High performance of homo-metallic tetracyanonickelate based coordination polymer towards water oxidation electrocatalysis

Abstract

The search of proficient, copious, economical and robust electrocatalyst is of prime prerequisite. Recently, the usage of cyanometallate based coordination polymers as electrocatalysts for water oxidation has acquired an expanding measure of attraction attributable to their high surface area and stability. In this study, a homo-metallic Ni based cyanometallate coordination polymer [{NiII(4,4ʹ-dipy)4}{Ni(CN)4}]n·(4,4ʹ-dipy)·3H2O·C2H6O2 (1) (4,4ʹ-dipy = 1,3-di(4-pyridyl)propane) is presented as an efficacious and robust electrocatalyst towards water oxidation reaction at pH = 13. The inimitable 3-D zig-zag topology of 1 has directed to ~28 times enhanced surface concentration (Γ) i.e. 39.5 nmol/cm2 as compared to the reported CoFe(CN)6 (Γ = 1.4 ± 0.2 nmol/cm2). The 1 presents a TOF of 0.25 s−1 at an overpotential (η) of 381 mV (vs. RHE) which is much larger than those reported for other cyanide bridged and Ni based coordination polymers for instance: CoFe(CN)6 (TOF = 2 × 10−3 s−1, η = 300 mV), CoFe(CN)5-PVP (TOF = 2 × 10−3 s−1, η = 284 mV), Codca2 (TOF = 2 × 10−3 s−1, η = 358 mV), Ni-UMOFNs (TOF = 0.18 s−1, η = 300 mV), bulk NiCo-MOFs (TOF = 0.15 s−1, η = 300 mV) and Ni-MOF/NF (TOF = 0.25 s−1, η = 400 mV).The overpotential (η) of of 315 mV is required to produce a current density (J) of 1 mA/cm2. Controlled potential electrolysis (CPE), PXRD and FT-IR experiments confirm that 1 remains active and chemically integrate over a 36,000 s test reaction. The outcomes of the comprehensive electrochemical investigations are prophesied to direct the imminent development in designing noble metal free, efficient and low-priced electrocatalysts for oxygen evolution reaction.