Unveiling multi-element synergy in polymetallic oxides for efficient nitrate reduction to ammonia

Electrocatalytic nitrate reduction reaction is considered as a promising and sustainable method for ammonia synthesis.However,the selectivity and yield rate of ammonia are limited by the competitive hydrogen evolution reaction and the complex eight-electron transfer process.Herein,we developed a(FeCoNiCu)Ox/CeO_(2)polymetallic oxide electrocatalyst for effective nitrate reduction to ammonia.The synergistic effects among the multiple elements in the electrocatalyst were clearly elucidated by comprehensive experiments.Specifically,Cu acted as the active site for reducing nitrate to nitrite,and Co facilitated the subsequent reduction of nitrite to ammonia,while Fe and Ni promoted water dissociation to provide protons.Furthermore,the incorporation of CeO_(2)increased the active surface area of(FeCoNiCu)Ox,resulting in an improved ammonia yield rate to meet industrial demands.Consequently,the(FeCoNiCu)Ox/CeO_(2)electrocatalyst achieved an ammonia current density of 382 mA cm^(-2)and a high ammonia yield rate of 30.3 mg h^(-1)cm^(-2)with a long-term stability.This work offers valuable insights for the future design of highly efficient multi-element electrocatalysts.

Catalytic hydrogenolysis of organosolv lignin: Cleaving C–O bonds over CuMgAlO_(x)-layered porous metal oxide catalysts for oriented monophenols production

To understand the catalytic conversion of lignin into high-value products,lignin depolymerization was performed using a layered polymetallic oxide(CuMgAlO_(x))catalyst.The effects of the conversion temperature,hydrogen pressure,and reaction time were studied,and the ability of CuMgAlO_(x)to break the C–O bond was evaluated.The CuMgAlO_(x)(Mg/Al=3:1)catalyst contained acidic sites and had a relatively homogeneous elemental distribution with a high pore size and specific surface area.Theβ-O-4 was almost completely converted by disassociating the C–O bond,resulting in yields of 14.74%ethylbenzene,47.58%α-methylphenyl ethanol,and 36.43%phenol.The highest yield of lignin-derived monophenols was 85.16%under reaction conditions of 280℃ and 3 Mpa for 4 h.As the reaction progressed,depolymerization and condensation reactions occurred simultaneously.Higher temperatures(>280℃)and pressures(>3 Mpa)tended to produce solid char.This study establishes guidelines for the high-value application of industrial lignin in the catalytic conversion of polymetallic oxides.