges for further optimization are further outlined.
author_names: Mathieu S Prevot

Kevin Sivula
title: Photoelectrochemical Tandem Cells for Solar Water Splitting
year: 2013

abstract: The magnitude of energy challenge not only calls for efficient devices but also for abundant, inexpensive, and stable photoactive materials that can enable efficient light harvesting, charge separation and collection, as well as chemical transformations. Photoelectrochemical systems based on semiconductor materials have the possibility to transform solar energy directly into chemical energy the so called "solar hydrogen." The current challenge lies in the harvesting of a larger fraction of electromagnetic spectrum by enhancing the absorbance of electrode materials. In this context, atomically precise thin films of metal oxide semiconductors and their multilayered junctions are promising candidates to integrate high surface areas with well defined electrode substrate interface. Given its self limited growth mechanism, the atomic layer deposition (ALD) technique offers a wide range of capabilities to deposit and modify materials at the nanoscale. In addition, it opens new frontiers for developing precursor chemistry that is inevitable to design new processes. Herein, the authors review the properties and potential of metal oxide thin films deposited by ALD for their application in photoelectrochemical water splitting application. The first part of the review covers the basics of ALD processes followed by a brief discussion on the electrochemistry of water splitting reaction. The second part focuses on different MOx films deposited by atomic layer deposition for water splitting applications; in this section, The authors discuss the most explored MOx semiconductors, namely, Fe2O3, TiO2, WO3, and ZnO, as active materials and refer to their application as protective coatings, conductive scaffolds, or in heterojunctions. The third part deals with the current challenges and future prospects of ALD processed MOx thin films for water splitting reactions.
author_names: Trilok Singh

Thomas Lehnen

Tessa Leuning

Sanjay Mathur
title: Atomic layer deposition grown MOx thin films for solar water splitting: Prospects and challenges
year: 2015

abstract: The generation and storage of renewable energy is one of the key challenges for the transition to a sustainable society. Hydrogen (H2) the most abundant element on earth, is believed to be an important energy carrier in the near future. It can be either used directly as a fuel, or further converted with CO2 to form hydrocarbons through well known catalytic processes. Water is the most sustainable resource for production of hydrogen. A highly promising approach to generate hydrogen from water is photoelectrochemistry. Such a device aims to integrate photovoltaics (solar panels) and electrolysis, potentially being an efficient energy conversion system. The research described in this thesis focuses on the development of photoelectrochemical devices for hydrogen generation from water. In particular, electrochemistry was utilized to coat flat and microwire structured silicon, one of the main materials in photovoltaic cells, with metals or semiconductors. These layers are necessary, among others, to facilitate oxygen or hydrogen evolution, improve the use of the solar spectrum, and increase photovoltage of devices. Silicon microwire structuring enhances light absorption and increases the active surface area for reaction. The findings of this work provide: i) a way to control the size and density of platinum particles on Si surfaces, ii) a method to deposit materials spatioselectively on top and bottom segments of microwires with axial p/n junctions, iii) a theory for deactivation of tungsten oxide in water oxidation, and iv) evaluation of the functionality of bismuth vanadate, when deposited onto silicon microwires.
author_names: Alexander Milbrat
title: Electrochemical coating of micro structured silicon for photoelectrochemical water splitting
year: 2018

abstract: Water photolysis is a sustainable technology to convert natural solar energy and water into chemical fuels and is thus considered a thorough solution to the forthcoming energy crises. Unassisted water splitting that could directly harvest solar light and subsequently split water in a single device has become an important research theme. Three types of tandem devices including photoelectrochemical (PEC) photovoltaic (PV) cell/PEC and PV/electrolyser tandem cells are proposed to realize water photolysis at different levels of integration and component. Recent progress in tandem water splitting devices is summarized, and crucial issues on device optimization from the perspective of each photo absorber functionalities in band edge potential, light absorptivity and transmittance are discussed. By increasing the performances of stand alone PEC or PV devices, a 20% solar to hydrogen efficiency is predicted that is a significant value towards further application in practice. Accordingly, the challenges for materials development and configuration optimization are further outlined.
author_names: Kan Zhang

Ming Ma

Ping Li

Dong Hwan Wang

Jong Hyeok Park
title: Water Splitting Progress in Tandem Devices: Moving Photolysis beyond Electrolysis
year: 2016

abstract: The work detailed in this thesis is organized in the following manner: In Chapter 1 we discuss electrochemical and photoelectrochemical catalysts in the context of their application for solar to hydrogen devices. During this introduction we will give an overview of the current state of the field, discussing the different kinds of materials that are being investigated before giving a brief description of some actual solar to hydrogen devices and finishing with a discussion of the current and future challenges in the field. Chapter 2 is a description of the different techniques used throughout this thesis. Once having set the bases, we shall start with the actual research, which corresponds to Chapters 3 to 5. Chapter 3 and 4 deal with the effect of trace metal impurities in electrochemical water splitting. In Chapter 3 we show that adventitious nickel at trace levels can act as a water oxidation catalyst in mildly basic aqueous solutions at overpotentials comparable to many recently reported water oxidation catalysts, therefore serving to raise the burden of proof required of new materials in this field. Chapter 4 shows how silver ions leaking from Ag/AgCl reference electrodes in aqueous buffers at low pH can deposit on the working electrode as Ag(0) and catalyze the hydrogen evolution reaction, calling into question the validity of any reports using these electrodes that cannot demonstrate significantly superior activity to the baseline we set in this chapter. In Chapter 5 we describe a direct hydrothermal deposition method to prepare Cobalt doped MoS2 thin films onto transparent Fluorine doped SnO2 substrate and demonstrate that the obtained films display good activity for the hydrogen evolution reaction from acid solution.
author_names: I Barba
title: Investigations into electrochemical water splitting
year: 2017

abstract: The key to successful deployment of photoelectrochemical (PEC) water splitting for commercial renewable hydrogen production will be in the identification and development of innovative semiconductor materials systems and devices, likely involving multijunction configurations. Multijunction approaches offer some of the best hope for achieving practical PEC hydrogen production in the near term, but complex materials and interface issues still need to be addressed by the scientific community. This chapter explores the challenges and benefits of large scale solar water splitting for renewable hydrogen production, with specific focus on the multijunction PEC production pathways. The technical motivation and approach in the R&D of multijunction PEC devices and systems are considered, and examples of progress in laboratory scale prototypes are presented.
author_names: Eric L Miller

Alexander Deangelis

Stewart A Mallory
title: Multijunction Approaches to Photoelectrochemical Water Splitting
year: 2012

abstract: One of the key challenges in photoelectrochemical water splitting is to identify efficient semiconductors with band gaps of the order of ~2 eV to operate as the large band gap component in water splitting tandem devices. Here, we address this challenge by extensive computational screening of ternary sulfides followed by synthesis and confirmation of the properties of one of the most promising materials. The screening focusses on materials with ABS3 composition taking both perovskite and non perovskite structures into consideration, and the material selection is based on descriptors for thermodynamic stability, light absorption, charge mobility, and defect tolerance. One of the most promising candidates identified is LaYS3. This material was synthesized directly in thin film form demonstrating its stability, crystal structure, light absorption, and strong photoluminescence. These data confirms its potential applicability in tandem photoelectrochemical devices for hydrogen production.
author_names: Korina Kuhar

Andrea Crovetto

Mohnish Pandey

Kristian Sommer Thygesen

Brian Seger

Peter C K Vesborg

Ole Hansen

Ib Chorkendorff

Karsten Wedel Jacobsen
title: Sulfide perovskites for solar energy conversion applications: computational screening and synthesis of the selected compound LaYS3
year: 2017