There is significant interest in synthesizing large-area graphene films at low temperatures by chemical vapor deposition (CVD) for nanoelectronic and flexible device applications. However, to date, low-temperature CVD methods have suffered from lower surface coverage because micro-sized graphene flakes are produced. Here, we demonstrate a modified CVD technique for the production of large-area, continuous monolayer graphene films from benzene on Cu at 100–300 °C at ambient pressure. In this method, we extended the graphene growth step in the absence of residual oxidizing species by introducing pumping and purging cycles prior to growth. This led to continuous monolayer graphene films with full surface coverage and excellent quality, which were comparable to those achieved with high-temperature CVD; for example, the surface coverage, transmittance, and carrier mobilities of the graphene grown at 300 °C were 100%, 97.6%, and 1,900–2,500 cm2 V−1 s−1, respectively. In addition, the growth temperature was substantially reduced to as low as 100 °C, which is the lowest temperature reported to date for pristine graphene produced by CVD. Our modified CVD method is expected to allow the direct growth of graphene in device manufacturing processes for practical applications while keeping underlying devices intact.

In this study, boron-incorporated palladium catalysts supported on carbon (PdBInc./C) were synthesized; they exhibited considerably improved catalytic activity for the oxidation of formate (HCOO–). Boron-induced lattice expansion and electronic modification of Pd were observed in this catalyst through various physicochemical analyses. Furthermore, the effective electronic modification between Pd and B was found to overcome the limitation due to the lattice expansion of Pd and the modification was confirmed from the downshift and broadening of the d-band center. The direction of electron transfer was observed from B to Pd. Based on the experimental results, it is possible to infer that PdBInc./C significantly contributes to the weakening of the hydrogen adsorption, which is regarded as a rate-determining step for the oxidation of HCOO–. As an anode electrode, PdBInc./C also showed an outstanding performance in a direct formate fuel cell owing to its modified electronic structure, which is considered an important property to facilitate hygroscopic fuel accessibility in a practical system.

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