Modulating surface segregation of Ni2P-Ru2P/CCG nanoparticles for boosting hydrogen evolution reaction in pH-universal

Transition metal phosphides with high catalytic activity and durability for the hydrogen evolution reaction (HER) are promising candidates. Herein, we synthesized various Ni2P-Ru2P nano catalysts with different Ni/Ru ratio supported on chemically converted graphene (CCG) under 10 vol% H-2/Ar-2 atmosphere. The average size of Ni2P-Ru2P nanoparticles monotonously increases from 2.98 nm to 6.40 nm with the increase of reduction temperature from 500 degrees Cto 800 degrees C. Meanwhile, the ratio of Ru/Ni is also monotonically increase from 0.67 to 0.85 according to the X-ray photoelectron spectroscopy, suggesting the segregation of Ni to the surface. The Ni2P-Ru2P/CCG-800 shows the best performance for HER with low overpotentials of 21.83 mV (1 M KOH), 113.38 mV (1 M PBS) and 49.42 mV (0.5 M H2SO4), when the current density reaches 10 mA cm(-2). Besides, its Tafel slope of Ni2P-Ru2P/CCG-800 is 56.92 mV dec(-1) in 1 M KOH (67.85 mV dec(-1) in 1 M PBS, 45.98 mV dec(-1) in 0.5 M H2SO4). The superior HER activity of Ni2P-Ru2P/CCG-800 can be ascribed to the synergistic effect of Ni and Ru near surface. Density functional theory calculations reveal that the introduction of Ni atom into Ru2P accelerates H2O dissociation at Ru sites and H-2 formation at Ni sites.

Automated summary

Transition metal phosphides, particularly Ni2P-Ru2P catalysts, have shown high catalytic activity for the hydrogen evolution reaction (HER) with promising durability. The Ni2P-Ru2P/CCG-800 catalyst exhibits superior performance for HER due to the synergistic effect of Ni and Ru near the surface, leading to efficient H2O dissociation and H-2 formation.