Reconstruction of Thiospinel to Active Sites and Spin Channels for Water Oxidation

Abstract

Water electrolysis is a promising technique for carbon neutral hydrogen production. A great challenge remains at developing robust and low‐cost anode catalysts. Many pre‐catalysts are found to undergo surface reconstruction to give high intrinsic activity in the oxygen evolution reaction (OER). The reconstructed oxyhydroxides on the surface are active species and most of them outperform directly synthesized oxyhydroxides. The reason for the high intrinsic activity remains to be explored. Here, a study is reported to showcase the unique reconstruction behaviors of a pre‐catalyst, thiospinel CoFe2S4, and its reconstruction chemistry for a high OER activity. The reconstruction of CoFe2S4 gives a mixture with both Fe–S component and active oxyhydroxide (Co(Fe)OxHy) because Co is more inclined to reconstruct as oxyhydroxide, while the Fe is more stable in Fe–S component in a major form of Fe3S4. The interface spin channel is demonstrated in the reconstructed CoFe2S4, which optimizes the energetics of OER steps on Co(Fe)OxHy species and facilitates the spin sensitive electron transfer to reduce the kinetic barrier of O–O coupling. The advantage is also demonstrated in a membrane electrode assembly (MEA) electrolyzer. This work introduces the feasibility of engineering the reconstruction chemistry of the precatalyst for high performance and durable MEA electrolyzers.

Synthesis, properties and catalytic performance of the novel, pseudo-spinel, multicomponent transition-metal selenides

“…Another group of TMCh exhibiting similar structural features to pentlandites, yet much less studied, are densepacked, Se-based, monoclinic C2/m-structured pseudo-spinels, characterized by the presence of only octahedral cationic sites. Similarly, as in pentlandites, the very close, intermetallic interactions between cations, together with a clear tendency for creation of Ch vacancies, have the potential for providing a high concentration of active sites, 31,[35][36][37] making them highly promising bifunctional catalysts. For instance, extremely high current densities of 400 mA cm −2 at an overpotential of 320 mV dec −1 (OER) were reported for monometallic Co 3 Se 4 anchored to cobalt foam.…”

Defect engineering of two-dimensional materials for advanced energy conversion and storage

“…The OER technology is vital to many energy-related fields, e.g., water splitting, metalair batteries, and fuel cells. [267][268][269][270][271] As a complex 4e À transfer process, OER can be operated in either acidic (2H 2 O -O 2 + 4H + + 4e À ) or alkaline (4OH À -O 2 + 2H 2 O + 4e À ) environments, which involves multiple O-containing intermediates (such as OH*, OOH* and O*) during the reaction. Up to now, the OER catalytic ability has been generally believed to be mainly related to intermediate adsorption/desorption and their interactions with catalysts.…”

Spin-Modulated Oxygen Electrocatalysis

“…Therefore, it is needed to build a spin-selective channel to filter the required spin electron. According to literatures, ,, a spin-selective channel can be formed by the FM oxides, which allows for the transfer of spin electrons with a particular orientation from the oxygen intermediates. For example, in PM oxide (with disordered spins, i.e., both spin up (↑) and spin down (↓) electrons exist), the spins are in antiparallel (↑↓), so the electrons with an antiparallel direction will transfer to the catalyst from oxygen intermediates (Figure C), according to the Pauli repulsion principle.…”