A pillar-layered binuclear 3D cobalt(ii) coordination polymer as an electrocatalyst for overall water splitting and as a chemosensor for Cr(vi) anion detection

Abstract

Based on binuclear {Co₂(COO)₄} SBUs, a pillar-layered 3D (4,6)-connected {4⁴·6¹⁰·8}{4⁴·6²} fsc net, was constructed via a mixed ligand strategy. Electrocatalytic research showed that the 1@NF electrode shows better OER performance than RuO₂@NF, reaching a current density of 10 mA cm⁻² when the overpotential of OER is was 370 mV in a 1.0 M KOH electrolyte, with a Tafel slope of 15.6 mV dec⁻¹. Moreover, the overpotential of HER of 246 mV at a current density of 10 mA cm⁻², with a Tafel slope of 23.1 mV dec⁻¹, also suggested that the HER performance of 1@NF is better than that of Pt/C@NF. The durability test manifested that the electrocatalytic activity of 1@NF can be maintained at 92.8% after 12 h in 1.0 M KOH. Besides, luminescence sensing experiments reveal that 1 is an efficient chemosensor, which exhibits high sensitivity, high selectivity, and good recyclability towards the detection of Cr(VI) anions in water even in the presence of other interfering anions. The detection limits are as low as 3.42 × 10⁻⁶ M for the CrO₄²⁻ anion and 2.96 × 10⁻⁷ M for the Cr₂O₇²⁻ anion. The electrocatalytic and luminescence sensing properties show that 1 is an excellent candidate for multifunctional materials in energy conversion and pollutant detection.