Designing High‐Valence Metal Sites for Electrochemical Water Splitting

Abstract

Electrochemical water splitting is a critical energy conversion process for producing clean and sustainable hydrogen; this process relies on low‐cost, highly active, and durable oxygen evolution reaction/hydrogen evolution reaction electrocatalysts. Metal cations (including transition metal and noble metal cations), particularly high‐valence metal cations that show high catalytic activity and can serve as the main active sites in electrochemical processes, have received special attention for developing advanced electrocatalysts. In this review, heterogenous electrocatalyst design strategies based on high‐valence metal sites are presented, and associated materials designed for water splitting are summarized. In the discussion, emphasis is given to high‐valence metal sites combined with the modulation of the phase/electronic/defect structure and strategies of performance improvement. Specifically, the importance of using advanced in situ and operando techniques to track the real high‐valence metal‐based active sites during the electrochemical process is highlighted. Remaining challenges and future research directions are also proposed. It is expected that this comprehensive discussion of electrocatalysts containing high‐valence metal sites can be instructive to further explore advanced electrocatalysts for water splitting and other energy‐related reactions.

High‐Performance Perovskite Composite Electrocatalysts Enabled by Controllable Interface Engineering

“…We note that Fe plays the role of a partner cation aiding the formation and stabilization of the RP or SP phase structure, whereas the Co-containing active center contributes mostly to the overall OER performance, as found in mixed CoFe perovskites more generally. [44] The Co 3.3+ -Co 3.4+ oxidation state is ideal for facilitating high OER activity, [45,46] arising from the substitution of Sr 2+ for La 3+ in the RP-or SP-phase LaSrCoFeO systems. [19] Oxide catalysts with a similar Co valence have demonstrated strong metal-oxygen covalency, [19,47,48] which may trigger a change in the mechanism of OER catalysis, from a conventional adsorbate evolution mechanism (AEM) to a lattice oxygen-mediated mechanism (LOM).…”

A Review of Transition Metal Oxygen-Evolving Catalysts Decorated by Cerium-Based Materials: Current Status and Future Prospects

“…2 Electrochemical water splitting to produce H 2 is considered as one of the simplest hydrogen production methods. [3][4][5][6] However, large-scale production of H 2 by this means is greatly hindered by the sluggish kinetics of the oxygen evolution reaction OOH. 7 The high energy barrier is the direct cause of high onset potential, high overpotential, and the resulting slow kinetics.…”

Ce‐Modified Ni(OH)2 Nanoflowers Supported on NiSe2 Octahedra Nanoparticles as High‐Efficient Oxygen Evolution Electrocatalyst

“…Figure S10 in the Supporting Information shows the polarization curve, collected from low to high potentials with a scan rate of 1 mV s −1 , of the Ce‐m‐Ni(OH) 2 @NiSe 2 electrode, where a convex peak (oxidation peak) exists. [ 40,41 ] The peak is at the potential range from ≈1.35 to 1.45 V, which is probably ascribed to the capacitive current deriving from Ni oxidation. [ 42 ] In order to minimize such an effect of the capacitive current, we recorded the polarization curves from high to low potentials with a scan rate of 1 mV s −1 according to previous reported method.…”