Direct Synthesis of Molybdenum Phosphide Nanorods on Silicon Using Graphene at the Heterointerface for Efficient Photoelectrochemical Water Reduction
Corresponding Author: Ho Won Jang
Nano-Micro Letters,
Vol. 13 (2021), Article Number: 81
Abstract
Transition metal phosphides (TMPs) and transition metal dichalcogenides (TMDs) have been widely investigated as photoelectrochemical (PEC) catalysts for hydrogen evolution reaction (HER). Using high-temperature processes to get crystallized compounds with large-area uniformity, it is still challenging to directly synthesize these catalysts on silicon photocathodes due to chemical incompatibility at the heterointerface. Here, a graphene interlayer is applied between p-Si and MoP nanorods to enable fully engineered interfaces without forming a metallic secondary compound that absorbs a parasitic light and provides an inefficient electron path for hydrogen evolution. Furthermore, the graphene facilitates the photogenerated electrons to rapidly transfer by creating Mo-O-C covalent bondings and energetically favorable band bending. With a bridging role of graphene, numerous active sites and anti-reflectance of MoP nanorods lead to significantly improved PEC-HER performance with a high photocurrent density of 21.8 mA cm−2 at 0 V versus RHE and high stability. Besides, low dependence on pH and temperature is observed with MoP nanorods incorporated photocathodes, which is desirable for practical use as a part of PEC cells. These results indicate that the direct synthesis of TMPs and TMDs enabled by graphene interlayer is a new promising way to fabricate Si-based photocathodes with high-quality interfaces and superior HER performance.
Highlights:
1 MoP nanorod-array catalysts were directly synthesized on graphene passivated silicon photocathodes without secondary phase.
2 Mo-O-C covalent bondings and energy band bending at heterointerfaces facilitate the electron transfer to the reaction sites.
3 Numerous catalytic sites and drastically enhanced anti-reflectance of MoP nanorods contribute to the high solar energy conversion efficiency.
Keywords
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D.M. Andoshe, S. Choi, Y.-S. Shim, S.H. Lee, Y. Kim et al., A wafer-scale antireflective protection layer of solution-processed TiO2 nanorods for high performance silicon-based water splitting photocathodes. J. Mater. Chem. A 4, 9477–9485 (2016). https://doi.org/10.1039/C6TA02987F
S. Deng, K. Zhang, D. Xie, Y. Zhang, Y. Zhang et al., High-index-faceted Ni3S2 branch arrays as bifunctional electrocatalysts for efficient water splitting. Nano-Micro Lett. 11, 12 (2019). https://doi.org/10.1007/s40820-019-0242-8
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