Rates of H2O2 electrogeneration by reduction of anodic O2 at RVC foam cathodes in batch and flow-through cells

Abstract

The Electro-Fenton process for in-situ H 2 O 2 electrogeneration is impacted by low O 2 utilization efficiency (<0.1%) and the need of acid for pH adjustment. An electrochemical flow-through cell can develop localized acidic conditions, coupled with simultaneous formation and utilization of O 2 to enhance H 2 O 2 formation. Multiple electrode configurations using reticulated vitreous carbon (RVC) foam and Ti/mixed metal oxides (MMO) are proposed to identify the optimum conditions for H 2 O 2 formation in batch and flow-through cells. A pH of 2.75±0.25 is developed locally in the flow-through cell that supports effective O 2 reduction. Up to 9.66 mg/L H 2 O 2 is generated in a 180 mL batch cell under 100 mA, at pH 2, and mixing at 350 rpm. In flow-through conditions, both flow rate and current significantly influence H 2 O 2 production. A current of 120 mA produced 2.27 mg/L H 2 O 2 under a flow rate of 3 mL/min in a 3-electrode cell with one RVC foam cathode at 60 min. The low current of 60 mA does not enable effective H 2 O 2 production, while the high current of 250 mA produced less H 2 O 2 due to parasitic reactions competing with O 2 reduction. Higher flow rates decrease the retention time, but also increase the O 2 mass transfer. Furthermore, 3-electrode flow-through cell with two RVC foam cathodes was not effective for H 2 O 2 production due to the limited O 2 supply for the secondary cathode. Finally, a coupled process that uses both O 2 and H 2 from water electrolysis is proposed to improve the H 2 O 2 yield further.

Hydrogen peroxide generation from O2 electroreduction for environmental remediation: A state-of-the-art review

“…The most frequently used carbon cathodes are commercially available materials, such as graphite (Da Pozzo et al, 2005), graphite felt (GF) (Zhou et al, 2013b;Zhou et al, 2014;Wang et al, 2015;Castañeda et al, 2017), carbon felt (CF) (Isarain-Chávez et al, 2010;Pérez et al, 2016;, reticulated vitreous carbon (RVC) foam (Li et al, 2014;Zhou et al, 2018b;Zhou et al, 2018d), and activated carbon fiber (ACF) (Wang et al, 2005;Lei et al, 2010;Wang et al, 2010).…”

“…Compared with the above materials, RVC foam is less frequently used for H 2 O 2 electrosynthesis due to its large resistance and fragile nature (Zhou et al, 2011). However, due to its 3D structure and macro-pores, RVC foam has advantages over others especially in flow-through reactors, where low resistance of water flow is required (Drogui et al, 2001;Li et al, 2014;Zhou et al, 2018d).…”

Efficient H2O2 electrogeneration at graphite felt modified via electrode polarity reversal: Utilization for organic pollutants degradation

“…Carbonaceous materials are the most widely used cathodes because they are non-toxic, stable, conductive and chemical resistant [3], exhibit high overpotential of H 2 evolution, and low catalytic activity for H 2 O 2 decomposition [12]. To date, graphite [4], graphite felt (GF) [9][12] [13] [14], carbon felt [15], activated carbon fiber [16], carbon-polytetrafluoroethylene (PTFE) [17], and reticulated vitreous carbon (RVC) [18] [19] [20] have been used as cathodes for the EF process. However, conventional carbonaceous materials usually show poor kinetics towards the 2-electron oxygen reduction reaction (ORR) resulting in poor performance for H 2 O 2 production.…”

Transformation of tetrachloroethylene in a flow-through electrochemical reactor

“…1) [26,27], which can directly and indirectly reduce the parent components tetrachloroethylene (PCE) and trichloroethylene (TCE) and stimulate microbial degradation [28][29][30][31]. In addition, hydrogen peroxide (H 2 O 2 ), which is a strong oxidant that can break down the chlorinated ethenes [32,33], can be effectively formed (Eq. 2) at a sufficiently high dissolved oxygen concentration, or if a catalyst like palladium (Pd) is applied to the cathode.…”

“…Hence, resistivity was 5 times higher in the porous matrix. An increase in potential difference as the alkaline front progresses towards the anode in a porous matrix has been observed[72].Vertical oriented reactors are applied in most studies on flow-through electrochemical removal of chlorinated ethenes[24,32,58,33,34,[40][41][42][43][44]55]. One major advantage is automatic venting of gases generated, since gases released from the electrodes will bubble up through the reactor and leave the reactor with the effluent.…”