Structural Modulation of Ni–Zn Intermetallic/Carbide Catalysts Using Forced Dynamic CO2 and CH4Reforming Conditions

Abstract

Alloys and intermetallics have been repeatedly reported to improve the catalytic activity or stability. However, many alloys are structurally unstable under reaction conditions. Here, we systematically investigate methods to understand, control, and modulate these dynamics for NiZn catalysts during dry (CO2) reforming of methane (CH4). Initially, we modulate the Ni-rich NiZn alloy and NiZn intermetallic by varying the Ni/Zn ratio, NiZn loading, and reduction temperature. Then, we study the structural modulation of the NiZn alloys and intermetallic compounds in steady and forced dynamic conditions in a packed bed reactor, operando DRIFTS-MS, in situ XRD, and in situ TEM, revealing that the NiZn intermetallic phase dynamically transforms into a stable Ni3ZnC0.7 phase, which acts as a carbon reservoir, mitigating coke accumulation and maintaining stable performance for 50 h under realistic reforming conditions. In contrast, the Ni-rich NiZn alloy irreversibly segregates to Ni and ZnO instead of forming Ni3ZnC0.7, resulting in severe coke deposition. These insights into the NiZn phase dynamics open avenues for rational catalyst control through phase modulation.