Anthraquinone-2-Sulfonate as a Microbial Photosensitizer and Capacitor Drives Solar-to-N₂O Production with a Quantum Efficiency of Almost Unity

Abstract

Semiartificial photosynthesis shows great potential in solar energy conversion and environmental application. However, the rate-limiting step of photoelectron transfer at the biomaterial interface results in an unsatisfactory quantum yield (QY, typically lower than 3%). Here, an anthraquinone molecule, which has dual roles of microbial photosensitizer and capacitor, was demonstrated to negotiate the interface photoelectron transfer via decoupling the photochemical reaction with a microbial dark reaction. In a model system, anthraquinone-2-sulfonate (AQS)-photosensitized Thiobacillus denitrificans, a maximum QY of solar-to-nitrous oxide (N2O) of 96.2% was achieved, which is the highest among the semiartificial photosynthesis systems. Moreover, the conversion of nitrate into N2O was almost 100%, indicating the excellent selectivity in nitrate reduction. The capacitive property of AQS resulted in 82–89% of photoelectrons released at dark and enhanced 5.6–9.4 times the conversion of solar-to-N2O. Kinetics investigation revealed a zero-order- and first-order- reaction kinetics of N2O production in the dark (reductive AQS-mediated electron transfer) and under light (direct photoelectron transfer), respectively. This work is the first study to demonstrate the role of AQS in photosensitizing a microorganism and provides a simple and highly selective approach to produce N2O from nitrate-polluted wastewater and a strategy for the efficient conversion of solar-to-chemical by a semiartificial photosynthesis system.

Metal‐Free Semiconductor‐Based Bio‐Nano Hybrids for Sustainable CO2‐to‐CH4Conversion with High Quantum Yield

“…Excess electrons may reduce O 2 from water splitting or fill the two π* orbitals of oxygen and form reactive oxygen species such as ⋅O 2 − and H 2 O 2 , [11] which change the redox microenvironment and oxidatively photodamage methanogens [12] . Although dissolved organic matter (DOM), such as anthraquinone‐2‐sulfonate, acts as an electron capacitor, [13] the driving force of photoelectrons from DOM might be insufficient to overcome the Gibbs free energy barrier for reduction CO 2 to CH 4 [14] . Therefore, to achieve a high production yield and product selectivity for CH 4 , it is imperative to develop an approach for engineering a biotic‐abiotic interface that can harness excess electrons and release them when necessary.…”

Sustained Biotic-Abiotic Hybrids Methanogenesis Enabled Using Metal-Free Black Phosphorus/Carbon Nitride

“…Nitrogen and hydrogen were used as the carrier and combustion gas, respectively, and the injection volume was 100 μL. The quantum yield (QY) of M. barkeri -BPCN x was calculated as previously reported ( Chen et al, 2022 ). In addition, to verify the source of CH 4 production, a control experiment was set up to replace NaH 12 CO 3 in the medium with NaH 13 CO 3 .…”

Research progress and prospect of low-carbon biological technology for nitrate removal in wastewater treatment

“…Besides, Anthraquinone-2-sulfonate (AQDS) is an electron shuttle and is also photosensitive (Xu et al, 2022;Zeng et al, 2023). When AQDS is used as the photosensitizer, nitrate is almost completely converted into N 2 O, and the quantum yield is higher than that of other semiconductor materials, acting as a capacitor (Chen et al, 2022). While N 2 O can serve as a propellant for rocket launches (Kamps et al, 2019), it is also a potent greenhouse gas, drawing considerable attention toward the need for its emissions reduction (Ravishankara et al, 2009).…”