CO2 hydrogenation to methanol over Cu/CeO2 and Cu/ZrO2 catalysts:Tuning methanol selectivity via metal-support interaction

Copper-based catalysts for CO2 hydrogenation to methanol are supported on ZrO2 and CeO2,respectively.Reaction results at 3.0 MPa and temperatures between 200 and 300°C reveal that Cu catalysts supported on ZrO2 and CeO2 exhibit better activity and selectivity than pure Cu catalyst due to Cu-support(ZrO2 and CeO2)interaction.Combining the structural characterizations with in-situ diffuse reflectance infrared Fourier transform spectroscopy(in-situ DRIFTS),Cu/CeO2 shows the higher methanol selectivity due to the formation of main carbonates intermediates,which are closely related with the oxygen vacancies over Cu/CeO2.In contrast,bicarbonate and carboxyl species are observed on Cu/ZrO2,which originates from the hydroxyl groups presented on catalyst surfaces.Difference in CO2 adsorption intermediates results in the distinct methanol selectivity over the two catalysts.

Coordination Effect-Promoted Durable Ni(OH)_(2) for Energy-Saving Hydrogen Evolution from Water/ Methanol Co-Electrocatalysis

Electrocatalytic water splitting is a viable technique for generating hydrogen but is precluded from the sluggish kinetics of oxygen evolution reactions(OER).Small molecule oxidation reactions with lower working potentials,such as methanol oxidation reactions,are good alternatives to OER with faster kinetics.However,the typically employed Ni-based electrocatalysts have poor activity and stability.Herein,a novel three-dimensional(3D)-networking Modoped Ni(OH)_(2) with ultralow Ni-Ni coordination is synthesized,which exhibits a high MOR activity of 100 mA cm^(−2) at 1.39 V,delivering 28 mV dec^(−1) for the Tafel slope.Meanwhile,hydrogen evolution with value-added formate co-generation is boosted with a current density of more than 500 mA cm^(−2) at a cell voltage of 2.00 V for 50 h,showing excellent stability in an industrial alkaline concentration(6 M KOH).Mechanistic studies based on density functional the-ory and X-ray absorption spectroscopy showed that the improved performance is mainly attributed to the ultralow Ni-Ni coordination,3D-networking structures and Mo dopants,which improve the catalytic activity,increase the active site density and strengthen the Ni(OH)_(2)3D-networking structures,respectively.This study paves a new way for designing electrocatalysts with enhanced activity and durability for industrial energy-saving hydrogen production.

CoxP@NiCo-LDH heteronanosheet arrays as efficient bifunctional electrocatalysts for co-generation of value-added formate and hydrogen with less-energy consumption

The inefficiency of water splitting is mainly due to the sluggish anodic water oxidation reaction. Replacing water oxidation with thermodynamically more favorable selective methanol oxidation reaction and developing robust bifunctional electrocatalysts are of great significance. Herein, a hierarchical heteronanostructure with Ni–Co layered double hydroxide(LDH) ultrathin nanosheets coated on cobalt phosphide nanosheets arrays(CoxP@NiCo-LDH) are fabricated and used for co-electrolysis of methanol/water to co-produce value-added formate and hydrogen with saving energy. Benefiting from the fast charge transfer introduced by phosphide nanoarrays, the synergy in nanosheets catalysts with hetero-interface,CoxP@NiCo-LDH/Ni foam(NF) exhibits superior electrocatalytic performance(10 mA cm-2@ 1.24 V and-0.10 V for methanol selective oxidation and hydrogen evolution reaction, respectively). Furthermore,CoxP@NiCo-LDH/NF-based symmetric two-electrode electrolyzer drives a current density of 10 m A cm-2 with a low cell voltage of only 1.43 V and the Faradaic efficiency towards the generation of formate and H2 are close to 100% in the tested range of current density(from 40 to 200 m A cm-2). This work highlights the positive effect of hetero-interaction in the design of more efficient eletrocatalysts and might guide the way towards facile upgrading of alcohols and energy-saving electrolytic H2 co-generation.