Biomimetic (Co, Ni, W)OxNy/WO3 photoelectrocatalyst for robust seawater oxidation

Abstract

As an intriguing strategy for massive hydrogen production, photoelectrochemical (PEC) seawater splitting compels the anode to be highly hypochlorite-resistant. Inspired by algae, we designed a robust photoelectrocatalyst that WO3 nanorods (NRs) are covered by N/W co-doped (Co, Ni, W)OxNy nanosheets (NSs). The NSs expose (111) faces and are decorated by (Co, Ni)WO4 nanoparticles. DFT calculations reveal that Co and Ni atoms on the (111) surface of N/W co-doped NSs are more likely to adsorb OH-, while W atoms are more favorable to adsorb Cl-. Secondly, the lattice distortion and multi-crystal phases of NSs are triggered by doped W atoms, and the evacuation of 5d electrons makes W atoms as donor centers, leading to enhanced catalytic activity of CoNi atoms and corrosion resistance to Cl-. Furthermore, the N atoms expand the valence band of CoNiOx and elevate the conduction band of (Co, Ni)WO4, facilitating more electrons to participate in PEC reaction and the realization of seawater full-splitting. Resultantly, the N/W co-doped (Co, Ni, W)OxNy/WO3 hetero-NRs (HNRs) demonstrate a PEC current density about 0.35 mA/cm2 at 1.23 VRHE with durability over 100 hours in seawater. This work provides a practical strategy towards the durable PEC anode for seawater splitting.