Phase engineering activation of low-cost iron-containing sulfide minerals for advanced electrocatalysis

Abstract

• A phase transformation strategy was designed for activating natural minerals. • These activated minerals could be used for advanced electrocatalysis. • The haycockite phase showed the best performance for acidic HER and alkaline OER. • Further optimization was performed by loading iridium clusters for alkaline OER. Sustainable energy conversion and storage provide feasible approaches towards green energy solutions and carbon neutralization. The high cost and complex fabrication process of advanced energy nanomaterials, however, has impeded the practical application of emerging sustainable technologies. The direct use of earth-abundant natural minerals which contain active elements for effective catalysis and energy storage should be a promising approach to achieve affordable sustainable energy supply and green fuel generations. Herein, as typical examples of activating natural minerals for electrocatalysis, two common minerals, pyrite and chalcopyrite, are activated via a one-step phase transformation strategy. Through a facile thermal reduction process, the minerals are completely transformed into active pyrrhotite (FeS) and haycockite (Cu 4 Fe 5 S 8 ) phases. The thermal reduction resulting phase transformation can lead to significant surface disordering and can contribute to the catalytic activity by offering favourable electronic structure for intermediates adsorption, abundant surficial active centres, and substantial surface redox pairs. The activated minerals are examined for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalysis. The obtained haycockite phase delivers the best performance towards acidic HER and alkaline OER. Further phase optimization is performed via loading a low percentage of iridium nanoclusters on the haycockite phase deposited onto a carbon cloth substrate, through which an overpotential as low as 310 mV for achieving 10 mA cm −2 and a small Tafel slope of 55.6 mV dec −1 are recorded for alkaline OER. This work demonstrates the feasibility of the direct use of cost-effective natural resources for addressing the current energy-related issues and paves a way to reach affordable practical emerging sustainable technologies.