Self-assembled IrO₂ nanoparticles on a DNA scaffold with enhanced catalytic and oxygen evolution reaction (OER) activities

Self-assembled IrO₂ nanoparticles (NPs) of two distinct chain-like morphologies were successfully synthesized on a DNA scaffold at room temperature by the reduction of a hydrated iridium salt precursor under continuous stirring. Different morphologies of IrO₂ NPs were formed by tuning the concentration ratio of DNA to iridium salt solution. The probable growth mechanisms of the IrO₂ NPs on DNA were elaborated. The potentiality of the DNA@IrO₂ NPs was tested in two important applications, one as a catalyst for the oxidation of 2-propanol to acetone and the other as an electrocatalyst for the oxygen evolution reaction (OER). The catalysis study revealed that the reaction completed in a short time with a higher product yield. The self-assembled, chain-like IrO₂ NPs were screened as a potential electrocatalyst for the OER study that required an overpotential of 312 mV, to produce anodic current densities of 10 mA cm^-2 (0.1 M NaOH) with a turnover frequency (TOF) of 7.88 s^-1. This is one among the lowest oxygen overpotentials reported for IrO₂ alone. The presence of phosphorous on the DNA-phosphate backbone on the IrO₂ NP surface is the key factor for the enhancement of OER activity. Though the conductivity of DNA@IrO₂ NPs modified GC is lower than that of bare GC, the synergism assisted enhancement by PO₄^3- from DNA in the overall OER activity makes it worthier still. The overall processes are simple, less time consuming, reproducible, occur at room temperature and can be extended to the synthesis of other important nano-catalysts at a short time scale for their applications in different interdisciplinary fields like organic catalysis and electrocatalysis.