Construction of efficient Pb(II) carboxylate catalysts for Oxygen and Hydrogen Evolution Reactions

Abstract

The development of cost-effective and efficient electrocatalysts can solve the problem in the production of energy via water splitting reactions. In this work, we focused on two lead-based coordination polymers (CPs) {[Pb2(TPBN)(HBTC)2]2⸱5H2O}n (CP1), and {[Pb2(TPBN)(NDC)2].H2O}n (CP2) that are synthesized by the self-assembly method at room temperature in good yields. Two dimensional structures of CP1 and CP2 were determined by the single crystal X-ray diffraction. Their phase purity and thermal stability were reconfirmed by powder diffraction and TGA analysis, respectively. In addition to this, Hirshfeld surface analysis of CP1 and CP2 also exhibits the key differences in the intermolecular interactions of both the CPs. Both CP1 and CP2 were employed for the HER and OER. It has been found that the change in the carboxylate from BTC to NDC resulted in better electrocatalytic activity towards water splitting reaction. This may be attributed to the presence of more π character in NDC as compared to BTC which makes the electron flow much easier for the HER process. CP1 and CP2 shows an overpotential values of 580 mV, and 550 mV, respectively, in 1 M H2SO4 to reach 10 mA cm−2 current density with Tafel slope of 31 mV dec−1, and 25 mV dec−1, respectively. For the OER process, CP1 and CP2 exhibit an overpotential of 590 mV and 470 mV, respectively, in 1 M KOH at a current density of 50 mA cm−2 with Tafel slope values of 56 mV dec−1, and 81 mV dec−1, respectively. Turnover frequency (TOF) of CP1 and CP2 as 1.05 s−1 and 3.21 s−1 for OER and 1.97 s−1 and 9.65 s−1, for HER, respectively.These results indicate that both CPs can act as highly efficient electrocatalysts for the clean energy production.