SnO2@WS2/p-Si Heterostructure Photocathode for Photoelectrochemical Hydrogen Production (original) (raw)
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MoS2/WS2 Heterojunction for Photoelectrochemical Water Oxidation
ACS Catalysis
The solar-assisted oxidation of water is an essential half reaction for achieving a complete cycle of water splitting. The search of efficient photoanodes which can absorb light in the visible range is of paramount importance to enable cost-effective solar energy-conversion systems. Here we demonstrate that atomically thin layers of MoS 2 and WS 2 can oxidize water to O 2 under incident light. Thin films of solution-processed MoS 2 and WS 2 nanosheets display n-type positive photocurrent densities of 0.45 mA cm-2 and O 2 evolution under simulated solar irradiation. WS 2 is significantly more efficient than MoS 2 , however, bulk heterojunctions of MoS 2 and WS 2 nanosheets results in a 10-fold increase in incident-photon-to-current-efficiency compared to the individual constituents. This proves that charge carrier lifetime is tailorable in atomically thin crystals by creating heterojunctions of different compositions and architectures. Our results suggest that the MoS 2 and WS 2 nanosheets and their bulk heterojunction blend are interesting photocatalytic systems for water oxidation, which can be coupled with different reduction processes for solar-fuel production.
MoS2/WS2 Heterojunction for Photoelectrochemical Water Oxidation
ACS Catalysis, 2017
The solar-assisted oxidation of water is an essential half reaction for achieving a complete cycle of water splitting. The search of efficient photoanodes which can absorb light in the visible range is of paramount importance to enable cost-effective solar energy-conversion systems. Here we demonstrate that atomically thin layers of MoS 2 and WS 2 can oxidize water to O 2 under incident light. Thin films of solution-processed MoS 2 and WS 2 nanosheets display n-type positive photocurrent densities of 0.45 mA cm-2 and O 2 evolution under simulated solar irradiation. WS 2 is significantly more efficient than MoS 2 , however, bulk heterojunctions of MoS 2 and WS 2 nanosheets results in a 10-fold increase in incident-photon-to-current-efficiency compared to the individual constituents. This proves that charge carrier lifetime is tailorable in atomically thin crystals by creating heterojunctions of different compositions and architectures. Our results suggest that the MoS 2 and WS 2 nanosheets and their bulk heterojunction blend are interesting photocatalytic systems for water oxidation, which can be coupled with different reduction processes for solar-fuel production.
Transition Metal Dichalcogenides [MX2] in Photocatalytic Water Splitting
Catalysts
The quest for a clean, renewable and sustainable energy future has been highly sought for by the scientific community over the last four decades. Photocatalytic water splitting is a very promising technology to proffer a solution to present day environmental pollution and energy crises by generating hydrogen fuel through a “green route” without environmental pollution. Transition metal dichalcogenides (TMDCs) have outstanding properties which make them show great potential as effective co-catalysts with photocatalytic materials such as TiO2, ZnO and CdS for photocatalytic water splitting. Integration of TMDCs with a photocatalyst such as TiO2 provides novel nanohybrid composite materials with outstanding characteristics. In this review, we present the current state of research in the application of TMDCs in photocatalytic water splitting. Three main aspects which consider their properties, advances in the synthesis routes of layered TMDCs and their composites as well as their photoc...
Recent Developments on Photocatalytic water Splitting using Semiconductors for Hydrogen Production
Hydrogen fuel has gained heed in the recent years as fossil fuels and other non-renewable sources of fuels are fast depleting. Hydrogen has been contemplated to be a prospective source of an alternative fuel, predominantly if it can be produced from a renewable and sustainable source such as water. Methods such as photocatalytic water splitting are arguably one of the simple methods to produce clean, green and renewable energy by disassociating water into H2 (hydrogen) and O2 (oxygen) using catalyst and sunlight. Numerous techniques have been developed to improve photocatalytic activity in materials such as TiO2. This paper describes the recent progress, state of art and the future challenges in photocatalytic water-splitting.
