Plasma-activated Co3(PO4)2 nanosheet arrays with Co3+-Rich surfaces for overall water splitting

• Published in: Journal of power sources 2018-10, Vol.400, p.190-197
• Main Authors: Liu, Haoxuan, Liu, Xijun, Mao, Zhiyong, Zhao, Zhe, Peng, Xianyun, Luo, Jun, Sun, Xiaoming
• Format: Article
• Language: English
• Subjects: Bifunctional electrocatalyst; Co3(PO4)2 nanosheet arrays; Co3+-rich surfaces; Overall water splitting; Plasma treatment
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2018.08.028

Highly efficient and stable bifunctional electrocatalyst for overall water splitting (OWS) are vital for large-scale hydrogen production. Herein, we demonstrate a novel bifunctional electrocatalyst – Co3(PO4)2 nanosheet arrays – prepared by a combined hydrothermal growth and plasma treatment. Owing to the large surface area, enhanced conductivity, the abundance of coordinately unsaturated Co3+ sites and numerous oxygen vacancies, the plasma activated Co3(PO4)2 nanosheet arrays exhibit low overpotentials for oxygen evolution reaction (240 mV) and hydrogen evolution reaction (50 mV) at 10 mA cm−2 with excellent stability. The overall performance is comparable to the best reports for precious-metal-free electrocatalysts. Also, the plasma activated Co3(PO4)2 nanosheet arrays show superior kinetics for hydrogen- and oxygen-evolution with Tafel slope values of 35 and 53 mV dec−1, respectively. The overall-water-splitting, with 10 mA cm–2 at a low voltage of 1.48 V, is achieved using the nanosheet arrays as both the anode and cathode and the performance surpasses that of the IrO2/CPt/C couple for sufficiently high overpotentials. This work presents a promising strategy for designing high-performance electrocatalysts toward overall water splitting. Plasma-activated Co3(PO4)2 nanosheet arrays are developed as a highly active bifunctional catalyst for HER and OER in alkaline solutions with overpotentials of 50 and 240 mV, respectively, to reach 10 mA cm−2, which are among the best reported for precious-metal-free electrocatalysts. The superior electrocatalytic performance corresponds to the large active surface area and the high content of Co3+. [Display omitted] •More Co3+ atoms on Co3(PO4)2 surface can be achieved via an plasma treatment.•The plasma-activated Co3(PO4)2 can catalyze oxygen-/hydrogen-evolution.•The plasma-activated Co3(PO4)2 exhibit electroactivity for overall water splitting.