Nickelo-Sulfurization of DNA Leads to an Efficient Alkaline Water Oxidation Electrocatalyst with Low Ni Quantity

Nonprecious metals based electrocatalysts are highly anticipated in electrocatalytic water splitting as the increasing energy demand can be handled by large scale H₂ production with minimum expenses. Herein, a facile and faster nickelo-sulfurization of DNA in ambient conditions has been developed that resulted in NiS anchored wirelike assemblies of DNA. The effect of DNA concentration on material stability and electrocatalytic activity was studied, and it was found that, with DNA to Ni²⁺ ratios of 0.048 and 0.072 M, the NiS anchored DNA colloidal solutions were stable. In addition, it was found that NiS(0.048) with a relatively lower DNA concentration showed better oxygen evolution reaction (OER) activity than NiS(0.072). Overpotentials of 352 and 401 mV were required by NiS(0.048) and NiS(0.072) to deliver a current density of 10 mA cm^-2 even with an ultralow quantity of NiS(0.0123 mg cm^-2) in both. The same trend was reflected in the Tafel slopes of NiS(0.048) and NiS(0.072) which showed 58.6 and 112.4 mV dec^-1 indicating that the optimum ratio for better OER activity is 0.048. In this study, DNA plays a versatile role such as acting as a stabilizer, scaffold, and a microstructural stage for NiS in solution. Moreover, DNA also acts as an efficient binder and as a conductor of both ions and electrons in its OER activity trend. The proposed method can be used for preparing stable colloids of other metal sulfide based nano-electro-catalysts and can directly be employed for water oxidation in alkaline conditions.