title: Coordination tuning of cobalt phosphates towards efficient water oxidation catalyst.
abstract: The development of efficient and stable water oxidation catalysts is necessary for the realization of practically viable water-splitting systems. Although extensive studies have focused on the metal-oxide catalysts, the effect of metal coordination on the catalytic ability remains still elusive. Here we select four cobalt-based phosphate catalysts with various cobalt- and phosphate-group coordination as a platform to better understand the catalytic activity of cobalt-based materials. Although they exhibit various catalytic activities and stabilities during water oxidation, Na2CoP2O7 with distorted cobalt tetrahedral geometry shows high activity comparable to that of amorphous cobalt phosphate under neutral conditions, along with high structural stability. First-principles calculations suggest that the surface reorganization by the pyrophosphate ligand induces a highly distorted tetrahedral geometry, where water molecules can favourably bind, resulting in a low overpotential (∼0.42 eV). Our findings emphasize the importance of local cobalt coordination in the catalysis and suggest the possible effect of polyanions on the water oxidation chemistry.
authors.affiliation: Department of Materials Science and Engineering, Research Institute of Advanced Materials (RIAM), Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea.
authors.forename: Hyunah
authors.initials: H
authors.lastname: Kim
authors.affiliation: Department of Materials Science and Engineering, Research Institute of Advanced Materials (RIAM), Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea.|Center for Biomaterials, Korea Institute of Science and Technology, 5, Hwarang-ro 14-gil, Seongbuk-gu, Seoul 136-791, Republic of Korea.
authors.forename: Jimin
authors.initials: J
authors.lastname: Park
authors.affiliation: Department of Materials Science and Engineering, Research Institute of Advanced Materials (RIAM), Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea.
authors.forename: Inchul
authors.initials: I
authors.lastname: Park
authors.affiliation: Department of Materials Science and Engineering, Research Institute of Advanced Materials (RIAM), Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea.
authors.forename: Kyoungsuk
authors.initials: K
authors.lastname: Jin
authors.affiliation: Western Seoul Center, Korea Basic Science Institute (KBSI), 150, Bukahyeon ro, Seodaemun-gu, Seoul 120-140, Korea.
authors.forename: Sung Eun
authors.initials: SE
authors.lastname: Jerng
authors.affiliation: Western Seoul Center, Korea Basic Science Institute (KBSI), 150, Bukahyeon ro, Seodaemun-gu, Seoul 120-140, Korea.
authors.forename: Sun Hee
authors.initials: SH
authors.lastname: Kim
authors.affiliation: Department of Materials Science and Engineering, Research Institute of Advanced Materials (RIAM), Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea.
authors.forename: Ki Tae
authors.initials: KT
authors.lastname: Nam
authors.affiliation: Department of Materials Science and Engineering, Research Institute of Advanced Materials (RIAM), Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea.|Center for Nanoparticle Research, Institute for Basic Science (IBS), Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea.
authors.forename: Kisuk
authors.initials: K
authors.lastname: Kang