Principles of Synthesizing Transition Metal Silicate Hydroxides for Catalyzing the Oxygen Evolution Reaction

Transition metal silicates (hydroxides) have been extensively studied as electrode materials, particularly as electrocatalysts for the oxygen evolution reaction (OER). However, their synthesis has not been thoroughly explored, leading to inconsistent products under different synthetic conditions. In this work, we elucidate the formation mechanisms of three types of cobalt silicates (hydroxides) and two bimetallic silicate hydroxides and establish their specific synthesis conditions. We demonstrate that the form and dissolution kinetics of the metal sources during the sacrificial template process are critical factors governing the synthesis. They determine the Co/Si ratios in the products and whether two metals can uniformly distribute in bimetallic silicate hydroxides. Moreover, we illustrate that the bimetallic effect modulates the energy difference between the d-band center of cobalt and the p-band center of oxygen (Δε_d-p), along with the filling of the e_g* orbitals, thereby enhancing the OER performance. The present work significantly advances the research and application of transition metal silicate (hydroxide) materials.