A team from the University of Houston and Hunan Normal University in China has developed an active and durable oxygen evolution reaction (OER) catalyst for water splitting that meets commercial crtieria for current densities at low overpotentials.
In a paper in the RSC journal Energy & Environmental Science, the report that together with a good hydrogen evolution reaction (HER) catalyst, they achieved current densities of 500 and 1,000 mA cm-2 at 1.586 and 1.657 V respectively, with very good stability—significantly lower than any previously reported voltage.
The researchers said that their discovery sets the stage for large-scale hydrogen production by water splitting using excess electrical power whenever and wherever available.
Water electrolyzers are promising commercial apparatus to produce high-purity hydrogen with unlimited water resources, among which alkaline water electrolyzers are more appealing than that based on proton exchange membrane (PEM) in acid. This is primarily because low-cost electrocatalysts, instead of noble meal-based catalysts, can be utilized in alkaline media.
However, efficient and mass hydrogen production in industry has not been widely deployed at present (<5% hydrogen production) due to the high cost of the noble metals as catalysts in acid and the low energy conversion efficiency of the non-noble metal catalysts in base. Although a variety of alkaline water electrolyzers have been constructed by designing robust electrocatalysts, most of them require cell voltages significantly larger than 1.8V to deliver 200 mA cm-2, unsatisfactory for the commercial requirements of 1.8-2.4 V for current densities of 200-400 mA cm-2.—Zhou et al.
The researchers constructed their new OER catalyst using three-dimensional porous interwoven (Ni, Fe) oxyhdroxide nanorod arrays. These arrays are mainly derived from amorphous Ni/Fe (oxy)hydroxide mesoporous films on Ni foams synthesized by a simple stirring process.
They paired the OER catalyst with a MoNi4 HER catalyst. The resulting system can be driven by different power sources, including an AA battery or a thermoelectric generator.
Haiqing Zhou, Fang Yu, Qing Zhu, Jingying Sun, Fan Qin, Yu Luo, Jiming Bao, Ying Yu, Shuo Chen and Zhifeng Ren (2018) “Water splitting by electrolysis at high current density under 1.6 volt” Energy & Environmental Science doi: 10.1039/C8EE00927A