Experimental insights and DFT analysis of metal-free DNA nanocatalyst with enhanced hydrogen evolution via phosphate-mediated proton acceptance

Abstract

Although platinum is widely recognized as a benchmark catalyst for realizing highly efficient hydrogen evolution reactions, its practical application is hindered by the scarcity and high cost of Pt. In this regard, metal-free organic catalysts are considered vital alternatives for producing H2 in green energy applications. In this study, we prepare binder-free electrocatalysts by combining salmon DNA with activated carbon (AC) (cacao pods) for H2 production. The AC-DNA (0.025 M DNA) sample requires an overpotential (h) of 106 mV to generate a current density of 10 mA cm-2, with a Tafel slope of 96 mV dec-1, in 0.5 M H2SO4. The phosphate-mediated proton acceptance of DNA facilitates the hydrogen evolution reaction (HER) in the presence of AC, resulting in excellent durability over 40 h at 10 mA cm-2 (h10 = 106 mV) and 100 mA cm-2 (h100 = 271 mV). In addition, the electro-catalyst exhibits a faradaic efficiency of 96.9%. The proton acceptance facilitated by the phosphate group in DNA achieves outstanding performance with a turnover frequency of 2.76 s-1 and an exchange current density of 2.08 x 10-3 A cm-2. Theoretical calculations support the in-depth H2 evolution mechanism at the DNA-anchored AC samples via proton capturing of phosphate groups during water splitting.(c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.