Electrochemical synthesis of H 2 O 2 through a selective two-electron (2e −) oxygen reduction reaction (ORR) is an attractive alternative to the industrial anthraquinone oxidation method, as it allows decentralized H 2 O 2 production. Herein, we report that the synergistic interaction between partially oxidized palladium (Pd δ+) and oxygen-functionalized carbon can promote 2e − ORR in acidic electrolytes. An electrocatalyst synthesized by solution deposition of amorphous Pd δ+ clusters (Pd 3 δ+ and Pd 4 δ+) onto mildly oxidized carbon nanotubes (Pd δ+-OCNT) shows nearly 100% selectivity toward H 2 O 2 and a positive shift of ORR onset potential by~320 mV compared with the OCNT substrate. A high mass activity (1.946 A mg −1 at 0.45 V) of Pd δ+-OCNT is achieved. Extended X-ray absorption fine structure characterization and density functional theory calculations suggest that the interaction between Pd clusters and the nearby oxygen-containing functional groups is key for the high selectivity and activity for 2e − ORR.

CRISPR-Cas systems inherently multiplex through CRISPR arrays—whether to defend against different invaders or mediate multi-target editing, regulation, imaging, or sensing. However, arrays remain difficult to generate due to their reoccurring repeat sequences. Here, we report a modular, one-pot scheme called CRATES to construct CRISPR arrays and array libraries. CRATES allows assembly of repeat-spacer subunits using defined assembly junctions within the trimmed portion of spacers. Using CRATES, we construct arrays for the single-effector nucleases Cas9, Cas12a, and Cas13a that mediated multiplexed DNA/RNA cleavage and gene regulation in cell-free systems, bacteria, and yeast. CRATES further allows the one-pot construction of array libraries and composite arrays utilized by multiple Cas nucleases. Finally, array characterization reveals processing of extraneous CRISPR RNAs from Cas12a terminal repeats and sequence- and context-dependent loss of RNA-directed nuclease activity via global RNA structure formation. CRATES thus can facilitate diverse multiplexing applications and help identify factors impacting crRNA biogenesis.

Ethanol is a green, sustainable, and high-energy-density liquid fuel that holds great promise for direct liquid fuel cells (DLFCs). However, it remains highly challenging to develop electrocatalysts that selectively promote the C–C bond scission for the ethanol oxidation reaction (EOR). Here, we report the facile synthesis of PtIr alloy core–shell nanocubes (NCs) with Ir-rich shells as effective EOR electrocatalysts. We find that (100)-exposed Pt38Ir NCs with one-atom-thick Ir-rich skin exhibit unprecedented EOR activity, high CO2 selectivity, and long-term stability, while pure Pt NCs and Pt17Ir NCs (two-atom thick Ir-rich skin) show less activity and lower CO2 selectivity. We demonstrate that the Pt38Ir NCs electrocatalyst can deliver a current density up to 4.5 times higher than that of Pt/C with a lower EOR onset potential by 320 mV. Its CO2 current density at 0.85 V is 14 times higher than that of commercial Pt/C. We show that the enhanced EOR activity is mainly due to the Ir-rich PtIr(100) facet that not only favors the splitting of the C–C bond by strongly adsorbing the *C x H y O/C x H y species but also promotes the desorption of CO from the PtIr surface. This work highlights the critical role of surface atom layers on shape-engineered catalysts and demonstrates a strategy for the design of efficient EOR electrocatalysts.

This review summarizes density functional theory (DFT) studies of TMCs and TMNs as electrocatalysts. It provides atomistic details of HER, OER, ORR, N2RR and CO2RR and also presents a future outlook in designing TMCs and TMNs based electrocatalysts.

In this study, the experimentally measured hydrogen evolution reaction exchange current densities for metal monolayer-modified transition metal carbides (TMCs) are correlated with density functional theory calculations of adsorbed hydrogen and hydroxyl binding energies. The correlation reveals a volcano relationship in alkaline electrolytes, while the hydroxyl binding energy does not appear to show a strong correlation. These results should provide guidance for further improving the electrocatalytic activity of metal-modified TMCs in an alkaline environment.