From inertness to efficiency: immobilizing Au-Bi heterostructures on a graphite substrate to drive the hydrogen...

In this study, we fabricated Au-Bi heterostructures on a pencil graphite (GP) support to generate hydrogen from water splitting under acidic conditions. Au particles, with their electronically filled 5d band, and Bi particles, known for their strong tendency toward surface oxide formation, exhibit limited intrinsic activity toward the HER. Remarkably, their integration produces an Au-Bi@GP electrode with substantially boosted hydrogen-evolution activity compared with the corresponding individual components. The Au@GP and Bi@GP electrodes require 486 mV and 442 mV to attain a 10 mA cm^-2 current, respectively. But, while Au and Bi particles are integrated on the GP surface, the resultant Au-Bi@GP electrode requires only 139 mV to achieve the same current intensity showcasing its efficient hydrogen production. A Tafel slope of 141.4 mV dec^-1 indicates that the HER is governed by the Volmer step indicating proton adsorption as the rate-limiting process. The electrode showed stable HER performance with negligible loss after 25 h of chronoamperometry test and 1000 voltametric runs. These results reveal an intriguing 'inert-to-active' transformation arising from the integration of two naturally sluggish HER (Au and Bi) elements and highlight interfacial engineering as an auspicious strategy for developing unconventional electrocatalysts for acidic hydrogen generation.