Ion-exchange-induced Bi and K dual-doping of TiOx in molten salts for high-performance electrochemical nitrogen reduction

Abstract

Electrocatalytic nitrogen reduction reaction (eNRR) at the ambient conditions is attractive for ammonia (NH3) synthesis due to its energy-efficient and eco-friendly features. However, the extremely strong N≡N triple-bonds in nitrogen molecules and the competitive hydrogen evolution reaction lead to the unsatisfactory NH3 yield and the Faradaic efficiency (FE) of eNRR, making the development of high-performance catalysts with adequate active sites and high selectivity essential for further development of eNRR. Addressing this, we herein report a Bi and K dual-doped titanium oxide (BTO@KTO) material, which is prepared by a cation exchange reaction between K2Ti4O9 and molten BiCl3, for high-performance eNRR catalysts. Benefiting from the controllable molten-salt cation exchange process, a highly active surface containing Bi/K sites and rich oxygen vacancies has been obtained on titanium oxide. Under the synergy of these two merits, an efficient eNRR catalysis, with the NH3 yield rate of 32.02 μg h−1 mgcat.−1 and the FE of 12.71%, has been achieved, much superior to that of pristine K2Ti4O9. This work thus offers a high-performance electrocatalyst for eNRR, and more importantly, a versatile cation-exchange strategy for efficiently manipulating materials' functionalities.