Stable photocatalysts with excellent optical adsorption and low reaction barrier are the key for the water splitting. Here, we find that a two-dimensional Janus WSSe monolayer possesses the compelling photocatalytic properties from density functional theory simulations, which can be well modulated with strain deformation. Comprehensive investigations indicate that the Janus material not only exhibits strong optical absorbance in the visible spectrum, suitable band edge potentials, high carrier separation, and transfer efficiency but also has adequate driving forces of photoexcited carrier for water redox reaction and good resistance against photoinduced corrosion. Janus WSSe is therefore predicted to be a promising photocatalyst for water splitting. Moreover, we also find that tensile strains could further improve the photocatalytic performance for water splitting by effectively increasing the energy conversion efficiency and reducing the exciton binding energy. Our results not only predict a photocatalyst, which can utilize the visible light for overall water splitting, but also propose an effective path to extend the absorption spectra and raise the photocatalytic efficiency.

Photocatalytic water splitting is a promising technology to solve the energy crisis and provide renewable and clean energies. Recently, although numerous 2D materials have been proposed as the photocatalytic candidates, the strategies to effectively modulate photocatalytic reactions and conversion efficiency are still lacking. Herein, based on first-principles calculations, we show that the photocatalytic activities and energy conversion efficiency can be well tuned by ferroelectric–paraelectric phase transition of a AgBiP2Se6 monolayer. It is found that the AgBiP2Se6 monolayer has a higher potential and driving forces of photogenerated holes for water oxidation in the ferroelectric phase, but higher corresponding values of photogenerated electrons for the hydrogen reduction reaction in the paraelectric phase. Besides, the solar-to-hydrogen energy conversion efficiency is also tunable with the phase transition; it is up to 10.04% at the ferroelectric phase due to the better carrier utilization, but only 6.66% at the paraelectric phase. Moreover, the exciton binding energy is always smaller in the paraelectric state than that in the ferroelectric state, indicating that the ferroelectric switch could also make a directional adjustment to the photoexcited carrier separation. Our theoretical investigation not only reveals the importance of ferroelectric polarization on water splitting, but also opens an avenue to modify the photocatalytic properties of 2D ferroelectric materials via a ferroelectric switch.

Shewanella oneidensis is an important model organism for its versatility of anaerobic respiration. CymA, a cytoplasmic membrane-bound tetraheme c-type cytochrome, plays a central role in anaerobic respiration by transferring electrons from the quinone pool to a variety of terminal reductases. Although loss of CymA results in defect in respiration of many electron acceptors (EAs), a significant share of the capacity remains in general. In this study, we adopted a transposon random mutagenesis method in a cymA null mutant to identify substituent(s) of CymA with respect to nitrite and nitrate respiration. A total of 87 insertion mutants, whose ability to reduce nitrite was further impaired, were obtained. Among the interrupted genes, the petABC operon appeared to be the most likely candidate given the involvement of the cytochrome bc1 complex that it encodes in electron transport. Subsequent analyses not only confirmed that the complex and CymA were indeed functionally overlapping in nitrate/nitrite respiration but also revealed that both proteins were able to draw electrons from ubiquinone and menaquinone. Furthermore, we found that expression of the bc1 complex was affected by oxygen but not nitrate or nitrite and by global regulators ArcA and Crp in an indirect manner.

Efficient and selective CO2 electroreduction into chemical fuels promises to alleviate environmental pollution and energy crisis, but it relies on catalysts with controllable product selectivity and reaction path. Here, by means of first-principles calculations, we identify six ferroelectric catalysts comprising transition-metal atoms anchored on In2Se3 monolayer, whose catalytic performance can be controlled by ferroelectric switching based on adjusted d-band center and occupation of supported metal atoms. The polarization dependent activation allows effective control of the limiting potential of CO2 reduction on TM@In2Se3 (TM = Ni, Pd, Rh, Nb, and Re) as well as the reaction paths and final products on Nb@In2Se3 and Re@In2Se3. Interestingly, the ferroelectric switching can even reactivate the stuck catalytic CO2 reduction on Zr@In2Se3. The fairly low limiting potential and the unique ferroelectric controllable CO2 catalytic performance on atomically dispersed transition-metals on In2Se3 clearly distinguish them from traditional single atom catalysts, and open an avenue toward improving catalytic activity and selectivity for efficient and controllable electrochemical CO2 reduction reaction.