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The water oxidation reaction (WOR) is a bottleneck in water splitting. Though many catalysts have been developed for this reaction, cost-effective, robust and efficient electrocatalysts based on non-precious metals are still highly desired. Herein reported are the synthesis, characterization and electrocatalytic properties of a dicopper(II) complex of the tetrapyridyl ligand N,N,N′,N′-tetrakis(2-pyridylmethyl)-1,4-butanediamine (tpbn) and 2,2′-bipyridine (bpy), [Cu2(tpbn)(bpy)2](ClO4)4·2CH3COCH3 (1). The X-ray single crystallography analysis revealed that the tpbn ligand bridges two copper(II) centers located in a square pyramidal environment composed of one bpy ligand as well as two pyridyl and one amino groups of a tpbn. Complex 1 was a molecular electrocatalyst for WOR in 0.1 M NaOAc–NaOH solutions of pH 11.0–14.0. It was demonstrated that the incorporation of the ancillary ligand bpy into the tpbn-bridged dicopper(II) complex is crucial for the stabilization of the catalytic system and the enhancement of the activity. This work provided an alternative to achieve robust homogeneous catalytic systems with better performance.

Herein reported are the catalytic properties of the composites derived from complex [Cu 2 (tpbn)(CH 3 OH) 4 (ClO 4 ) 2 ](ClO 4 ) 2 ( 1 ) of tetrapyridyl ligand N,N,N′,N′-tetrakis(2-pyridyl-methyl)-1,4-butanediamine (tpbn). Complex 1 was a precursor of the composites catalytically active for water oxidation and CO 2 reduction reactions. Under the anodic potential of +1.20 V vs. Ag/AgCl, composites deposited on tin-doped indium oxide (ITO) electrodes from the solutions of complex 1 at pH 9.0–13.5 are highly active for water oxidation reaction (WOR). In contrast, under the cathodic potential of −1.20 V vs. Ag/AgCl, the species deposited on the copper surface from the solutions of complex 1 at pH 6.7 can efficiently catalyze CO 2 reduction to CO. Scanning electron microscopy (SEM) showed that the composites on ITO and Cu surfaces were particulate materials. X-ray photoelectron spectroscopy (XPS) and x-ray-excited Auger electron spectroscopy (XAES) analysis revealed that the composites mainly contain cuprous oxide (Cu 2 O) and copper oxide (CuO) in different ratios, which showed different catalytic activity to water oxidation and CO 2 reduction reactions in copper-free aqueous solutions under low overpotentials. This work demonstrated that metal complexes are good candidates for preparing robust, noble-metal-free catalysts for reactions relevant to renewable energy sources.

Based on the biological purification technology combined with the engineering measures, the enhanced nitrogen purification biological experiment is implemented in Wenyu River in Beijing. The water in the river mainly is the outflow from the sewage treatment plant, in which the ammonium (NH4-N) has been effectively removed for the deeply nitrification, while treatment of the nitrate nitrogen (NO3-N) and total nitrogen (TN) is incomplete due to the denitrification. The water has low C/N value and has poor biodegradability. In this study, aiming at the water feature of low C/N and poor biodegradability, the effective way to strengthen denitrification by some enhanced techniques, such as increasing the microorganisms number and biodegradability (ie, improved nitrogen ratio), changing denitrification rates and so on, has been studied. The experimental results show that under the condition of water flow (Q) as 15 ~ 27L/hr, hydraulic detention time as (HRT) 10 ~ 18h, concentration of nitrate nitrogen (NO3-N) as 12.20 ~ 31.44mg / L, and total nitrogen (TN) as 14.50 ~ 34.71 mg / L, the removal rates of NO3-N and TN are over 30%.