Sulfur vacancies engineered self-supported Co3S4 nanoflowers as an efficient bifunctional catalyst for electrochemical water splitting

Optimizing electron distribution and expediting electron transfer efficiency are two of the major strategies for developing non-noble difunctional catalysts in the overall water splitting (OWS). Defect engineering is an emerging technology in catalysis field, and introducing vacancy defects into the crystal structure can promote the electrocatalytic water splitting performance. Hence, the 3D spinel-structured Co3O4 or Co3S4 nanoflowers with anion vacancy are synthesized on nickel foam (Vo-Co3O4@NF, Vs-Co3S4@NF) and compared as electrodes for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Notably, Vs-Co3S4@NF requires merely overpotential of 245 mV to reach 100 mA·cm−2 for OER, 45 mV to reach 10 mA·cm−2 for HER, which exhibit an excellent catalytic activity in alkaline electrolyte. In addition, using Vs-Co3S4@NF as bifunctional catalyst to drive OWS, the current density of 20 mA·cm−2 is reached with a cell voltage of only 1.53 V, along with good stability for successive 200 h test.