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Understanding the transformation of graphitic carbon nitride (g-C3N4) is essential to assess nanomaterial robustness and environmental risks. Using an integrated experimental and simulation approach, our work has demonstrated that the photoinduced hole (h+) on g-C3N4 nanosheets significantly enhances nanomaterial decomposition under •OH attack. Two g-C3N4 nanosheet samples D and M2 were synthesized, among which M2 had more pores, defects, and edges, and they were subjected to treatments with •OH alone and both •OH and h+. Both D and M2 were oxidized and released nitrate and soluble organic fragments, and M2 was more susceptible to oxidation. Particularly, h+ increased the nitrate release rate by 3.37–6.33 times even though the steady-state concentration of •OH was similar. Molecular simulations highlighted that •OH only attacked a limited number of edge-site heptazines on g-C3N4 nanosheets and resulted in peripheral etching and slow degradation, whereas h+ decreased the activation energy barrier of C–N bond breaking between heptazines, shifted the degradation pathway to bulk fragmentation, and thus led to much faster degradation. This discovery not only sheds light on the unique environmental transformation of emerging photoreactive nanomaterials but also provides guidelines for designing robust nanomaterials for engineering applications.

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The corrosion behavior of single-phase Mg-Al alloys has been examined using a combination of aqueous, atmospheric and ionic liquid based techniques. Our results show preferential rapid dissolution of Mg along with redistribution and enrichment of the effectively more "noble" Al component. During aqueous free corrosion experiments immediate pH increases were measured at the solid-liquid interface in aqueous chloride. Using inductively coupled plasma mass spectroscopy the oxide/hydroxide chemical dissolution rates were determined to be 0.222 per atomic site/s for Mg 2+ and 0.022 per atomic site/s for Al 3+ from the elemental alloy components. Atmospheric corrosion studies measured a 60 • contact angle decrease during 20 hour free corrosion corresponding to a small 0.04 Jm −2 reduction in the MgO/water interfacial free energy. Rotating disk electrode and ionic liquid dissolution techniques revealed mud cracking, platelet formation and nanowire morphologies that can result from selective dissolution of Mg in single-phase Mg-Al alloys. The evolution of these morphologies is described in terms of a step-flow dissolution mechanism.

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We report on a study of morphology evolution following de-lithiation of Li-Pb alloys, produced by the electrochemical lithiation of Pb particulate and sheet electrodes. Electrochemical titration and time of flight measurements were performed in order to determine the intrinsic diffusivity of Li, DLi , as a function of alloy composition, which ranged from 10 −12 -10 −10 cm 2 s −1 . Morphology evolution was studied under conditions of galvanostatic and potentiostatic dealloying. For the particulate electrodes, we observed dealloyed morphologies corresponding to Kirkendall voids, negative dendrites, void nodules and conventional bicontinuous nanoporous structures. In the case of Pb sheets, similar dealloyed morphologies were obtained under galvanostatic dealloying conditions, however, in the case of potentiostatic dealloying, we did not observe the formation of large volume bicontinuous nanoporous structures. For Pb sheets lithiated to a composition corresponding to the Li 8 Pb 3 phase and galvanostatically dealloyed at current densities ∼1 mAcm −2 , voltage oscillations were observed with periods of 70-90 s and amplitudes ranging from 20-130 mV. Current oscillations were also observed for potentiostatic dealloying at 1 V vs Li + /Li. The possible mechanism of these oscillations is discussed and attributed to a salt film precipitation and lift-off process.