Platinum Nanostructure/Nitrogen‐Doped Carbon Hybrid: Enhancing its Base Media HER/HOR Activity through Bi‐functionality of the Catalyst

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The design and synthesis of an active catalyst for the hydrogen evolution reaction/hydrogen oxidation reaction (HER/HOR) are important for the development of hydrogen‐based renewable technologies. The synthesis of a hybrid of platinum nanostructures and nitrogen‐doped carbon [Pt‐(PtOx)‐NSs/C] for HER/HOR applications is reported herein. The HER activity of this Pt‐(PtOx)‐NSs/C catalyst is 4 and 6.5 times better than that of commercial Pt/C in acids and bases, respectively. The catalyst exhibits a current density of 10 mA cm−2 at overpotentials of 5 and 51 mV, with Tafel slopes of 29 and 64 mV dec−1 in 0.5 m H2SO4 and 0.5 m KOH. This catalyst also showed superior HOR activity at all pH values. The HER/HOR activity of Pt‐(PtOx)‐NSs/C and PtOx‐free Pt‐nanostructures on carbon (PtNSs/C) catalysts are comparable in acid. The presence of PtOx in Pt‐(PtOx)‐NSs/C makes this Pt catalyst more HER/HOR‐active in basic media. The activity of the Pt‐(PtOx)‐NSs/C catalyst is fivefold higher than that of the PtNSs/C catalyst in basic medium, although their activity is comparable in acid. The hydrogen‐binding energy and oxophilicity are two equivalent descriptors for HER/HOR in basic media. A bifunctional mechanism for the enhanced alkaline HER/HOR activity of the Pt‐(PtOx)‐NSs/C catalyst is proposed. In the bifunctional Pt‐(PtOx)‐NSs/C catalyst, PtOx provides an active site for OH− adsorption to form OHads, which reacts with hydrogen intermediate (Hads), present at neighbouring Pt sites to form H2O; this leads to enhancement of the HOR activity in basic medium. This work may provide an opportunity to develop catalysts for various renewable‐energy technologies.