Abstract
Engineered solid–liquid interfaces will play an important role in the development of future energy storage and conversion (ESC) devices. In the present study, defective graphene oxide (GO) and reduced graphene oxide (rGO) structures were used as engineered interfaces to tune the selectivity and activity of Pt disk electrodes. GO was deposited on Pt electrodes via the Langmuir–Blodgett technique, which provided compact and uniform GO films, and these films were subsequently converted to rGO by thermal reduction. Electrochemical measurements revealed that both GO and rGO interfaces on Pt electrodes exhibit selectivity toward the oxygen reduction reaction (ORR), but they do not have an impact on the activity of the hydrogen oxidation reaction in acidic environments. Scanning transmission electron microscopy at atomic resolution, along with Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), revealed possible diffusion sites for H2 and O2 gas molecules and functional groups relevant to the selectivity and activity of these surfaces. Based on these insights, rGO interfaces are further demonstrated to exhibit enhanced activity for the ORR in nonaqueous environments and demonstrate the power of our ex situ engineering approach for the development of next-generation ESC devices.
Highlights
The solid−liquid interface (SLI) is a crucial part of every energy storage and conversion (ESC) device, and yet despite decades of research is still poorly understood at the atomic level
Uniform monolayers are required to test the selectivity of ex situ engineered interfaces, and to this end, we developed a reproducible method for covering the whole surface area of a Pt disk electrode with graphene oxide (GO)
GO monolayers were deposited on Pt polycrystalline disk electrodes by transferring them from a Langmuir trough using the modified Langmuir−Blodgett (LB) approach shown in Figure 1a and dipping angle to minimize strain on the monolayer during deposition.[19]
Summary
The solid−liquid interface (SLI) is a crucial part of every energy storage and conversion (ESC) device, and yet despite decades of research is still poorly understood at the atomic level. The structure of the SLI, in turn, determines many of its important properties, in particular its activity, stability, and selectivity. It is highly questionable why we would leave these important properties at the mercy of a spontaneous process. In this respect, surface engineering of metal catalysts can play a significant role in tuning the chemical and physical properties of the interface in an advantageous way. Surface engineering approaches are often divided into in situ or ex situ methods, where the presence of various additives in the electrolyte of batteries, supercapacitors, or fuel cells leads to in situ formation of the SLI and where the pretreatment of electrode materials to yield an engineered interface (e.g., a film or coating) represents an ex situ approach to tuning the SLI composition
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