Electrochemical oxidation can be used for decentralized wastewater treatment without the addition of chemicals. Antimony-doped tin oxide (Sb-SnO 2 : AT) provides a catalytic anode coating that is easily prepared at a relatively low cost. However, there is the potential of Sb leaching during use. To overcome this problem, a heterojunction anode is developed that uses an AT oxide layer as an ohmic contact and a nickel-doped AT oxide layer (NAT) with a substantially lower Sb content as an outer catalytic layer (NAT/AT). The two-layer NAT/AT anode has significantly longer operational lifetimes, lower Sb leaching potential, and higher activities for free radical generation and ozone production than either layer when used alone. Based on experimental results in combination with theory, an anodic ozone activation pathway at the acidic electrode/ electrolyte interface is identified as a key • OH source coupled with direct • OH production via water electrolysis. The NAT/AT anode outperforms commercial anodes (e.g., boron-doped diamond and IrO 2 ) for organic compound destruction and for microbial disinfection. The 1-log removal of carbamazepine (surface area-normalized first-order rate constant k CBZ,SA = 1.13 × 10 −3 m/s) and 5-log inactivation of E. coli and MS2 virus are achieved within 60 s in synthetic electrolytes. Even though the electrochemical efficiency is lower in the case of latrine wastewater treatment, the energy consumption (e.g., 3.9−14.0 kWh/m 3 ) is low compared to previously reported values.

Hydrogen peroxide (HP) production via electrochemical oxygen reduction reaction (ORR-HP) is a critical reaction for energy storage and environmental remediation. The onsite production of high-concentration H 2 O 2 using gas diffusion electrodes (GDEs) fed by air is especially attractive. However, many studies indicate that the air–GDE combination could not produce concentrated H 2 O 2 , as the [H 2 O 2 ] leveled off or even decreased with the increasing reaction time. This study proves that the limiting factors are not the oxygen concentration in the air but the anodic and cathodic depletion of the as-formed H 2 O 2 . We proved that the anodic depletion could be excluded by adopting a divided electrolytic cell. Furthermore, we demonstrated that applying poly(tetrafluoroethylene) (PTFE) as an overcoating rather than a catalyst binder could effectively mitigate the cathodic decomposition pathways. Beyond that, we further developed a composite electrospun PTFE (E-PTFE)/carbon black (CB)/GDE electrode featuring the electrospun PTFE (E-PTFE) nanofibrous overcoating. The E-PTFE coating provides abundant triphase active sites and excludes the cathodic depletion reaction, enabling the production of >20 g/L H 2 O 2 at a current efficiency of 86.6%. Finally, we demonstrated the efficacy of the ORR-HP device in lake water remediation. Cyanobacteria and microcystin-LR were readily removed along with the onsite production of H 2 O 2 .

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