Intrinsic Effect of Carbon Supports on the Activity and Stability of Precious Metal Based Catalysts for Electrocatalytic Alcohol Oxidation in Fuel Cells: A Review

Abstract

Electrocatalyst supports, in particular carbonaceous materials, play critical roles in the electrocatalytic activity and stability of precious metal group (PMG)‐based catalysts such as Pt, Pd, and Au for the electrochemical alcohol oxidation reaction (AOR) of fuels such as methanol and ethanol in polymer electrolyte membrane fuel cells (PEMFCs). Carbonaceous supports such as high surface area carbon provide electronic contact throughout the catalyst layer, isolate PMG nanoparticles (NPs) to maintain high electrochemical surface area, and provide hydrophobic properties to avoid flooding of the catalyst layer by liquid water produced. Compared to high surface area carbon, PMG catalysts supported on 1D and 2D carbon materials such as graphene and carbon nanotubes show enhanced activity and durability due to the intrinsic effect of the underlying carbonaceous supports on the electronic states of PMG NPs. The modification of the electronic environment, in particular the d‐band centers of PMG NPs, weakens the adsorption of AOR intermediates, facilitates breaking of the C−C bonds, and thus enhances the electrocatalytic activity of PMG catalysts. The doping of heteroatoms further facilitates the electrocatalytic activity for the AOR through the structural, bifunctional, and electronic effects, in addition to the enhanced dispersion of PMG NPs in the carbon support. The prospects for the development of effective PMG‐based catalysts for high‐performance alcohol‐fuel‐based PEMFCs is discussed.

Multiple Twin Boundary‐Regulated Metastable Pd for Ethanol Oxidation Reaction

“…[ 1–3 ] Carbon‐supported nanoparticles (NPs) of noble metal (such as Pt and Pd) are the most widely used commercial catalysts for alcohols oxidation reactions (AOR). [ 4–6 ] Nevertheless, not only the high cost of noble metal catalysts but also their catalytic performance and toxic carbon intermediates (such as CO) tolerance are far unsatisfactory in the practice of long‐term efficient operation. [ 7,8 ] The catalytic characteristics of catalyst materials strongly depend on their structure, especially their surface microstructure, and the corresponding physical and chemical properties.…”

Recent developments of nanocarbon based supports for PEMFCs electrocatalysts

“…This suggests that there should be greater focus on the control of pore morphology in the design of novel carbon materials. Moreover, we believe that there will be many opportunities to improve the electrocatalytic properties of nanocarbon-supported catalysts once the pore morphology dependence of the catalyst is revealed, considering that modern nanocarbons have various pore morphologies, for example, ranging from disordered to ordered [61], from spherical to tubular [62], or from isolated to continuous [15].…”

“…As an essential component of PEMFCs, the electrocatalyst support can affect various physical properties (such as particle size, dispersion, and specific surface area) and electrochemical properties (such as activity and stability) of the electrocatalysts. Moreover, support materials can also influence both the electron and proton transfer processes; therefore, they will appreciably correlate with the catalyst performance [15]. Suitable support is beneficial for dispersing and anchoring catalyst nanoparticles, increasing the effective active area, improving the catalyst activity and stability, constructing an efficient electrocatalytic reaction interface, and reducing the cost of PEMFCs [16][17][18][19]].…”

“…Suitable support is beneficial for dispersing and anchoring catalyst nanoparticles, increasing the effective active area, improving the catalyst activity and stability, constructing an efficient electrocatalytic reaction interface, and reducing the cost of PEMFCs [16][17][18][19]]. An ideal catalyst support needs to possess the following properties, namely, (1) suitable pore structure, (2) high active specific surface area, (3) high conductivity, and (4) good thermal and electrochemical stability [15,16,20]. Among all the promising supporting materials, carbon is the most desirable and widely adopted one because of its distinguishing features, namely, (1) high stability (in both acidic and basic media, even at high temperature), (2) controllable pore structure, (3) tractable physical form, (4) modifiable surface chemistry, and (5) low cost [21,22].…”

A study on the high efficiency reduction of p-nitrophenol (4-NP) by a Fe(OH)3/Fe2O3@Au composite catalyst

“…[20][21][22] However, the stability of the application of precious metals is still a common problem due to the tendency of precious metals to aggregate, which leads to a gradual decline in catalytic activity. 23 In addition, it is difficult to separate and recover precious metal nanoparticles aer each use due to their small size. Moreover, the cost of precious metals is very high, and better separation and recovery are very important under the shortage of resources and huge industrial demand.…”