C≡N vacancy engineering of Prussian blue analogs for the advanced oxygen evolution reaction

Hydrogen production by electrocatalytic water splitting suffers from the sluggish kinetics of the oxygen evolution reaction (OER) and large power consumption and hence, efficient OER electrocatalysts are required to enhance the energy conversion efficiency. Vacancies can create active unsaturated coordination, regulate the electronic structure, and enhance the charge transfer efficiency to improve both the intrinsic and extrinsic catalytic activities. This work aims to construct an efficient OER electrocatalyst through precise control of the C≡N vacancies (VC≡N) in NiFe- and NiCo-Prussian blue analogs (PBAs) leading to outstanding OER characteristics and improved energy conversion efficiency. The amount of VC≡N has been regulated precisely via thermal treatment. The electronic interactions occur between Ni and Fe sites during the introduction of VC≡N. As a result, the synergistic effects of Ni-Fe electronic interactions and VC≡N lead to outstanding OER characteristics such as a small overpotential of 270 mV to achieve a high current density of 50 mA cm−2 as well as excellent stability over 80 h, which are better than those of the pristine PBAs electrocatalyst. The results demonstrate a precise strategy to produce VC≡N in PBAs-based electrocatalysts for advanced OER and efficient hydrogen production.