Electrochemical CO 2 reduction reaction (CO 2 RR) is an attractive strategy for sustainable production of chemicals and has mainly been implemented in alkaline or neutral electrolytes. However, part of input CO 2 is consumed by the formation of carbonate under these conditions. Herein, a space-confined strategy is proposed for CO 2 RR in acidic media, and Ni nanoparticles are encapsulated inside N-doped carbon nanocages as yolk−shell nanoreactors. By confining CO 2 RR in the cavities of nanoreactors, a Faradaic efficiency (FE) of 93.2% for CO is achieved at pH 7.2 and 84.3% FE for CO at pH 2.5. The inhibited proton diffusion within the Nernst layer of a nanoreactor is responsible for suppression of competing hydrogen evolution in acid. Moreover, CO 2 RR in an acidic flow electrolysis system offers enhanced current density and sustainable operation, in comparison with the conventional neutral pH system. This work shows that steering of mass transport via a unique structure is a viable avenue toward selective CO 2 conversion, and it provides a further understanding of the structure−performance relationship of electrocatalysts.

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A possible mechanism to explain the impact of La doping on electron transfer process in wide band gap semiconductor In(OH)3.

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We report a free template strategy for the fabrication of nickel/cobalt double hydroxide microspheres (Ni/ Co-DHMs) in a tertbutanol-water (TBA-H 2 O) medium. This study demonstrates that the nanostructure and morphology of the Ni/Co-DHMs can be easily tuned by altering the ratio of TBA/H 2 O. When the reaction is performed in a solvent mixture with a low water content, the as-synthesized Ni/Co-DHMs form as pure nanoflakes with a good hydrotalcite structure, but increasing the ratio of water leads first to a mixture of nanoflakes and nanorods, and then increasing it further gives rise to a mixture of pure a-Co(OH) 2 and a-Ni(OH) 2 nanorods. In this work, three typical Ni/Co-DHM materials were prepared using TBA/H 2 O ratios of 9 : 1, 8 : 2 and 6 : 4. Since the unique architecture of the synthesised Ni/Co-DHM materials leads to greatly improved faradaic redox reaction and mass transfer, these Ni/Co-DHM electrodes offer high electrochemical performance for application in supercapacitors. Their specific capacities are 1800.4 F g 21 , 1603.2 F g 21 and 1430.8 F g 21 at a current density of 1 A g 21 , and 98.7%, 95.1% and 90.1% of these specific capacities are retained at a current density of 10 A g 21 after 3000 cycles, respectively. This study also provides a promising approach for the design and synthesis of structure tunable materials with largely enhanced electrochemical characteristics, which can be potentially applied in various energy storage/ conversion devices.

Direct electrochemical CO2 reduction to formic acid (FA) instead of formate is a challenging task due to the high acidity of FA and competitive hydrogen evolution reaction. Herein, 3D porous electrode (TDPE) is prepared by a simple phase inversion method, which can electrochemically reduce CO2 to FA in acidic conditions. Owing to interconnected channels, high porosity, and appropriate wettability, TDPE not only improves mass transport, but also realizes pH gradient to build higher local pH micro‐environment under acidic conditions for CO2 reduction compared with planar electrode and gas diffusion electrode. Kinetic isotopic effect experiments demonstrate that the proton transfer becomes the rate‐determining step at the pH of 1.8; however, not significant in neutral solution, suggesting that the proton is aiding the overall kinetics. Maximum FA Faradaic efficiency of 89.2% has been reached at pH 2.7 in a flow cell, generating FA concentration of 0.1 m. Integrating catalyst and gas–liquid partition layer into a single electrode structure by phase inversion method paves a facile avenue for direct production of FA by electrochemical CO2 reduction.

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