NiFe-based tungstate@layered double hydroxide heterostructure supported on graphene as efficient oxygen evolution reaction catalyst

Oxygen evolution reaction (OER) plays a key role in water splitting and rechargeable metal-air batteries, thus eagerly demanding efficient, robust, and low-cost electrocatalysts. Two-dimension layered double hydroxides (LDHs) have been widely recognized as one of the most promising OER catalysts due to the high activity and large specific surface area. However, the insufficient electrical conductivity and resis-tance against corrosion seriously restrict their capabilities of charge transport and long-term stability. Herein, a NiFe-based heterostructure catalyst is proposed by the coupling of NiFe-based LDH (termed NiFe-LDH) nanosheets and amorphous NiFe-tungstate (termed NiFeWO4) nanoparticles, both of which possess the same stoichiometric Ni/Fe ratio (3:1), on graphene substrate (termed NiFeWO4@NiFe-LDH/ G). Attributed to the synergy of individual components, NiFeWO4@NiFe-LDH/G exhibits superb elec-trocatalytic activity for OER in an alkaline electrolyte, with extremely low overpotential of 222 mV at a current density of 10 mA cm-2 and Tafel slope of 32.1 mV dec-1, far surpassing the benchmark IrO2 catalyst. Furthermore, NiFeWO4@NiFe-LDH/G exhibits superior stability and durability to IrO2. Comprehensive characterizations and electrochemical measurements together with DFT calculations reveal that the hetero-assembly of NiFe-LDH and NiFeWO4 generates more efficient NiFe active sites than that of the individual components via a strong chemical binding interaction, which can modulate the electronic structures and optimize the energetics of active sites for OER intermediates. As a result, a low cell voltage of 1.48 V is achieved for the water splitting in two-electrode Pt/CkNiFeWO4@NiFe-LDH/G electrolysis cell at 10 mA cm-2, overwhelmingly prevailing over the 1.69 V for the Pt/CkIrO2 benchmark cell. This work provides an ingenious heterostructure design for efficient and stable OER electrocatalysts. (c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

In this study, a NiFe-based heterostructure catalyst composed of NiFe-based LDH nanosheets and amorphous NiFe-tungstate nanoparticles on a graphene substrate was proposed. The catalyst exhibited superb electrocatalytic activity for oxygen evolution reaction (OER) in an alkaline electrolyte, surpassing the benchmark IrO2 catalyst in terms of overpotential and Tafel slope. Moreover, it showed superior stability and durability compared to IrO2. The hetero-assembly of NiFe-LDH and NiFeWO4 generated more efficient active sites for OER, leading to improved performance.