Trace levels of PtRu on NiMo foam electrodes towards hydrogen evolution reaction

Abstract

Electrochemical water splitting plays a critical role in high purity hydrogen production. To lower capital cost and energy consumption, efficient catalysts are required to boost the hydrogen evolution reaction (HER), especially in alkaline media. Although PtRu alloy materials are still considered the state-of-the-art catalyst for the HER under alkaline media, large-scale application is hindered by its scarcity and high cost. NiMo alloy catalysts can be potential Pt-free alternatives to drive the sluggish kinetics of the HER under alkaline media, but their HER activity is still not ideal due to the limitation of Volmer step. Herein, we investigated the impact of trace levels of PtRu catalysts on NiMo electrodes towards the HER by incorporating advantages of both PtRu and NiMo catalysts to minimize cost and maintain a promising HER activity. Trace levels of PtRu catalysts from 0.0173 to 0.2648 mg cm−2 were loaded on commercial NiMo foam electrodes by a facile electrodeposition technique utilizing ppm concentration levels of PtRu in electrolyte. The results show that 0.0173 mg cm−2 PtRu loading on NiMo electrode can significantly enhance HER activity compared to the pristine NiMo foam electrode (Tafel slopes drop from ∼170 to ∼60 mV dec−1) due to the remarkable decline of energy barriers towards water dissociation and hydrogen adsorption. Meanwhile, the rate determining step (RDS) switches from the Volmer step to the Heyrovsky step when the PtRu loading increases to 0.0675 mg cm−2. Promising catalytic stability is observed at 100 mA cm−2 over the course of 50 h with a PtRu loading of 0.1198 mg cm−2. This work demonstrates a potential strategy to decrease the cost and simultaneously maintain superior HER performance by integrating trace levels of PtRu catalyst with NiMo foam electrodes.