In the recent past, there has been a paradigm shift towards renewable sources of energy in order to address the concerns pertaining to environmental degradation and dwindling fossil fuels. A variety of alternative green energy sources such as solar, wind, hydrothermal, tidal, etc., have been gaining attention to reduce global carbon footprints. One of the key challenges with these energy generation technologies is that they are intermittent and are not continuously available.
The water dissociation process, alternatively known as artificial photosynthesis, traditionally employs electricity to split the water molecule through two half reactions in an electrochemical cell. The hydrogen evolution reaction occurs at the cathode where hydrogen fuel is generated and the water oxidation occurs at the anode where breathable oxygen is released. Although water is a simple molecule that is constituted by only three atoms, the process of dissociating it is quite intense and challenging.
The initial energy, known in scientific terms as the overpotential, plays a crucial role in influencing the progress of the reaction. For the materials explored so far, the initial energy required to trigger the hydrogen evolution at the cathode and oxygen evolution at the anode is so high that the process escalates the overall cost of the reaction, thereby, adversely affecting its commercial utilization. This is particularly a major concern at the anode because the oxygen evolution reaction involves the transfer of four electrons which demands a higher initial energy as compared to the reaction at the cathode.
The research team has observed, with the aid of advanced microscopy techniques and electrochemical measurements, that the fabricated anode aids in reducing the initial energy, which accelerates the four-electron transfer process in the oxygen evolution reaction. The research finding of Prof. Yagi’s team has immense potential in improving the long-term performance and stability of the electrochemical cell.
Zaki N. Zahran et al, Electrocatalytic water splitting with unprecedentedly low overpotentials by nickel sulfide nanowires stuffed into carbon nitride scabbards, Energy & Environmental Science (2021). DOI: 10.1039/D1EE00509J