Stainless steel mesh-based CoSe/Ni3Se4 heterostructure for efficient electrocatalytic overall water splitting

The construction of high-efficiency bifunctional electrocatalysts is still a main challenge for hydrogen production from water splitting, in which comprehensive structure regulation plays a key role for synergistically boosting the intrinsic activity and charge collection. Here, we used a two-step hydrothermal method for construction of an interjaculated CoSe/Ni3Se4 heterostructure from NiCo LDH nanosheets grown on stainless steel (SS) meshes as bifunctional electrocatalysts for overall water splitting. The SS meshes containing Fe and Ni act as an excellent 3D scaffold for catalyst growth and charge collection. The SS@CoSe/Ni3Se4 composite exhibits outstanding electrocatalytic performances with low overpotentials of 97 mV for hydrogen evolution and 230 mV for oxygen evolution to reach a current density of 10 mA cm−2, respectively. Moreover, by using SS@CoSe/Ni3Se4 as both the cathode and anode, the assembled electrolyze only required 1.55 V to reach 10 mA cm−2 for overall water splitting. The outstanding performance of SS@CoSe/Ni3Se4 benefits from the synergy between excellent charge collection capability of SS meshes and the abundant active sites at the CoSe/Ni3Se4 heterointerface formed with the in-situ conversion of NiCo LDH nanosheets. Electrochemical active surface area and impedance spectrum indicate that the CoSe/Ni3Se4 loaded on SS has the most abundant electrochemically active sites and the smallest electrochemical resistance, thereby exposing more active sites and enhancing the charge transfer to promote the catalytic activity. By integrating the delicate nanoscale heterostructure engineering with the microscale SS mesh scaffold, our work provides a new perspective for the preparation of high-performance and cheap electrocatalysts that are easy to be integrated with industrial applications.