Rapid Synthesis of Ultrathin Ni:FeOOH with In Situ-Induced Oxygen Vacancies for Enhanced Water Oxidation Activity and Stability of BiVO<sub>4</sub> Photoanodes
Mayur A. Gaikwad, Uma V. Ghorpade, Umesh P. Suryawanshi, Priyank V. Kumar, Suyoung Jang, Jun Sung Jang, Lan Tran, Jong‐Sook Lee, Hyojung Bae, Seung Wook Shin, Mahesh P. Suryawanshi, Jin Hyeok Kim
Abstract
The coupling of oxygen evolution reaction (OER) catalysts with photoanodes is a promising strategy for enhancing the photoelectrochemical (PEC) performance by passivating photoanode’s surface defect states and facilitating charge transfer at the photoanode/electrolyte interface. However, a serious interface recombination issue caused by poor interface and OER catalysts coating quality often limits further performance improvement of photoanodes. Herein, a rapid Fenton-like reaction method is demonstrated to produce ultrathin amorphous Ni:FeOOH catalysts with in situ-induced oxygen vacancies (Vo) to improve the water oxidation activity and stability of BiVO 4 photoanodes. The combined physical characterizations, PEC studies, and density functional theory calculations revealed that the reductive environment in a Fenton-like reaction in situ produces abundant Vo in Ni:FeOOH catalysts, which significantly improves charge separation and charge transfer efficiency of BiVO 4 while also offering abundant active sites and a reduced energy barrier for OER. As a result, Ni:FeOOH-Vo catalysts yielded a more than 2-fold increased photocurrent density in the BiVO 4 photoanode (from 1.54 to 4.15 mA cm –2 at 1.23 V RHE ), accompanied by high stability for 5 h. This work not only highlights the significance of abundant Vo in catalysts but also provides new insights into the rational design and fabrication of efficient and stable solar water-splitting systems.