(681b) Unveiling Flexibility of IrO2 Crystal Structure: An Approach Towards Efficient Oer Catalysis

Currently, substantial efforts are being devoted to cutting down the dependency on fossil fuels. In this regard, energy from renewables has prospected as the best long-term replacement for fossil fuels. Due to the intermittency of renewable sources, a major energy storage pairing is necessarily required if these sources are to dominate the total energy supply of the future. In this regard, hydrogen is contemplated to best serve as an energy storage medium from renewable sources at times of excess renewable electricity, which can be later converted back to electricity via other technologies like fuel cell. Although extensive research is being conducted to economize hydrogen production from different routes; however, electrocatalytic hydrogen production via water splitting is the most environmentally benign approach. Despite being the most suitable path, the overall efficiency of the process is momentously hampered due to sluggish anodic reactions. Especially, for the anodic half-cell reaction there is only a limited range of materials for catalysis that are able to sustain the high electrode potential along with the acidic environment ²⁶. Mostly, the potential materials are based on the oxides of iridium which are very expensive and scarce with their annual production being far below platinum. Therefore, to efficiently and economically harness the energy from renewables via water electrolyzers utmost efforts are needed to drastically reduce the iridium metal consumption to be used as an anode for improving the kinetics of oxygen evolution reactions (OER). In order to confront this challenge efforts are being carried out to enhance the mass-specific utilization of iridium. The enhancement in catalytic activity from all such efforts originates either by increasing the interfacial exposure of iridium sites or by intrinsically improving all the active sites. In this context, solid solutions of IrO₂ via doping are contemplated as a promising approach for positively tailoring the intrinsic metallic properties along with the reduction in precious metal content. However, doped structures realize a certain limit concerning the dopant fraction in a single phase. In here, it is presented that codoping, concurrent doping of more than one metal, facilitates further inclusion of dopants in the host structure rather than single metal due to lowered crystal formation energy. This approach of codoping was verified both experimentally and computationally while selecting cobalt and nickel as dopants for the Iridium dioxide host structure. It was evidenced that codoped IrO₂ nanoparticles performed more efficient OER catalysis than individually doped structures and reflected an overpotential value of just 285 mV at a current density of 10 mA/cm², while presenting a comparatively steeper tafel slope of 53 mV dec^−1 than 68 mV dec^−1 for pure IrO₂. Conclusively, codoping approach introduces a new strategy to effectively design OER catalysts with extensive reduction of precious metals.