Abstract
Developing strategies for producing hydrogen economically and in greener ways is still an unaccomplished goal. Photoelectrochemical (PEC) water splitting using photoelectrodes under neutral electrolyte conditions provides possibly one of the greenest routes to produce hydrogen. Here, we demonstrate that chlorophyll extracts can be used as an efficient exfoliant to exfoliate bulk MoS2 and WS2 to form a thin layer of a MoS2/WS2 heterostructure. Thin films of solution-processed MoS2 and WS2 nanosheets display photocurrent densities of −1 and −5 mA/cm2, respectively, and hydrogen evolution under simulated solar irradiation. The exfoliated WS2 is significantly more efficient than the exfoliated MoS2; however, the MoS2/WS2 heterostructure results in a 2500% increase in photocurrent densities compared to the individual constituents and over 12 h of PEC durability under a neutral electrolyte. Surprisingly, in real seawater, the MoS2/WS2 heterostructure exhibits stable hydrogen production after solar illumination for 12 h. The synthesis method showed, for the first time, how the MoS2/WS2 heterostructure can be used to produce hydrogen effectively. Our findings highlight the prospects for this heterostructure, which could be coupled with various processes towards improving PEC efficiency and applications.
Highlights
Our findings highlight the prospects for this heterostructure, which could be coupled with various processes towards improving PEC efficiency and applications
People’s demand for energy has increased year by year, and the massive energy supplies are from fossil fuels, which lead to environmental pollution and extreme climate change
MoS2 monolayer, which shows that the solution exfoliation method offers the presence of a large amount of exfoliated monolayer structures [23,24]
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The materials absorb solar energy to induce water splitting to generate H2 fuel, which was limited by the following factors: (1) poor absorption in the visible region, (2) fast electron–hole recombination, and (3) limited active sites [5] To overcome these bottlenecks, several strategies such as co-catalysts [6,7,8], band gap Nanomaterials 2021, 11, 2436. According to computational studies [16], the valence band position of MoS2 and WS2 thin sheets is more positive than the water oxidation potential (1.23 V vs standard hydrogen electrode (SHE)) [17,18] Their bulk forms do not achieve the thermodynamic criteria for PEC water splitting. We believe that our findings will inspire the further development of novel heterostructure strategies that will provide the ability to enhance PEC performance and long-term stability for a multitude of 2D materials
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