Lanthanides-based graphene catalysts for high performance hydrogen evolution and oxygen reduction

The design of efficient electrocatalysts for hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) has received enormous consideration due to their effectiveness in modern renewable energy technologies such as fuel cells, electrolyzers, and metal-air batteries. Herein, we present a facile method to fabricate lanthanides (L = La, Eu, Yb)-doped graphene materials as catalyst for the HER and ORR that show desirable electrocatalytic activities as well as long-term stability. The Eu-graphene hybrid has showed unbeatable HER performance such as small values of onset potential (81 mV), overpotential (160 mV), and Tafel slope (52 mV dec(-1)), along with a high exchange current density (7.55 x 10(-6)A cm(-2)). The L-graphenes also exhibit superior electrocatalytic activity for ORR, including small Tafel slopes (96, 66, and 105 mV dec(-1) for La-Gr, Eu-Gr, and Yb-Gr, respectively), positive onset potential (similar to 0.83-0.92V), high electron transfer numbers (similar to 3.84-4.03), and excellent enduring strength, analogous to those of viable Pt/C catalysts. The excellent electrocatalytic performance is attributed to the synergistic effect of abundant edges and doping sites, high electrical conductivity, large active surface areas and fast charge transfer; which renders lanthanide-based graphene hybrids as potentially great candidate for energy conversion systems. (C) 2016 Elsevier Ltd. All rights reserved.