Uniform OsP2 nanoparticles anchored on N,P-doped carbon: A new electrocatalyst with enhanced activity for hydrogen generation at all pH values

Exploring hydrogen evolution reaction (HER) catalysts with high activity over the wide range of pH (0-14) is of great significance, but extremely challenging. Noble-metal phosphides are newly developed electrocatalysts that can function well at all pH values. Despite the pivotal role Os compounds have played in the progress of catalytic chemistry, its phosphides have never been demonstrated to mediate the HER. Herein, we report a new OsP2-based electrocatalyst that consists of fine OsP2 nanoparticles (NPs) dispersed over N,P co-doped carbon film (OsP2@NPC) using a combination of template and pyrolysis methods. Impressively, this novel OsP2@NPC exhibits improved HER activity compared with Os@NPC, with small overpotentials of 38, 54, and 70 mV at 10 mA cm(-2) and Tafel slopes of 40, 82, and 67 mV dec(-1), and better stability than commercial Pt/C in 0.5 M H2SO4, 1.0 M phosphate buffer solution, and 1.0 M KOH, respectively. The experimental and computational results indicate that both the unique structure of the porous interconnected network and the interaction between OsP2 NPs and NPC contribute to the robust activity. Meanwhile, the similar to 40 mV dec(-1) Tafel slope in 0.5 M H2SO4 and the density functional theory (DFT) calculations suggest the predominant Volmer-Heyrovsky mechanism for the OsP2-catalyzed HER, with electrochemical desorption of hydrogen as the rate-limiting step. This new electrocatalyst is expected to enlarge the growing family of transition metal phosphides for the HER. (C) 2019 Elsevier Inc. All rights reserved.