Influence of the metal loading on the electrocatalytic activity of carbon-supported (100) Pt nanoparticles

Abstract

The influence of the metal loading (i.e. interparticle distance) of shape-controlled Pt nanoparticles on their electrocatalytic properties is evaluated for the first time. For this purpose, carbon-supported cubic Pt nanoparticles (~17 nm) with different metal loadings were prepared, characterized and electrochemically tested. To avoid differences in particle size and shape/surface structure of the Pt nanoparticles between samples, all samples used in this work were prepared from a single batch. The surface structure of the Pt nanoparticles was evaluated through the so-called hydrogen region and showed a preferential (100) orientation. Interestingly, the electroactive surface area of the samples, estimated both from the H or CO stripping processes, was directly proportional to the total Pt mass, independently of the metal loading. The CO stripping profile was also found to be unaffected by the metal loading. However, for ammonia and formic acid electrooxidation, the activity obtained was dependent on the metal loading. For ammonia oxidation, the optimal loading was found to be about 20-30 wt%. Nevertheless, this trend may be altered by different factors including (i) active surface area, (ii) metal loading and (ii) thickness of the catalytic layer. For formic acid electrooxidation, the results obtained showed a clear decrease of the activity for increasing metal loadings which is explained in terms of formic acid consumption on the top layers of the catalyst.

Enhancement of electrodes modified by electrodepositedPEDOT‐nanowires with dispersedPt nanoparticles for formic acid electro‐oxidation

“…but with significantly lower values . The obtained results confirm that the presence of platinum nanoparticles hampers CO formation, noting that in this case the Pt nanoparticles showed excellent catalytic performance, comparable to what has been reported by other authors …”

“…Consequently, the nanoparticles have been supported on conducting materials, but catalytically inactive, such as coal, which has maintained the catalytic properties at low Pt concentrations, even though they are affected by the presence of carbon that being in higher proportion, contaminates the active metal surface . Moreover, conducting polymers have also been used as support of these noble metals .…”

Loading effect of carbon-supported platinum nanocubes on oxygen electroreduction

“…As expected, the voltammetric profiles are essentially similar despite the different electric double layer charging contribution. Figure 2A analogous Pt nanocubes prepared using other synthetic routes [46,48,51] and denote the existence of a (100) predominant surface structure. Figure 2B reports the voltammetric responses of the samples having different metal loading.…”

“…On the other hand, and taking into consideration that i) all Pt/C inks were prepared using the same total amount of catalyst (5 mg) and ii) the catalyst-modified GC electrodes were prepared by depositing the same volume of different inks (3 µL), the correct proportionality of the Pt electrochemically accessible surface area (Ar) of the Pt nanoparticles is warranted, particularly for high metal loading where an evident agglomeration of the Pt nanoparticles takes place (see Figure 1F). As described in previous contributions [46,50], to estimate if the agglomeration of Pt nanoparticles induces a loss of the electroactive surface area, two analyses can be carried out, a) plotting the estimated Ar versus the corresponding metal loading (experimentally measured by TG analyses) and b) measuring the current ratio at 0.27 and 0.44 V vs RHE in the absence of any double layer charging correction and plotting this ratio versus the corresponding Pt loading. In both cases, as discussed in previous works [46,50], a linear relationship should be observed.…”

“…The unique way of fulfilling these requirements is preparing all samples containing different metal loading from a single synthesis batch. A similar strategy has been previously used to study the effect of the metal loading towards other relevant electrocatalytic reactions such as ammonia and formic acid electrooxidation for which the metal loading was shown to importantly affect the resulting electrocatalytic activity [46].…”