Ternary g-C3N4/Co3O4/CeO2 nanostructured composites for electrochemical energy storage supercapacitors

Extensive use of fossil fuels causes heavy discharge of carbon dioxide, depleting energy resources and this requires environmentally friendly and effective energy storage materials. Hybrid supercapacitors (HSCs) are recently developed as effective energy storage materials enabling high capacitance retention rate and quick charging. Herein, synthesis of two-dimensional g-C3N4 nanosheets supported onto three-dimensional flower-like Co3O4/CeO2 (CoCe) ternary synergistic heterostructures are developed as effective electrodes for hybrid supercapacitor applications. Addition of g-C3N4 produces substantial surface active sites, enabling its synergistic effect with CoCe to enhance electrochemical performance having exceptional conductivity. The CoCe/g-C3N4 ternary composite electrode exhibits a higher specific capacitance of 1088.3 F g-1 at 1 A g-1 with 96 % of recycling stability over 5000 cycles, which is ∼5.5 and ∼5 folds higher specific capacitance than the pristine g-C3N4 and CoCe electrodes. EIS analysis revealed that CoCe/g-C3N4 electrode offered reduced charge transfer resistance compared to pristine electrodes. The fabricated two-electrode HSC device displays outstanding retention after 10,000 cycles with an ultra-high specific capacitance of 119.8 F g-1, excellent energy density 37.4 Wh kg-1 and power density of 749.9 W kg-1. This research showcases the perspectives of CoCe/g-C3N4 ternary electrodes in hybrid supercapacitors and other renewable energy storage devices.

Emerging high-ammonia‑nitrogen wastewater remediation by biological treatment and photocatalysis techniques

The bacterial and photocatalysis techniques have been widely applied into the remediation of ammonia nitrogen wastewater. Although traditional microbial methods had been verified useful; more efficient, energy-saving and controllable candidate treatment methods are still urgently needed to cover the increasingly diverse ammonia nitrogen pollution cases. The bacterial treatment technique for ammonia nitrogen mainly depends on the ammonia nitrogen oxidation-reduction (e.g. nitrification, denitrification) by nitrifying bacteria and denitrifying bacteria, but these reactions suffer from slow denitrifying kinetic process and uncontrolled disproportionation reaction. In comparison, the photocatalysis technique based on photoelectrons is more efficient and has some advantages, such as low temperature reaction and long life, while the photocatalysis technique can not perform multiple complex biochemical reactions. Despite much scientific knowledge obtained about this issue recently, such research has yet not been widely adopted in the industry because of many concerns about subsequent catalyst stability and economic feasibility. This review summarized and discussed the very recent achievements and key problems on remediation of high-ammonia‑nitrogen wastewater and oxidation driven by bacterial treatment and photocatalysis techniques, as well as the most promising future directions for these two techniques, especially the potential of jointly bacterial-photocatalysis techniques.

Synthesis of Porous Graphitic Carbon Nitride with N3C Nitrogen Vacancy by CaCO3 Template for Improved Photocatalytic H2 Evolution

Porous graphitic carbon nitride with nitrogen vacancy (N-CN) has been successfully synthesized by a facile CaCO3 template method. The porous structure contributed to increased surface area of obtained N-CN photocatalyst....