Solid Diamond Bipolar Electrode Erosion Resistance
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Solution Overview
Problem
Electrochemical reactors with diamond electrodes face challenges in achieving long operational lifetimes due to issues like pin-holes in diamond-coated electrodes and erosion of heavily doped regions in solid diamond electrodes, particularly at high current densities, which necessitate additional processing steps and increased costs.
Innovation Solution
A reactor design utilizing solid diamond bipolar electrodes with a dopant concentration of at least 8×10^19 atoms/cm^3 to a depth of 50 nm, ensuring conductivity and minimizing the need for passivation layers, thereby extending operational lifetimes without additional production steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If diamond coated electrodes are used, then production cost is reduced, but operational lifetime is shortened due to pin-holes causing liquid penetration and delamination
Solution Approach 1:
The patent applies local quality by creating a heavily doped region (10^20 to 10^21 atoms/cm³) at the surface of the solid diamond electrode within a depth of 50 nm, while the bulk diamond maintains lower doping concentration. This localized high doping concentration at the surface provides enhanced resistance to electrochemical attack and erosion, extending operational lifetime without requiring additional coating layers.
Solution Approach 2:
The patent changes the doping concentration parameter of the diamond electrode, specifically creating a gradient where the surface region has significantly higher boron doping concentration (10^20 to 10^21 atoms/cm³) compared to the bulk material. This parameter change transforms the surface properties to resist erosion and electrochemical attack, solving the lifetime problem while maintaining electrical conductivity.
2Reliability
If heavily doped solid diamond electrodes are used, then conductivity is achieved, but erosion rate increases due to etching by organic solvents
Solution Approach 1:
The patent applies local quality by creating a heavily doped region (10^20 to 10^21 atoms/cm³) at the surface of the solid diamond electrode within a depth of 50 nm, while the bulk diamond maintains lower doping concentration. This localized high doping concentration at the surface provides enhanced resistance to electrochemical attack and erosion, extending operational lifetime without requiring additional coating layers.
Solution Approach 2:
The patent converts the potential harm of heavy doping (which normally increases erosion susceptibility) into a benefit by localizing the heavy doping only at the surface region. The heavily doped surface layer becomes more resistant to electrochemical attack and erosion, while the bulk diamond maintains lower doping to preserve mechanical integrity and reduce overall erosion.
3Duration of action of stationary object
If additional passivation layers are added to reduce erosion, then operational lifetime is extended, but production complexity and cost increase
Solution Approach 1:
The patent merges the electrode substrate and the erosion-resistant surface layer into a single integrated solid diamond structure with a doping gradient. Instead of adding a separate passivation layer coating, the erosion resistance is built into the electrode itself through localized heavy doping during the diamond growth process, eliminating additional production steps.
Solution Approach 2:
The patent applies preliminary action by incorporating the heavy doping into the surface region during the diamond electrode fabrication process itself, before the electrode is put into service. The doping gradient is established during crystal growth, pre-configuring the surface to resist erosion and electrochemical attack from the outset, eliminating the need for subsequent passivation layer application.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution results in significantly longer operational lifetimes of the bipolar electrodes, even at high current densities, without requiring additional production steps or altering dopant concentrations, thus reducing electrode replacement costs and maintaining required conductivity.
Implementation Method 1
the diamond comprises a dopant such that the diamond is conductive and has an electrical resistivity of 1 MΩcm or less and wherein the average concentration of the dopant in a region of at least one of the major working surfaces, to a depth of 50 nm, is at least 8×10^19 atoms/cm³
Implementation Method 2
Electrochemical oxidation of waste water is a well known method for reducing the amount of pollutants present
Data Source
AI summary
The present invention provides a solid diamond electrode, a reactor, in particular a reactor comprising an anode, a cathode and at least one bipolar electrode having first and second major working surfaces positioned therebetween wherein the at least one bipolar electrode consists essentially of diamond, and methods in which the reactors are used.