The design of more efficient electrochemical reactors with enhanced turbulence. Optimizing the shape/configuration of carbon-based cathodes by employing gas diffusion electrodes (GDEs) in flow-by electrochemical reactors instead of flow-through electrode reactors. Performing the electrochemical operation under high pressure and at low temperature so as to improve oxygen solubility. As reported in the literature, to help tackle this problem, some important progress has been made by Improvement of oxygen supply in the electrochemical cell since the low solubility of oxygen in the cell causes the efficiency of the process to be controlled by diffusion. Improvement of the catalytic properties of the cathode this can be done by studying and developing new highly efficient cathode materials based on carbon black (CB) or through the addition/doping of organic or inorganic catalysts into carbonaceous materials (4,11,14−18) As demonstrated in the literature, through the application of carbon-based cathode materials, O 2 is easily reduced to H 2O 2 via the transfer of two electrons at a potential of 0.682 V vs SHE (4,11−13) (1)Some studies reported in the literature have pointed out different ways to improve the production of H 2O 2 through ORR via the 2-electron pathway some of these ways include the following: (i) (7,8) There have been several reports in the literature regarding the mechanism of operation of the ORR process.
Over the past few years, there has been a huge interest among researchers in the use of ORR via the 2-electron pathway for the electrogeneration of H 2O 2 this technique has become extremely popular because it is an energy-intensive multistep process, which has been proven to have the following advantages: high efficiency, good operational safety, and low environmental impact. (2,4,9−11) The ORR technique employs oxygen as the raw material in the electrochemical process.
To meet the increasing demand for H 2O 2, alternative efficient techniques for the production of the oxidant are currently being studied, and one of the techniques that have been found to be highly promising is the electrochemical production of H 2O 2 via oxygen reduction reactions (ORR)─see eq 1. (2,7−9) Most of the current production of H 2O 2 occurs through the anthraquinone process. The range of application of H 2O 2 has progressively increased in recent years, and the annual consumption of this oxidant is estimated to increase to 6 million tons in 2027. Precisely, a specific production of H 2O 2 as high as 131 g kWh –1 was obtained at 25 mA cm –2 the energy efficiency (in terms of H 2O 2 production) values obtained in this study based on the application of the proposed GDE in a flow-by reactor at low current densities were found to be within the range of values recorded for H 2O 2 production techniques that employ flow-through reactors. It should be noted, however, that the application of the electrocatalyst at lower current densities resulted in higher energy efficiency in terms of H 2O 2 production. The application of the proposed PL6C-based GDE led to the generation of accumulated H 2O 2 of over 3 g L –1 at a high current density. The results obtained in this study show that unlike what is expected in flow-through reactors, the efficiency in the H 2O 2 production is not affected by the solubility of oxygen when GDE is employed in the electrochemical process (using the flow-by reactor) i.e., the efficiency of H 2O 2 production is not significantly dependent on O 2 solubility, temperature, and pressure. To conduct this study, a highly efficient Printex L6 carbon-based gas diffusion electrode (GDE) as a cathode was employed for the electrogeneration of H 2O 2 in a flow-by reactor and evaluated the effects of lowering the operation temperature (to increase solubility) and increasing the air supply in the system on H 2O 2 electrogeneration. This work examines the role of oxygen supply in the improvement of the hydrogen peroxide (H 2O 2) electrochemical production efficiency and the generation of high H 2O 2 concentrations in electrochemical processes operated in a discontinuous mode.
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