Scalable synthesis of self-assembled bimetallic phosphide/N-doped graphene nanoflakes as an efficient electrocatalyst for overall water splitting.

In order to achieve clean hydrogen energy through overall water splitting, it is vitally important but still challenging to develop highly efficient and low-cost electrocatalysts to replace the noble metal-based electrocatalysts (e.g. Pt- and Ru-based catalysts). To address this issue, herein, we present a facile and scalable spray drying and subsequent phosphorization approach to synthesize iron-cobalt bimetallic nanoflakes encapsulated in N-doped graphene (FCP@NG). The optimized FCP@NG exhibits excellent performance in the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and overall water splitting. It demonstrates remarkable performance in the HER and superior activity in the OER, even outperforming the state-of-the-art RuO2 catalyst. Being employed as both the cathode and anode on nickel foams, this FCP@NG hybrid demonstrates promising performance in overall water splitting with a very low potential of 1.63 V to deliver a current density of 10 mA cm-2, which is superior among most of the recently reported transition-metal-based catalysts and comparable to the commercial Pt/RuO2 cell. The outstanding electrocatalytic performance of FCP@NG is attributed to a synergistic effect of its bi-metallization, unique nanoflake structure and conductive N-doped graphene encapsulation. This work provides a scalable and low-cost strategy to synthesize nonprecious and bi-functional transition-metal-based catalysts with unique nanoarchitecture and outstanding catalytic performance for overall water splitting.