Simultaneous utilization of electro-generated O2 and H2 for H2O2 production: An upgrade of the Pd-catalytic electro-Fenton process for pollutants degradation

Abstract

• Pd/Activated carbon/stainless steel mesh (PACSS) hybrid cathode was fabricated. • H 2 and O 2 from water electrolysis were both utilized by PACSS cathode for H 2 O 2 generation. • PACSS cathode can support effective H 2 O 2 generation and activation simultaneously. • The novel process is more effective for pollutants degradation than Pd-catalytic EF process. The Electro-Fenton (EF) process is one of the promising advanced oxidation processes (AOPs) for environmental remediation. The H 2 O 2 yield of EF process largely determines its performance on organic pollutants degradation. Conventional Pd-catalytic EF process generates H 2 O 2 via the combination reaction of anodic O 2 and cathodic H 2 . However, the relatively expensive catalyst limits its application. Herein, a hybrid Pd/activated carbon (Pd/AC)-stainless steel mesh (SS) cathode (PACSS) was proposed, which enables more efficient H 2 O 2 generation. It utilizes AC, the support of Pd catalyst, as part of cathode for H 2 O 2 generation via 2-electron anodic O 2 reduction, and SS serve as a current distributor. Moreover, H 2 O 2 could be catalytically decomposed upon AC to generate highly reactive OH, which avoids the use of Fe 2+ . Compared with conventional Pd catalyst, H 2 O 2 concentration obtained by PACSS cathode is 248.2% higher, the O 2 utilization efficiency was also increased from 3.2% to 10.8%. Within 50 min, 26.3%, 72.5%, and 94.0% H 2 O 2 was decomposed by Pd, AC, and Pd/AC. Fluorescence detection results implied that Pd/AC is effective upon H 2 O 2 activation for OH generation. Finally, iron-free EF process enabled by PACSS cathode was examined to be effective for reactive blue 19 (RB19) degradation. After continuous running for 10 cycles (500 min), the PACSS cathode was still stable for H 2 O 2 generation, H 2 O 2 activation, and RB19 degradation, showing its potential application for organic pollutants degradation without increase in the running cost.