Construction of efficient Pb(ii) carboxylate catalysts for the oxygen and hydrogen evolution reactions†

Abstract

The development of cost-effective and efficient electrocatalysts can solve the problems associated with the production of energy via water-splitting reactions. In this work, we have focused on two lead-based coordination polymers (CPs), namely, {[Pb₂(TPBN)(HBTC)₂]₂·2.5H₂O}_n (CP1) and {[Pb₂(TPBN)(NDC)₂]·H₂O}_n (CP2), that were synthesized by self-assembly method at room temperature in good yields. The two-dimensional structures of CP1 and CP2 were determined by single-crystal X-ray diffraction studies. Their phase purity and thermal stability were confirmed by powder X-ray diffraction and TGA analysis, respectively. In addition to this, Hirshfeld surface analysis of CP1 and CP2 revealed the key differences in their intermolecular interactions. Both CP1 and CP2 were employed for 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 reactions. This may be attributed to the presence of more π character in NDC compared to BTC, which makes the electron flow much easier for HER process. CP1 and CP2 showed overpotential values of −0.58 V and −0.55 V, respectively, in 1 M H₂SO₄ to reach a 10 mA cm⁻² current density with Tafel slopes of 31 mV dec⁻¹ and 25 mV dec⁻¹, respectively. For the OER process, CP1 and CP2 exhibited overpotentials 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 81 mV dec⁻¹ and 56 mV dec⁻¹, respectively. Turnover frequency (TOF) values of CP1 and CP2 were 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 clean energy production.