Shouqi Yuan

A Hierarchical Z‑Scheme α‐Fe2O3/g‐C3N4 Hybrid for Enhanced Photocatalytic CO2 Reduction

The challenge in the artificial photosynthesis of fossil resources from CO2 by utilizing solar energy is to achieve stable photocatalysts with effective CO2 adsorption capacity and high charge-separation efficiency. A hierarchical direct Z-scheme system consisting of urchin-like hematite and carbon nitride provides an enhanced photocatalytic activity of reduction of CO2 to CO, yielding a CO evolution rate of 27.2 µmol g-1 h-1 without cocatalyst and sacrifice reagent, which is >2.2 times higher than that produced by g-C3 N4 alone (10.3 µmol g-1 h-1 ). The enhanced photocatalytic activity of the Z-scheme hybrid material can be ascribed to its unique characteristics to accelerate the reduction process, including: (i) 3D hierarchical structure of urchin-like hematite and preferable basic sites which promotes the CO2 adsorption, and (ii) the unique Z-scheme feature efficiently promotes the separation of the electron-hole pairs and enhances the reducibility of electrons in the conduction band of the g-C3 N4 . The origin of such an obvious advantage of the hierarchical Z-scheme is not only explained based on the experimental data but also investigated by modeling CO2 adsorption and CO adsorption on the three different atomic-scale surfaces via density functional theory calculation. The study creates new opportunities for hierarchical hematite and other metal-oxide-based Z-scheme system for solar fuel generation.

Low cost and green preparation process for α-Fe2O3@gum arabic electrode for high performance sodium ion batteries

Conventional electrode manufacturing processes for lithium ion batteries involve the use of toxic organic solvents (such as N-methyl-2-pyrrolidone, NMP). A low cost and green preparation process for high performance electrodes for sodium ion batteries (SIBs) is important to address simultaneously the environmental and health risks of production processes and the shortage of lithium metal. Herein, gum arabic (GA), which is a non-toxic biodegradable biopolymer, is used as a water soluble binder to design a water-based electrode preparation process to fabricate α-Fe2O3 electrodes (i.e., α-Fe2O3@GA electrode). The α-Fe2O3@GA electrode demonstrates better mechanical properties and binding capability than that of the α-Fe2O3 electrode with poly(vinylidene fluoride) (PVDF) as the binder (α-Fe2O3@PVDF electrode). Due to these merits, a higher rate and cycling performance of the α-Fe2O3@GA electrode are achieved compared with the α-Fe2O3@PVDF electrode when both electrodes are used for SIBs application. The α-Fe2O3@GA electrode demonstrates high initial discharge and charge capacities of 2437 and 1102 mA h g−1 at the current density of 0.2 A g−1. The α-Fe2O3@GA electrode maintains a high reversible discharge capacity of 492 mA h g−1 at the current density of 5 A g−1 after 500 cycles with a fading rate of 0.08% per cycle after the first cycle, which indicates a superior cycling performance. The outstanding performance of the resultant SIBs suggests that the green fabrication process of the α-Fe2O3@GA electrode would play a critical role in the future battery industry.

Graphitic carbon nitride/BiOCl composites for sensitive photoelectrochemical detection of ciprofloxacin

Ciprofloxacin, as a second generation of fluoroquinolone antibiotics, has been proved to cause environmental harm and exhibits toxic effects on the wastewater and surface water even at low concentrations due to their continuous input and persistence. Despite tremendous efforts, developing ciprofloxacin detection method with accuracy and sensitivity at low-cost remains a great challenge. Herein, graphitic carbon nitride/BiOCl composite (g-CN/BiOCl) has been designed for a facile and sensitive photoelectrochemical (PEC) monitoring platform of ciprofloxacin at first time. BiOCl can be modified with the g-CN nanosheets which are obtained via solvothermal process at low-temperature conditions. The use of g-CN is shown to strongly enhance the PEC response of BiOCl due to the formation of heterojunctions. The photocurrent generated at the g-CN/BiOCl-modified ITO (with 13wt%g-CN content) is much higher and more stable than that of a BiOCl-modified ITO. Based on these findings, the g-CN/BiOCl-modified ITO was used to design a PEC assay for the antibiotic ciprofloxacin. Furthermore, the limit of detection of the ciprofloxacin PEC sensor has been significantly lowered to 0.2ngmL(-1). In addition, the PEC sensor can detect ciprofloxacin in the wide range of 0.5-1840ngmL(-1).

Nature-based catalyst for visible-light-driven photocatalytic CO2 reduction

We demonstrate a rational fabrication of hierarchical treated rape pollen (TRP), a biological material used as a metal-free catalyst for visible-light-driven photocatalytic CO2 reduction. The TRP catalyst exhibits excellent visible-light-driven carbon monoxide (CO) formation of 488.4 μmol h−1 g−1 with 98.3% selectivity, using no co-catalyst or sacrifice reagent, accompanied by a high quantum efficiency of over 6.7% at 420 nm. The CO evolution rate obtained on the TRP catalyst is roughly 29.4 and 25.6 times higher than those of the most commonly reported photocatalysts, such as g-C3N4 (16.6 μmol h−1 g−1) and P25 TiO2 (19.1 μmol h−1 g−1), and is the highest among the reported carbon-based photocatalysts. In situ Fourier transform infrared spectrometry analysis disclosed that formic acid is a major intermediate. The considerable photocatalytic CO2 reduction activity observed on the TRP catalyst can be ascribed to the following factors: (i) the unique hollow porous structure of the TRP favours visible light harvesting and CO2 adsorption capacity; and (ii) the interior cavity of the TRP can decrease the diffusion length of the photogenerated reactive charge carrier from bulk to surface, thus promoting charge carrier separation. We anticipate that such a nature-based sustainable photocatalyst can provide new insights to facilitate the design of metal-free catalysts with outstanding visible-light-driven CO2 reduction performance.