Strategies for Semiconductor/Electrocatalyst Coupling toward Solar‐Driven Water Splitting
Advanced Science
with the consumption of fossil fuels. [1,2] Hydrogen (H 2) and fuel cell technologies have shown significant potential to empower this transition, able to substantially reduce carbon dioxide (CO 2) emissions and create a huge new market, as predicted recently by the Hydrogen Council. [3] Although H 2 is a clean energy carrier and shows flexibility of linking different energy sectors and energy transmission and distribution networks, the production of H 2 is currently not that "clean"-nearly 96% of global H 2 production is from thermochemical processes, [4] which not only deplete fossil fuels but also emit a large amount of CO 2. To decarbonize H 2 production, fossil-free processes such as electrochemical water splitting using "green" electricity or direct photoelectrochemical (PEC) water splitting must be widely deployed. PEC water splitting takes advantage of semiconductors as both the light absorber and energy converter, to store solar energy in the form of H 2 fuel. To make full use of the photogenerated electron-hole pairs, effective separation of electrons from holes and rapid charge transfer from the space charge region to the semiconductor/liquid junction that enables the chemical reaction are very important. For most semiconductors, even if their conduction/valence band edge is properly positioned with respect to the proton reduction potential or the water oxidation potential, the hydrogen evolution reaction (HER) or the oxygen evolution reaction (OER) kinetics on the bare semiconductor surfaces is usually so sluggish that Hydrogen (H 2) has a significant potential to enable the global energy transition from the current fossil-dominant system to a clean, sustainable, and low-carbon energy system. While presently global H 2 production is predominated by fossil-fuel feedstocks, for future widespread utilization it is of paramount importance to produce H 2 in a decarbonized manner. To this end, photoelectrochemical (PEC) water splitting has been proposed to be a highly desirable approach with minimal negative impact on the environment. Both semiconductor light-absorbers and hydrogen/oxygen evolution reaction (HER/OER) catalysts are essential components of an efficient PEC cell. It is well documented that loading electrocatalysts on semiconductor photoelectrodes plays significant roles in accelerating the HER/OER kinetics, suppressing surface recombination, reducing overpotentials needed to accomplish HER/OER, and extending the operational lifetime of semiconductors. Herein, how electrocatalyst coupling influences the PEC performance of semiconductor photoelectrodes is outlined. The focus is then placed on the major strategies developed so far for semiconductor/ electrocatalyst coupling, including a variety of dry processes and wet chemical approaches. This Review provides a comprehensive account of advanced methodologies adopted for semiconductor/electrocatalyst coupling and can serve as a guideline for the design of efficient and stable semiconductor photoelectrodes for use in water splitting.
Water splitting for H2 production using visible-light-responsive photocatalysts
2013
Photocatalytic water splitting using semiconductor materials has attracted considerable interest due to its potential for clean production of H 2 from water through the conversion of abundant solar energy into chemical energy. This article briefly analyzed the trend and progress in the research and development of visible-light-responsive photocatalysts for water splitting in the past few years. Particularly, metal sulfides and composite photocatalysts were discussed. This brief review article aims at facilitating a search of stable and efficient photocatalysts for water splitting, and revealing fundamental insight into the development of novel visible light-adsorbing photocatalysts.
Catalysts
Visible-light-driven photoelectrochemical (PEC) and photocatalytic water splitting systems featuring heterogeneous semiconductor photocatalysts (oxynitrides, oxysulfides, organophotocatalysts) signify an environmentally friendly and promising approach for the manufacturing of renewable hydrogen fuel. Semiconducting electrode materials as the main constituents in the PEC water splitting system have substantial effects on the device’s solar-to-hydrogen (STH) conversion efficiency. Given the complication of the photocatalysis and photoelectrolysis methods, it is indispensable to include the different electrocatalytic materials for advancing visible-light-driven water splitting, considered a difficult challenge. Heterogeneous semiconductor-based materials with narrower bandgaps (2.5 to 1.9 eV), equivalent to the theoretical STH efficiencies ranging from 9.3% to 20.9%, are recognized as new types of photoabsorbents to engage as photoelectrodes for PEC water oxidation and have fascinated ...
An Overview of the Photocatalytic H2 Evolution by Semiconductor-Based Materials for Nonspecialists
Journal of the Brazilian Chemical Society, 2020
The solar-to-chemical energy conversion is promising to tackle sustainability challenges toward a global future. The production of H 2 from sunlight represents an attractive alternative to the use of carboniferous fossil fuels to meet our energy demands. In this context, the water splitting reaction photocatalyzed by semiconductors that can be excited under visible or near-infrared light excitation represents an attractive route to the clean generation of H 2. In this review, we present an overview of the most important concepts behind the H 2 generation, from water splitting, promoted by semiconductor-based systems for readers that were recently introduced to the water splitting topic. Then, we present the main classes of photocatalysts based on semiconductors. For each class of semiconductors, we focused on the examples that lead to the highest activities towards the H 2 production and discuss the operation principles, advantages, performances, limitations, and challenges. We cover metal oxides, sulfides, and nitrides. We also discuss strategies in which these materials are combined, including hybridization with metal nanoparticles, other semiconductors, and carbon dots, to achieve improved performances and circumvent the limitations of the individual counterparts.
THE EFFECT OF BAND ENGINEERING OF SEMICONDUCTORS ON PHOTOCATALYIC WATER SPLITTING: A REVIEW
The direct conversion of solar energy using a photocatalyst in a water splitting reaction is a source of a sustainable and clean hydrogen supply. In general, photocatalysts are semiconductors that possess valence and conduction bands. These energy bands permit the absorption of photon energy to excite electrons in the outer orbitals of the photocatalysts. Photoexcited electron and hole pairs can subsequently induce a watersplitting reaction to produce hydrogen and oxygen. Photocatalytic water splitting is affected by the band level and crystallinity of the photocatalyst. Therefore, band engineering using chemical modifications such as cationic and anionic modification could createa photocatalyst suitable for the large-scale production of hydrogen. In this paper, cationic and anionic modifications of photocatalysts and the effects of these modifications onphotocatalytic water splitting are reviewed.