On the way to raising the technology readiness level of diamond electrolysis

During the last decades, hundreds of scientific papers have focused on the use of anodes consisting of conductive diamond coatings, pointing out their outstanding capacity for the mineralization of organic pollutants contained in wastewater. Most of the works consist of the evaluation of the removal of different types of organics, with concentrations ranging from a few micrograms up to several grams per liter, in different matrices, from synthetic solutions containing large concentrations of sulfate or chloride to real wastewater. However, the technology readiness level has been stagnant in the lab at levels 4-5 and, because of the promising results published, there is a need to raise the readiness levels to values that indicate the full-scale applicability. In this review, two of the main challenges that need to be overcome to reach higher readiness levels are reviewed. The first is the improvement in the formulation of the doped diamond coatings targeting to be tailored for dedicated applications. Its significance is explained in terms of the high influence of these anodic surfaces on the efficiencies of the degradation of complex anthropogenic organics and, overall, on the efficient production of oxidants, that extend the oxidation of pollutants from the nearness of the anode surface to the bulk of the wastewater during electrolysis. The second advantage is the improvement in the design of the electrochemical cell that integrates the diamond anode, trying to take advantage of the outstanding properties of the diamond not only by improving the mass transport rates but also by optimizing the combination of its very efficient oxidation paths with other non-electrochemical oxidation mechanisms.