Exceptional Performance for Oxygen Reduction Reaction over Transition-Metal Doped PtNi Octahedra
Huang, X. ; Zhao, Z. ; Cao, L. ; Chen, Y. ; Zhu, E. ; Lin, Z. ; Li, M. ; Yan, A. ; Zettl, A. ; Wang, Y. M. ; Duan, X. ; Mueller, T. ; Huang, Y.
Science 348, 1230-1234 (2015)
Bimetallic PtNi structures represent an emerging class of newly discovered electrocatalysts that are expected to exhibit exciting oxygen reduction reaction (ORR) activity. Despite considerable efforts, the limitations in terms of catalytic activity and durability have largely hindered the practical applications of PtNi nanocrystals. Here we report a surface engineering strategy based on the incorporation of various transition metal dopants onto the surface of dispersive PtNi/C octahedra (termed as M‐PtNi/C, M=V, Cr, Mn, Fe, Co, Mo, W and Re). We demonstrate that these surface engineered PtNi catalysts exhibit impressive activity in the ORR, and their performance is highly dopant‐dependent with Mo showing the best performance to date. Mo‐PtNi/C shows simultaneously the highest specific activities of 10.3 mA/cm2 to date and the unprecedented mass activity of 6.98 A/mgPt, approaching two orders of magnitude higher (81 and 73‐fold enhancement in mass and specific activities, respectively) than that of the state‐of‐the‐art commercial Pt/C catalyst (Alfa Aesar, 20 wt% Pt, 0.127 mA/cm2 and 0.096 A/mgPt ). Significantly the Mo‐doped PtNi/C also exhibit outstanding durability showing negligible changes in the activity over the course of potential sweeps, in contrast to the obvious losses observed in its undoped PtNi/C counterpart. Theoretical calculations suggest Mo prefers subsurface positions near the particle edges in vacuum and surface vertex / edge sites in oxidizing conditions, and it plays important roles in enhancing both the performance and the stability of the PtNi catalyst. Our studies open up exciting opportunities in catalyst design through fine tuning the chemical and electronic properties of the surface layer to achieve optimal performance which can impact broad catalytic applications including fuel cells, batteries and chemical production.