Yena Kim1 Hye Ryung Byon2

1, RIKEN, Wako, , Japan
2, KAIST, Daejeon, , Korea (the Republic of)

Platinum nanocrystals (Pt NCs) have been widely used as the ideal electrocatalyst for hydrogen evolution reaction (HER). Although non-noble metal catalysts have been extensively developed to reduce the material expense and replace Pt in recent, their catalytic activities have been still far inferior to Pt in acidic media [1]. However, HER performance with Pt catalyst is swiftly decreased for long-time operation. One of the critical reasons for such a poor stability is the weak-binding interaction with carbon electrode, which leads to coalescence, detachment and dissolution of Pt NCs from carbon [2]. Therefore, the rigid immobilization of Pt NCs to electrode is crucial to suppress the loss of active sites and to retain HER activity. Here we develop Pt nanocrystals that are implanted in molybdenum sulfide selenide (MoSSe) alloy layer, and this Pt NCs/MoSSe layers coaxially coat carbon nanotube (CNT) electrode. The MoSSe/CNT was prepared through hydrothermal reaction, and Pt NCs were subsequently synthesized through photochemical reduction reactions. The MoSSe was grown along to the sidewall of CNT with bilayer or trilayer, which may allow for smooth electron transfer in between Pt NCs and CNT electrode. In addition, the attached Pt NCs are uniformly distributed with an average diameter of ~2 nm on the catalyst support of MoSSe. The Pt/MoSSe/CNT shows higher catalytic activity for HER in comparison with commercial Pt/carbon (C) in 0.5 M H2SO4 at 25 oC. When Pt loading is controlled to ~20 wt%, the Pt/MoSSe/CNT shows an onset potential of 21 mV vs RHE, a Tafel slope of 29.7 mV dec−1 and negligible HER activity loss up to 3000 cycles of cyclic voltammetry (-0.3 ~0.7 V vs RHE). By comparison, commercial Pt/C exhibits an onset potential of 35 mV and a significant decrease in HER activity within 3000 cycles. This remarkable HER activity for Pt/MoSSe/CNT may be attributed to modulation of electronic structure of Pt NCs from MoSSe in addition to low electrical resistance of bilyaer/trilayer MoSSe. Besides, the strong attachment of Pt NCs to MoSSe layer, which might be achieved from photochemical reduction process, enhances the stability. In this presentation, I will discuss the structural advantage of Pt/MoSSe/CNT we prepared and the correlated catalytic performance in details.

[1] Adv. Mater. 2017, 29, 1605838.
[2] Topics in Catalysis, 2007, 46, 285–305.