Trinuclear Nickel Catalyst for Water Oxidation: Intramolecular Proton-Coupled Electron Transfer Triggered Trimetallic Cooperative O–O Bond Formation

Abstract

Herein we reported a molecular trinuclear nickel catalyst (defined as TNC-Ni) for water oxidation. This TNC-Ni catalyst exhibits high catalytic performance and stability under neutral conditions (pH 7). Electrochemical studies disclose that the cooperation among the three nickel sites plays a vital role in both charge accumulation and O-O bond formation. This trinuclear nickel catalyst can accomplish the 4eoxidation of water by involving all three nickel sites and the O-O bond formation is trigged by the charge distribution process from 5 to 5 dp via proton-coupled electron transfer.

Characterization of Reaction Intermediates Involved in the Water Oxidation Reaction of a Molecular Cobalt Complex

“…Eventually, those catalysts can be attached to the surface of the electrode for WO under heterogeneous conditions. − Substantial progress has been achieved in developing molecular Ru- or Ir-catalyzed WO reactions. ,, However, knowledge about 3d transition-metal complex-catalyzed WO reactions is limited. ,, Unlike 4d or 5d metal complexes, a major obstacle in developing the 3d transition-metal complexes as WO catalysts are the labile metal–ligand bonds, which rapidly degrade under highly oxidizing conditions. In addition, achieving higher oxidation states, which is an essential requirement for extracting electrons and protons from water, is difficult in 3d metal complexes. , Nevertheless, molecular Mn, Fe, − Co, − Ni, − and Cu − catalysts have been developed in recent years for both electro- and photocatalytic WO reactions. Late-transition-metal (LTM) complexes are attractive candidates for making efficient molecular WO catalysts.…”

Molecular versus Silica‐Supported Iridium Water Oxidation Catalysts

“…[1,2] Owing to the high kinetic requirements of the reaction, the development of efficient and robust water oxidation catalysts (WOCs) is nevertheless still an open challenge. Over the last decades, relevant progress has been made in the design of earth-abundant metals WOCs, [3][4][5][6][7][8][9] even though those based on noble metals (i. e. Ir and Ru) exhibit the best performance so far. [10][11][12] Various strategies have been proposed for minimizing the metal content and optimizing the catalytic efficiency, according to the noble metal economy principle, in order to improve sustainability and reduce costs.…”

Bio‐inspired Design of Bidirectional Oxygen Reduction and Oxygen Evolution Reaction Molecular Electrocatalysts

“…[15,16] Oxygen evolution reaction from water and oxygen reduction reaction to produce water involve a fourelectron process, which combines with the concurrent exchange of four protons. [6,[17][18][19][20][21][22][23] The sluggish nature of the OER and ORR reactions makes it difficult to implement them in the sustainable energy system as they decelerate the overall reaction pathway. [24][25][26] The oxygen evolution reaction (OER) typically occurs as an anodic half-cell reaction during the water-splitting reaction.…”

“…The produced hydrogen can be directly utilized in fuel cells to produce energy, where hydrogen and oxygen are combined to produce benign water as a carbon‐neutral by‐product [15,16] . Oxygen evolution reaction from water and oxygen reduction reaction to produce water involve a four‐electron process, which combines with the concurrent exchange of four protons [6,17–23] . The sluggish nature of the OER and ORR reactions makes it difficult to implement them in the sustainable energy system as they decelerate the overall reaction pathway [24–26] …”