Manfang Mai,Lianke Ma,Yulan Zhou,Side Fu,Wenhao Deng,Xiaowen Wang,Xinzhou Ma
To overcome the rapid charge recombination and sluggish water oxidation kinetics, FeOOH/V O -BiVO 4 photoanodes were rationally prepared. The highest photocurrent density of 3.5 mA cm −2 was generated by the FeOOH/V O -BiVO 4 photoanodes at 1.23 V RHE , which was 3.5-fold higher than that of the pristine BiVO 4 . The dominate enhancement mechanism can be ascribed to significantly increased charge transfer efficiency by the FeOOH overlayers. Intensity-modulated photocurrent spectroscopy revealed that such increased charge transfer efficiency was resulted from the strong suppression of surface recombination by the FeOOH overlayers. Rate constant of surface recombination was strongly reduced to approximately 10 −2 s −1 at 0.93–1.23 V RHE . The strongly suppressed surface recombination was attributed to the storage capacity of the FeOOH for the photogenerated holes. Meanwhile, oxygen vacancies just had a minor impact on the kinetics of charge transfer and surface recombination but slightly increased the charge separation efficiency in the bulk. This work clarifies the roles of oxygen vacancies and the FeOOH overlayers in the increased photocurrent density, facilitating the rational design of high-performance BiVO 4 -based photoanodes.
Yanjun Feng,Yongbo Bing,Ze Wang,Shengya Zhang,Zhengang Han,Shuhui Huo,Zhentong Zhu,Jing Chen,Xiaoquan Lu
Although the catalytic effect can be enhanced by using sacrificial agents, it still faces numerous difficulties in large-scale production applications. Investigating the improvement of photocatalytic efficiency without sacrificial agents is therefore crucial. This study proposes a cost-effective and efficient photochemical modification system that utilizes a seed layer of BiVO 4 to improve photoelectrochemical (PEC) performance, the result shows that the photocurrent density of BiVO 4 with a seed layer thickness of 312 nm was improved by 40% to 0.99 mA cm −2 at 1.23 V RHE without any sacrificial agent. Meanwhile, Electrochemical impedance spectroscopy (EIS) and intensity modulated photocurrent spectroscopy (IMPS) demonstrated that the introduction of the seed layer effectively prevents the recombination of electron-hole pairs and improves the charge transfer efficiency, leading to a “slow” decrease in the current density of the composite photoanode (from 32% to 9.8%) in combination with the linear sweep voltammetry (LSV) results. We exhibit the scanning photoelectrochemical microscopy (SPECM) method to in-situ quantitatively study the hole transfer kinetics with different seed layer thicknesses using the feedback model and find those photoelectrodes with a thickness of 312 nm has the highest kinetic rate constant of 0.62 × 10 −2 cm s −1 which is approximately 5 times higher than that of the pristine photoelectrode (0.11 × 10 −2 cm s −1 ).
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