Enhanced Nitrate-to-Ammonia Activity on Copper-Nickel Alloys via Tuning of Intermediate Adsorption.

Electrochemical conversion of nitrate (NO3-) into ammonia (NH3) recycles nitrogen and offers a route to the production of NH3, which is more valuable than dinitrogen gas. However, today's development of NO3- electroreduction remains hindered by the lack of a mechanistic picture of how catalyst structure may be tuned to enhance catalytic activity. Here we demonstrate enhanced NO3- reduction reaction (NO3-RR) performance on Cu50Ni50 alloy catalysts, including a 0.12 V upshift in the half-wave potential and a 6-fold increase in activity compared to those obtained with pure Cu at 0 V vs reversible hydrogen electrode (RHE). Ni alloying enables tuning of the Cu d-band center and modulates the adsorption energies of intermediates such as *NO3-, *NO2, and *NH2. Using density functional theory calculations, we identify a NO3-RR-to-NH3 pathway and offer an adsorption energy-activity relationship for the CuNi alloy system. This correlation between catalyst electronic structure and NO3-RR activity offers a design platform for further development of NO3-RR catalysts.

Carbon-Coated Co(3+)-Rich Cobalt Selenide Derived from ZIF-67 for Efficient Electrochemical Water Oxidation.

Oxygen evolution reaction (OER) electrocatalysts are confronted with challenges such as sluggish kinetics, low conductivity, and instability, restricting the development of water splitting. In this study, we report an efficient Co(3+)-rich cobalt selenide (Co0.85Se) nanoparticles coated with carbon shell as OER electrocatalyst, which are derived from zeolitic imidazolate framework (ZIF-67) precursor. It is proposed that the organic ligands in the ZIF-67 can effectively enrich and stabilize the Co(3+) ions in the inorganic-organic frameworks and subsequent carbon-coated nanoparticles. In alkaline media, the catalyst exhibits excellent OER performances, which are attributed to its abundant active sites, high conductivity, and superior kinetics.

Polarization-independent and fast tunable microlens array based on blue phase liquid crystals.

This work investigates a polarization-independent and fast response microlens array. This array is composed of a concave polymer microlens array and blue phase liquid crystals (BPLCs). The microlens array can be either positive or negative, depending on the birefringence of the BPLCs. The experimental results show that the microlens array is fast switched between positive and negative focal lengths via controlling the electric fields, and the response time is a few hundred microseconds. Additionally, the focusing efficiency is independent of the polarization of the incident light.