DNA-based low resistance palladium nano-spheres for effective hydrogen evolution reaction

Abstract

The emergence of green biomolecules in the field of nanomaterial (NM) synthesis effectively supports the development of various size- and shape-controlled NMs for numerous applications. Accordingly, deoxyribonucleic acid (DNA) is a polymeric biomolecule that can act as a stabilizer for the fabrication of NMs due to its unique self-assembling quality. However, the use of DNA-based NMs for electrocatalytic water splitting has not been explored much although it can reduce the metal loading significantly, by as much as 20 times the commercial loading (0.205 mg cm⁻²). In this work, we developed palladium nano-spheres (Pd NSs) loaded on DNA as an alternative for the state-of-catalyst Pt for the electrocatalytic hydrogen evolution reaction (HER) in acidic condition. Here, the DNA plays multiple roles including stabilizing Pd NSs in aqueous medium, as a structure-directing agent and binder in electrochemical studies, avoiding the use of external binders. In the electrochemical studies, Pd/DNA (0.06 M) showed excellent activity and low resistivity towards HER in 0.5 M H₂SO₄. To reach a current density of 10 mA cm⁻², it required the overpotential of just 79 mV with good kinetics observed with its low Tafel value of 31 mV dec⁻¹ (0.06 M). Also, the stability of Pd/DNA was verified in a chronoamperometric study carried out for 12 h, which results no loss in intrinsic activity of the catalyst. In the electrochemical impedance spectroscopic (EIS) analysis, Pd/DNA (0.06 M) showed very low resistivity of 1.7 Ω. Additionally, the turnover frequency (TOF) was calculated at 200 mV to be 0.055 s⁻¹ and the high mass activity of 4814 A g⁻¹ was observed at the overpotential of 150 mV for Pd/DNA (0.06 M) with the ultralow loading of 0.01 mg cm⁻². Hence, DNA-based NMs can be developed as efficient electrocatalysts towards H₂ fuel production technology in the near future.