Self-supported Co(CO3)0.5(OH)·0.11H2O nanoneedles coated with CoSe2-Ni3Se2 nanoparticles as highly active bifunctional electrocatalyst for overall water splitting

The development of relatively inexpensive and highly active electrocatalyst for water splitting is essential to the energy conversion and sustainable economic improvement. In this work, based on nanostructure engineering, the CoSe 2 -Ni 3 Se 2 nanoparticles coated Co(CO 3 ) 0.5 (OH)·0.11H 2 O nanoneedles supported on the surface of Ni foam (NF) composite (CoSe 2 -Ni 3 Se 2 /NF) had been synthesized by a facile hydrothermal selenization method. Benefiting from the adequate nanostructure and moderate degree of selenization treatment, the obtained sample CoSe 2 -Ni 3 Se 2 /NF-0.4 using 0.4 g Se powder as selenium source shows remarkable electrocatalytic performance and electrochemical stability for either hydrogen evolution reaction (HER) or oxygen evolution reaction (OER). CoSe 2 -Ni 3 Se 2 /NF-0.4 only required 98 mV (vs. RHE) to reach the 10 mA cm −2 for HER and 344 mV (vs. RHE) to reach 100 mA cm −2 for OER in 1.0 M KOH solution. This work provides a simple strategy to controllably synthesize transitional metal diselenium-based electrocatalyst with adjustable amount of active phase, which are very important for the future development of the bifunctional electrocatalyst.