Ni(II) and Cu(II) grafted porphyrin-pyrene based conjugated microporous polymers as bifunctional electrocatalysts for overall water splitting

The development of a robust, sustainable and inexpensive bifunctional material for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) via electrochemical overall water splitting is very challenging and essential for energy generation and conversion processes. Herein, we have developed two 3d transition metals Ni (II) and Cu(II)-porphyrin based conjugated microporous polymeric electrocatalysts having high specific surface areas (1400 and 1350 m2g- 1). Both catalysts showed good performance towards overall water splitting under alkaline pH conditions. These metal-coordinated porous polymers Ni-Por-Py and Cu-Por-Py are well character-ized using different analytical instruments. Ni-Por-Py and Cu-Por-Py displayed a low overpotential of 213 mV and 250 mV, respectively to attend a current density of 10 mA/cm2 for HER using Ni-foam as substrate. The OER activity under alkaline condition with an overpotentials of 164 and 170 mV for Ni-Por-Py and Cu-Por-Py, respectively were achieved to drive a current density of 10 mA/cm2 under similar conditions. The excellent electrocatalytic activity of Ni-Por-Py and Cu-Por-Py could be attributed to the presence of transition metal co-ordinated porphyrin building blocks in the pi-conjugated polymer skeletons, which facilitates the electron transfer processes along with inherent microporosity and high surface areas.