Artificial photosynthesis part 2: Scientific advances in the imitation of the oxygen-evolving complex
Dear Steemians,
Imitating the function of plants, algae, and cyanobacteria which provide us with oxygen and carbohydrates through photosynthesis is an ongoing challenge in materials science. In this article, I will explain how researchers have addressed the difficult task of replicating the molecular structure of the natural oxygen-evolving organometallic complex (OEC).
The natural OEC is a biological catalyst that has a deformed cube-shaped molecular structure with four manganese atoms, five oxygens, and one calcium [1]. The two main difficulties in replicating it lie in the incorporation of calcium because it has a larger atomic radius (231 picometers) than manganese (161 pm) and oxygen (48 pm). The other difficult part is the formation of an unstable oxo-manganese bridge (O-Mn-O bond) outside the cube structure.
Figure 1: Schematic comparison of similar structures to the oxygen-evolving complex. Source: Image created by @ritch.
The active centers of performing the water oxidation reaction are attributed to the oxo bonds that form the manganese atoms. Calcium, on the other hand, has the function of stabilizing (modulating) and completing this catalytic reaction, as well as of adsorbing water molecules [2]. Besides, it is established in several publications that manganese presents oxidation states of III and IV, which facilitates the release of molecular oxygen [3].
Plants are known to contain small traces of elements such as manganese and iron. Even once we analyzed the chemical composition of a scorpion's stinger by energy dispersive X-ray spectroscopy (EDS) and found a high manganese percentage in it. This manganese is probably coming from the plants that consume scorpions, and it gives them the mechanical properties to its stinger.
In 2012, Dr. Nocera's research group employed material science to fabricate an artificial leaf with the ability to dissociate water molecules at neutral pH [4]. What they called artificial leaf was the combination of layers of semiconductor materials bonded to catalysts on a steel plate. A catalyst can transform one product into another; in this case it splits water into hydrogen and oxygen.
On one side of the steel plate is deposited a catalyst containing NiMoZn to produce hydrogen, which replaced the use of the commonly used metal (platinum). On the other side of the plate, a cobalt-based catalyst with a structural arrangement similar to that of the natural OEC. This synthetic Co-OEC consists of a cube with cobalt and oxygen atoms. In Figure 1, the presence of an M (moderator) element completes the cube, and it is probably made of alkaline metal ions, as in the case of cobaltates [4].
In my point of view, cobalt has been extensively studied for the water splitting because of to its high oxidation potential of 1.82 V. Understanding that the oxidation potential is the ability of a material to gain or remove electrons from a nearby compound. I would like to point out that taking into account the oxidation or reduction potentials of the elements helps us to design more efficient catalytic materials in a given reaction.
In an interview, Dr. Nocera demonstrates one of the potential applications of artificial leaves, video in youtube [5]. Using a lamp, a small solar cell and a mini fuel cell, you can turn on a fan. This seems expensive at first glance, but they are simple containers to hold liquids and gases that can be made from low-cost materials. In terms of operation, the solar cell captures energy from the lamp to transmit it to the artificial leaf through wires, which in turn dissociates water molecules. Subsequently, the hydrogen obtained is used to generate electricity in the fuel cell, which allows the fan to operate.
Another approach to obtain the structure of the natural OEC was to use the chemistry of organometallic compounds. Zhang and collaborators (2015) synthesized a molecule containing manganese and calcium very similar to the desired structure, see Figure 1. However, it was not possible to obtain one of the oxo bonds of manganese out of the cube. Its artificial OEC contains proteins anchored to the molecular structure that resembles the natural OEC and is the most similar so far [6].
Despite great scientific advances on this subject, it remains a challenge to obtain an identical structure to that of the natural OEC. We trust in the scientific community that has given these brushstrokes in the way of imitating nature to take the next step.
If you liked this article, support it with your upvote and share it to reach more people.
Kind regards,
References:
[1] J. Yano, J. Kern, K. Sauer, M.J. Latimer, Y. Pushkar, J. Biesiadka, B. Loll, W. Saenger, J. Messinger, A. Zouni, V.K. Yachandra. Where Water Is Oxidized to Dioxygen: Structure of the Photosynthetic Mn4Ca Cluster. Science, 314:821–825, 2006.
[2] J.P. McEvoy, G.W. Brudvig. Water-Splitting Chemistry of Photosystem II. Chemical Reviews 106:4455–4483, 2006.
[3] J. Yano, V. Yachandra. Mn4Ca Cluster in Photosynthesis: Where and How Water is Oxidized to Dioxygen. Chemical Reviews 114:4175–4205, 2014.
[4] D.G. Nocera. The artificial leaf. Accounts of Chemical Research 45:767-776, 2012.
[5] Adam Shaw [BBC Studios]. (June 17, 2013). Artificial leaves replicate photosynthesis? [Video file]. Recovered from [youtube].
[6] C. Zhang, C. Chen, H. Dong, J.R. Shen, H.Dau, J. Zhao. A synthetic Mn4Ca-cluster mimicking the oxygen-evolving center of photosynthesis. Science 348:690-693, 2015.
You may be interested in reading the first part of this article:
Artificial photosynthesis part 1: Understanding the structure of the oxygen-evolving complex.
The scientist's prediction (in the youtube vid) said 5 years, and that was 1 year ago :D 'nough waiting, high time we went from petroculture to hydroculture!
Improving the efficiency of a solar to fuel device is a difficult task. Cheers!
Posted using Partiko Android
Congratulations! This post has been upvoted from the communal account, @minnowsupport, by ritch from the Minnow Support Project. It's a witness project run by aggroed, ausbitbank, teamsteem, someguy123, neoxian, followbtcnews, and netuoso. The goal is to help Steemit grow by supporting Minnows. Please find us at the Peace, Abundance, and Liberty Network (PALnet) Discord Channel. It's a completely public and open space to all members of the Steemit community who voluntarily choose to be there.
If you would like to delegate to the Minnow Support Project you can do so by clicking on the following links: 50SP, 100SP, 250SP, 500SP, 1000SP, 5000SP.
Be sure to leave at least 50SP undelegated on your account.
This post has been voted on by the SteemSTEM curation team and voting trail. It is elligible for support from @curie and @utopian-io.
If you appreciate the work we are doing, then consider supporting our witness stem.witness. Additional witness support to the curie witness and utopian-io witness would be appreciated as well.
For additional information please join us on the SteemSTEM discord and to get to know the rest of the community!
Please consider setting @steemstem as a beneficiary to your post to get a stronger support.
Please consider using the steemstem.io app to get a stronger support.
Thanks for using eSteem!
Your post has been voted as a part of eSteem encouragement program. Keep up the good work! Install Android, iOS Mobile app or Windows, Mac, Linux Surfer app, if you haven't already!
Learn more: https://esteem.app
Join our discord: https://discord.gg/8eHupPq
Congratulations @ritch! You have completed the following achievement on the Steem blockchain and have been rewarded with new badge(s) :
You can view your badges on your Steem Board and compare to others on the Steem Ranking
If you no longer want to receive notifications, reply to this comment with the word
STOP
Vote for @Steemitboard as a witness to get one more award and increased upvotes!
Hi @ritch!
Your post was upvoted by Utopian.io in cooperation with @steemstem - supporting knowledge, innovation and technological advancement on the Steem Blockchain.
Contribute to Open Source with utopian.io
Learn how to contribute on our website and join the new open source economy.
Want to chat? Join the Utopian Community on Discord https://discord.gg/h52nFrV