Silicon Microwire Arrays Decorated with Amorphous Heterometal-doped Molybdenum Sulfide for Water Photoelectrolysis

doi:10.1016/j.nanoen.2016.12.045

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Title:	Silicon Microwire Arrays Decorated with Amorphous Heterometal-doped Molybdenum Sulfide for Water Photoelectrolysis
Authors:	Chen, C. J.;Yang, K. C.;Liu, C. W.;Lu, Y. R.;Dong, C. L.;Wei, D. H.;Hu, S. F.;Liu, R. S.
Keywords:	Water splitting;Co-catalyst;Molybdenum sulfide;Silicon microwire array;Solar hydrogen evolution
Date:	2017-02
Issue Date:	2020-07-06 12:10:33 (UTC+8)
Publisher:	Elsevier BV
Abstract:	Silicon is a promising photocathode material for solar hydrogen evolution because of its small band gap, negative conduction band position, and ideal theoretical current density. In this study, p-type Si microwire (p-Si MW) arrays were prepared as photocathodes because of the large surface area and high light-harvesting capability. However, Si MWs suffered from low photocatalytic activity because of slow photo-induced carriers during driving of water-splitting reaction. Therefore, molybdenum sulfide (MoS2) with appropriate band alignment with p-Si material was employed for surface modification to function as a co-catalyst for collecting photo-generated minority carriers and reducing recombination possibility. The onset potential and current density at 0 V versus reversible hydrogen electrode (RHE) of Si@MoS2 MWs were +0.122 V and −8.41 mA cm−2. Heterometal atoms were employed to dope MoS2 co-catalyst and expose more sulfur-terminated active sites to further boost photoelectrochemical performance. Optimal activity of Si@MMoSx (M = Fe, Co, Ni) was achieved by doping Co heteroatoms, and its turn-on voltage and photocurrent density at 0 V (vs. RHE) were respectively increased to +0.192 V and −17.2 mA cm−2. X-ray absorption spectroscopy was applied to demonstrate that Fe ions of FeMoSx were dichalcogenide materials, forming a composite with MoS2 and contributing better photoelectrolytic efficiency. By contrast, two-valent heteroatoms of CoMoSx and NiMoSx substituted the Mo4+ ions in MoS2. For charge compensation, more defects and edges were revealed as active sites of solar hydrogen production by adding Co or Ni dopants in MoS2 co-catalyst, which led to lower overpotential.
Relation:	Nano Energy 32, p.422-432
DOI:	10.1016/j.nanoen.2016.12.045
Appears in Collections:	[Graduate Institute & Department of Physics] Journal Article

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