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Nickel phosphide polymorphs with an active (001) surface as excellent catalysts for water splitting

Since the emergence of hydrogen generation by water-splitting as a core renewable-energy technology, the development of related catalysts with high efficiency, long-term stability, and low cost has been vigorously pursued. We report the temperature-controlled synthesis of two nickel phosphide polymo...

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Published in:CrystEngComm 2019, Vol.21 (7), p.1143-1149
Main Authors: Jung, Chan Su, Park, Kidong, Lee, Yeron, Kwak, In Hye, Kwon, Ik Seon, Kim, Jundong, Seo, Jaemin, Ahn, Jae-Pyoung, Park, Jeunghee
Format: Article
Language:English
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Summary:Since the emergence of hydrogen generation by water-splitting as a core renewable-energy technology, the development of related catalysts with high efficiency, long-term stability, and low cost has been vigorously pursued. We report the temperature-controlled synthesis of two nickel phosphide polymorphs, Ni 2 P and Ni 5 P 4 , by phosphorization of Ni foil or foam using phosphine gas. The hexagonal phase Ni 2 P nanowires and Ni 5 P 4 nanosheets were grown on Ni substrates with vertical alignment, and uniformly exposed active (001) planes. The Ni 5 P 4 nanosheets possess significant stacking faults along the [0001] direction. Both Ni 2 P and Ni 5 P 4 exhibit excellent electrocatalytic activity toward the hydrogen evolution reaction (HER). Their overpotential for 10 mA cm −2 was 0.126 and 0.114 V, and the Tafel slope was 42 and 34 mV dec −1 in 0.5 M H 2 SO 4 electrolyte, respectively. A decrease in HER performance was observed for Ni 5 P 4 , but the change was negligible for Ni 2 P. Strain mapping using a precession-assisted nanobeam electron diffraction technique showed that only Ni 5 P 4 underwent degradation of basal (001) planes during HER, which explains the lower stability of catalytic activity. Furthermore, the Ni 2 P nanowires demonstrated excellent catalytic activity toward overall water splitting, which could be attributed to the stable surface as well as the highly conductive crystal structures. We report the temperature-controlled synthesis of two nickel phosphide polymorphs, Ni 2 P and Ni 5 P 4 , by phosphorization of Ni foil or foams using phosphine gas, and their excellent catalytic activity toward hydrogen evolution reaction.
ISSN:1466-8033
1466-8033
DOI:10.1039/c8ce01884g