The role of copper in the synthesis of platinum based catalysts and in their efficiency for the hydrogen evolution reaction

Abstract

In this work, we synthesized two hybrid copper–platinum composites and two mono-metallic control samples on the carbon black (CB) support with the use of the polyol-formaldehyde method. The bi-metallic composites were prepared by the two different experimental protocols: consecutive deposition of the two metals CB/CuPt-1 and co-deposition of CB/CuPt-2. With both methods, the use of copper facilitates deposition of platinum, leading to a higher platinum content in the products, compared to the mono-metallic CB/Pt control sample. SEM and HRTEM images show that, in monometallic CB/Cu, copper does not form any nanoparticles, being atomically dispersed on the CB surface. The other three samples have uniformly dispersed nanoparticles with a size of 2–4 nm, densely covering the CB support. XRD and XPS data suggest that copper facilitates more efficient reduction of platinum, and is incorporated into the nanoparticles. Next, all the synthesized composites were tested for the hydrogen evolution reaction (HER). The two bi-metallic composites outperform not only the mono-metallic CB/Pt sample, but also the commercial catalyst with a similar or an even higher platinum content. Interestingly, the catalytic efficiency is not directly related to the platinum content in the tested materials. As a result, CB/CuPt-2, which has a lower Pt content, demonstrates greater efficiency in certain parameters compared to CB/PtCu-1, which contains a higher Pt content. This observation suggests that incorporation of copper into the structure of the composite materials leads to synergistic effects. Our results show the role of copper in the efficiency of the platinum catalysts for the HER and open routes for increasing the efficiency of the hydrogen generation reaction on an industrial scale.