High-quality Si photoelectrodes with novel Sn nanowire catalysts convert solar energy to reduce CO2 to formic acid with high selectivity.

No abstract

As atmospheric levels of carbon dioxide (CO2) continue to increase, there is an immediate need to balance the carbon cycle. Current approaches require multiple processes to fix CO2 from the atmosphere or flue gas and then reduce it to value-added products. The zinc­(II) catalyst Zn­(DMTH) (DMTH = diacetyl-2-(4-methyl-3-thiosemicarbazonate)-3-(2-pyridinehydrazonato)) reduces CO2 from air to formate with a faradaic efficiency of 15.1% based on total charge. The catalyst utilizes metal–ligand cooperativity and redox-active ligands to fix, activate, and reduce CO2. This approach provides a new strategy that incorporates sustainable earth-abundant metals that are oxygen and water tolerant.

Efficient electroreduction of carbon dioxide has been a widely pursued goal as a sustainable method to produce value‐added chemicals while mitigating greenhouse gas emissions. Processes have been demonstrated for the electroreduction of CO2 to CO at nearly 100 % faradaic efficiency, and as a consequence, there has been growing interest in the further electroreduction of carbon monoxide. Oxide‐derived copper catalysts have promising performance for the reduction of CO to hydrocarbons but have still been unable to achieve high selectivity to individual products. A pulsed‐bias technique is one strategy for tuning electrochemical selectivity without changing the catalyst. Herein a pulsed‐bias electroreduction of CO was investigated on oxide‐derived copper catalyst. Increased selectivity for single‐carbon products (i.e., formate and methane) was achieved for higher pulse frequencies (<1 s pulse times), as well as an increase in the fraction of charge directed to CO reduction rather than hydrogen evolution.

Figure 1. Band alignment of photoanode and photocathode semiconductors relative to water oxidation and reduction potentials and material selfoxidation and self-reduction potentials. Reproduced with permission. [12]

The in situ photocorrosion of GaP is studied with a widely applicable spectroelectrochemical method, yielding insights on n vs. p+ corrosion.

A pair of bis‐thiosemicarbazonato‐Ni(II) complexes with pendant polyamines, (N,N′‐(dimethylethylenediaminothiosemi‐carbazonato)‐4‐(methylthiosemi‐carbazonato)butane‐2,3‐diimine)‐nickel(II) (1) and (N,N′‐bis(dimethylethyl‐enediaminothiosemi‐carbazonato)butane‐2,3‐diimine)‐nickel(II) (3), have been synthesized. Methylation at the terminal amines yields the cationic derivatives 2 and 4. All complexes are fully characterized by spectroscopic, electrochemical, and single‐crystal X‐ray diffraction methods. Single crystal X‐ray diffraction studies on all four Ni(II) complexes confirm a square planar Ni(II) framework with no significant changes in the coordination environment as a function of the pendant groups. Spectroscopic studies are consistent with a similar electronic structure in all complexes. However, electrochemical investigations reveal significant cathodic shifts in the Ni(II)L/Ni(II)L·– and Ni(II)L·–/Ni(I)L·2– reduction potentials of the methylated vs. non‐methylated species. The HER activity of all four nickel complexes were evaluated in acetonitrile with glacial acetic acid. The 3 complex was shown to have the highest activity with a TOF of 6.3 × 103 s‐1, an overpotential of 0.56 V, and faradaic efficiency of 100 %.

Molecular NiATSM on p-Si durably photocatalyzed hydrogen evolution from water at practical conditions in acid with greater activity than Ni metal.