Ultrathin Metal Silicate Hydroxide Nanosheets with Moderate Metal–Oxygen Covalency Enables Efficient Oxygen Evolution

Abstract

Exploring efficient, cost-effective, and durable electrocatalysts for electrochemical oxygen evolution reaction (OER) is pivotal for the large-scale application of water electrolysis. Recent advance has demonstrated that the activity of electrocatalysts exhibits a strong dependence on the surface electronic structure. Herein, a series of ultrathin metal silicate hydroxide nanosheets (UMSHNs) M3Si2O5(OH)4 (M = Fe, Co, and Ni) synthesized without surfactant are introduced as highly active OER electrocatalysts. Cobalt silicate hydroxide nanosheets show an optimal OER activity with overpotentials of 287 and 358 mV at 1 and 10 mA cm−2, respectively. Combining experimental and theoretical studies, it is found that the OER activity of UMSHNs is dominated by the metal–oxygen covalency (MOC). High OER activity can be achieved by having a moderate MOC as reflected by a σ*-orbital (eg) filling near unity and moderate [3d]/[2p] ratio. Moreover, the UMSHNs exhibit favorable chemical stability under oxidation potential. This contribution provides a scientific guidance for further development of active metal silicate hydroxide catalysts.