Probing the active sites of Co3O4 for the acidic oxygen evolution reaction by modulating the Co2+/Co3+ ratio

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2018-01, Vol.6 (14), p.5678-5686
• Main Authors: Kai-Li, Yan, Jun-Feng, Qin, Jia-Hui, Lin, Dong, Bin, Jing-Qi, Chi, Zi-Zhang, Liu, Fang-Na, Dai, Yong-Ming, Chai, Chen-Guang, Liu
• Format: Article
• Language: English
• Subjects: Carbon dioxide; Cobalt; Cobalt oxides; Electrocatalysts; Low temperature; Oxygen; Oxygen evolution reactions; Photoelectron spectroscopy; Silver; Sulfuric acid
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c8ta00070k

Exploring active and stable electrocatalysts for the acidic oxygen evolution reaction (OER) is necessary to broaden the practical applications of proton exchange membrane electrolyzers. Unfortunately, the active sites of electrocatalysts for the acidic OER, which are the most powerful tool for designing and optimizing OER electrocatalysts, still remain ambiguous. Herein, we synthesize Ag doped Co3O4 with different atomic ratios of Co2+/Co3+ and investigate the effect of preferential exposure of Co2+ in Co3O4 on the acidic OER through systematic experiments for the first time. X-ray photoelectron spectroscopy is used to probe the atomic ratio of Co2+/Co3+ on the surface of Co3O4. The results demonstrate that Co3O4 richer in Co2+ shows the best acidic OER performance, and affords a current density of 10 mA cm−2 at an overpotential of 470 mV along with having a satisfactory stability in H2SO4 solution. Moreover, low-temperature calcination treatment is found to be an effective method to aid preferential growth of Co2+ on the surface of Co3O4, further making our synthesis process more practical and universal. Therefore, this work provides some insight into designing non-precious electrocatalysts for the acidic OER, by identifying active sites and offering a versatile modulation strategy on the preferential growth of real active sites.