ABSTRACT
Precise adjustment of the metal site structure in single-atom catalysts (SACs) plays a key role in addressing the oxygen evolution reaction (OER). Herein, we report the synthesis of O-doped Ni SACs anchored on porous graphene-like carbon (Ni-O-G) using molten salts (ZnCl2 and NaCl) as templates, in which the unique Ni-O4 structure serves as the active sites. Ni-O-G, with an overpotential of only 238 mV (@ 10 mA cm-2), is one of the more advanced catalysts. An array of characterizations and density functional theory calculations show that the Ni-O4 coordination enables Ni to be closer to the Fermi level compared to traditional Ni-N4, enhancing the electronic metal-support interaction to facilitate OER kinetics. Thus, this work offers an alternative strategy for the structural modulation of Ni SACs and the effect of different coordination elements with the same atomic coordination structure on the intrinsic OER activity.
ABSTRACT
The rational design and preparation of advanced electrocatalysts for the hydrogen evolution reaction (HER) under alkaline conditions is the key to achieving sustainable hydrogen production. Herein, a new type of nitrogen-doped porous carbon nanosheets (NPCN) loaded with platinum group metals (Pd, Pt or Ru) were prepared. The introduction of melamine not only realized the doping of N-species, but also optimized the morphology and surface functional groups of the prepared catalysts. The prepared Pd-NPCN, Pt-NPCN and Ru-NPCN with a metal loading of about 10 wt% showed outstanding HER activity (21, 9 and 11 mv at 10 mA cm-2 current density), small Tafel slopes (49, 30 and 30 mV dec-1) and good stability in 1.0 M KOH. In addition, the mechanism of the introduction of melamine to improve the catalytic performance of HER was also discussed. Therefore, this work provides promising alternatives to traditional Pt-based catalysts, and is instructive for the design of high-efficiency alkaline HER catalysts.
