Recent studies indicated that water treatment polymers such as poly(epichlorohydrin dimethylamine) (polyamine) and poly(diallyldimethylammonium chloride) (polyDADMAC) may form N-nitrosodimethylamine (NDMA) when in contact with chloramine water disinfectants. To minimize such potential risk and improve the polymer products, the mechanisms of how the polymers behave as NDMA precursors need to be elucidated. Direct chloramination of polymers and intermediate monomers in reagent water was conducted to probe the predominant mechanisms. The impact of polymer properties including polymer purity, polymer molecular weight and structure, residual dimethylamine (DMA), and other intermediate compounds involved in polymer synthesis, and reaction conditions such as pH, oxidant dose, and contact time on the NDMA formation potential (NDMA-FP) was investigated. Polymer degradation after reaction with chloramines was monitored at the molecular level using FT-IR and Raman spectroscopy. Overall, polyamines have greater NDMA-FP than polyDADMAC, and the NDMA formation from both polymers is strongly related to polymer degradation and DMA release during chloramination. Polyamines' tertiary amine chain ends play a major role in their NDMA-FP, while polyDADMACs' NDMA-FP is related to degradation of the quaternary ammonium ring group.
Using renewable electricity to synthesize ammonia from nitrogen paves a sustainable route to making value-added chemicals but yet requires further advances in electrocatalyst development and device integration. By engineering both electrocatalyst and electrolyzer to simultaneously regulate chemical kinetics and thermodynamic driving forces of the electrocatalytic nitrogen reduction reaction (ENRR), we report herein stereoconfinement-induced densely populated metal single atoms (Rh, Ru, Co) on graphdiyne (GDY) matrix (formulated as M SA/GDY) and realized a boosted ENRR activity in a pressurized reaction system. Remarkably, under the pressurized environment, the hydrogen evolution reaction of M SA/GDY was effectively suppressed and the desired ENRR activity was strongly amplificated. As a result, the pressurized ENRR activity of Rh SA/GDY at 55 atm exhibited a record-high NH3formation rate of 74.15 μg h−1⋅cm−2, a Faraday efficiency of 20.36%, and a NH3partial current of 0.35 mA cm−2at −0.20 V versus reversible hydrogen electrode, which, respectively, displayed 7.3-, 4.9-, and 9.2-fold enhancements compared with those obtained under ambient conditions. Furthermore, a time-independent ammonia yield rate using purified15N2confirmed the concrete ammonia electroproduction. Theoretical calculations reveal that the driving force for the formation of end-on N2* on Rh SA/GDY increased by 9.62 kJ/mol under the pressurized conditions, facilitating the ENRR process. We envisage that the cooperative regulations of catalysts and electrochemical devices open up the possibilities for industrially viable electrochemical ammonia production.
As af avorite descriptor,t he size effect of Cu-based catalysts has been regularly utilized for activity and selectivity regulation toward CO 2 /CO electroreduction reactions (CO 2 / CORR). However,l ittle progress has been made in regulating the sizeofCunanoclusters at the atomic level. Herein, the sizegradient Cu catalysts from single atoms (SAs) to subnanometric clusters (SCs,0.5-1 nm) to nanoclusters (NCs,1-1.5 nm) on graphdiyne matrix are readily prepared via an acetylenicbond-directed site-trapping approach.E lectrocatalytic measurements showasignificant sizeeffect in both the activity and selectivity towardC O 2 /CORR. Increasing the sizeo fC u nanoclusters will improve catalytic activity and selectivity towardC 2+ productions in CORR. Ahigh C 2+ conversion rate of 312 mA cm À2 with the Faradaic efficiency of 91.2 %a re achieved at À1.0 Vv ersus reversible hydrogen electrode (RHE) over Cu NCs.T he activity/selectivity-sizer elations provideaclear understanding of mechanisms in the CO 2 / CORR at the atomic level.
Developing cheap, stable, and efficient electrocatalysts is of
extreme importance in the effort to replace noble metal electrocatalysts
for use in the hydrogen evolution reaction (HER) and oxygen evolution
reaction (OER). We report a three-dimensional self-supported Cu
3
P nanobush (NB) catalyst directly grown on a copper mesh via
a one-step method. This nanostructure exhibits a superior catalytic
activity of achieving a current density of 10 mA cm
–2
at 120 mV and exhibits a long-term stability in acid solutions.
It shows a Tafel slope of 72 mV dec
–1
and an onset
potential of −44 mV. This catalyst displays a good catalytic
activity in basic electrolytes, reaching a current density of 10 mA
cm
–2
at the overpotential values of 252 and 380
mV for HER and OER, respectively. The bifunctional Cu
3
P
NB/Cu catalyst exhibits better catalytic performances than the Pt/C
and IrO
2
catalysts in a two-electrode electrolyzer for
overall water splitting.
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