Active-Site-Enriched Iron-Doped Nickel/Cobalt Hydroxide Nanosheets for Enhanced Oxygen Evolution Reaction

Highly active, durable, and inexpensive nanostructured catalysts are crucial for achieving efficient and economical electrochemical water splitting. However, developing efficient approaches to further improve the catalytic ability of the well-defined nanostructured catalysts is still a big challenge. Herein, we report a facile and universal cation-exchange process for synthesizing Fe-doped Ni(OH)2 and Co(OH)2 nanosheets with enriched active sites toward enhanced oxygen evolution reaction (OER). In comparison with typical NiFe layered double hydroxide (LDH) nanosteets prepared by the conventional one-pot method, Fe-doped Ni(OH)2 nanosheets evolving from Ni(OH)2 via an Fe3+/Ni2+ cation-exchange process possess nanoporous surfaces with abundant defects. Accordingly, Fe-doped Ni(OH)2 nanosheets exhibit higher electrochemical active surface area (ECSA) and improved surface wettability in comparison to NiFe LDH nanosheets and deliver significantly enhanced catalytic activity over NiFe LDH. Specifically, a low overpotential of only 245 mV is required to reach a current density of 10 mA cm-2 for Ni0.83Fe0.17(OH)2 nanosheets with a low Tafel slope of 61 mV dec-1, which is greatly decreased in comparison with those of NiFe LDH (310 mV and 78 mV dec-1). Additionally, this cation-exchange process is successfully extended to prepare Fe-doped Co(OH)2 nanosheets with improved catalytic activity for oxygen evolution. The results suggest that this cation-exchange process should have great potential in the rational design of defect-enriched catalysts toward high-performance electrocatalysis.