Engineering Catalytically Active Sites by Sculpting Artificial Edges on MoS2 Basal Plane for Dinitrogen Reduction at a Low Overpotential

Engineering catalytically active sites have been a challenge so far and often relies on optimization of synthesis routes, which can at most provide quantitative enhancement of active facets, however, cannot provide control over choosing orientation, geometry and spatial distribution of the active sites. Artificially sculpting catalytically active sites via laser-etching technique can provide a new prospect in this field and offer a new species of nanocatalyst for achieving superior selectivity and attaining maximum yield via absolute control over defining their location and geometry of every active site at a nanoscale precision. In this work, a controlled protocol of artificial surface engineering is shown by focused laser irradiation on pristine MoS₂ flakes, which are confirmed as catalytic sites by electrodeposition of AuNPs. The preferential Au deposited catalytic sites are found to be electrochemically active for nitrogen adsorption and its subsequent reduction due to the S-vacancies rather than Mo-vacancy, as advocated by DFT analysis. The catalytic performance of Au-NR/MoS₂ shows a high yield rate of ammonia (11.43 × 10⁻⁸ mol s⁻¹ cm⁻²) at a potential as low as −0.1 V versus RHE and a notable Faradaic efficiency of 13.79% during the electrochemical nitrogen reduction in 0.1 m HCl.     

Improving Effective Impervious Estimates to Inform Stormwater Management

Water Resources Management - Sizing stormwater runoff control facilities and their performance relies on the amount of runoff generated from impervious cover in the watershed. Total impervious area...     

Investigating the Potential for Ongoing Pollution from an Abandoned Pyrite Mine

Davis Mine was the largest working pyrite mine in the state of Massachusetts during its lifetime between 1882 and 1911. Since abandonment, a highly-polluting mine water discharge has emerged from the site of an old mine shaft and a waste rock pile and is contaminating the nearby Davis Mine Brook. During the past 90 years, no attempt has been made to implement any pollution abatement measures. This paper assesses the likely current volume of mine waste on the site and compares this figure with the amount of mine waste produced during the lifetime of the mine based on old mine plans and production figures. A simple mass balance model allowed us to compute the loadings of contaminants into Davis Mine Brook and to calculate the ratio of loadings from different sources of pollution, namely the mine shaft discharge and ground water discharge from the waste pile. Results for 2004 indicated that the proportion of mine water flowing from the shaft varies seasonally, with the greatest discharge in spring and lowest in summer. These results allow us to assess the potential lifetime of the discharge if left untreated and determine what flow pathways are important if a treatment scheme were to be implemented at the site.