A Solid-Solution with Asymmetric Ni-O-Cr Sites for Boosting Protonation toward Anodic Oxidation

Replacing the slow protonation process of oxygen evolution reaction (OER) with the fast protonation of alcohol electro-oxidation can decrease the driving potentials, thus improving overall efficiency of electrochemical devices. However, the formation of effective catalytic sites for alcohol oxidation remains challenging in accelerating protonation to inhibit metal leaching and improve catalyst stability. Herein, asymmetric Ni-O-Cr sites are constructed by alloying Cr into the NiO matrix to optimize coordination environments, showing significantly enhanced stability during alcohol electro-oxidation. The asymmetric Ni-O-Cr can maintain constant valence states of Cr and Ni during alcohol oxidation, efficiently suppressing metal dissolution even at high oxidation potentials. In situ electrochemical characterizations combined with theoretical calculations indicate that asymmetric Ni-O-Cr can improve adsorption and activation of OH* and alcohol molecules compared to pure NiO, thus increasing anodic kinetics. The theoretical results also indicate that the smaller gap of Ni 3d-O 2p in asymmetric Ni-O-Cr strengthens charge transfer, leading to fast protonation of catalytic sites with enhanced stability. This work gives insights into boosting anodic protonation using asymmetric sites-enriched solid-solution electrocatalysts. A solid-solution with asymmetric Ni-O-Cr sites can maintain constant valence states of Cr and Ni even at high potentials for boosted protonation process, thus inhibiting Ni and Cr dissolution and enhancing long-term operation stability. Cr alloying also lowers anodic overpotentials by optimizing Ni site coordination environments via Ni-O-Cr bridge. image