(603j) Heterogeneity at heterogeneous interfaces: Understanding the influence of low-level contaminants on (photo)electrochemical kinetics

Heterogeneous electrocatalysis offers a green alternative (when coupled with renewably-sourced electrons) to conventional carbon-intensive commodity chemical and fuel production processes. Reaction intermediates are stabilized at solid-liquid interfaces, where the composition and structure of the solid surface dictates the adsorption energetics and activation barriers underpinning the reaction free energy landscape. Understanding the physicochemical parameters that dictate catalyst performance is then crucial to deriving fundamental understanding towards the design of increasingly efficient catalyst architectures. Here, we discuss examples where (photo)electrochemical performance is dependent on nuanced distinctions between catalytic surfaces.

Here, we explore the role of mechanically-applied strain on the oxygen evolution reaction (OER) over rutile TiO₂ thin films, grown by thermally annealing the superelastic alloy nitinol (NiTi). Rather than strain controlling kinetics, we find that OER kinetic parameters (overpotential and Tafel slope) trend with the areal density of Ni active sites, quantified by the intensity of NiOOH/NiO redox features assessed by cyclic voltammetry. We find OER kinetics change most drastically at <1% Ni site coverage (<10¹³ Ni/cm²_geo), at or below the detection limit of many common surface characterization techniques and raising questions regarding the minimum characterization threshold of electrochemically “clean” surfaces.