Metal–CO2 batteries represent a promising priority for sustainable energy and the environment. However, CO2 utilization in nonaqueous electrolytes mostly involves difficult CO2 electrochemistry, leading to poor selectivity and limited cycle performance. Herein, an aqueous rechargeable Zn–CO2 electrochemical cell that tunably produced CO fuel gas (90% Faradaic efficiency) during cell discharge (cathodic reaction: CO2 + 2e− + 2H+ → CO + H2O) and O2 during cell charge at ≈2 V (cathodic reaction: H2O → 1/2O2 + 2e− + 2H+), mimicking the separate steps of CO2 fixation and water oxidation during photosynthesis while exhibiting the advantages of high efficiency, tunable products, and operation independent of sunlight is proposed and realized. The cell achieves a remarkable energy efficiency of 68% with fuel generation, providing an alternative for the green, efficient, and safe utilization of CO2 by metal–CO2 batteries.

Photo/electrochemical CO splitting is impeded by the low cost-effective catalysts for key reactions: CO reduction (CDRR) and water oxidation. A porous silicon and nitrogen co-doped carbon (SiNC) nanomaterial by a facile pyrolyzation was developed as a metal-free bifunctional electrocatalyst. CO -to-CO and oxygen evolution (OER) partial current density under neutral conditions were enhanced by two orders of magnitude in the Tafel regime on SiNC relative to single-doped comparisons beyond their specific area gap. The photovoltaic-driven CO splitting device with SiNC electrodes imitating photosynthesis yielded an overall solar-to-chemical efficiency of advanced 12.5 % (by multiplying energy efficiency of CO splitting cell and photovoltaic device) at only 650 mV overpotential. Mechanism studies suggested the elastic electron structure of -Si(O)-C-N- unit in SiNC as the highly active site for CDRR and OER simultaneously by lowering the free energy of CDRR and OER intermediates adsorption.

Novel dual-model Zn–CO2/Zn–O2 batteries were proposed and realized with trifunctional NiPG catalysts and variable supply gases.

Developing an efficient, stable yet cost-effective electrocatalyst is the key link along the path to hydrogen fuels produced by water splitting. The current bottleneck in the water electrolysis technology is the sluggish oxygen-evolving reaction (OER) which is also central to the rechargeable metal-air batteries. Herein, we report a promising mixed-metal-organic framework (MMOF) self-template strategy to synthesize CoFe hybrid oxyphosphides with highly porous morphology. Aided by the porous hybrid bulk structure beneficial to fast-ion diffusion to abundant highly active sites, the as-synthesized CoFePO exhibited excellent electrocatalytic activity toward OER, with an overpotential of 291 mV at 10 mA cm and a low Tafel slope of 85 mV dec. With the underpinnings of MMOF maintaining the structural rigidity and stability, the material also showed long life for OER without  discernible activity decay.

No abstract

Photo/electrochemical CO2 splitting is impeded by the low cost‐effective catalysts for key reactions: CO2 reduction (CDRR) and water oxidation. A porous silicon and nitrogen co‐doped carbon (SiNC) nanomaterial by a facile pyrolyzation was developed as a metal‐free bifunctional electrocatalyst. CO2‐to‐CO and oxygen evolution (OER) partial current density under neutral conditions were enhanced by two orders of magnitude in the Tafel regime on SiNC relative to single‐doped comparisons beyond their specific area gap. The photovoltaic‐driven CO2 splitting device with SiNC electrodes imitating photosynthesis yielded an overall solar‐to‐chemical efficiency of advanced 12.5 % (by multiplying energy efficiency of CO2 splitting cell and photovoltaic device) at only 650 mV overpotential. Mechanism studies suggested the elastic electron structure of −Si(O)−C−N− unit in SiNC as the highly active site for CDRR and OER simultaneously by lowering the free energy of CDRR and OER intermediates adsorption.

The development of efficient oxygen reduction reaction (ORR) electrocatalysts composed of low cost and earth abundant elements is imperative for several energy systems.

No abstract