Innovative InAg–carbon nanocomposites: mesoporous design for OER enhancement†

Abstract

To produce clean and sustainable hydrogen energy through water electrolysis, the sluggish oxygen evolution reaction (OER) needs to be accelerated sustainably by using stable and highly effective electrocatalysts. Bimetallic nanocomposites have been recently recognized as an interesting class of electrocatalysts because of their synergistic behaviour, tunable morphology, and high catalytic efficiency. Herein, InC, AgC, and InAgC nanocomposites were synthesised via a hydrothermal method using a mesoporous carbon support derived from the carbonisation of giant cane. The structural characterisation revealed that the InC composite has tetragonal In with a minor presence of cubic In₂O₃, whereas AgC and InAgC are well aligned with cubic Ag and tetragonal In. Electron microscopy revealed that InC has a 3D plate-like structure, while InAgC exhibits a spherical shape and is uniformly dispersed across the carbon surface. InAgC showed excellent activity and durability for the OER, with a notably low overpotential of 480 mV at a current density of 100 mA cm⁻², a Tafel slope of 97 mV dec⁻¹, and an oxygen production turnover frequency of 10.19 s⁻¹. The chronoamperometric (i–t) study of InAgC at 1.58 V vs. RHE for 20 h in 1 M KOH indicates that the catalyst is highly stable for the OER in alkaline electrolytes. The electrochemical double-layer capacitance (C_dl) value in the non-faradaic potential region of InAgC is greater (52.14 mF cm⁻²) than those of mesoporous carbon (16.54 mF cm⁻²), AgC (33.10 mF cm⁻²), and InC (48.77 mF cm⁻²), which is attributed to InAgC having more accessible active sites for the OER. This work presents numerous possibilities for developing effective nanocomposites using giant cane as a natural carbon source.