Application of Heterojunction Ni–Sb–SnO2 Anodes for Electrochemical Water Treatment
- Yi ZhangYi ZhangLinde Laboratories, California Institute of Technology, Pasadena, California 91125, United StatesMore by Yi Zhang,
- Yang YangYang YangLinde Laboratories, California Institute of Technology, Pasadena, California 91125, United StatesDepartment of Civil and Environmental Engineering, Clarkson University, Potsdam, New York 13699, United StatesMore by Yang Yang,
- Shasha YangShasha YangDepartment of Civil and Environmental Engineering, Clarkson University, Potsdam, New York 13699, United StatesMore by Shasha Yang,
- Estefanny Quispe-CardenasEstefanny Quispe-CardenasDepartment of Civil and Environmental Engineering, Clarkson University, Potsdam, New York 13699, United StatesMore by Estefanny Quispe-Cardenas, and
- Michael R. Hoffmann*
Electrochemical oxidation can be used for decentralized wastewater treatment without the addition of chemicals. Antimony-doped tin oxide (Sb-SnO2: 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 IrO2) for organic compound destruction and for microbial disinfection. The 1-log removal of carbamazepine (surface area-normalized first-order rate constant kCBZ,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/m3) is low compared to previously reported values.
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