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Twin structure in Photoanodes for Enhanced Water Oxidation Performance

Recently, Prof. Hongwei ZHU’s group at School of Materials and Engineering, Tsinghua University, and Prof. Zhihong LI from Institute of Microelectronics, Peking University co-published a research article titled “Twin Structure in BiVO4 Photoanodes Boosting Water Oxidation Performance through Enhanced Charge Separation and Transport” in Advanced Energy Materials.


In recent years, monoclinic bismuth vanadate (BiVO4, BVO) has emerged as one of the most promising photoanode materials for oxygen evolution reaction (OER) because of its appropriate band structure, stability in near-neutral electrolytes, and wide availability. However, the oxygen evolution efficiency achieved by BVO to date has been far below the level expected because the material suffers from severe charge recombination caused by slow carrier separation and transport. Twin structure in semiconductors has been found effective in promoting charge separation by the “back to back” potentials that were provided by the formed homojunctions thus enhancing the photocatalytic activity. Herein, this work presented a new method combining an electrodeposition of BiOI nanosheets and thermo-chemical conversion to prepare BVO photoanodes with twin structure.


Experimental results have demonstrated the “back to back” potentials and directional diffusion that originated from homojunction could facilitate the charge separation and transport of BVO single crystals. Hence, BVO single crystals with twin structure can significantly boost water oxidation performance by reducing their bulk recombination (namely improved charge separation efficiency). As expected, photoelectrocatalytic tests of the BVO photoanode with preferable twin structure (BL-BVO) demonstrated a significant improvement in the oxygen evolution efficiency over the control sample (SL-BVO) (Fig. 1).


Fig.1 The mechanism of the twin structure in boosting water oxidation performance


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