Plasma assisted H₂O₂ synthesis from water and oxygen: Looking at the interface

Hydrogen Peroxide (H2O2) is considered the preferred green chemical for many industrial processes given that water is the only H2O2 degradation product. Since the common H2O2 synthesis process (Anthraquinone Auto-Oxidation) is not environmentally friendly, many alternatives have been proposed. One of them is the direct synthesis from H2 and O2 in the presence of a catalyst. Nevertheless, effective catalysts for this reaction usually involve noble metals deployment, affecting the sustainability of such process.
Plasmas are an alternative platform for a decentralized H2O2 production that do not require noble metals, have instant on/off time, and can activate molecules such as oxygen and water. Promising results have been reported for discharge and gliding arc plasma reactors regarding yield and selectivity to H2O2. Microwave plasmas are not usually studied in this process, but they are very interesting since they can handle higher gas flow rates, do not require electrodes and have shown potential for efficient use of energy in comparison with the other plasmas. Nevertheless, the direct combination of H2 and O2 at high temperatures usually present in microwave plasmas (up to 3000K) are a concern for safety reasons. ... mehr
In this sense, in line with decentralized concepts, it is proposed to directly use water in combination with oxygen to produce H2O2. The interface between water and plasma would be the main study object, along with the mixing regime, spray conditions and flow pulses which have shown to affect both the efficiency and yield of the reaction, balancing the increased contact of plasmas and water together with the reaction control inside the aqueous phase. When plasma is in contact with water, the plasma-water interactions can lead to many direct reactions at the plasma-water interface and indirect side reactions in the bulk water.