V⁵⁺-Doped Potassium Ferrite as an Efficient Trifunctional Catalyst for Large-Current-Density Water Splitting and Long-Life Rechargeable Zn–Air Battery

Abstract

Developing non-noble metal catalyst with super trifunctional activities for efficient overall water splitting (OWS) and rechargeable Zn–air battery (ZAB) is urgently needed. However, catalysts with excellent oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER) performances are relatively few. Although metal-ionic-conductor K2Fe4O7 (KFO) can output large current densities for OER/HER even in 10.0 M KOH electrolyte, its water-splitting property still needs to be further improved. Herein, we introduced V5+ directly into KFO and synthesized the binder-free nickel foam (NF) basal V-KFO nanoparticles (labeled as V-KFO/NF). Both the theoretical analysis and actual experimental data certify that V5+ doping enhances the instinct water-splitting property of V-KFO/NF. Additionally, V-KFO/NF can directly serve as the air cathode of liquid/flexible ZABs. The assembled liquid ZAB can continue the charge–discharge cycling testing with a lower voltage gap (0.834 V) and a longer operation life (>550 h) at 10 mA cm–2. Meanwhile, the assembled flexible ZAB can drive the two-electrode water-splitting unit of V-KFO/NF and needs only 1.54 V to achieve the current density of 10 mA cm–2, which is much lower than that of KFO/NF (1.59 V). This work not only provides a novel and efficient trifunctional catalyst for a self-powered water-splitting device but also is the foundation support for other heteroatom-doped low-cost materials.

CoNi2S4@CoNi-LDH heterojunction grown on SSM as a highly efficient trifunctional catalyst for water-splitting and Zn–air batteries

“…Thus, compared with the physical loading materials, self-supported catalysts can avoid various uncertainties that may arise and will have better stability. 17,18 Additionally, due to the high concentration of alkaline in the operating environment of ZABs, carbon cloth (CC), 19 carbon paper (CP), 20 nickel foam (NF), 21 SSM, 22 and other substrates are widely reported conductive substrates. Among them, the lower-cost SSM can maintain the original structural characteristics even after high-temperature calcination.…”

Potassium ferrite nanosheets with tin doping for enhanced large-current-density H2 production and ultra-long life rechargeable Zn–air batteries

“…In this work, both KFO and Pt/C-RuO 2 are used as air-electrodes for comparison. According to some reported studies 30,31 and our previous experience, 16 we assembled ZABs with a Sn-KFO electrode as the air-cathode, and a Zn-plate as the metal-anode, and the corresponding applied electrolyte is a solution mixture of 6.0 M KOH and 0.02 M Zn(OAc) 2 .…”

“…15 Considering that its hydrolysis activity still needs further improvement, we use the strategy of metal heteroatom doping to improve the electrocatalytic activity of KFO. V-doping is an efficient strategy; 16 however, whether the introduced-Sn has the same influence with doped-V 5+ is still unknown. Herein, we introduced Sn 4+ to confirm the potential effects it may cause.…”

NiFeCu phosphides with surface reconstruction via the topotactic transformation of layered double hydroxides for overall water splitting

“…In general, the OER pathway is a four-electron transfer step, including: * + H 2 O → *OH + (H + + e − ), *OH → *O + (H + + e − ), *O + H 2 O − → *OOH + (H + + e − ), and *OOH → * + O 2 + (H + + e − ). 37,38 The adsorption energies of oxygen-containing intermediates (OH*, O* and OOH*) on the catalysts at U = 0 V and 1.23 V are calculated to explain the mechanism of the excellent OER performance (Fig. 7a).…”