Regulation of Rh Single-Atom Coordination for Enhanced Reverse Hydrogen Spillover and Efficient Electrochemical Dechlorination
Qian Zheng, Hengyue Xu, Yancai Yao, Jie Dai, Guangming Zhan, Jiaxian Wang, Bing Zhou, Ruizhao Wang, Kaiyuan Wang, Rui Zhao, Bo Yang, Lizhi Zhang
Abstract
Reverse hydrogen spillover (RHS) from the surface oxygen of titanium oxide to single-atom catalytic centers enables efficient electrochemical hydrogenation via atomic hydrogen (H*) transfer, a process critically dependent on the coordination environment and electronic structure of the active site. In this study, we reveal that a four-oxygen-coordinated Rh single-atom electrode (Rh 1 O 4 ) exhibits superior RHS capability during water electrolysis of titanium foam compared to its five- or three-coordinated counterparts (Rh 1 O 5 or Rh 1 O 3 ). The Rh–O coordination number directly modulates the relative position of the Rh d-band center to the Fermi level, thereby regulating H* adsorption on Rh and the RHS efficiency between titanium oxide’s surface oxygen and the Rh single atom on the titanium foam electrode. Remarkably, the four-coordinated Rh 1 O 4 configuration achieves an optimized hydrogen adsorption Gibbs free energy (Δ G H* ) of +0.08 eV, approaching that of the coordinating oxygen atoms (−0.47 eV), which drastically reduces the RHS energy barrier to +0.55 eV, significantly lower than those of Rh 1 O 5 and Rh 1 O 3 . This structural optimization translates to exceptional electrochemical hydrogenation performance, exemplified by a 4-chlorophenol degradation rate constant of 4.65 h –1, surpassing Rh 1 O 5 (1.18 h –1 ) and Rh 1 O 3 (0.16 h –1 ) by 4- and 29-folds, respectively. Our findings highlight the pivotal role of single-atom coordination engineering in tailoring atomic-level hydrogen transfer dynamics and provide a strategic framework for designing high-performance single-atom electrocatalysts for sustainable electrochemical hydrogenation applications.