Ultra-dispersed copper nanoparticles constructing crystalline-amorphous interface sites for alkaline water splitting

The dense crystalline-amorphous heterointerface (Fe 2 O 3 /Cu-PNC) was constructed on porous nitrogen-doped carbon using ultra-dispersed Cu nanoparticles, which facilitated the electron transfer with the tuned electronic structures as well as the favorable adsorption of surface oxygen species. • The Fe 2 O 3 /Cu-PNC has a dense crystalline Fe 2 O 3 /amorphous Cu interface. • There were rich defects and vacancies in the Fe 2 O 3 /Cu-PNC. • The Fe 2 O 3 /Cu-PNC/NF water electrolyzer delivered a current density of 10 mA cm -2 at 1.65 V. In literature, the creation of an interface between a highly conductive crystalline phase and an amorphous phase with unsaturated sites has been proven to be an effective strategy in the design of electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). However, the procedural complexity and limited formation of interfaces have compromised the envisioned effects. In this work, the dense crystalline Fe 2 O 3 /amorphous Cu interface was created simultaneously by the combination of solverthermal and annealing processes. The results showed that the ultra-dispersed Cu nanoparticles attributed to the formation of crystalline-amorphous (c-a) interface sites, which facilitated the electron transfer with the tuned electronic structures as well as the favorable adsorption of surface oxygen species. As a result, the developed Fe 2 O 3 /Cu-PNC catalyst outperformed most of the competing bifunctional catalysts reported for both OER and HER operations.