Heterogeneous Photocatalysis

From Fundamentals to Applications in Energy Conversion and Depollution

Jennifer Strunk

• Publisher: Wiley-VCH
• Year: 2021
• Print ISBN:
  9783527344642
• eBook ISBN:
  9783527815265
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Biochemistry

Discover the latest research in photocatalysis combined with foundational topics in basic physical and chemical photocatalytic processes

In Heterogeneous Photocatalysis: From Fundamentals to Applications in Energy Conversion and Depollution, distinguished researcher and editor Jennifer Strunk delivers a rigorous discussion of the two main topics in her field—energy conversion and depollution reactions. The book covers topics like water splitting, CO2 reduction, NOx abatement and harmful organics degradation.

In addition to the latest research on these topics, the reference provides readers with fundamental information about elementary physical and chemical processes in photocatalysis that are extremely practical in this interdisciplinary field. It offers an excellent overview of modern heterogeneous photocatalysis and combines concepts from different viewpoints to allow researchers with backgrounds as varied as electrochemistry, material science, and semiconductor physics to begin developing solutions with photocatalysis.

In addition to subjects like metal-free photocatalysts and photocarrier loss pathways in metal oxide absorber materials for photocatalysis explored with time-resolved spectroscopy, readers will also benefit from the inclusion of:

• Thorough introductions to kinetic and thermodynamic considerations for photocatalyst design and the logic, concepts, and methods of the design of reliable studies on photocatalysis
• Detailed explorations of in-situ spectroscopy for mechanistic studies in semiconductor photocatalysis and the principles and limitations of photoelectrochemical fuel generation
• Discussions of photocatalysis, including the heterogeneous catalysis perspective and insights into photocatalysis from computational chemistry
• Treatments of selected aspects of photoreactor engineering and defects in photocatalysis

Perfect for photochemists, physical and catalytic chemists, electrochemists, and materials scientists, Heterogeneous Photocatalysis will also earn a place in the libraries of surface physicists and environmental chemists seeking up-to-date information about energy conversion and depollution reactions.

1
Kinetic and Thermodynamic Considerations for Photocatalyst Design

Frank E. Osterloh

University of California, Department of Chemistry, One Shields Avenue, Davis, CA, 95616, USA

1.1 Introduction

Photochemical processes play a central role on Earth. While natural photosynthesis powers our biosphere and economic growth (through the use of photosynthesis-derived fossil fuels), additional photochemical processes are involved in shaping the “photogeochemistry” of our planet [1]. Light reactions play a role in the creation and function of the ozone ultraviolet (UV) filter in the atmosphere, the degradation of plant materials, man-made chemicals and plastics, and even in the chemical conversion of Earth-abundant minerals.

The potential of photochemical processes for technical applications was first demonstrated by A.E. Becquerel in 1839 when he discovered the photovoltaic effect. Interestingly, it took over a century before this knowledge was applied to practical photovoltaic cells [2]. In 1968, Gerischer's discovery of the dye sensitization effect at illuminated semiconductor surfaces [3] paved the way for Grätzel's construction of the first dye-sensitized photovoltaic cell 1991 [3] and also inspired for the production of hydrogen fuel from illuminated TiO₂ photoanodes [4, 5].

Since then, the interest in photochemical reactions for environmental remediation [6–10] and for the production of sustainable fuels has gained steadily [11–17]. In 2018, over 6000 articles were published with the term photocatalytic or photocatalyst in the title. This is about 60 times as many as published on this topic in 1991 when Grätzel's dye-sensitized solar cells made headlines. In contrast, the number of papers published on photosynthesis has been relatively steady in the past three decades, with approximately 1000 publications per year.

In the science community, photochemical reaction systems are typically referred to as “photocatalysts,” or as “photosynthetic systems” or sometimes as devices for “artificial photosynthesis.” Interestingly, there is no strong differentiation between these terms. For example, the International Union of Pure and Applied Chemistry (IUPAC) defines a “photocatalyst” as a “Catalyst able to produce, upon absorption of light, chemical transformations of the reaction partners. The excited state of the photocatalyst repeatedly interacts with the reaction partners forming reaction intermediates and regenerates itself after each cycle of such interactions.” [18] This definition makes no distinction between reactions that deposit photochemical energy in the products and reactions that do not.

According to Nozik [19] and Bard [20], excitonic reactions can be divided into photosynthetic and photocatalytic processes, depending on the thermodynamics of the associated reaction: [21].

“Photoelectrolytic cells … can be classified as photosynthetic or photocatalytic. In the former case, radiant energy provides a Gibbs energy to drive a reaction such as H₂O + H₂ + ½ O₂, and electrical or thermal energy may be later recovered by allowing the reverse, spontaneous reaction to proceed. In a photocatalytic cell the photon absorption promotes a reaction with ΔG < 0 so there is no net storage of chemical energy, but the radiant energy speeds up a slow reaction.” [22]

As we will show here, this distinction between photocatalytic and photosynthetic devices becomes very significant to the understanding of their function and also to their optimization. An overview of the fundamental processes in photochemical reaction systems is presented in the following sections.

1.2 Mechanistic Aspects of Photochemical Reaction Systems

Photochemical (excitonic) reaction systems generally rely on the creation and transfer of charge carriers to induce the transformation of reagents in the vicinity of the light absorber. Usually, the process begins with the absorption of one or several photons (step 1), as shown in Figure 1.1a. This generates photoelectrons and holes, which s...

Table of contents

• Cover
• Table of Contents
• Title Page
• Copyright
• Preface
• 1 Kinetic and Thermodynamic Considerations for Photocatalyst Design
• 2 Design of Reliable Studies on Photocatalysis: Logic, Concepts, and Methods
• 3 In Situ Spectroscopy for Mechanistic Studies in Semiconductor Photocatalysis
• 4 Principles and Limitations of Photoelectrochemical Fuel Generation
• 5 Photocatalysis – The Heterogeneous Catalysis Perspective
• 6 Insights into Photocatalysis from Computational Chemistry
• 7 Selected Aspects of Photoreactor Engineering
• 8 Defects in Photocatalysis
• 9 Photocarrier Loss Pathways in Metal Oxide Absorber Materials for Photocatalysis Explored with Time-Resolved Spectroscopy: The Case of BiVO4
• 10 Metal-free Photocatalysts
• 11 Photocatalytic Water Splitting: Fundamentals and Current Concepts
• 12 Photocatalytic CO2 Reduction and Beyond
• 13 Photocatalytic NOx Abatement
• 14 Photoactive Nanomaterials: Applications in Wastewater Treatment and Their Environmental Fate
• Index
• End User License Agreement