In situ electrochemical regeneration of active 1,4-NADH for enzymatic lactic acid formation via concerted functions on Pt-modified TiO2/Ti

Nicotinamide adenine dinucleotide (NAD+) and its reduced form (NADH) are key cofactors serving as essential hydrogen acceptors and donors to facilitate energy and material conversions under mild conditions. We demonstrate direct electrochemical conversion to achieve highly efficient regeneration of enzymatically active 1,4-NADH using a Pt-modified TiO2 catalyst grown directly on a Ti mesh electrode (Pt-TOT). Spectral analyses revealed that defects formed by the inclusion of Pt species in the lattice of TiO2 play a critical role in the regeneration process. In particular, Pt-TOT containing approximately 3 atom% of Pt exhibited unprecedented efficiency in the electrochemical reduction of NAD+ at the lowest overpotential to date. This exceptional performance led to the production of active 1,4-NADH with a significantly high yield of 86 ± 3% at -0.6 V vs. Ag/AgCl (-0.06 V vs. RHE) and an even higher yield of 99.5 ± 0.4% at a slightly elevated negative potential of -0.8 V vs. Ag/AgCl (-0.2 V vs. RHE). Furthermore, the electrochemically generated NADH was directly applied in the enzymatic conversion of pyruvic acid to lactic acid using lactate dehydrogenase.

Cu Modified TiO2 Catalyst for Electrochemical Reduction of Carbon Dioxide to Methane

Electrochemical reduction of CO2 (ECO2R) is gaining attention as a promising approach to store excess or intermittent electricity generated from renewable energies in the form of valuable chemicals such as CO, HCOOH, CH4, and so on. Selective ECO2R to CH4 is a challenging target because the rate-determining step of CH4 formation, namely CO* protonation, competes with hydrogen evolution reaction and the C–C coupling toward the production of longer-chain chemicals. Herein, a Cu-TiO2 composite catalyst consisting of CuOx clusters or Cu nanoparticles (CuNPs), which are isolated on the TiO2 grain surface, was synthesized using a one-pot solvothermal method and subsequent thermal treatment. The Cu-TiO2 catalyst exhibited high selectivity for CH4, and the ratio of FE for CH4 to total FE for all products in ECO2R reached 70%.

Heterointerface Created on Au-Cluster-Loaded Unilamellar Hydroxide Electrocatalysts as a Highly Active Site for the Oxygen Evolution Reaction

The oxygen evolution reaction (OER) is a critical element for all sorts of reactions that use water as a hydrogen source, such as hydrogen evolution and electrochemical CO₂ reduction, and novel design principles that provide highly active sites on OER electrocatalysts push the limits of their practical applications. Herein, Au-cluster loading on unilamellar exfoliated layered double hydroxide (ULDH) electrocatalysts for the OER is demonstrated to fabricate a heterointerface between Au clusters and ULDHs as an active site, which is accompanied by the oxidation state modulation of the active site and interfacial direct OO coupling ("interfacial DOOC"). The Au-cluster-loaded ULDHs exhibit excellent activities for the OER with an overpotential of 189 mV at 10 mA cm^-2 . X-ray absorption fine structure measurements reveal that charge transfer from the Au clusters to ULDHs modifies the oxidation states of trivalent metal ions, which can be active sites on the ULDHs. The present study, supported by highly sensitive spectroscopy combining reflection absorption infrared spectroscopy and modulation-excitation spectroscopy and density functional theory calculations, indicates that active sites at the interface between the Au clusters and ULDHs promote a novel OER mechanism through interfacial DOOC, thereby achieving outstanding catalytic performance.

Selectivity enhancement in the electrochemical reduction of oxalic acid over titanium dioxide nanoparticles achieved by shape and energy-state control

The morphology of TiO2 nanoparticles has a substantial impact on the product selectivity in an electrochemical reduction reaction.