Hierarchical CoFe-layered double hydroxide and g-C3N4 heterostructures with enhanced bifunctional photo/electrocatalytic activity towards overall water splitting

Abstract

To achieve sustainable and clean energy for the hydrogen economy, developing efficient earth-abundant and non-noble transition metal photo/electrocatalysts toward overall water splitting is highly desirable. In this work, layered double hydroxide (LDH)@g-C₃N₄ composites with hierarchical flower-like micro/nanosheets and a high surface area have been synthesized by a solvothermal method. HRTEM images exhibit that the surface of the g-C₃N₄ nanosheets is highly orientated with the main exposure of the (002) plane. Compared with pristine CoFe-LDH, the hierarchical nanocomposite presents an excellent and stable elecrocatalytic performance in 1.0 M KOH, with a small Tafel slope of 58 mV dec⁻¹ and an overpotential of about 275 mV at a current density of 10 mA cm⁻². Simultaneously, CoFe-LDH@g-C₃N₄ exhibits an exceptional performance for the HER in 1.0 M KOH electrolyte, with an overpotential of 417 mV at a current density of 10 mA cm⁻² and a small Tafel slope of 77 mV dec⁻¹. Therefore, this work not only accomplishes improved catalytic activity of CoFe-LDH by the introduction of g-C₃N₄ nanosheets, but also provides an insight into the correlation between hierarchical flower-like morphologies and photo/electrochemical catalytic activity for overall water splitting.