Two-dimensional Co/Ni coordination polymers: structure-activity relationship and bifunctional performance for...

Two two-dimensional layered porous coordination polymers (Co-MOCP and Ni-MOCP) were synthesized via a hydrothermal route. Both materials possess high crystallinity, uniform elemental distribution and excellent structural stability in an alkaline environment. Electrochemical measurements show that Co-MOCP has better bifunctional electrocatalytic performance for the HER and OER, with Tafel slopes of 132.7 mV dec^-1 and 64.96 mV dec^-1, and a double-layer capacitance of 1.849 mF cm^-2. For supercapacitors, Co-MOCP delivers a specific capacitance of 602 F g^-1 at 1 A g^-1 and a capacity retention of 80.1% after 10 000 cycles, outperforming Ni-MOCP in all electrochemical indicators. Frontier molecular orbital calculations indicate that Co-MOCP has a narrow HOMO-LUMO band gap of 0.1463 eV and delocalized orbitals, which facilitate electron transfer and redox reactions. In contrast, Ni-MOCP has a band gap of 0.91 eV with localized orbitals, resulting in restricted charge transport and weak redox activity. This study elucidates the regulatory effect of metal centers on material properties and provides guidance for designing low-cost high-performance multifunctional electrode materials.