Improving Charge Transfer Kinetics of Ni Hydroxide Through Chromium: Efficient Production of Benzoic Acid at Ampere‐Level Current Density

Hybrid water electrolysis with the simultaneous generation of hydrogen and value-added chemicals enhances the viability of the water electrolysis process. A remarkably high current density of 1.4 A cm^-2 toward benzyl alcohol oxidation (BOR) at a low potential of 1.45 V reported in this work suggests that the oxygen evolution reaction (OER) can be replaced with BOR by selecting a suitable catalyst. A chromium oxide-treated Ni foam (Cr-NF) synthesized through a simple hydrothermal route offers 100% conversion and 99.5% faradaic efficiency toward benzoic acid. The surface nature of NF is significantly modified by chromium oxide, known for its hydrophilic nature and pore-forming abilities, resulting in enhanced active sites. In situ Raman analysis confirms the reversible electrochemical conversion of Ni hydroxides to NiOOH, which converts benzyl alcohol (BA) to benzoic acid (PhCOOH) by chemical oxidation. The theoretical analysis suggests accelerated electronic transport and lower free energy for the sorption of intermediates utilizing the Cr₂O₃/NiOOH surface. In a two-electrode arrangement, Cr-NF demonstrates excellent performance, achieving a current density of 2.5 A cm^-2 at an applied potential of 3.1 V, which is highly significant compared to OER-based systems. This system can further be studied for commercial applications.