Xiao Chang

Effects of Sulfur Doping and Humidity on CO2 Capture by Graphite Split Pore: A Theoretical Study

By use of grand canonical Monte Carlo calculations, we study the effects of sulfur doping and humidity on the performance of graphite split pore as an adsorbent for CO2 capture. It is demonstrated that S doping can greatly enhance pure CO2 uptake by graphite split pore. For example, S-graphite split pore with 33.12% sulfur shows a 39.85% rise in pure CO2 uptake (51.001 mmol/mol) compared with pristine graphite split pore at 300 K and 1 bar. More importantly, it is found that S-graphite split pore can still maintain much higher CO2 uptake than that by pristine graphite split pore in the presence of water. Especially, uptake by 33.12% sulfur-doped S-graphite split pore is 51.963 mmol of CO2/mol in the presence of water, which is 44.34% higher than that by pristine graphite split pore at 300 K and 1 bar. In addition, CO2/N2 selectivity of S-graphite split pore increases with increasing S content, resulting from stronger interactions between CO2 and S-graphite split pore. Moreover, by use of density functional theory calculations, we demonstrate that S doping can enhance adsorption energy between CO2 molecules and S-graphene surface at different humidities and furthermore enhance CO2 uptake by S-graphite split pore. Our results indicate that S-graphite split pore is a promising adsorbent material for humid CO2 capture.

Superior Selective CO2 Adsorption of C3N Pores: GCMC and DFT Simulations

Development of high-performance sorbents is extremely significant for CO2 capture due to its increasing atmospheric concentration and impact on environmental degradation. In this work, we develop a new model of C3N pores based on GCMC calculations to describe its CO2 adsorption capacity and selectivity. Remarkably, it exhibits an outstanding CO2 adsorption capacity and selectivity. For example, at 0.15 bar it shows exceptionally high CO2 uptakes of 3.99 and 2.07 mmol/g with good CO2/CO, CO2/H2, and CO2/CH4 selectivity at 300 and 350 K, separately. More importantly, this adsorbent also shows better water stability. Specifically, its CO2 uptakes are 3.80 and 5.91 mmol/g for and 0.15 and 1 bar at 300 K with a higher water content. Furthermore, DFT calculations demonstrate that the strong interactions between C3N pores and CO2 molecules contribute to its impressive CO2 uptake and selectivity, indicating that C3N pores can be an extremely promising candidate for CO2 capture.

High-performance WO3−x-WSe2/SiO2/n-Si heterojunction near-infrared photodetector via a homo-doping strategy

It is demonstrated that homo-doping is a simple and effective strategy to improve near-infrared (NIR) photoresponsive performance of a WO3−x-WSe2/SiO2/n-Si heterojunction. Our systematic studies showed that an air thermal annealing treatment can enrich the p-WO3−x dopants of WSe2, which was essential to greatly enhance the NIR photoresponsive performance of the WO3−x-WSe2/SiO2/n-Si heterojunction. Moreover, this heterojunction exhibited excellent selectivity and good stability to the incident light of 900 nm with high photoresponsivity of ∼137.7 A W−1, superior detectivity (D*) of ∼2.27 × 1014 Jones (1 Jones = 1 cm Hz1/2 W−1), and prominent sensitivity (S) of ∼1.19 × 108 cm2 W−1. When compared with the WSe2/SiO2/n-Si heterojunction, D* was increased by a factor of 7 and S was enhanced by a factor of 35. Comprehensive performance analyses indicate that the device fabricated in this work is not only significantly better than most of the reported Si based devices, but also can be comparable with 0D and 2D based nanostructure heterojunction devices. Systematic NIR photoresponsive studies demonstrate that the enhanced photoresponsive performance can be mainly attributed to the down-shift of the Fermi level of p–p homo-doped WO3−x-WSe2, which generates the larger interface barrier height between WO3−x-WSe2 and n-Si and the weaker dark current of the p–p homo-doped WO3−x-WSe2/SiO2/n-Si heterojunction. Our studies demonstrate that the homo-doping approach may be extended to fundamentally modify other semiconductor based photodetectors.

Me–N–C (Me = Fe, Cu, and Co) nanosheet as a promising charge-controlled CO2 capture material

It is necessary to explore advanced materials with high CO2 selectivity and simple CO2 regeneration to weaken the greenhouse effect. Therefore, in this study, we report a comprehensive investigation of CO2, CH4, H2, C2H2, C2H4 and C2H6 on different Me–N–C nanosheets with different charge densities via density functional theory calculations. Our results demonstrate that CO2 is weakly absorbed on neutral and positively charged Me–N–C monolayer, whereas CO2 adsorption strength can be dramatically strengthened on a negatively charged Me–N–C monolayer, especially the Fe–N–C nanosheet. The adsorption energy of CO2 on the negatively charged Fe–N–C nanosheet with a negative charge density of 15.27 × 1013 e− cm−2 is −3.07 eV, which is about 10 times larger than that (−0.283 eV) on neutral one; in addition, it also shows high CO2 selectivity from mixtures containing CH4, H2, C2H2, C2H4 and C2H6. This investigation can provide valuable information for designing feasible adsorbent materials having high CO2 adsorption capacity and selectivity.