Efficient Visible-Light-Driven Z-Scheme Overall Water Splitting Using a MgTa2O6-xNy/TaON Heterostructure Photocatalyst for H2 Evolution

An (oxy)nitride-based heterostructure for powdered Z-scheme overall water splitting is presented. Compared with the single MgTa2O6-xNy or TaON photocatalyst, a MgTa2O6-xNy/TaON heterostructure fabricated by a simple one-pot nitridation route was demonstrated to effectively suppress the recombination of carriers by efficient spatial charge separation and decreased defect density. By employing Pt-loaded MgTa2O6-xNy/TaON as a H-2-evolving photocatalyst, a Z-scheme overall water splitting system with an apparent quantum efficiency (AQE) of 6.8% at 420 nm was constructed (PtOx-WO3 and IO3- /I- pairs were used as an O-2-evolving photocatalyst and a redox mediator, respectively), the activity of which is circa 7 or 360 times of that using Pt-TaON or Pt-MgTa2O6-xNy as a H-2-evolving photocatalyst, respectively. To the best of our knowledge, this is the highest AQE among the powdered Z-scheme overall water splitting systems ever reported.