Tailored Heterojunction Active Sites for Oxygen Electrocatalyst Promotion in Zinc‐Air Batteries

Abstract

Rechargeable zinc‐air batteries (ZABs) are promising energy storage systems due to their low‐cost and safety. However, the working principle of ZABs is based on oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), which display sluggish kinetic and low stability. Herein, this work proposes a novel method to design a heterogeneous CoP/CoO electrocatalyst on mesopore nanobox carbon/carbon nanotube (CoP/CoO@MNC‐CNT) that enriched active sites and synergistic effect. Moreover, the well‐defined heterointerfaces could lower the energy barrier for intermediate species adsorption and promote OER and ORR electrochemical performances. The CoP/CoO@MNC‐CNT electrocatalyst presents a high half‐wave potential of 0.838 V for ORR and a small overpotential of 270 mV for OER. The ZABs‐based CoP/CoO@MNC‐CNT air‐cathode shows an open‐circuit voltage of 1.409 V, the long‐term cycle life of 500 h with a small voltage difference change of 7.7%. Additionally, the flexible ZABs exhibit highly mechanical stability, demonstrating their application potential in wearable electronic devices.

l-Alanine-Assisted Synthesis of a Hierarchically Porous Co@N–C/N-Ketjenblack Carbon Catalyst for Oxygen Reduction in Zn–Air Batteries

“…The high open-circuit voltage and power density of the Co@N–C/N–KB-built cell surpassed most recently reported cobalt-based catalysts (Table S1). ,,,,,− These results illustrated that Co@N–C/N–KB offered excellent performance in primary ZABs. Figure d shows that the Co@N–C/N–KB-built ZAB delivered a much higher specific capacity (790 mA h gZn –1 ) at a discharge current density of 5 mA cm –2 compared to the Pt/C-built cell (474 mA h gZn –1 ).…”

“…The ORR performance of Co@N–C/N–KB is among the best of recently reported cobalt-based catalysts (Table S1). ,,,,,− Koutecky–Levich (K–L) plots for ORR on Co@N–C/N–KB, extracted from LSV curves collected at rotation speeds ranging from 400 to 2500 rpm, are shown in Figure d. Apparently, the kinetic current density displayed a proportional increment upon elevating the rotation rate with accompaniment of a distinct diffusion-limited current density platform.…”

Sodium Tartrate-Assisted Synthesis of High-Purity NiFe2O4 Nano-Microrods Supported by Porous Ketjenblack Carbon for Efficient Alkaline Oxygen Evolution

“…More profoundly, the introduction of cheap and commercially available KB during the synthesis of NiFe 2 O 4 /KB and CoFe 2 O 4 /KB produced catalysts with much higher OER activities compared with the corresponding ferrite counterparts (NiFe 2 O 4 and CoFe 2 O 4 ). The η 10 value of 258 mV (vs RHE) measured for NiFe 2 O 4 /KB is one of the smallest values yet reported for ferrite-based electrocatalysts during OER (Table S1), − ,,,,,,− outperforming NiFe 2 O 4 /carbon cloth (340 mV vs RHE), NiFe 2 O 4 /FeNi 3 foam (262 mV vs RHE), NiFe 2 O 4 /Ti 3 C 2 (266 mV vs RHE), NiFe 2 O 4 /Ni@C (330 mV vs RHE), NiFe 2 O 4 -hollow nanoparticles/CNTs (260 mV vs RHE), and NiFe 2 O 4 /rGO (302 mV vs RHE) . Few ferrite-based composite catalysts have been reported with η 10 values lower than NiFe 2 O 4 /KB, though most have complicated compositions and cumbersome preparation routes, such as phosphided NiFe/NiFe 2 O 4 embedded into porous N-doped carbon nanospheres (P-FeNi/FeNiO/CNS, 220 mV vs RHE) or 3D porous CoFe 2 O 4 /C nanorod arrays supported on Ni foam@polyaniline (Ni foam@NC-CoFe 2 O 4 /C, 240 mV vs RHE) …”

“…The Brunauer–Emmett–Teller (BET) specific surface area of NiFe 2 O 4 /KB was determined as 929 m 2 g –1 . The high BET specific surface area and mesoporous structure of NiFe 2 O 4 /KB are expected to be beneficial for maximizing the exposure of active sites and enhancing mass transport of reactants/products and electrolyte during OER. , The transmission electron microscopy (TEM) image of NiFe 2 O 4 /KB (Figure b) verified the introduction of NiFe 2 O 4 nano-microrods into the KB matrix. Lattice fringes with spacings of 0.251 and 0.147 nm in the high-resolution TEM (HRTEM) image of NiFe 2 O 4 /KB (Figure c) could readily be assigned to the (311) and (440) crystal planes, respectively, of NiFe 2 O 4 .…”

LaCoO3−δ–CoO–Partially Exfoliated Carbon Nanotube Composites as Efficient Oxygen Reduction Catalysts for Zn–Air Batteries

“…Benefiting from the collisions among the balls during the ball milling, abundant oxygen vacancies were produced in LaCoO 3−δ . The addition of CoO with good ORR catalytic activity − and the partially exfoliated CNTs with more edges and higher surface area greatly promotes the catalytic performance of LaCoO 3−δ .…”