Enhancing the photocatalytic water electrolysis performance of Zn2SnO4 nanostructures via post-synthesis nitrogen doping

Abstract

Nitrogen-doped Zn<inf>2</inf>SnO<inf>4</inf> nanostructures were developed via hydrothermal treatment. Urea (CH<inf>4</inf>N<inf>2</inf>O) was used as the nitrogen source to achieve post-growth nitrogen doping in Zn<inf>2</inf>SnO<inf>4</inf> nanostructures. Nitrogen doping resulted in morphological distortion. The elemental study proved that nitrogen concentration increased with an increase in the concentration of urea in the precursor solutions. The vibration modes corresponding to the Zn-N and Sn-N bonds confirmed the incorporation of nitrogen into the crystal lattice of Zn<inf>2</inf>SnO<inf>4</inf>. XPS analysis revealed that higher nitrogen doping concentrations led to the substitutional incorporation of nitrogen. Nitrogen doping in Zn<inf>2</inf>SnO<inf>4</inf> introduced impurity levels in the electronic band structure and reduced its optical band gap (from 2.7 eV to 2.4 eV). Consequently, the Zn<inf>2</inf>SnO<inf>4</inf> nanostructure with approximately 1.9 at% nitrogen showed the highest photocurrent density of 124 μA cm−2 at 1.23 V vs. RHE, representing approximately 2.6-fold improvement in photocurrent compared to that of undoped Zn<inf>2</inf>SnO<inf>4</inf> nanostructures. Optimized nitrogen doping resulted in approximately 89% charge injection efficiency along with the lowest charge transfer resistance. © 2025 Elsevier B.V., All rights reserved.