Rapid synthesis of NiMo-based electrocatalysts at room temperature for efficient oxygen and hydrogen evolution in seawater

Electrocatalytic splitting of seawater instead of scarce freshwater is considered as a feasible way to produce clean hydrogen energy. However, the corrosiveness of seawater poses more requirements for the electrocatalysts to alleviate the damage of chlorine chemistry. The cathode Mo0.84Ni0.16/MoNiOx and anode Fe(OH)3/ MoNiOx derived from Prussian blue analogues (PBAs) were rapidly synthesized by electrodeposition and complexation at room temperature within only 30 min. The overall water splitting device assembled with Fe(OH)3/ MoNiOx and Mo0.84Ni0.16/MoNiOx requires 1.54 V and 1.575 V to drive the current density of 10 mA cm-2 in 1 M KOH and 1 M KOH + seawater, respectively. Additionally, the device maintains catalytic actssivity at the current density of 100 mA cm-2 for over 120 h in 1 M KOH and modulated alkaline seawater, respectively. The Mo element with high valence state in Fe(OH)3/MoNiOx is dissolves after anodic oxidation, and the Ni(Fe)OOH species generated by in-situ transformation on the surface of catalyst actsss as the actssive center for oxygen evolution reactssion (OER). Furthermore, the Ni and Mo species in Mo0.84Ni0.16/MoNiOx with low valence states could strengthens the water dissociation ability and decreases the hydrogen adsorption energy barrier of the Volmer step in the hydrogen evolution reactssion (HER), thus accelerating the chemical reactssion kinetics. This work provides beneficial implications for the design of non-noble metal electrocatalysts for seawater splitting.

Automated summary

Electrocatalytic splitting of seawater is a feasible way to produce clean hydrogen energy. This study synthesized cathode Mo0.84Ni0.16/MoNiOx and anode Fe(OH)3/ MoNiOx derived from Prussian blue analogues for seawater splitting devices. The device showed good stability and efficient catalytic activity in both alkaline and modulated seawater conditions.