Anion substitution-induced CuCoSe hollow nanotubes as multifunctional electrode materials for supercapacitors and overall water splitting

Developing highly efficient non-noble-metal electrode materials for energy storage and conversion is crucial for advancing sustainable and renewable energy. In this study, a facile and effective anion substitution-induced approach was designed to synthesize uniform CuCoSe hollow nanotubes. Impressively, the obtained CuCoSe hollow nanotubes reach an exceptional mass-specific capacitance of 2,853.1F·g−1 at 10 A·g−1, with intriguing rate capability and desirable capacitance retention after 5,000 cycles. The assembled CuCoSe//CuCoSe symmetrical supercapacitor device exhibits a high energy density of 218.9 Wh·kg−1 at a power density of 4,000 kW·kg−1. Furthermore, the CuCoSe hollow nanotubes show exceptional performances in both oxygen and hydrogen evolution reactions, necessitating low overpotentials of 94.4 and 33.4 mV at 10 mA·cm−2. When used as a bifunctional electrocatalyst, the assembled CuCoSe||CuCoSe electrolytic cell affords a low cell voltage of 1.40 V to drive 10 mA·cm−2, significantly superior to other commercial electrolyzers and most reported bifunctional electrocatalysts. Experimental and density functional theory calculations suggest that selenides substituted CuCo-layered double hydroxides can greatly enhance the electrochemical performances. This work will be beneficial for the design of the next generation of energy storage and conversion technologies.