Janus electrocatalytic flow-through membrane enables highly selective singlet oxygen production

Abstract

The importance of singlet oxygen (1O2) in the environmental and biomedical fields has motivated research for effective 1O2 production. Electrocatalytic processes hold great potential for highly-automated and scalable 1O2 synthesis, but they are energy- and chemical-intensive. Herein, we present a Janus electrocatalytic membrane realizing ultra-efficient 1O2 production (6.9 mmol per m3 of permeate) and very low energy consumption (13.3 Wh per m3 of permeate) via a fast, flow-through electro-filtration process without the addition of chemical precursors. We confirm that a superoxide-mediated chain reaction, initiated by electrocatalytic oxygen reduction on the cathodic membrane side and subsequently terminated by H2O2 oxidation on the anodic membrane side, is crucial for 1O2 generation. We further demonstrate that the high 1O2 production efficiency is mainly attributable to the enhanced mass and charge transfer imparted by nano- and micro-confinement effects within the porous membrane structure. Our findings highlight a new electro-filtration strategy and an innovative reactive membrane design for synthesizing 1O2 for a broad range of potential applications including environmental remediation.

A resurrection of the Haber–Weiss reaction

“…Experimental conditions and nomenclature need to be discussed too. Elimelech et al 1 . use scavengers at a single concentration, with the exception of terephthalate which was used at two concentrations.…”

“…s Elimelech et al 1 point out, there is a legitimate need for a method that produces singlet dioxygen ( 1 Δ g O 2 ) efficiently, because this species plays a role in a research fields like environmental science and biochemistry. They 1 describe a flow-through filtration process whereby singlet dioxygen is generated electrochemically.…”

“…They 1 describe a flow-through filtration process whereby singlet dioxygen is generated electrochemically. The mechanism proposed by Elimelech et al 1 for its production is based on the reduction of hydrogen peroxide by superoxide, the infamous Haber-Weiss reaction, and is therefore incorrect. Furthermore, the evidence for formation of singlet dioxygen is questionable.…”

Reply to “A resurrection of the Haber-Weiss reaction”

“…n our recent published paper 1 , we presented an entirely new design of a Janus electrocatalytic membrane and demonstrated its efficient water decontamination performance. The Janus electrocatalytic membrane demonstrated in situ singlet oxygen ( 1 O 2 ) formation inside the membrane porous structure, enabling enhanced removal of contaminants from water in a single-pass electrofiltration at very low energy consumption and without the addition of chemical precursors.…”

“…Given this situation, we employed other detection agents-furfuryl alcohol (FFA) and sulfamethoxazole (SMX)-to confirm 1 O 2 formation. The oxidized products of FFA and SMX by 1 O 2 (Figs. S11 and S17 in the Supporting Information of our article 1 ) were in agreement with previously reported results 7,8 .…”