DNA–cisplatin modified single-walled carbon nanotubes for the hydrogen evolution reaction

Abstract

A three-component catalyst material has been developed for the hydrogen evolution reaction (HER) from preformed DNA–cisplatin (cisPt) adducts functionalised on single-walled carbon nanotubes (SWCNTs) under acidic conditions (pH 3). The DNA was used as a scaffold for platinum placement at ultra-low loadings, sourced from the anticancer drug cisplatin (cisPt). The SWCNTs were successfully functionalised with DNA, cisPt, and DNA–cisPt adducts, with each evaluated for their catalytic performance for HER. The dispersion efficiency of the nanotube functionalisation process was optimised as a function of the molar ratio of SWCNT to DNA–cisPt and the sonication time employed, with 1 : 1 and 45 minutes respectively proving optimal. Scanning Transmission Electron Microscopy (STEM) was used to study the resulting changes to the surface morphology for each condition. Overall, the reaction time of the functionalisation process had a greater influence on the resulting platinum nanocluster size than the employed molar ratio of SWCNT to DNA–cisPt. Cyclic voltammetry measurements revealed that the highest mass activity for the HER could be attained through functionalisation of SWCNTs with DNA–cisPt adducts as opposed to with cisPt alone, validating the essential role of DNA in this catalyst design. The activity was found to correlate to the Pt nanocluster size and distribution, which was optimal at a 1 : 1 molar ratio of SWCNT to DNA–cisPt. The importance of the role of both the DNA and the SWCNTs was validated via the mass activity measurements of the Pt, with the performance attained for the three-component SWCNT–DNA–cisPt catalyst (18.4 ± 0.9 mA mg⁻¹_Pt) being higher than that for SWCNT–cisPt (11.9 ± 0.6 mA mg⁻¹_Pt), DNA–cisPt (10.0 ± 0.5 mA mg⁻¹_Pt) and bulk cisPt (7.4 ± 0.4 mA mg⁻¹_Pt). The superior activity is consistent with optimized Pt dispersion in the 1 : 1 SWCNT to DNA–cisPt combination. While the measured nanocluster size of the three-component system (1.23 ± 0.65 nm) is statistically similar to that of SWCNT–cisPt (1.27 ± 0.46 nm) in the absence of DNA, the nucleic acid scaffold appears to promote more effective utilization of Pt active sites.