One-Step Electrodeposition of Nanocrystalline Zn_xCo_3–xO₄ Films with High Activity and Stability for Electrocatalytic Oxygen Evolution

Abstract

The development of highly active, environmentally friendly, and long-term stable oxygen evolving catalysts at low costs is critical for efficient and scalable H production from water splitting. Here, we report a new and facile one-step electrodeposition of nanocrystalline spinel-type ZnCoO films from an alkaline Zn-Co-tartrate solution. The electrodeposited ZnCoO electrode could be directly used as the anode for the water electrolysis without any post treatment. The ZnCoO film shows a low and stable overpotential of ∼0.33 V at 10 mA cm (and ∼0.35 V at 20 mA cm) for over 10 h and a Tafel slope of ∼39 mV dec toward the oxygen evolution reaction (OER) in 1 M NaOH, comparable to the best performance of the nonprecious OER catalysts reported for alkaline media. The enhanced OER activity of ZnCoO compared to CoO could be attributed to the surface structural modification and higher density of the accessible active Co sites induced by the incorporation of Zn. The electrodeposition method in this paper could also be used to synthesize other binary and ternary metal oxide based catalytic electrodes for reactions such as the OER and oxygen reduction reaction (ORR).

Recent Progress on Multimetal Oxide Catalysts for the Oxygen Evolution Reaction

“…Han et al also reported the preparation of a nanocrystalline spineltype Zn x Co 3−x O 4 thin film using a one-step electrodeposition method. [130] Benefiting from the increased density of Co 3+ in octahedral sites induced by Zn 2+ , all the produced Zn−Co films exhibited better OER performance than a pure Co 3 O 4 film. Among the considered Zn/Co ratios, Zn 0.45 Co 2.55 O 4 exhibited the best performance with η = 330 mV at 10 mA cm −2 .…”

Simultaneous Modulation of Composition and Oxygen Vacancies on Hierarchical ZnCo2O4/Co3O4/NC‐CNT Mesoporous Dodecahedron for Enhanced Oxygen Evolution Reaction

“…[61] The rate-determining step in the OER is the formation of CoOOH,w hich further forms CoO 2 through CoOOH + OH À !CoO 2 + H 2 O + e À . [23] The highly oxidized Co 4 + sites under OER conditions were observed by Favaroe tal. [62] through in operando photoelectron spectra and Zhang et al [63] through time-resolved FTIR spectroscopy;t hese authors proposedt hat increasing Co 4 + =Od ensity led to the creationo fa djacent oxo-bridged Co 4 + centers at which the concerted oxidation of water to molecular oxygen occurred with af ast turnover frequency (TOF).…”

“…The most widely accepted mechanism on transition‐metal oxides is known as the four‐electron‐transfer mechanism . The rate‐determining step in the OER is the formation of CoOOH, which further forms CoO 2 through CoOOH+OH − →CoO 2 +H 2 O+e − . The highly oxidized Co 4+ sites under OER conditions were observed by Favaro et al .…”

“…[2,5,[13][14][15] Different doping at the surface/interface or homogenous metal mixing provides the possibility of tuning the inherent electronic and/or surface structures of the host material. [13,[16][17][18][19][20][21][22][23][24] Improvementint he OER performance is mainly ascribed to the changing electronic and structural nature to achieve al arger active surface area and lower charge-transfer resistance. Coupling Co 3 O 4 with conductive substrates, such as graphene, carbon nanotubes( CNTs), and titanium foils, is anothers trategy to improve OER performance.…”

Impact of network heterogeneity on electrokinetic transport in porous media

“…The diffusion-limited current can only be exceeded (leading to OLC) if the preceding assumptions break down, by providing additional ions (via water splitting 11,51 or membrane discharge 22 ), activating new transport mechanisms (such as electro-osmotic instability, 9,11 surface conduction or electro-osmotic flow 12,13,16,31 ), or effectively shortening the diffusion length (by dendritic growth instability 33,34,49 ).…”