Combination of Pd–Cu Catalysis and Electrolytic H₂ Evolution for Selective Nitrate Reduction Using Protonated Polypyrrole as a Cathode

Abstract

Pd–Cu catalysis is combined with in situ electrolytic H2 evolution for NO3 – reduction with protonated polypyrrole (PPy) as a cathode. The surface of PPy is not only beneficial for H2 evolution, but exclusive for NO3 – adsorption, and thus inhibits NO3 – reduction. Meanwhile, the in situ H2 generation exhibits a much higher utilization efficiency because of the smaller bubble size and higher dispersion. The Pd–Cu catalysts with the ratios of 6:1 and 4:1 exhibit the highest NO3 ––N removal (100%) and N2 selectivity (93–95%) after 90 min. In comparison with the results obtained with other cathode materials (Ti, Cu, Co3O4, and Fe2O3) and obtained by other researchers, the new process shows a faster NO3 ––N reduction rate and much higher N2 selectivity. However, the O2 generated on the anode can oxidize Cu to Cu2O that may work as the catalyst for NO3 ––N reduction to NH4 +–N by H2, resulting in more than 60% NH4 +–N generated without a proton exchange membrane. Both the PPy film and Pd–Cu catalyst exhibit good stability and there is no Cu2+ or Pd2+ in solution after reaction. Real industrial wastewater is further treated in this system, the NO3 ––N is reduced from 670 mg L–1 to less than 100 mg L–1 in 90 min, and only little amount of NH4 +–N is generated.

Synergistic Effect of Co(III) and Co(II) in a 3D Structured Co3O4/Carbon Felt Electrode for Enhanced Electrochemical Nitrate Reduction Reaction

“…Compared to traditional physicochemical treatments, like physisorption, biological reduction, and ion exchange, − electrochemical reduction of nitrate has received more and more attention due to its characteristics such as simple operation, environment friendliness, and low cost. , The electrochemical nitrate reduction reaction (ENRR) is a complex reaction involving many intermediates . More importantly, the first step of electrochemically reducing nitrates to nitrites is the rate-determining step for the overall ENRR. , Thus, it is necessary to develop efficient cathodes for improving the rate of nitrate reduction.…”

Para-Chlorophenol (4-CP) Removal by a Palladium-Coated Biofilm: Coupling Catalytic Dechlorination and Microbial Mineralization via Denitrification

“…On the one hand, discharge of phenol or cyclohexanone is not acceptable, as they are sources of COD and have their own toxic impacts . On the other hand, precious-metal catalysts normally cannot catalyze NO 3 – reduction to nitrite (NO 2 – ), unless they are modified by a promotor such as Cu or In . These modification processes require energy-consuming and environmental unfriendly treatments, such as a high reaction temperature (mostly above 120 °C), organic solvents, and/or calcining. , …”

Alloying effect-induced electron polarization drives nitrate reduction to ammonia

“…[1][2][3] Therefore, greater demand for NH3 is foreseeable. [4][5] The industrial NH3 synthesis through the classical Haber-Bosch process demands drastic reaction conditions of high pressures (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25) and temperatures (300-550 o C), 6 which consumes 1-2% of the world's annual energy supply. [7][8][9] Considering such extremely harsh condition and fossil fuels shortage, NH3 production at atmospheric pressure and under ambient temperature is one of the greatest challenges and has been pursued actively for over a century.…”

“…[15][16] In view of energy consumption, exploring the electrocatalytic NITRR makes perfect sense for low temperature NH3 synthesis. [17][18][19][20][21][22][23] Currently, the reduction treatment of exhaust gas NOx (such as NO and NO2) from the stationary sources requires considerable energy since this process is conducted at high temperature (> 400 °C). [1][2] Our approach is to convert NOx into NO3solution by oxidation and leaching absorption process and subsequent effectively convert NO3into value-added NH3.…”