Investigating the behavior of various cocatalysts on LaTaON₂ photoanode for visible light water splitting

Abstract

We performed a comparative study on the photoelectrochemical performance of LaTaON loaded with NiO, NiFeO, CoO and IrO as cocatalysts. Ni-based oxides lead to the highest improvement on the photoelectrochemical performance, while CoO and IrO also enhance the performance though to a lower extent, but they simultaneously introduce more pseudocapacitive current thus resulting in an inefficient utilization of the photo-generated holes. Repetitive voltage cycling between 1.0 V and 1.6 V transforms the NiO and NiFeO into oxyhydroxides known to possess higher catalytic activities. However, these oxyhydroxides lead to lower photoelectrochemical performance compared to the as-loaded oxides, most probably due to the decay of the passivation centers at the photoelectrode-cocatalyst interface. High catalytic activities cannot be achieved without sufficient passivation of surface recombination states. Despite that the photoelectrochemical performance of LaTaON can be improved by cocatalysts, the maximum achievable photocurrent density is still not comparable to that reported for other oxynitride compounds. Our study suggests that poor electronic conductivity or severe bulk recombination of the photo-generated electron-hole pairs are the main limiting factors for the photon-to-current conversion efficiency in LaTaON photoanodes.

Tailoring of an unusual oxidation state in a lanthanum tantalum(IV) oxynitride via precursor microstructure design

“…La 2 O 3 or Ta 2 O 5 ) 3,4,13 or ternary oxides (e.g. LaTaO 4 ) 14,15 , which are either prepared by solid state reactions (SSR) or via a Pechini method. The latter allows mild reaction conditions providing excellent product homogeneity 2 .…”

Black-Si as Photoelectrode

“…Semiconductor modification with oxygen/hydrogen evolution (OER/HER) cocatalysts is a common strategy to increase the efficiency of photoelectrochemical water splitting reactions [20]. In this study 150 nm thick layer of cobalt oxide CoO x was deposited on b-Si fabricated for 20 min and coated with 10 nm TiO 2 .…”

Core–Shell‐Structured LaTaON2 Transformed from LaKNaTaO5 Plates for Enhanced Photocatalytic H2 Evolution

“…Increasing the nitridation temperature significantly increased the intensity of the diffraction peaks generated by the LaTaON 2 phase and decreased the (001) peak of LaKNaTaO 5 (Figures B and S4), indicating the transformation of LaKNaTaO 5 into LaTaON 2 . Pure LaTaON 2 was obtained after 4 h at a nitridation temperature of 1223 K. For comparison, irregular‐shaped LaTaON 2 was also prepared by the nitridation of LaTaO 4 derived via a solid state reaction . It is notable that the intensity ratio between the (040) and (−202) diffraction peaks of the plate‐like LaTaON 2 nitrided from LaKNaTaO 5 at 1223 K for 4 h was higher than that for conventional LaTaON 2 prepared from LaTaO 4 (0.94 versus 0.22).…”