Synthetic diamond steps closer to next generation of high performance electrochemical applications

(Press-News.org) 27 June 2012: Element Six, the world leader in synthetic diamond supermaterials, and academic researchers from the University of Warwick's Departments of Chemistry and Physics, have demonstrated the key factors that determine the electrochemical properties of metal-like boron-doped synthetic diamond. The research shows that boron-doped synthetic diamond has outstanding electrochemical properties while retaining the full strength and durability of its chemical structure. This research opens the possibility of exploiting synthetic diamond's electrochemical technologies in a wide range of applications ranging from sensors to electrocatalysis.

The study's material science findings have been published in Angewandte Chemie Intl. Ed. under the title: Electrochemical Mapping Reveals Direct Correlation between Heterogeneous Electron-Transfer Kinetics and Local Density of States in Diamond Electrodes (DOI: 10.1002/anie.201203057). The paper demonstrates that the material's electrochemistry is determined by its local boron levels and the corresponding density of electronic states. The amount of boron doping in the material, coupled with a reduction in graphitic content to below detectable levels, makes synthetic diamond an ideal material for the study of electrochemical reactions over a wide potential measurement range.

The research was made possible by the high quality boron-doped synthetic diamond samples grown by Element Six through chemical vapour deposition (CVD), and optimised specifically for electrochemical applications. Element Six has a number of patents and patent applications covering its boron-doped synthetic diamond materials suitable for electrochemical applications, part of its portfolio of 600+ granted patents worldwide.

The collaborative research managed to overcome the challenge of creating a synthetic diamond material that is electrochemically active without affecting its chemical structure. The study revealed that it was possible to both dope the material with sufficiently high levels of boron to enable metal electrode-like behaviour, but at the same time suppress the formation of graphitic carbon to below detectable levels, which is normally found in this class of material. As a result, the team has delivered an optimised material which maximises the range of analytes that can be detected in solution in combination with a lowering of detection limits.

The boron-doped synthetic diamond electrodes with optimised characteristics will enable electrochemical sensors that have enhanced sensitivity, selectivity and reliability. These sensors would be able to exploit the hard-wearing properties of synthetic diamond while being able to withstand harsh environments and abrasive cleaning.

Steve Coe, Element Six Group Innovation Director, said: "We've been working closely with the University of Warwick team for six years and this is a tremendous achievement for everyone involved. We're particularly proud to have created such a high quality material with our chemical vapour deposition technology. To create high enough levels of boron doping without any significant graphitic content was a real challenge – but the successful result allowed us to demonstrate the material's electrochemical properties and open up the possibility of useful applications such as extremely sensitive and reliable electrochemical sensors."

One of the lead researchers on the paper, Professor Julie MacPherson from the University of Warwick, Department of Chemistry, added: "This research clearly demonstrates what an extremely useful material boron-doped synthetic diamond is. It could well be the material of choice for the electrochemical applications of the future."

The synthetic diamond technical work was completed by the Element Six R&D team based at Ascot in the UK who developed novel processes for growing synthetic diamond using CVD techniques, whilst the electrochemical studies were carried out by the Electrochemistry and Interfaces Group in the Department of Chemistry, the University of Warwick.



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Notes to Editors:

About Element Six

Element Six (www.e6.com) is an independently managed synthetic diamond supermaterials company. Element Six is part of the De Beers Family of Companies. Element Six is a global leader in the design, development and production of synthetic diamond supermaterials, and operates worldwide with its head office registered in Luxembourg, and primary manufacturing facilities in China, Germany, Ireland, Sweden, South Africa and the UK.

Element Six supermaterial solutions are used in applications such as cutting, grinding, drilling, shearing and polishing, while the extreme properties of synthetic diamond beyond hardness are already opening up new applications in a wide array of industries such as optics, power transmission, water treatment, semi-conductors and sensors.

About the boron-doped synthetic diamond electrochemistry research collaboration

The study was a partnership between the following organisations: Element Six, Ascot, UK, The University of Warwick, UK (Departments of Chemistry and Physics)

Funding for some of this research was provided by Element Six and the European Research Council.

Technical details of the research

The researchers at the University of Warwick used state-of-the-art high resolution electrochemical imaging, developed by Professor Patrick Unwin, to probe the electrochemical properties of metal-like boron doped diamond electrode, which was grown by Element Six and optimised specifically for electrochemical applications. The research findings open the way for the rational design of electrochemical technologies for a wide range of applications ranging from sensors to electrocatalysis.

Boron-doped synthetic diamond is an extremely interesting electrode material in the electrochemical arena given its corrosion resistance, durability at elevated temperatures and pressures, wide solvent window and low background currents. However, it is a challenge to produce the material where the boron dopant levels are high enough to induce metallic conductivity/metal-like behaviour, but graphitic carbon levels remain below detection, with the surface devoid of non-diamond-like impurities and yet it can still function as a metal electrode. Element Six used CVD processes to achieve this in close partnership with Professors Julie MacPherson, Mark Newton and Patrick Unwin at the University of Warwick. Together, they have demonstrated that the material is ideal for electrochemical applications.

The published study in Angewandte Chemie details how the electrochemistry of the Element Six material is determined by the local boron levels in the material, and corresponding density of electronic states. The electron transfer rates across the surface were high enough that, in traditional electrode configurations, the material acted like a metal electrode, but with the added benefits of very low background currents resulting from the low capacitance and electrochemically inactive surface chemistry. The material was used in an oxygen terminated state which is the preferred surface termination for electrochemical applications given the stability of the surface.

Key to the elucidation of the surface electrochemical properties was the use of two newly developed imaging techniques, by Professor Patrick Unwin and co-workers, called intermittent contact scanning electrochemical microscopy (Unwin et al, Anal. Chem., 2010, 82 (15), 6334-6337) and scanning electrochemical cell microscopy (Unwin et al, Anal Chem., 2010, 82 (22), 9141-9145). This enabled both the electrochemical electron transfer properties and local capacitive properties of the surface to be quantitatively elucidated on a pixel by pixel basis across the surface of the electrode, shedding new light on what controls the electron transfer properties of high quality boron doped diamond electrodes grown specifically for electrochemical applications.