AsianScientist (Jul 11, 2014) – Scientists have invented a method to split water into hydrogen and oxygen even at a neutral pH, paving the way for the development of green energy generation. The study describing these findings has been published in the journal Nature Communications.
Developing catalysts that can split water to yield molecular oxygen has been the subject of intense research. Plants do this naturally via the process of photosynthesis, producing glucose and oxygen from water and carbon dioxide. Nature’s own water-splitting catalysts are incredibly efficient, attracting the attention of scientists seeking to mimic their efficient processes.
One basic riddle is why nature always uses manganese rather than more common metals such as iron or copper. The exclusive use of manganese is particularly surprising considering that manganese is inactive at neutral pH, which is how water is found in nature. Scientists have been able to devise many artificial manganese-based catalysts of their own, but have not been able to make them active at neutral pH. Now, a team from the RIKEN Center for Sustainable Resource Science led by Ryuhei Nakamura has reported the discovery of a mineral-based catalyst that can efficiently split water into oxygen and hydrogen ions at neutral pH.
They key to this work, according to Nakamura, was the insight that the catalysis of water splitting can only be efficient if the transfer of electrons and protons is properly synchronized. Normally, artificial catalysts do not do this. With this in mind, the team devised a new strategy for remedying this mismatch of electron- and proton-transfer timing and were able to achieve a significant improvement in the catalytic activity of manganese oxides at neutral pH.
According to Nakamura, “The alpha-manganese oxide we used in this work is a main component of naturally occurring manganese minerals. We were surprised to discover that even mineral-like manganese oxides can split water efficiently at neutral pH once the timing of the electron and proton transfer is synchronized. This finding inspired us to think about how nature engineered the normally inactive manganese mineral to become an active catalyst for water splitting.”
Renewable energy sources such as solar, wind, hydroelectric and geothermal fluctuate over time, and storing this energy is a crucial task for creating a sustainable society. Water splitting can be used to transform energy into hydrogen that can then be combined with oxygen from the atmosphere in clean fuel cells or with carbon dioxide in the oceans or atmosphere to create raw materials for hydrocarbon fuels and materials. Nakamura hopes to use this new knowledge to construct an electrochemical water splitting device that can operate at neutral pH, thus exploiting water as a resource to create new fuels.
For Nakamura, this work has exciting future potential. “Plants can use even tap water as a resource to make fuels. They do not need acid and base solutions. In other words, nature utilizes a safe, clean, and abundant form of water, thereby creating truly sustainable ecosystems. I hope that our findings will be able to contribute to the use of water at a neutral pH as a resource for generating renewable energy, which is one of the foundations for sustainable human societies,” he says.
The article can be found at: Yamaguchi et al. (2014) Regulating proton-coupled electron transfer for efficient water splitting by manganese oxides at neutral pH.
——-
Source: RIKEN; Photo: Ilya Sedykh/Flickr/CC.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.
