Direct electrolytic CO2 capture solution (e.g., bicarbonate), which bypasses the energy-intensive processes of CO2 desorption, offers a unique route for CO2 conversion to fuels or value-added chemicals. Nonprecious Ni single-atom catalysts (SACs) anchored on metal–organic frameworks (MOFs) possess abundant porous structures and exhibit a high selectivity for CO production. However, these MOF-derived Ni SACs are usually synthesized by a series of complex procedures, and their abundant micropores (<2 nm) also reduce the local reactant transport in the catalysts. Herein, we report a simple one-step pyrolysis method to prepare a MOF-derived Ni SAC that can efficiently boost bicarbonate conversion to CO. The abundant mesopores around 35.4 nm significantly enhance the transport of local reactants in the catalysts. At a high current density of 100 mA/cm2, the tailored catalyst shows 67.2% Faradaic efficiency of CO, which, to the best of our knowledge, exceeds the state-of-the-art precious Ag nanoparticle catalysts reported so far. This study highlights the significance of developing nonprecious catalysts for employment in large-scale bicarbonate electrolysis conversion devices.

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Developing a low-cost and high-performance thermally regenerative battery (TRB) is significant for recovering low-grade waste heat. A self-stratified TRB induced by the density difference between electrolytes is proposed to remove the commercial anion exchange membrane (AEM) and avoid ammonia crossover. The simulation and experiment results show the uneven distribution of NH3, verifying the feasibility of self-stratified electrolytes. For better power generation performance, nanoprism Cu covering Ni electrodes with a high specific surface area and a stable framework are adopted to provide more reaction active sites for fast charge transfer during discharge. A maximum power density (12.7 mW cm–2) and a theoretical heat-to-electricity conversion efficiency of 2.4% (relative to Carnot efficiency of 27.5%) are obtained in the self-stratified TRB employing nanoprism Cu covering Ni electrodes. Moreover, the cost-effectiveness, simple structure, and sustainable discharge operation indicate that it will be a potential choice for energy conversion from low-grade heat.