skip to main content

Title: Rational Design of Photoelectrodes with Rapid Charge Transport for Photoelectrochemical Applications

Photoelectrode materials are the heart of photoelectrochemical (PEC) cells, which hold great promise to address global energy and environmental issues by converting solar energy into electricity or chemical fuels. In recent decades, significant research efforts have been devoted to the design and construction of photoelectrodes for the efficient generation and utilization of charge carriers to boost PEC performance. Herein, insights from a literature study on the relationship between the architecture and charge dynamics of photoelectrodes are presented. After briefly introducing the fundamental theories of charge dynamics in nanostructured photoelectrodes, the development of photoelectrode design in 1D polycrystalline nanotube arrays, 1D single‐crystalline nanowire arrays, and hierarchical and mesoporous nanowire arrays is reviewed with a focus on the interplay between architecture and charge transport properties. For each design, commonly used synthetic approaches and the corresponding charge transport properties are discussed. Subsequently, the applications of these photoelectrodes in PEC systems are summarized. In conclusion, future challenges in the rational design of photoelectrode architecture are presented. The basic relationships between the architectures and charge dynamics of photoelectrode materials discussed here are expected to provide pertinent guidance and a reference for future advanced material design targeting improved light energy conversion systems.

more » « less
Award ID(s):
Author(s) / Creator(s):
 ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Advanced Materials
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Photoelectrochemical (PEC) water splitting has been intensively studied in the past decades as a promising method for large-scale solar energy storage. Among the various issues that limit the progress of this field, the lack of photoelectrode materials with suitable properties in all aspects of light absorption, charge separation and transport, and charge transfer is a key challenge, which has attracted tremendous research attention. A large variety of compositions, in different forms, have been tested. This review aims to summarize efforts in this area, with a focus on materials-related considerations. Issues discussed by this review include synthesis, optoelectronic properties, charge behaviors and catalysis. In the recognition that thin-film materials are representative model systems for the study of these issues, we elected to focus on this form, so as to provide a concise and coherent account on the different strategies that have been proposed and tested. Because practical implementation is of paramount importance to the eventual realization of using solar fuel for solar energy storage, we pay particular attention to strategies proposed to address the stability and catalytic issues, which are two key factors limiting the implementation of efficient photoelectrode materials. To keep the overall discussion focused, all discussions were presented within the context of water splitting reactions. How the thin-film systems may be applied for fundamental studies of the water splitting chemical mechanisms and how to use the model system to test device engineering design strategies are discussed. 
    more » « less
  2. Photoelectrochemical (PEC) CO2reduction (PEC CO2R) is a prospective approach for utilizing solar energy to synthesize a variety of carbon-containing chemicals and fuels, the most valuable of which are multicarbon (C2+) products, such as ethylene and ethanol. While these products can be produced with high faradaic efficiency using Cu, this occurs over a relatively narrow potential range, which, in turn, imposes constraints on the design of a device for PEC CO2R. Herein, we used continuum-scale modeling to simulate the solar-to-C2+(STC2+) efficiency of PEC CO2R devices fed with CO2-saturated, 0.1 M CsHCO3. We then explored how cell architecture and the use of single or dual photoelectrode(s) alters the optimal combination of photoelectrode bandgaps for high STC2+efficiency. Ultimately, this work provides guidance for the co-design of the device architecture and photoelectrode bandgaps required to achieve high STC2+efficiency. The insights gained are then used to identify systems that yield the highest amount of C2+products throughout the day and year.

    more » « less
  3. Solar rechargeable battery combines the advantages of photoelectrochemical devices and batteries and has emerged as an attractive alternative to artificial photosynthesis for large‐scale solar energy harvesting and storage. Due to the low photovoltages by the photoelectrodes, however, most previous demonstrations of unassisted photocharge have been realized on systems with low open circuit potentials (<0.8 V). In response to this critical challenge, here it is shown that the combined photovoltages exceeding 1.4 V can be obtained using a Ta3N5nanotube photoanode and a GaN nanowire/Si photocathode with high photocurrents (>5 mA cm–2). The photoelectrode system makes it possible to operate a 1.2 V alkaline anthraquinone/ferrocyanide redox battery with a high ideal solar‐to‐chemical conversion efficiency of 3.0% without externally applied potentials. Importantly, the photocharged battery is successfully discharged with a high voltage output.

    more » « less
  4. Abstract

    Organic–inorganic hybrids offer great promise as solution‐processable thermoelectric materials. However, they have struggled to surpass the performance of their rigid inorganic counterparts due, in part, to a lack of synthetic control and limited understanding of how inorganic nanostructure dimensions impact overall charge transport. While it has been hypothesized that length, diameter, and aspect ratio (AR) all impact electronic transport in hybrid nanowires, the field lacks clarity on the relative role of each. In this study, the experimental parameter of ligand molecular weight (MW) is investigated as a synthetic knob for modulating nanowire dimensions, as well as the deconvolution of nanowire length versus diameter impacts on electron transport. By increasing ligand MW, larger nanowire AR dispersions occur and an optimal power factor of ≈130 μWm−1K−2is achieved for a modest AR of 73. Power factors of this magnitude are thought to only be achievable in ultrahigh AR systems; representing a 183% increase in performance over literature reports with similar AR. Additionally, nanowire diameter is demonstrated to be a far more sensitive parameter for enhancing performance than modulating length. This study provides improved fundamental insight into rational synthetic design avenues for future enhancements in the performance of hybrid materials.

    more » « less
  5. Abstract

    A multifaceted Mo:BiVO4(mf‐BVO) photoanode is grown on F‐doped‐SnO2substrates via achemical bath deposition, and the crystal reconstruction process of mf‐BVO is found to boost the charge transport efficiency significantly for photoelectrochemical (PEC) water splitting. The mf‐BVO exhibits columnar grains with an uncommon (121) texture with high‐index facets such as (112), (020), (132), and (204). The texture and high‐index facets facilitate rapid surface melting and grain fusion during thermal annealing, thus leading to crystal reconstructed micron‐sized BVO grains (cr‐BVO). The cr‐BVO has a photocurrent density ≈50 times larger than that of mf‐BVO. The reason is identified as the significantly improved charge transport efficiency resulting from the dopant activation (increased carrier concentration) and bulky grains (fewer defects). Additionally, the cr‐BVO exhibits improved photocorrosion resistance compared to the nanoparticle‐based BVO. After coating the oxygen evolution catalyst, the photocurrent density of cr‐BVO is further increased to 4.4 mA cm−2for water oxidation reaction at 1.23 V versus the reversible hydrogen electrode, maintaining a high and stable faradaic efficiency of over 88% for 24 h. These results demonstrate that crystal reconstruction is a facile and effective pathway to improve the charge transport efficiency, opening a new avenue for developing efficient photoelectrodes for PEC water splitting.

    more » « less