Carbon-Nanotube-Supported Bio-Inspired Nickel Catalyst and Its Integration in Hybrid Hydrogen/Air Fuel Cells

A biomimetic nickel bis-diphosphine complex incorporating the amino acid arginine in the outer coordination sphere was immobilized on modified carbon nanotubes (CNTs) through electrostatic interactions. The functionalized redox nanomaterial exhibits reversible electrocatalytic activity for the H<inf>2</inf>/2 H⁺interconversion from pH 0 to 9, with catalytic preference for H<inf>2</inf>oxidation at all pH values. The high activity of the complex over a wide pH range allows us to integrate this bio-inspired nanomaterial either in an enzymatic fuel cell together with a multicopper oxidase at the cathode, or in a proton exchange membrane fuel cell (PEMFC) using Pt/C at the cathode. The Ni-based PEMFC reaches 14 mW cm⁻², only six-times-less as compared to full-Pt conventional PEMFC. The Pt-free enzyme-based fuel cell delivers ≈2 mW cm⁻², a new efficiency record for a hydrogen biofuel cell with base metal catalysts.