ACS_Sustainable Chemistry & Engineering


ACS_Sustainable Chemistry & Engineering

February 6, 2023

Volume 11, Issue 5

Pages 1618-2013

Porous Cuboidal SrNbO2N Crystals Grown on a Nb Substrate as an Active Photoanode for Neutral Seawater Splitting under Sunlight

Photoelectrochemical (PEC) water splitting using n-type SrNbO2N is beneficial for hydrogen production because its narrow-band-gap energy allows it to harvest visible light up to 700 nm. However, the oxygen evolution reaction (OER) activity of oxynitride at neutral pH is very limited, hindering its application to commercial PEC devices. Herein, we report enhanced seawater-splitting activity at neutral pH over porous cuboidal SrNbO2N crystals grown on a Nb substrate under simulated sunlight. The oxynitride photoanode was prepared via bottom-up fabrication including oxidation of the Nb substrate and flux-assisted nitridation using NaCl–KCl. The oxidation process was necessary for enhancing the oxygen concentration at the Nb surface and producing a crystalline Nb2O5 layer. Then, the Nb2O5/Nb substrate was subjected to a two-step nitridation, which was very effective in the generation of SrNbO2N crystals with a large surface area and high crystallinity. The bottom-up-fabricated SrNbO2N/Nb photoanode exhibited milliampere-level photocurrent during seawater splitting in an aqueous 0.5 M NaCl electrolyte at pH 6.4. Chlorine evolution reaction was preferentially catalyzed during seawater splitting compared with competitive OER. This work is the first to demonstrate the PEC neutral seawater splitting by active SrNbO2N crystals originating from bottom-up fabrication, which has never been reported in photoreactions using perovskite AB(O,N)3.

  • Van-Huy Trinh
  • Jeongsuk Seo

Image created by minjeong Kim / Nanosphere