Synergistic Activity of Co and Fe in Amorphous Cox–Fe–B Catalyst for Efficient Oxygen Evolution Reaction

• Published in: ACS applied materials & interfaces Vol. 9; no. 46; pp. 40333 - 40343
• Main Authors: Chen, Huayu, Ouyang, Shuxin, Zhao, Ming, Li, Yunxiang, Ye, Jinhua
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 22.11.2017
• Subjects: active sites; catalysts; cobalt; copper; electrochemistry; electrodes; energy conversion; iron; materials science; oxidation; oxygen production; photovoltaic cells; population growth; silicon; synergism; X-ray photoelectron spectroscopy; electrocatalyst; oxygen evolution reaction; photovoltaic water splitting; boride; 3d metal
• ISSN: 1944-8244; 1944-8252; 1944-8252
• DOI: 10.1021/acsami.7b13939

Water splitting has been greatly limited by the sluggish kinetics of the oxygen evolution reaction (OER). High-oxidation-state metal species are required as the favorable active sites in OER. Here, amorphous Cox–Fe–B (x is the molar ratio of Co/Fe), Co–B, and Fe–B compounds were successfully synthesized as the oxygen evolution electrocatalysts. The calculation of turnover frequency (TOF) indicates that both the Co and Fe sites are active for OER. Cyclic voltammetry, X-ray photoelectron spectroscopy, and long-term stability curves were used to demonstrate that Fe can stabilize Co in a higher oxidation level and meanwhile promote the generation of OOH-like species (the key intermediates for OER). The reduced impedance for Co2–Fe–B (compared with that for Fe–B and Co–B) obtained from the electrochemical impedance spectra confirms the enhanced conductivity for the Co2–Fe–B. This optimal sample on Cu substrate shows a low overpotential of 0.298 V at the current density of 10 mA cm–2 with a decreased overpotential of 42 mV compared to that of Co–B. The Co2–Fe–B catalyst also exhibits a small Tafel slope of 62.6 mV/dec and good stability. The enhanced performance could be attributed to the synergistic effect of the increased population of high-oxidation-state metal–OOH species and the promoted conductivity of the catalyst. A solar-to-hydrogen energy conversion efficiency of 4.2% and a Faradaic efficiency of 97.2% can be achieved by connecting the HER and as-prepared OER electrodes to a crystalline silicon solar cell.