Ternary FeNiS2 ultrathin nanosheets as an electrocatalyst for both oxygen evolution and reduction reactions

High-performance and cost-effective electrocatalysts are essential for both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Herein, we provide the first report about a facile colloidal method to fabricate 2D ultrathin ternary FeNiS 2 nanosheets (NSs). When serving as an OER catalyst under alkaline conditions, they exhibited superior electrocatalytic performance over RuO 2 and achieved a current density of 10   mA   cm −2 with a potential of 1.54   V and a Tafel slope of 46   mV decade − 1 . Meanwhile, an ORR catalytic activity was also achieved with an onset potential of 0.78   V, a Tafel slope of 107   mV   decade − 1 , and a high selectivity with electron transfer number of 3.92 and H 2 O 2 % of 3.6% at 0.3   V under neutral conditions, which were comparable to those of the commercial Pt/C. The ternary FeNiS 2 -NSs were superior over the binary FeS NSs and Ni 9 S 8 nanorods synthesized via the same routes. More importantly, with the resistance for the corrosion and poison from the alkaline and phosphate buffer solution , the FeNiS 2 NSs exhibited superior stability without apparent OER or ORR catalytic activity loss over long-term operation. Their enhanced electrocatalytic performance compared to their binary counterparts indicate that a new strategy to prepare high performance OER and ORR catalysts was developed. In addition, the as-prepared FeNiS 2 NSs could serve as a noble-metal-free catalyst for OER or ORR with good electrocatalytic activities and long-term stability for practical applications.