Understanding the Role of (W, Mo, Sb) Dopants in the Catalyst Evolution and Activity Enhancement of Co 3 O 4 during Water Electrolysis via In Situ Spectroelectrochemical Techniques.

Unlocking the potential of the hydrogen economy is dependent on achieving green hydrogen (H 2 ) production at competitive costs. Engineering highly active and durable catalysts for both oxygen and hydrogen evolution reactions (OER and HER) from earth-abundant elements is key to decreasing costs of electrolysis, a carbon-free route for H 2 production. Here, a scalable strategy to prepare doped cobalt oxide (Co 3 O 4 ) electrocatalysts with ultralow loading, disclosing the role of tungsten (W), molybdenum (Mo), and antimony (Sb) dopants in enhancing OER/HER activity in alkaline conditions, is reported. In situ Raman and X-ray absorption spectroscopies, and electrochemical measurements demonstrate that the dopants do not alter the reaction mechanisms but increase the bulk conductivity and density of redox active sites. As a result, the W-doped Co 3 O 4 electrode requires ≈390 and ≈560 mV overpotentials to reach ±10 and ±100 mA cm -2 for OER and HER, respectively, over long-term electrolysis. Furthermore, optimal Mo-doping leads to the highest OER and HER activities of 8524 and 634 A g -1 at overpotentials of 0.67 and 0.45 V, respectively. These novel insights provide directions for the effective engineering of Co 3 O 4 as a low-cost material for green hydrogen electrocatalysis at large scales.