Temporally Decoupled Ammonia Splitting by a Zn–NH₃ Battery with an Ammonia Oxidation/Hydrogen Evolution Bifunctional Electrocatalyst as a Cathode

Abstract

Ammonia splitting to hydrogen is a decisive route for hydrogen economy but is seriously limited by the complex device and low efficiency. Here, we design and propose a new rechargeable Zn−NH 3 battery based on temporally decoupled ammonia splitting to achieve efficient NH 3 -to-H 2 conversion. In this system, ammonia is oxidized into nitrogen during cathodic charging (2NH 3 + 6OH − → N 2 + 6H 2 O + 6e − ) with external electrical energy conversion and storage, while during cathodic discharging, water is reduced to hydrogen (2H 2 O + 2e − → H 2 + 2OH − ) with electrical energy generation. In this loop, continuous and efficient H 2 production without separation and purification is achieved. With the help of the ammonia oxidation reaction (AOR) and hydrogen evolution reaction (HER) bifunctional catalyst of Mo 2 C/NiCu@C, a rechargeable Zn−NH 3 battery is realized that exhibits a high NH 3 -to-H 2 FE of 91.6% with outstanding durability for 900 cycles (300 h) at 20 mA/cm 2 , enabling efficient and continuous NH 3 -to-H 2 conversion.

Tuning the electrocatalytic nitric oxide reduction activity of copper through alloying with nickel for NH3 production at low overpotentials

“…Moreover, previous studies on the nitrogen reduction reaction (NRR) and nitrate reduction reaction (NO 3 − RR) to NH 3 synthesis also demonstrated the various intermediate stabilizations over CuNi alloys as compared to Cu. 44–47 On the other hand, a few reports also emphasized that the nitrogen intermediate species will exclusively bind to the Cu surface while H* intermediates stabilize on the Ni surface. 48–50 The synergistic coupling between Cu and Ni enhances hydrogenation kinetics and NH 3 formation.…”

Dual-independent active sites for efficient hydrogen production

“…13,29–31 With regard to the HER electrocatalysts, transition metal carbides (TMCs) with a special metallic packed structure have been extensively investigated for electrocatalysts because of their high thermal and electrical conductivity, excellent mechanical strength and chemical stability, wide pH compatibility and durability. 32–34 Although some progress on HER/HzOR electrocatalysts has been achieved, very few candidates can satisfy the needs for practical applications owing to the totally different catalytic reaction mechanism and active sites. 35,36 Therefore, the design of high-performance materials with incorporation of two independent active sites for the HzOR and HER is of significance.…”