Catalyst design by scanning probe block copolymer lithography.

Abstract

Scanning probe block copolymer lithography (SPBCL), in combination with density-functional theory (DFT), has been used to design and synthesize hydrogen evolution catalysts. DFT was used to calculate the hydrogen adsorption energy on a series of single-element, bimetallic, and trimetallic (Au, Pt, Ni, and Cu) substrates to provide leads that could be synthesized in the form of alloy or phase-separated particles via SPBCL. PtAuCu (18 nm, ∼1:1:1 stoichiometry) has been identified as a homogeneous alloy phase that behaves as an effective hydrogen evolution catalyst in acidic aqueous media, even when it is made in bulk form via solution phase methods. Significantly, the bulk-prepared PtAuCu/C nanocatalyst discovered via this process exhibits an activity seven times higher than that of the state-of-the-art commercial Pt/C catalyst (based upon Pt content). The advantage of using SPBCL in the discovery process is that one can uniformly make particles, each consisting of a uniform phase combination (e.g., all alloy or all phase-segregated species) at a fixed elemental ratio, an important consideration when working with polyelemental species where multiple phases may exist.