Interfacial Electron Delocalization in Engineering Nanosized Anti-Perovskite Nitride for Efficient CO₂ Electroreduction

Anti-perovskites represent a type of newly arising functional materials with a well-defined cubic lattice crystal structure; they provide an excellent entity for studying structure–activity relationship in heterogeneous catalysis. Herein, nitride-based anti-perovskite CuNNi3 was synthesized, and its catalytic properties in electroreduction of carbon dioxide (CO2RR) to syngas were explored for the first time. The introduction of N into the body center of the face-centered cubic cell of CuNi3 was found to create abundant Lewis basic sites with various strengths and thus favored stronger adsorption of the relevant critical species, thus leading to significant improvement in the efficiency of CO2RR and hydrogen reduction compared with that of CuNi3. More importantly, when a thin CuNNi3 nanoshell is coated on a CuNi3 alloy core, significant nanosizing and interfacial interaction effects are noticed, which change the catalytic behaviors of the anti-perovskite. On one hand, the nanosizing effect leads to occurrence of Ni2+ species with a higher oxidative state and consequently deactivates the weak Lewis basic sites in the CuNNi3 nanoshell, which accordingly inhibits hydrogen evolution; the CuNi3@CuNNi3 nanocomposite thus delivers CO Faradaic efficiency up to 96% in comparison to a value of 70% yielded by the bulky counterpart. On the other hand, evident interfacial electron delocalization from the CuNi3 alloy core to the CuNNi3 nanoshell was observed, which was found to increase the N escape energy in the cubic cell of CuNNi3 and consequently enhance its chemical stability; as a result, the CuNi3@CuNNi3 nanocomposite displays much improved catalytic stability compared with the bulky counterpart in CO2RR. This work for the first time explores the interesting electrocatalytic behavior of nitride-based anti-perovskites in electrochemical reduction of CO2, which spells a grand opportunity for the structure–relationship study in CO2RR.