A new strategy for boron cluster-based metal boride (Co₂B) synthesis and its applicability to electrocatalytic nitrate reduction

To achieve efficient conversion of nitrate to ammonia, it is necessary to design and develop electrode materials with high activity and efficiency for the electrocatalytic reduction reaction of nitrate (NO₃RR). Due to its unique semi-metallic properties, the vacancy orbitals of boron are prone to accommodate electrons, so doping element B with transition metals is expected to change the local electronic configuration of the metal, which in turn affects the corresponding catalytic reaction. Here, we propose a new strategy for the preparation of metal borides by using dodecahydro-closo-dodecaborate and Co²⁺ complexed and calcined to prepare a novel metal boride-Co₂B for electrocatalytic nitrate reduction. This modification considerably enhances the performance of NO₃RR. Co₂B exhibited a Faradaic efficiency of NH₄⁺ (FE_NH4+) as high as 96.61 % at −0.5 V vs. RHE, achieving a remarkable NH₄⁺ yield of 5.73 mg h⁻¹ mg_cat⁻¹. This study provides a new approach for designing catalysts for environmentally-friendly ammonia synthesis.