Investigation of the Synergistic Effect in Polypyrrole/Ni-Doped NASICON Composites for an Enhanced Hydrogen Evolution Reaction
Ajay Kumar, Saurabh Kumar, Subhajit Jana, Rajiv Prakash
Abstract
Electrocatalysts with a synergistic combination of low-cost, eco-friendly, and highly electrochemical active properties are frequently used in hydrogen evolution reactions (HERs) without utilizing any noble or toxic metals. Herein, a simple chemical oxidative polymerization method has been used to synthesize a set of nanocomposites of polypyrrole (PPy) and Ni-doped NASICON-structured Na 3 Ni x Fe (2– x ) (PO 4 )(SO 4 ) 2 [NFPS(Ni x )], which shows remarkable HER activity. Among them, as-synthesized uniform spherical-shaped PPy/NFPS(Ni 0.5 ) (optimized ratio) was found to show the lowest onset overpotential, −13 mV versus reversible hydrogen electrode (RHE), with a lesser Tafel slope of 58 mV dec –1, which is comparable to Pt/C and superior among the majority of the polymer-based HER catalysts. Also, it offers a current density of 10 mA/cm 2 at a noticeably lower overpotential of −111 mV versus RHE. Moreover, the nanocomposite also exhibits notable long-sustaining environmental and catalytic stability along with exceptional durability. In PPy/NFPS(Ni 0.5 ), improved electrocatalytic activity comes from the synergistic effect of the NFPS(Ni 0.5 ) and PPy matrix, which results in enormous electrocatalytically active sites and facilitates easy charge transportation. Thus, real-world hydrogen production may hold possibilities for the as-synthesized PPy/NFPS(Ni 0.5 ) nanocomposite as well as an alternative to a Pt-based electrocatalyst for the HER.