CO2 bubble-assisted in-situ construction of mesoporous Co-doped Cu2(OH)2CO3 nanosheets as advanced electrodes towards fast and highly efficient electrochemical reduction of nitrate to N2 in wastewater.

The development of high-efficient and cost-effective electrocatalysts is crucial to remove nitrate pollutant in wastewater. Herein, we design and prepare mesoporous Co-doped Cu2(OH)2CO3 malachite nanosheets as an electrocatalyst toward highly efficient nitrate reduction using a facile CO2 bubble-assisted coprecipitation synthesis. The electrocatalytic performance is subject to the Co/Cu ratio of this malachite. Remarkably, compared with the pristine monometal Cu or Co-based electrocatalyst, the optimal electrocatalyst, 0.3Co@Cu2(OH)2CO3, displays fast and highly efficient removal capacity of nitrate with an impressive high total nitrogen (TN) removal of 8628.99 mg N g-1CoCu (398.79 mg N gcat-1 h-1), N2 selectivity of 97.11% as well as negligible nitrite product at 100 mg L-1 NO3--N and 2000 mg L-1 Cl- neutral electrolyte. Above all, high total nitrogen removal efficiency (81.92%) and chemical oxygen demand (73.74%) in actual wastewater. Its excellent electrocatalytic performance is achieved by regulating the electronic structure and the adsorption/desorption of the intermediate. This study discovers a new type of electrode materials for nitrate removal in wastewater.

Rational Construction of a N, F Co-doped Mesoporous Cobalt Phosphate with Rich-Oxygen Vacancies for Oxygen Evolution Reaction and Supercapacitors.

Transition-metal phosphates have been widely applied as promising candidates for electrochemical energy storage and conversion. In this study, we report a simple method to prepare a N, F co-doped mesoporous cobalt phosphate with rich-oxygen vacancies by in-situ pyrolysis of a Co-phosphate precursor with NH4 + cations and F- anions. Due to this heteroatom doping, it could achieve a current density of 10 mA/cm2 at lower overpotential of 276 mV and smaller Tafel slope of 57.11 mV dec-1 on glassy carbon. Moreover, it could keep 92 % of initial current density for 35 h, indicating it has an excellent stability and durability. Furthermore, the optimal material applied in supercapacitor displays specific capacitance of 206.3 F g-1 at 1 A ⋅ g-1 and maintains cycling stability with 80 % after 3000 cycles. The excellent electrochemical properties should be attributed to N, F co-doping into this Co-based phosphate, which effectively modulates its electronic structure. In addition, its amorphous structure provides more active sites; moreover, its mesoporous structure should be beneficial to mass transfer and electrolyte diffusion.

Rational Design of a N,S Co-Doped Supermicroporous CoFe-Organic Framework Platform for Water Oxidation.

It remains a challenge to rational design of a new metal-organic framework (MOF) as highly efficient direct electrocatalysts for the oxygen evolution reaction (OER). Herein, we developed a simple and effective method to explore a new pillared-layered MOF with syringic acid as a promising OER electrocatalyst. The isostructural mono-, heterobimetallic MOF and N,S co-doped MOF by mixing thiourea were quickly synthesized in a high yield under solvothermal condition. Moreover, the optimized N,S co-doped MOF exhibits the lowest overpotential of 254 mV at 10 mA cm-2 on a glass carbon electrode and a small Tafel slope of 50 mV dec-1 , especially, this catalyst also possesses long-term electrochemical durability for at least 16 h. According to the characterization, the incorporation of N and S atoms into this heterobimetallic CoFe-based MOF could modify its pore structure, tune the electronic structure, accordingly, improve the mass and electron transportation, and facilitate the formation of active species, as a consequence, the improved activity of this new N,S co-doped MOF for OER should be mainly be ascribed to higher electrochemical activation toward the active species via in situ surface modification during the OER process.