Exploration of the oxygen reduction reaction activity of four transition metal borates: synthesis, structure and characterization

Abstract

Four new transition metal borates, [Co(1-MI)₂]·B₅O₇(OH)₃ (1, 1-MI = 1-methylimidazole), Co₂(PZ)₈(SO₄)₂·2H₃BO₃ (2, PZ = pyrazole), K₇{(BO₃)Co[B₁₂O₁₈(OH)₆]}·H₂O (3) and K₂{[Ni(PY)₂]₂·[(C₄H₂O₆)₂B]}₂ (4, PY = pyridine), have been successfully synthesized by a mild method. Their structures were determined by X-ray single crystal diffraction. These compounds were further characterized by FTIR, PXRD and UV-vis-NIR. It is worth noting that the catalytic properties of catalysts based on these four borates were explored, and that organically templated borate 1- and 2-based catalysts showed better ORR catalytic performance compared to 3- and 4-based catalysts. This may be caused by the supramolecular skeletons of 1 and 2 providing sufficient space and porosity.