CoNi-LDH nanosheets and TiO2 nanotubes interfaces synergistically boost electrochemical nitrite reduction to ammonia

Electrocatalytic nitrite reduction reaction (NO 2 - RR), being a green and mild-conditioned approach, is regarded as an ideal alternative to the energy- and emission-intensive Haber-Bosch process for clean and efficient ammonia (NH 3 ) production. Exploring economical, high-efficiency and stable catalysts is therefore important to achieve the goal, representing a new challenge in this field. Herein, a cobalt and nickel layered double hydroxide supported on titanium dioxide nanotube array (CoNi-LDH/TiO 2 ) is proposed for electrocatalytic NO 2 - -to-NH 3 conversion. It is demonstrated that the free-standing CoNi-LDH/TiO 2 achieves a high NH 3 yield of ~17.6 mg h −1 cm −2 and an outstanding Faradaic efficiency of ~97.1% with good cycling stability in alkaline electrolyte. Its electrocatalytic performance significantly surpasses that of CoNi-LDH as well as TiO 2 counterparts profiting from their synergistic effect, and even recently reported transition metal-based catalysts without and with TiO 2 support. This synergy possibly stems from the intrinsic activity difference between CoNi-LDH and TiO 2 , which induces the interfacial charge transfer of CoNi-LDH/TiO 2 , thereby reducing its energy barrier of the rate-determining step toward electrocatalytic NO 2 - RR. Furthermore, integration of the CoNi-LDH/TiO 2 into a zinc-nitrite battery achieves simultaneously the NO 2 - -containing sewage treatment, electrical power output, and NH 3 synthesis. Thus, this study is of great significance to the environment and sustainable development.