Catalytic H2 evolution with CoO, Co(OH)2 and CoO(OH) NPs generated from a molecular polynuclear Co complex

Marcos Gil-Sepulcre; Carolina Gimbert-Suriñach; David Aguila; Veronica Velasco; Jordi Garcia-Anton; Antoni Llobet; Guillem Aromi; Roger Bofill; Xavier Sala

Index: 10.1002/ejic.201800033

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Abstract

Electrochemical water reduction by employing first row transition metal nanoparticles (NPs) constitutes a sustainable way for the generation of H2. We have synthesized Co‐based NPs from a molecular CoII/CoIII precursor after its reductive decomposition at ‐1.86 V vs. NHE in different organic solvents. These NPs are able to electrochemically reduce water at pH 14. SEM, EDX and XPS analyses have allowed the determination of the chemical nature of the as‐deposited NPs: CoO when using MeCN as solvent and CoO(OH) when employing either dichloromethane (DCM) or MeOH. After 2h of constant polarization at 10 mA·cm‐2, the electrocatalytic activity of the NPs obtained in MeCN and DCM decreases, whereas for those obtained in MeOH increases. In this solvent, the overpotential is reduced by 215‐220 mV and the specific current density is triplicated. Interestingly, during this activation process in MeOH the precursor CoO(OH) NPs are converted into Co(OH)2. The implications of these results in the context of the current research in the field are also discussed.