Bo Zhang

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Controllable CO adsorption determines ethylene and methane productions from CO2 electroreduction

Yang Li, Jun Li, Hao Yang, Bo Zhang, Zhiwen Zhou

Among all CO2 electroreduction products, methane (CH4) and ethylene (C2H4) are two typical and valuable hydrocarbon products which are formed in two different pathways: hydrogenation and dimerization reactions of the same CO intermediate. Theoretical studies show that the adsorption configurations of CO intermediate determine the reaction pathways towards CH4/C2H4. However, it is challenging to experimentally control the CO adsorption configurations at the catalyst surface, and thus the hydrocarbon selectivity is still limited. Herein, we seek to synthesize two well-defined copper nanocatalysts with controllable surface structures. The two model catalysts exhibit a high hydrocarbon selectivity toward either CH4 (83%) or C2H4 (93%) under identical reduction conditions. Scanning transmission electron microscopy and X-ray absorption spectroscopy characterizations reveal the low-coordination Cu-0 sites and local Cu-0/Cu+ sites of the two catalysts, respectively. CO-temperature programed desorption, in-situ attenuated total reflection Fourier transform infrared spectroscopy and density functional theory studies unveil that the bridge-adsorbed CO (COB) on the low-coordination Cu-0 sites is apt to be hydrogenated to CH4, whereas the bridge-adsorbed CO plus linear-adsorbed CO (COB + COL) on the local Cu-0/Cu+ sites are apt to be coupled to C2H4. Our findings pave a new way to design catalysts with controllable CO adsorption configurations for high hydrocarbon product selectivity. (C) 2020 Science China Press. Published by Elsevier B.V. and Science China Press. All rights reserved.

ELSEVIER2021

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Multimetal oxyhydroxides have recently been reported that outperform noble metal catalysts for oxygen evolution reaction (OER). In such 3d-metal-based catalysts, the oxidation cycle of 3dmetals has been posited to act as the OER thermodynamic-limiting process; however, further tuning of its energetics is challenging due to similarities among the electronic structures of neighbouring 3dmetal modulators. Here we report a strategy to reprogram the Fe, Co and Ni oxidation cycles by incorporating high-valence transition-metal modulators X (X = W, Mo, Nb, Ta, Re and MoW). We use in situ and ex situ soft and hard X-ray absorption spectroscopies to characterize the oxidation transition in modulated NiFeX and FeCoX oxyhydroxide catalysts, and conclude that the lower OER overpotential is facilitated by the readier oxidation transition of 3dmetals enabled by high-valence modulators. We report an similar to 17-fold mass activity enhancement compared with that for the OER catalysts widely employed in industrial water-splitting electrolysers.

NATURE RESEARCH2020

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High-Valent Nickel Promoted by Atomically Embedded Copper for Efficient Water Oxidation

Jun Li, Ning Wang, Bo Zhang

Efficient and low-cost electrocatalysts for oxygen evolution reaction (OER), particularly in neutral conditions, are of significant importance for renewable energy technologies such as CO2 reduction and seawater splitting electrolysis. High-valent transition-metal sites have been considered as OER active sites; however, the rational design and construction of these sites remain a big challenge. Here, we report a trimetallic NiFeCu oxyhydroxide electrocatalyst, in which high-valent Ni sites are promoted and stabilized by the atomically embedded Cu, as evidenced by X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. Through compositional optimization, Ni6Fe1Cu1 catalysts achieved an overpotential of 385 mV at 10 mA cm(-2), a Tafel slope of 164 mV dec(-1), and a stability of 100 h at pH = 7.2. Density function theory calculations demonstrated that the Cu-doping facilitates the formation of high-valent Ni and thus promotes OER electrocatalysis through modulating the d-band center of Ni and reducing the adsorption energy of oxygenated intermediates on the surface of the catalyst. This work paves a promising avenue for the construction of desired high-valent metal OER catalysts by embedding redox inactive metals.

AMER CHEMICAL SOC2020

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