A novel anammox self-forming dynamic membrane bioreactor (SFDMBR) was proposed to achieve an efficient anammox process with high biomass retention and cost-effective operation. The cake layer formed on nylon mesh (pore size, 20−25 μm) was referred to as a dynamic membrane (DM). The high permeability of the DM layer contributed to low transmembrane pressure (TMP), which kept below 10 kPa for 50 days in one filtration cycle of 82 days. Compared to the high TMP (mainly > 20 kPa) in the MBR using polyvinylidene fluoride (PVDF) microfiltration membrane, energy can be significantly conserved in the SFDMBR. Besides, the mature DM layer achieved efficient biomass retention comparable to that of PVDF membrane, which favored anammox bacteria enrichment. Concomitantly, an appropriate microenvironment for autotrophic anammox bacterial growth with wellcontrolled extracellular polymeric substances (EPS) concentration (33.22 mg•g −1 VSS) was achieved in SFDMBR. According to specific filtration resistance (SFR) analysis, reducing the EPS concentration in the bulk sludge improves sludge filterability and alleviate fouling, which was achieved in the SFDMBR system with a low SFR of 1.47 × 10 12 m −1 •kg −1 . Our results show that the cost-effective operations and technical merits make anammox SFDMBRs promising for practical applications.
The
synthesis of inexpensive and efficient electrocatalysts with
an excellent stability for the electrochemical oxygen reduction reaction
(ORR) in both alkaline and acid media through a facile environment-friendly
strategy is extremely desirable but remains challenging. In this study,
a single-atom iron electrocatalyst with exclusively Fe–N4 moieties anchored on nitrogen-doped carbon nanorods (denoted
as Fe–SA/NCS) is synthesized through a one-step pyrolysis of
Fe-doped zeolitic imidazole framework-8 (ZIF8) nanorods that are synthesized
in an aqueous system without acid leaching assistance. Profiting from
the synergistic effect of the hierarchically porous carbon support
with a rodlike structure and the large number of Fe–N4 moieties, the newly prepared Fe–SA/NCS exhibits excellent
ORR catalysis activities with a half-wave potential of 0.91 V vs RHE
in 0.1 M KOH as well as 0.77 V vs RHE in 0.1 M HClO4. Furthermore,
better stability in alkaline or acid conditions was also observed
for Fe–SA/NCS compared with Pt/C. The high open-circuit voltage
of 1.53 V and high power density of 141.6 mW cm–2 of a zinc–air battery (ZAB) with Fe–SA/NCS as the
cathode material indicate excellent electrochemical performances.
The ZAB with the Fe–SA/NCS catalysts exhibits a remarkable
cycling performance for more than 300 h with a high voltaic efficiency
of 78.6%. The present work could pave the way for the rational construction
of highly efficient and stable single-atom electrocatalysts through
green synthesis for sustainable energy technologies.
The
highly active bimetallic single-atom electrocatalysts are desirable
for the oxygen reduction reaction (ORR) and hydrogen evolution reaction
(HER) but remain challenging. Herein, Fe/Pt single-atom bifunctional
electrocatalysts (Fe1Pt1/NC) are initially fabricated
by nitrogen doping during the pyrolysis of porphyra and adsorbed urea
at high temperature with subsequent nitrogen anchoring of Pt4+ in aqueous solution with the as-synthesized nitrogen-doped carbon.
The as-synthesized Fe1Pt1/NC electrocatalysts
have been intensively characterized by HAADF-STEM, XAFS, HRTEM, XRD,
and Raman analysis. Particularly, the Fe1Pt1/NC presents excellent electrocatalytic activity toward HER, with
relatively low overpotential of 27 mV at 10 mA cm–2 and small Tafel slopes of 28 mV dec–1. Furthermore,
the Fe1Pt1/NC electrocatalyst possesses superior
ORR activity with an onset potential of 1.04 V and half-wave potential
of 0.91 V. This work provides a feasible way to synthesize electrocatalysts
with abundant single-atom sites using renewable biomass as a precursor.
Seawater splitting powered by solar or wind sources is a significant renewable energy storage technology for the production of green hydrogen energy. However, both the chlorine evolution reaction and chloride corrosion are intractable issues in seawater splitting. Here, a porous electrode based on a phosphate-intercalated NiFe (oxy)hydroxide shell coated on a nickel molybdate (NiMoO4) micropillar core (denoted as P-NiFe@NiMoO4) is synthesized through an electrochemical oxidation strategy. During the electrochemical oxidation process, the etching of MoO2 promotes the reconstruction of NiFe (oxy)hydroxide and the formation of porous structures in an alkaline solution. The optimized P-NiFe@NiMoO4 electrocatalysts afford a low overpotential of 258 mV at a current density of 100 mA/cm2 in alkaline seawater. By pairing the anode with a cathode of as-synthesized P-NiMoO, the electrolyzer presents a low voltage of 1.63 V at 100 mA/cm2 in alkaline seawater with excellent stability. Moreover, the remarkable stability of the anode seems to be attributed to the in-situ phosphate formed during the electrochemical oxidation process to passivate chloride corrosion.
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