Self-directed hierarchical Cu3(PO4)2/Cu-BDC nanosheets array based on copper foam as an efficient and durable electrocatalyst for overall water splitting

Highlights: • Cu₃(PO₄)₂/Cu-BDC foam electrocatalysts with different morphologies are synthesized. • Optimized Cu₃(PO₄)₂/Cu-BDC foam shows overpotentials of 241 mV and 145 mV for OER and HER at 10 mA cm⁻² in 1 M KOH. • Cu₃(PO₄)₂/Cu-BDC foam shows high and durable activity for overall water splitting. • This work presents a facile way to develop 2D MOF as direct electrocatalyst. -- Abstract: Overall water splitting is a promising approach to produce sustainable energy. For the practical application of overall water splitting, easy-to-operate catalysts as well as catalysis of oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in identical electrolyte are critical. Herein, we report a high-efficiency electrocatalyst with hierarchical Cu₃(PO₄)₂/copper metal-organic framework (Cu₃(PO₄)₂/Cu-BDC) nanosheets array supported by copper foam. In this work, Cu₃(PO₄)₂ nanosheets are firstly prepared on the surface of copper foam by means of in-situ growth method. Subsequently, Cu-BDC nanosheets array are synthesized via self-directed growth. In each step of this reaction, copper ions are all released from the substrate, which is facile and controllable. The effect of reaction temperature and reaction time on the morphology of Cu-BDC was discussed in detail. The optimal electrocatalyst (Cu₃(PO₄)₂/Cu-BDC-150-6 foam) exhibited excellent electrocatalytic performance for OER and HER in 1 M KOH, delivering a current density of 10 mA cm⁻² at low overpotential of 241 mV and 145 mV, respectively. Using Cu₃(PO₄)₂/Cu-BDC-150-6 foams as both anode and cathode electrocatalyst in 1 M KOH, a current density of 10 mA cm⁻² was achieved at a low cell voltage of 1.56 V. In addition, the Cu₃(PO₄)₂/Cu-BDC foam showed excellent catalytic stability and thus will be promising for application in industrial overall water splitting.