Surface-derived phosphate layer on NiFe-layered double hydroxide realizes stable seawater oxidation at the current density of 1 A°cm−2
Chaoxin Yang, Zhengwei Cai, Jie Liang, Kai Dong, Zixiao Li, Hang Sun, Shengjun Sun, Dongdong Zheng, Hui Zhang, Yongsong Luo, Yongchao Yao, Yan Wang, Yuchun Ren, Qian Liu, Luming Li, Wei Chu, Xuping Sun, Bo Tang
Abstract
Seawater electrolysis, especially in coastlines, is widely considered as a sustainable way of making clean and high-purity H2 from renewable energy; however, the practical viability is challenged severely by the limited anode durability resulting from side reactions of chlorine species. Herein, we report an effective Cl− blocking barrier of NiFe-layer double hydroxide (NiFe-LDH) to harmful chlorine chemistry during alkaline seawater oxidation (ASO), a pre-formed surface-derived NiFe-phosphate (Pi) outer-layer. Specifically, the PO43−-enriched outer-layer is capable of physically and electrostatically inhibiting Cl− adsorption, which protects active Ni3+ sites during ASO. The NiFe-LDH with the NiFe-Pi outer-layer (NiFe-LDH@NiFe-Pi) exhibits higher current densities (j) and lower overpotentials to afford 1 A·cm−2 (η1000 of 370 mV versus η1000 of 420 mV) than the NiFe-LDH in 1 M KOH + seawater. Notably, the NiFe-LDH@NiFe-Pi also demonstrates longer-term electrochemical durability than NiFe-LDH, attaining 100-h duration at the j of 1 A·cm−2. Additionally, the importance of surface-derived PO43−-enriched outer-layer in protecting the active centers, γ-NiOOH, is explained by ex situ characterizations and in situ electrochemical spectroscopic studies.