Abstract
We have recently demonstrated in a previous work an appreciable photoelectrocatalytic (PEC) behavior towards hydrogen evolution reaction (HER) of a MoS2/Ag2S/Ag nanocomposite electrochemically deposited on a commercial writable Digital Versatile Disc (DVD), consisting therefore on an interesting strategy to convert a common waster product in an added-value material. Herein, we present the conjugation of this MoS2/Ag2S/Ag-DVD nanocomposite with thiol-terminated tetraphenylporphyrins, taking advantage of the grafting of thiol groups through covalent S-S bridges, for integrating the well-known porphyrins photoactivity into the nanocomposite. Moreover, we employ two thiol-terminated porphyrins with different hydrophilicity, demonstrating that they either suppress or improve the PEC-HER performance of the overall hybrid, as a function of the molecule polarity, sustaining the concept of a local proton relay. Actually, the active polar porphyrin—MoS2/Ag2S/Ag-DVD hybrid material presented, when illuminated, a better HER performance, compared to the pristine nanocomposite, since the porphyrin may inject photoelectrons in the conduction band of the semiconductors at the formed heterojunction, presenting also a stable operational behavior during overnight chopped light chronoamperometric measurement, thanks to the robust bond created.
Highlights
Transition metal dichalcogenides (TMDCs) are currently considered the flagship structures in the “beyond graphene realm” of material science research and development [1,2]
We have recently demonstrated in a previous work an appreciable photoelectrocatalytic (PEC) behavior towards hydrogen evolution reaction (HER) of a MoS2/Ag2S/Ag nanocomposite electrochemically deposited on a commercial writable Digital Versatile Disc (DVD), consisting on an interesting strategy to convert a common waster product in an added-value material
The first one appeared at a binding energy (BE) of 160.9 eV, which is in total agreement with the presence of Ag2S [29]; a second doublet is found at 161.5 eV of BE, in the typical position of MoS2
Summary
Transition metal dichalcogenides (TMDCs) are currently considered the flagship structures in the “beyond graphene realm” of material science research and development [1,2]. The scientific community is currently undertaking huge efforts to exploit the excellent properties of TMDCs for sustainable PEC-HER catalysts [7] to replace the expensive and critical materials based on platinum-group metals traditional catalysts [10]. The strategy consisted of the short potentiostatic electroreduction of (NH4)2MoS4 (typically a 3–4 min long procedure), using the clean nano-patterned 1 μm thick Ag layer of the DVD as electrode. This methodology allowed the in situ formation of amorphous MoS2 over the DVD surface, while releasing, at the same time, HS− anions which react with the metallic Ag [11], forming a heterostructure composed of MoS2 and Ag2S (hereafter MoS2/Ag2S/Ag-DVD). The two sulphides produced a composite with a type II p-n junction on a highly conductive material like Ag that is able to boost the PEC-HER activity [12]
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