Energy-efficient hydrogen production coupled with methanol oxidation using NiFe LDH@NiMo alloy heterostructure

The traditional electrochemical water splitting is extremely restricted by the sluggish kinetics of the anodic oxygen evolution reaction (OER). In this context, replacing OER with a more thermodynamic favorable oxidation reaction, such as methanol oxidation reaction (MOR), is an effective strategy to improve the hydrogen evolution reaction (HER) efficiency while still obtaining some valuable by -prod-ucts. In this work, nickel-iron layered double-hydroxide [NiFe LDH]@NiMo alloy heterostructure is synthesized by electrodeposition process and its bi-functional electrocatalytic activities for both hydrogen evolution reaction (HER) and methanol oxidation reaction (MOR) are evaluated. For the HER, the catalyst exhibits low overpotential of 82.5 mV at 100 mA/cm2, with a Tafel slope of 61 mV/dec as well as splendid long-term stability. For the MOR, the required potential decreases by 74 mV at 100 mA/cm2 compared to oxygen evolution reaction (OER). Moreover, 97% process yields toward value-added formic acid (HCOOH) are obtained at the anode, with a faradaic efficiency of approximately 100% for HER at the cathode. The superior catalytic performance results from the synergic contribution of NiFe LDH and NiMo alloy. The formation of NiFe LDH@NiMo alloy heterostructure leads to the redistribution of electrons among nickel (Ni), iron (Fe) and molybdenum (Mo) elements. Therefore, the charge transfer process has been greatly promoted. This study provides a scalable energy saving strategy for hydrogen energy development.(c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

Replacing the sluggish oxygen evolution reaction with methanol oxidation reaction is an effective strategy to improve the efficiency of hydrogen evolution reaction while obtaining valuable by-products.