Key Takeaways & Executive Findings
- •• Comprehensive review of direct formic acid fuel cells spanning from atomic-scale catalytic mechanisms to meter-scale device fabrication. • Highlights the critical gap between highly active formic acid oxidation catalysts and unsatisfactory device performance. • Discusses multiscale challenges including catalyst design, electrode structure, and mass transfer limitations. • Provides perspectives and opportunities to bridge the gap between catalyst activity and practical electrode performance.
Abstract
Direct formic acid fuel cells are promising energy devices with advantages of low working temperature and high safety in fuel storage and transport. They have been expected to be a future power source for portable electronic devices. The technology has been developed rapidly to overcome the high cost and low power performance that hinder its practical application, which mainly originated from the slow reaction kinetics of the formic acid oxidation and complex mass transfer within the fuel cell electrodes. Here, we provide a comprehensive review of the progress around this technology, in particular for addressing multiscale challenges from catalytic mechanism understanding at the atomic scale, to catalyst design at the nanoscale, electrode structure at the micro scale and design at the millimeter scale, and finally to device fabrication at the meter scale. The gap between the highly active electrocatalysts and the poor electrode performance in practical devices is highlighted. Finally, perspectives and opportunities are proposed to potentially bridge this gap for further development of this technology.
1. Introduction
Over the last decades, the pace of research and development of clean and sustainable energy technologies has sharply increased, motivated by the growing energy demand and pressures of environmental challenges. Proton exchange membrane fuel cells (PEMFC), as one of the clean power generation technologies, have become a crucial industrial sector for global sustainable economic development [1]. In the history of the PEMFC, most of the efforts were spent on hydrogen-PEMFC. By contrast, these intensive studies can still not solve the inherent limitation of hydrogen, in particular, the challenges facing hydrogen storage and distribution. Driven by this limitation and the requirements of alternative clean power sources, liquid fuels, including methanol, ethanol, formic acid, ammonia, etc., have received more attention in the fuel cell area. Most of these fuels are considered as safe and convenient for storage and operation, and can be obtained either through sustainable approaches, or by catalytic reforming of abundant fossil fuels such as natural gas. Besides, most liquid fuels have a competitive energy density compared with high-pressure or even liquid hydrogen (shown in Fig. 1), which can even be several orders of magnitude larger than that of the Li-ion battery [2].
The history of the first liquid fuel cell can be traced back to 1845 [3], six years after the first fuel cell (in the former time, it was known as "gas battery") demonstrated by Sir William Grove [4], in which he used gas battery to ascertain voltaic relation of oxygen and alcohol. In light of the advancements in hydrocarbon fuel infrastructure, in the early studies on liquid fuel cells, researchers had several attempts on hydrocarbons, such as using diesel or jet fuel as the power sources [5]. However, these studies showed less positive results due to the large challenges in the electrooxidation of hydrocarbons at both low- and intermediate-temperature. This limitation later made the research focus shift to direct methanol fuel cells (DMFC). Since the last century, huge efforts have been carried out on DMFC research [6–10]. The fast development of advanced electrochemical equipment provided opportunities to investigate the mechanism of the methanol oxidation reaction (MOR); thus, a great number of studies were conducted in order to increase the power performance of DMFC [11–17]. Driven by the great development of DMFC at that period, the idea of the "Methanol Economy" was proposed as an alternative energy source to the "Hydrogen Economy" [18].
While the studies on the DMFC had been developed for a long time, many challenges remained unaddressed, in particular, catalyst poisoning and fuel crossover [19]. Therefore, scientists began to explore alternative liquid fuels. Formic acid is a safe liquid on the list of food additives published by the US Food and Drug Administration (FDA). The thermodynamic potential (E0) of formic acid oxidation (FAOR) is -0.25 V vs RHE, compared to the hydrogen oxidation (0 V vs RHE) and MOR (
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Yang Li, Ming-Shui Yao, Yanping He, Shangfeng Du (2025). Recent Advances of Electrocatalysts and Electrodes for Direct Formic Acid Fuel Cells: from Nano to Meter Scale Challenges. Nano-Micro Letters. https://doi.org/10.1007/s40820-025-01648-w
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Frequently Asked Questions
What are the main challenges in direct formic acid fuel cells?
The main challenges include slow reaction kinetics of formic acid oxidation and complex mass transfer within the fuel cell electrodes, leading to high cost and low power performance.
How does this review address the multiscale challenges?
The review addresses challenges from atomic-scale catalytic mechanism understanding, to nanoscale catalyst design, microscale electrode structure, millimeter-scale design, and meter-scale device fabrication.
What is the significance of formic acid as a fuel?
Formic acid is safe, has a low working temperature, and is easy to store and transport, making it a promising fuel for portable electronic devices.
What is the gap highlighted in the review?
The gap between highly active electrocatalysts and the poor electrode performance in practical devices is highlighted, emphasizing the need for bridging this gap.
What are the future perspectives proposed?
The review proposes perspectives and opportunities to bridge the gap between catalyst activity and device performance, potentially through improved electrode design and mass transfer management.
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