A nanoscopic insight into electrocatalytic origins of the mercury monolayer carbon fiber electrode depicted by fast cyclic voltammetry

• We examined electrocatalytic origins of mercury monolayer carbon fiber electrode.
• The open nanopore of carbon fiber as a source of ballistic electrons is described.
• The Schottky contact formed in carbon nanopore by mercury monolayer is explained.

With the aim to unveil the origins of the electrocatalytic properties of the low-dimensional mercury monolayer carbon fiber electrode (MMCFE) the study of the cathodic and anodic background currents, specified by the proton reduction and the hydrogen oxidation, on bare and covered by a mercury monolayer carbon fiber electrode, in a wide domain of potentials and pH was carried out by means of fast (v = 0.1–20,000 V s−1) cyclic voltammetry.It was found a large difference between the electric charges passed during the negative- and the positive-going semi-cycles controlled by the magnitude of the applied negative potential (E), which abruptly increases when E < −1.4 V(SHE), specifying appearance of an unpaired anodic peak around E = 0.7 V (attributed to the electrooxidation of ‘absorbed’ atomic hydrogen (H0)) and reaches a maximum at E < −1.8 V followed by the appearance of the second anodic peak around E = −1.9 V (attributed to the oxidation of H0 diffused into the bulk electrolyte).The significant excess (>103) of the anodic electric charge, caused by the electrooxidation of H0, is explained by its homogeneous (nonfaradaic) generation by conversion of the field emitted electron.The Fowler–Nordheim plot denotes the source of electron emission as an open nanopore (with a width of 3–4 Å) formed between two external graphene sheets of the carbon fiber, where the electric field attains a maximal value of nearly 3 × 107 V cm−1.The electrolytic deposition of a single metal atom, matching the open nanopore dimension increases the electron emission by more than two orders on MMCFE, fact explained by formation there of the Schottky nanojunction between the semiconducting carbon fiber and the metallic mercury layer.