Tuning the electronic structure of layered Co-based serpentine nanosheets for efficient oxygen evolution reaction

Abstract

As low-cost and abundant catalysts, layered cobalt-based hydroxides that are composed of Co–OH octahedron slabs have promising prospect in electrocatalytic oxygen evolution reaction (OER). However, the layered hydrotalcite and brucite structure hydroxides usually possess inferior activity and poor stability. Herein, we developed layered cobalt-based serpentine nanosheets with a tuned electronic structure and stable active phase by using Ge–O and Si–O tetrahedron slabs to coordinate with Co–(O)OH octahedron slabs for efficient OER. Theoretical calculations reveal that Co–(O)OH octahedron slabs that coordinate with Ge–O tetrahedron slabs possess an optimal electronic structure and smaller reaction energy barriers for OER. Inspired by the calculations, the layered Co3Ge2O5(OH)4, Co3Si2O5(OH)4 and brucite Co(OH)2 nanosheets are synthesized. The coordination of Ge–O tetrahedron decreases the size and crystallinity of Co–(O)OH octahedron slabs, simultaneously enhancing the stability of Co–(O)OH octahedron slabs during OER, thus improving the activity and stability. As a result, Co3Ge2O5(OH)4 nanosheets present an outstanding OER activity (overpotential is 287 mV at 10 mA cm–1, lower than that of Co3Si2O5(OH)4 and Co(OH)2) and a remarkable stability for water splitting (working continuously more than 100 h without decay, much higher than that of Co(OH)2 (<36 h)). The solar driven water splitting process achieves a high Faradaic efficiency of 98.8%, and the solar-to-hydrogen energy conversion efficiency is 7.2%. Such a strategy of tuning the electronic structure of Co–O(OH) octahedron by coordination with a Ge–O tetrahedron offers an effective method for designing highly efficient Co-based electrocatalysts.