Alloying of Cu with Ru Enabling the Relay Catalysis for Reduction of Nitrate to Ammonia

Abstract

Involving eight electron transfer process and multiple intermediates of nitrate (NO3−) reduction reaction leads to a sluggish kinetic and low Faradaic efficiency, therefore, it is essential to get an insight into the reaction mechanism to develop highly efficient electrocatalyst. Herein, a series of reduced‐graphene‐oxide‐supported RuCu alloy catalysts (RuxCux/rGO) are fabricated and used for the direct reduction of NO3− to NH3. It is found that the Ru1Cu10/rGO shows the ammonia formation rate of 0.38 mmol cm−2 h−1 (loading 1 mg cm−2) and the ammonia Faradaic efficiency of 98% under an ultralow potential of −0.05 V versus Reversible Hydrogen Electode (RHE), which is comparable to Ru catalyst. The highly efficient activity of Ru1Cu10/rGO can be attributed to the synergetic effect between Ru and Cu sites via a relay catalysis, in which the Cu shows the exclusively efficient activity for the reduction of NO3− to NO2− and Ru exhibits the superior activity for NO2− to NH3. In addition, the doping of Ru into Cu tunes the d‐band center of alloy and effectively modulates the adsorption energy of the NO3− and NO2−, which promotes the direct reduction of NO3− to NH3. This synergetic electrocatalysis strategy opens a new avenue for developing highly efficient multifunctional catalysts.

Laser-controlled tandem catalytic sites of CuNi alloys with ampere-level electrocatalytic nitrate-to-ammonia reduction activities for Zn–nitrate batteries

“…3g. 7,9,[28][29][30] Obviously, the concentration range of NO 3 À suitable for most catalysts was very narrow. In addition, the FEs of NH 3 production fluctuated dramatically, when the concentration of NO 3 À in the electrolyte slightly changed.…”

“…3h and Tables S2, S3 (ESI †). 3,8,9,12,30,31,[33][34][35][36] To further confirm the NIRR activity origin of the CuNi NPs/ CF, we analyzed the NO 3 À reduction process by the electrochemical active surface areas (ECSA) in 1 M NaOH with 44.3 g L À1 NO 3 À . The ECSA was evaluated by the electrochemical double-layer capacitances in the non-faradaic interval, which played a prominent role in calculating the kinetic parameters of the electrochemical reaction.…”

“…8 The important roles played by the tandem sites are as follows: (1) the introduced site might change the adsorption energies of NIRR intermediates via adjusting the electronic structure of another site. [9][10][11] (2) The introduced site might cause changes in the reaction pathway, thereby accelerating the reaction kinetics based on the excellent supply capacity of active hydrogen (H*). 12 Thus, the adsorption state of NIRR intermediates can be well hydro-reduced in time at the tandem sites, which is instrumental in N-O bond cracking and N-H bond formation.…”

Sustainable Ammonia Electrosynthesis from Nitrate Wastewater Coupled to Electrocatalytic Upcycling of Polyethylene Terephthalate Plastic Waste

“…The NO 3 RR of Ru-Co­(OH) 2 /NF is also better than those of some reported electrocatalysts under alkaline conditions (Table S1). According to literature reports, Ru as a dopant can significantly improve the catalytic performance of the host catalyst for the NO 3 RR by optimizing the adsorption and hydrogenation of the reaction intermediates. , Therefore, the adsorption energy of H before and after Ru incorporation is calculated by density functional theory (DFT). The results show that Ru-Co­(OH) 2 (−0.57 eV) exhibits a larger H adsorption energy than that of Co­(OH) 2 (−0.40 eV, Figure c–e).…”

Electrochemical Co-Production of Ammonia and Biodegradable Polymer Monomer Glycolic Acid via the Co-Electrolysis of Nitrate Wastewater and Waste Plastic

“…Therefore, as a green and sustainable solution, the use of electrocatalytic technology to upcycle polluting waste into high value-added chemicals is reliable. For example, the electroreduction process can convert NO 3 – into nontoxic nitrogen (N 2 ) or value-added ammonia (NH 3 ) under mild operating conditions. − Notably, compared to the useless N 2 , NH 3 is largely needed as a basic raw material for various chemicals and an important carbon-free energy carrier. − Meanwhile, the traditional NH 3 synthesis relies on the Haber–Bosch (H–B) process under high temperature and pressure operating conditions, resulting in serious environmental pollution and fossil energy consumption. − On the contrary, the electrochemical nitrate reduction reaction (NO 3 RR) can achieve value-added ammonia production while treating nitrate wastewater, which is a win–win environmentally friendly process. − In addition, the application of electrochemical oxidation in PET plastic waste upcycling can realize the conversion of EG from PET hydrolysate into value-added products (e.g., formate, glycolic acid (GA)). − However, most of the previous reports have focused on the conversion of EG to formate (C1), and less on C2 products. As a biodegradable material with high mechanical strength, high biocompatibility, and rapid degradation, polyglycolic acid (PGA) plastics are widely used in biomedical fields. , Nevertheless, limited GA production and high prices have resulted in insufficient PGA production.…”