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

Four new transition metal borates, [Co(1-MI) 2 ]·B 5 O 7 (OH) 3 (1, 1-MI = 1-methylimidazole), Co 2 (PZ) 8 (SO 4 ) 2 ·2H 3 BO 3 (2, PZ = pyrazole), K 7 {(BO 3 )Co[B 12 O 18 (OH) 6 ]}·H 2 O (3) and K 2 {[Ni(PY) 2 ] 2 ·[(C 4 H 2 O 6 ) 2 B]} 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.