A shape-memory V3O7·H2O electrocatalyst for foldable N2 fixation

Abstract

Shape-memory materials can retain their functionalities during mechanical deformation, and thus hold great promise for utilizations in versatile, wearable and portable systems. Here, we report a shape-memory V₃O₇·H₂O monolith that works as a new emerging foldable electrocatalyst for nitrogen reduction reaction (NRR). Remarkably, the electrocatalyst has been designed according to our unexpected observation that metal oxides, commonly considered as a class of tough and brittle materials, can show shape-memory properties after anisotropic alignment of their microstructures via an ice-templated freeze-casting method. We demonstrate the V₃O₇·H₂O electrocatalyst for promoting the NRR characteristic of excellent performances, including an ammonia yield rate of 36.42 μg h⁻¹ mg⁻¹, faradaic efficiency of 14.20% at −0.55 V (vs. RHE), and operation for seven cycles without activity or structural degradation. Remarkably, NRR faradaic efficiencies do not change during electrode deformations, while ammonia yield rates only show a slight decline even after significant foldings. We further elucidate through density function theory that NRR proceeds at vanadium active sites of V₃O₇·H₂O via the associative distal pathway with *N₂ + H⁺ → *N₂H as the rate-limiting step.