Bimetal−Organic Framework Derived High‐Valence‐State Cu‐Doped Co₃O₄ Porous Nanosheet Arrays for Efficient Oxygen Evolution and Water Splitting

Abstract

Developing low‐cost, high‐efficient, and robust electrocatalysts for oxygen evolution reaction (OER) holds promise for the future hydrogen economy through overall water splitting. Herein, Cu doped Co3O4 porous nanosheet arrays were synthesized on three‐dimensional (3D) nickel foam (Cu−Co3O4 NAs/NF) by a facile pyrolysis process of bimetal−organic frameworks precursors. The systematic experiments evidence that the Cu doping in Co3O4 materials not only results in affluent trivalent cobalt as active sites for OER electrocatalysis, but also modulates the nanosheet morphology to achieve high specific surface area and well‐exposed active sites. Moreover, the 3D electrode configuration simultaneously offers open‐channels for electron transport and gas products release. Benefitting from the exotic geometric and electronic structure, the engineered Cu−Co3O4 NAs/NF electrode exhibits outstanding activity (an overpotential of 230 mV at 10 mA cm−2) and long‐term durability toward OER, much better than the benchmark IrO2/NF. Together with its remarkable HER activity, our Cu−Co3O4 NAs/NF electrode enables a low voltage of 1.58 V to generate a current density of 10 mA cm−2 for overall water splitting, which is comparable to those of current Co‐based bifunctional electrocatalysts. This work may open up opportunities to explore other advanced electrocatalysts with high valence Co3+ and 3D porous architectures for scale‐up water electrolysis.

Nanocage‐Shaped Co3−xZrxO4 Solid‐Solution Supports Loaded with Pt Nanoparticles as Effective Catalysts for the Enhancement of Toluene Oxidation

“…The lattice fringes of 0.230 and 0.250 nm are attributed to the (111) crystal planes of Pt and the (311) crystal planes of the Co 2.73 Zr 0.27 O 4 solid‐solution support, respectively. [ 21–23 ] Furthermore, the high‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM) image of the 2.0 wt% Pt/Co 2.73 Zr 0.27 O 4 catalyst confirms the presence and homogeneous distribution of the 2.0 nm Pt nanoparticles, as shown in Figure S1, Supporting Information. Additionally, the energy‐dispersive X‐ray spectroscopy elemental mappings (Figure 2k) also show the uniform dispersions of Co, O, Zr, and Pt elements in the 2.0 wt% Pt/Co 2.73 Zr 0.27 O 4 catalyst.…”

Recent advances in vacancy engineering of metal‐organic frameworks and their derivatives for electrocatalysis

“…Pyrolysis at elevated temperatures will cause the loss of oxygen atoms, which promotes the formation of oxygen vacancies. 84,151,152 The pyrolysis treatment was generally carried out at a specific heating ramp rate and temperature in a vacuum system under carrier gas (eg, Ar, N 2 , and O 2 ). With the constant flow rate and a desire pressure, the Ding and coworkers proposed a two-step pyrolysisoxidation strategy to fabricate bifunctional electrocatalysts with a Co-based MOF (ZIF-67) as the precursor.…”

Comprehensively Probing the Contribution of Site Activity and Population of Active Sites toward Heterogeneous Electrocatalysis

“…[3,9.10] In connection with advanced projects for significantly increasing the efficiency of water electrolysis, two noticeable research domains are adopted. The first one is to create high surface areas of electrocatalysts for improving the number of exposed active sites, while the second one is to design a new electrocatalyst for enhancing intrinsic activity (Table ) . Loading or in‐situ generation of electrocatalysts on two‐dimensional/three‐dimensional frameworks, such as graphene derivatives or metal‐organic frameworks, bears large specific area for improving the exposure of active sites.…”

“…Controlling nanostructured shape, array and size of electrocatalysts is another strategy to increase the population of active sites . On the other hand, doping elements, tuning ratio of transition metal complexes, replacing substrate or anchoring atoms to modulate local coordination environments have been a frequent approach for promoting the activity of electrocatalysts …”

“…However, resistances from electrocatalyst, electrocatalyst‐support electrode interface, and electrolyte also influence the obtained Tafel slopes, suggesting Tafel slopes did not truly reflect the intrinsic activity of electrocatalysts. This phenomenon was observed in the comparison of numerous studies which revealed the ranking of Tafel slopes did not correspond to those of η 10 (Figure b) …”