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Abstract Active catalysts for HER/HOR are crucial to develop hydrogen‐based renewable technologies. The interface of hetero‐nanostructures can integrate different components into a single synergistic hybrid with high activity. Here, the synthesis of PdO−RuO 2 −C with abundant interfaces/defects was achieved for the hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR). It exhibited a current density of 10 mA cm −2 at 44 mV with a Tafel slope of 34 mV dec −1 in 1 m KOH. The HER mass activity was 3 times higher in base and comparable to Pt/C in acid. The stability test confirmed high HER stability. The catalyst also exhibited excellent HOR activity in both media; in alkaline HOR it outperformed Pt/C. The exchange current density i 0,m of PdO−RuO 2 /C was 522 mA mg −1 in base, which is 58 and 3.4 times higher than those of Pd/C and Pt/C. The HOR activity of PdO−RuO 2 /C was 22 and 300 times higher than those of PdO/C in acid and base. Improvement of HER/HOR kinetics in different alkaline electrolytes was observed in the order K + <Na + <Li + , and increase of HER as well decrease of HOR kinetics was observed with increasing Li + concentration. It was proposed that OH ad ‐M + ‐(H 2 O) x in the double‐layer region could influence HER/HOR activity in base. Based on the hard and soft acid and base (HSAB) theory, the OH ads ‐M + ‐(H 2 O) x could help to remove more OH ads into the bulk, leading to increase in HER/HOR activity in alkaline electrolyte (K + <Na + <Li + ) and increasing the HER with increasing Li + concentration. The decrease of HOR activity of PdO−RuO 2 /C with increasing M + was due to M + ‐induced OH ads destabilization through the bifunctional mechanism. The high HER/HOR activity of PdO−RuO 2 /C could be attributed, among other factors, to interface engineering and strong synergistic interaction. This work provides an opportunity to design oxide‐based catalysts for renewable energy technologies.
Samanta et al. (Wed,) studied this question.