A collaborative team of researchers bettered the microenvironment of a ruthenium (Ru) catalyst. This innovation led to an order of magnitude improvement in the catalyst’s overall efficiency for alkaline hydrogen oxidation reactions (HOR). This study was spearheaded by Tsinghua University’s Wang Hui. Utilizing his experience, he worked with Professors Zheng Fangcai and Luo Qiquan from Anhui University, and the three of them published their results in Nano Letters journal. Ru’s novel catalytic activity positions it as a powerful alternative to traditional platinum (Pt) catalysts in HOR applications. It provides a more efficient and less expensive way to conduct these procedures.
In this work, the key idea was to systematically optimize the localized electronic structure of the Ru catalyst to further boost its catalytic activity. By incorporating Ru atoms into the manganese oxide lattices, the team designed specific interfacial Ru–O bonds. Such strategic modification tuned the reaction intermediates adsorption energetics. Moreover, it reduced the free energy barrier for the water production step, which is crucial for a fast hydrogen oxidation reaction.
Impressive Performance Metrics
The optimized Ru catalyst provided a high mass activity (1.26 mA µg −1 Ru). This extraordinary performance was achieved in a 0.1 M potassium hydroxide (KOH) solution. This groundbreaking performance achieved more than 13 times the performance of a state-of-the-art benchmark Ru/C catalyst. In so doing, their new Ru catalyst outperformed commercial Pt/C catalysts by eightfold. This outstanding performance further demonstrates its potential to shake up the existing market for hydrogen oxidation catalysts.
And indeed, the research team was able to directly observe interfacial Ru–O bonds with electron spin resonance (ESR) spectroscopy. The water-friendly experiments for demonstrating salt-water electrodes were conducted by Mr. This validation offered key guidance into the structural changes that led to enhanced catalytic activity in alkaline environments.
Challenges and Innovations
Although Ru has appeared to be an attractive replacement for Pt in HOR catalysts, its propensity for denuding its catalytic activity has been an issue. Under alkaline conditions strong adsorption of hydrogen (H*) and hydroxyl (OH*) intermediates has been shown to poison it. The team took a novel approach that leveraged interfacial engineering. We found this strategy indeed led to decrease of the d-band center of Ru atoms to enhance their interaction with the intermediates.
This study demonstrates that Ru is a more sustainable, environmentally friendly and economical substitute for platinum. It clears the path for further research focused on performance enhancement of catalysts through new and different engineering strategies.