Transformation of Co(OH)<sub>2</sub> to CoOOH for Photocatalytic Oxygen Evolution Reaction
Yuanxing Wang, Yi Zhang, Yujia Ding, Ying-Ming Li, Xinxin Xing, Dezhi Wang, Carlo U. Segre, Houyu Zhu, Jiming Bao
Abstract
The development of efficient and economical oxygen evolution reaction (OER) catalysts is highly desired, and cobalt-based nanomaterials are promising candidates. In this work, we tackle one key question for cobalt-assisted photocatalytic OER: What is the true active species of Co(OH) 2 for the photocatalytic OER? Hence, we investigated photocatalytic OER on nanostructured Co(OH) 2 and Co 3 O 4 for comparison. We found that there was a significant transformation of Co(OH) 2 during the photocatalytic process with a [Ru(bpy) 3 ] 2+ /S 2 O 8 2– buffer. Specifically, the Co(OH) 2 nanosheets were oxidized and mainly converted to CoOOH nanoparticles, one type of highly active material for the OER. The converted CoOOH exhibits higher photocatalytic OER performance than Co 3 O 4 nanoparticles. CoOOH is the true active catalyst for the photocatalytic OER on Co(OH) 2 . Furthermore, potential-determining steps calculated by theoretical calculations also indicate that Co(OH) 2 is unlikely to be the catalyst for the OER, and CoOOH exhibits better OER activity than Co 3 O 4 .