Two-dimensional perovskite SrNbO_(2) N with Zr doping for accelerating photoelectrochemical water splitting

The superior ability of perovskite-type SrNbO_(2) N to absorb intensive visible light makes it a potential semiconductor to produce hydrogen and oxygen by photoelectrochemical(PEC)water splitting under sunlight.The surface morphologies,such as shape and structure,of the oxynitride strongly affect its photoactivity,although the mechanism has been hardly studied.Herein,we report a two-dimensional(2D)porous SrNbO_(2) N plate with Zr doping,nitrided from layered perovskite Sr_(5)Nb_(4)O_(15) and also its largely enhanced PEC water splitting activity.Zr^(4+)was doped in Sr_(5)Nb_(4)O_(15) during flux-assisted calcination using KCl,producing 2D-type truncated-octahedral Sr_(5)Nb_(4)O_(15):Zr plates approximately 50 nm in thickness.The nitridation completely transformed Sr_(5)Nb_(4)O_(15):Zr to 2D single-crystalline SrNbO_(2) N:Zr with a large surface area,which was subsequently used to fabricate a thin and uniform photoanode by the spin coating method.As a result,the Co(OH)_(x)/SrNbO_(2) N:Zr/FTO photoanode capable of absorbing visible light of up to 680 nm exhibited an activity of 2.0 mA cm^(-2) at 1.23 V vs the reversible hydrogen electrode for water splitting under AM 1.5G simulated sunlight.This improvement in photoactivity mainly originated from the 2D surface morphology of SrNbO_(2) N:Zr,which is clearly distinguishable from 3D-type oxynitrides.According to electrochemical analyses,the 2D structure of SrNbO_(2) N:Zr boosted the separation and accelerated the transfer of charges photogenerated during the water splitting,thus driving the reaction further.Therefore,the result empirically demonstrates that controlling the surface morphology of SrNbO_(2) N is an effective strategy to suppress the recombination of charges and minimize their diffusion pathway,eventually enhancing the PEC activity.