Synthesis and characterization of mixed metal oxides as electrocatalysts for the oxygen evolution reaction
Presently, global energy supply relies heavily on fossil fuels, whose combustion emits greenhouse gases that harm the environment. Green hydrogen could present a more sustainable option, but the oxygen evolution reaction (OER) is considered the main bottleneck for green hydrogen production due to its low efficiency and high energy costs. This limits large-scale applications of hydrogen as a clean energy carrier. In his thesis, Faiz Sultan develops low-cost OER electrocatalysts based on bimetallic oxides of different transition metals (iron, nickel, cobalt, and manganese) by three different approaches.
First, Sultan prepared nickel-iron and cobalt-iron oxides by a bicontinuous microemulsion method. He evaluated the prepared samples as OER electrocatalysts. Cobalt-iron oxide exhibited higher current densities than nickel-iron oxide, which is attributed to higher availability of active sites and higher electrical conductivity, making the reaction more efficient.
Second, Sultan prepared nickel-manganese oxides by a simple co-precipitation method and calcined at two different temperatures (350 °C and 550 °C). He evaluated their electrochemical performance using two protocols, with only one of them following best practices in electrochemistry. The overall results differed substantially between the two protocols, highlighting the importance of following best practices in electrochemical testing methods.
Third, Sultan prepared nickel-cobalt materials with Ni:Co compositions 1:1 and 1:2 by a hydrothermal method and tested these under both lab and industry-like alkaline water electrolysis conditions. The cobalt-rich sample showed higher performance than its counterpart and underwent substantial activation due to metal impurities in the electrolyte.
This work highlights the importance of testing electrocatalysts under industry-like conditions and the influence of electrolyte impurities on the overall performance.