Search

Porous graphene represents promising electrocatalysts or substrates of composite electrocatalysts for various electrochemical reactions, and is well-established for renewable energy conversion and environmental remediation. Unfortunately, the lack of comprehensive understanding on the active sites of porous graphene hinders the further development of high-performance electrocatalysts. Herein, porous graphene was established for electrochemical filtration of wastewater, with results indicating that porous graphene exhibited excellent electrochemical activity in terms of high efficiency of oxidation or reduction of organic pollutants. It was experimentally and theoretically demonstrated that the –OH groups generated on the edge of porous graphene served as the active sites for the electrocatalytic reactions. The augmentation of –OH groups at the edges of graphene benefited the inner-sphere electron transfer of the electrocatalytic reactions, improving the electron transfer rates by nearly four times (from 0.034 s−1 to 0.135 s−1). Through providing these fundamental insights into the role of the active sites on the pores of porous graphene, this work furnishes future directives for the design of porous graphene-based electrocatalysts.

About 3.93 billion tons of wastewater containing heavy metal complexes are discharged (e.g., from the electroplating industry) every year in China alone. It is challenging to appropriately treat su...

Membrane distillation (MD) is a promising green technology that can harness waste or solar heat to treat water. Since such heat sources suffer from temporal variations, a complementary, efficient means is necessary. Induction heating is attractive in providing localized heating at the feed-membrane interface where the heat matters, but the typical conductive materials (e.g., metal, alloy) corrode readily in the high-salinity, high-temperature environment. In this work, a superior induction material was proposed, namely, reduced graphene oxides (rGO) coated onto a porous Nickel foam by Nafion (rGO/Nafion/Ni), which exhibited superior and sustained performance for membrane distillation. Results indicate that rGO/Nafion/Ni achieved up to 28.1% higher water flux (6.42 ± 0.36 Lm−2h−1) and 37.5% lower energy consumption (3.13 kWhL−1) compared to other carbon materials coated on Ni or the bare Ni foam. The mechanism underlying the enhanced MD performance was the higher absorption of the electromagnetic waves via multiple internal reflections and larger eddy currents generated by rGO, leading to higher temperatures at the feed-membrane interface that increased the driving force for distillation and thereby the energy efficiency of MD. Our work demonstrated that the induction heating of rGO has high potential for augmenting MD performance in water treatment. Economic Development Board (EDB) Ministry of Education (MOE) This work was supported by the Singapore GSK (GlaxoSmithKline) – EDB (Economic Development Board, Singapore) Trust Fund and the Singapore Ministry of Education Tier 1 Grant (2019-T1-002-065) .

The employment of electrochemical technology in membrane filtration promises high separation efficiency with minimal membrane fouling. Herein, we fabricated single cobalt atom and nitrogen atom codoped graphene (NG-Co) as a conductive membrane, and showed that it achieved 99.5% rejection at a small voltage of 2.5 V and exhibited excellent reusability. The turnover frequency of the single Co site was about 13.5 times larger than that of traditional Co-based nanocatalysts, because the single Co site served as the key electrochemical active site to degrade the organic pollutants, while the nitrogen-doped groups of graphene served as efficient binding sites for the immobilization of the single Co site to improve the intrinsic catalytic activity of the Co sites. This study has important implications for the design of graphene-based conductive membranes in the electrochemical remediation of wastewater. Economic Development Board (EDB) This work was supported by the Singapore GSK (GlaxoSmithKline) – EDB (Economic Development Board) Trust Fund.

The need for highly efficient and environmentally friendly catalysts for pollutants removal sustainably has drawn extensive attention. In particular, piezocatalysis is promising for harnessing low-frequency vibration (e.g., wind) to enable high-performance degradation of organic pollutants. Herein, we synthesized a sandwich-like piezocatalyst by fabricating MoS2 nanosheets onto S, N-codoped graphene (MoS2@SNG) through a facile hydrothermal strategy. Results indicate that the MoS2@SNG exhibited ultrahigh piezocatalytic activities for both oxidation and reduction degradation of pollutants. Benefiting from the reduced stacking of MoS2 nanosheets and accelerated electron transfer of heterogeneous graphene, MoS2@SNG had a sharply enhanced electric field (i.e., 29.3 mV of MoS2@SNG versus 4.7 mV of MoS2). Moreover, the abundance of active sites of Mo4+ being exposed over MoS2@SNG remarkably promoted the redox reaction. This study provided evidence that layered piezoelectric materials represent an attractive strategy for environmental remediation.

Adsorption is a classical process widely used in industry and environmental protection, and the regeneration of exhausted adsorbents, as the reverse process of adsorption, is vital to achieving a sustainable adsorption process. Chemical and thermal regeneration, which feature high costs and environmental side effects, are classical but not environmentally friendly methods. Herein, a new regeneration method based on an electrochemical process using graphene aerogel (GA) as a model conductive adsorbent was proposed. First, 3D GA was prepared to adsorb organic and inorganic pollutants, avoiding the inconvenience of using powdered graphene. Then, the exhausted GA was cleaned by the electrochemical desorption and degradation of adsorbed organic pollutants if undesired and the electrorepulsion of adsorbed metal ions in the absence of any additional chemicals, showing a high processing capability of 1.21 L g–1 GA h–1 and low energy consumption (∼0.2 kWh m–3 solution). The mechanisms involved in the electrochemis...

Iron is one of the most abundant elements in aquatic environments, and plays important roles in the fate and transport of environmental contaminants. Previous studies on the photochemical properties of Fe(III) species have largely focused on complexes formed between Fe(III) and environmental ligands such as natural organic matter (NOM) under UV irradiation, whereas the potentially important roles of hydrolysis species of Fe(III) in Fe(III)-mediated photo-transformation of environmental contaminants under solar light are not fully understood. In this study, the solar light-driven photochemical activities of hydrolysis species of Fe(III) were further explored, using a system containing only 0.5 mM Fe2(SO4)3 and bisphenol A. The important role of colloidal [Fe(OH)3]m, formed from the hydrolysis of Fe3+, as a core photochemical species of Fe(III) was proposed and verified. Interestingly, O2− , rather than OH, was identified (via electron spin resonance) as the key active radical responsible for the degradation of bisphenol A. We propose that unlike Fe(OH)2+, which under UV irradiation can yield OH (Fe(OH)2+ + hv → Fe2+ + OH), colloidal [Fe(OH)3]m produces O2− even in sunlight ([Fe(OH)3]m + 2O2 + hv → Fe(II) + 2O2− + H2O). The fact that Fe(III) can produce strong radicals in sunlight may have important environmental implications.