Enhanced borohydride oxidation on a Pd–Ni(OH)2/C catalyst via hydroxyl enrichment on nearby active sites

Abstract

Direct borohydride fuel cells (DBFCs) have been widely investigated due to their practical significance in mobile and portable devices. Pd-based catalysts exhibit superior performance as anode catalysts in DBFCs, but their too strong adsorption of H intermediates (H_ad) impedes the regeneration of active sites, significantly restricting their stability and final industrial application. In this work, we introduced Ni(OH)₂ into a Pd/C matrix to enrich OH⁻ for removing H_ad species. The obtained bimetallic oxides supported on the carbon powder (Pd–Ni(OH)₂/C) showed a peak power density of 625 mW cm⁻² in a DBFC (with air as the cathode oxidant), which is 2.3 times higher than that of Pd/C, and afforded a remarkable stability for over 120 h at 200 mA cm⁻². In situ spectroscopy studies and the theoretical results have revealed that the enriched OH⁻ microenvironment induced by Ni(OH)₂ facilitates the oxidative removal of H_ad on nearby Pd sites, thereby enhancing the regeneration of active sites and substantially boosting the electrocatalytic performance.