• Energy Research

Summary: Due to the highly complex polyphenolic structure of lignin, depolymerization without a prior chemical treatment is challenging, and new catalysts are required. Atomically dispersed catalysts are able to maximize the atomic efficiency of noble metals, simultaneously providing an alternative strategy to tune the activity and selectivity by alloying with other abundant metal supports. Here, we report a highly active and selective catalyst comprising monodispersed (single) Pt atoms on Ni nanoparticles supported on carbon (denoted as Pt1Ni/C, where Pt1 represents single Pt atoms), designed for the reductive depolymerization of lignin. Selectivity toward 4-n-propylsyringol and 4-n-propylguaiacol exceeds 90%. The activity and selectivity of the Pt1Ni/C catalyst in the reductive depolymerization of lignin may be attributed to synergistic effects between the Ni nanoparticles and the single Pt atoms.

The oxygen evolution reaction (OER) is an essential anode reaction for the generation of fuels through water splitting or CO2 electroreduction. Mixed metal oxides containing Co, Fe or Ni have proved to be the most promising OER electrocatalysts in alkaline media. However, the active sites and reaction mechanisms of these catalysts are difficult to study due to their heterogeneous nature. Here we describe a general synthesis of Co-, Fe- and Ni-containing double-atom catalysts from their single-atom precursors via in situ electrochemical transformation. Characterization reveals molecule-like bimetallic active sites for these supported catalysts. For each catalyst, we propose a catalytic cycle; all exhibit bimetallic cooperation and follow a similar O–O bond-forming step. However, the mechanisms diverge in the site and source of OH− for O–O bond formation, as well as the order of proton and electron transfer. Our work demonstrates double-atom catalysts as an attractive platform for fundamental studies of heterogeneous OER electrocatalysts. Oxygen evolution reaction (OER) catalysts often comprise multiple metal ions in various configurations, hampering mechanistic understanding of how catalysis proceeds. Now, researchers prepare a series of double-atom OER catalysts based on Ni, Fe and Co, which act as molecular-like models and are more amenable to mechanistic study.