Single‐Atom Nickel on Carbon Nitride Photocatalyst Achieves Semihydrogenation of Alkynes with Water Protons via Monovalent Nickel

Abstract

Prospects in light‐driven water activation have prompted rapid progress in hydrogenation reactions. We describe a Ni2+−N4 site built on carbon nitride for catalyzed semihydrogenation of alkynes, with water supplying protons, powered by visible‐light irradiation. Importantly, the photocatalytic approach developed here enabled access to diverse deuterated alkenes in D2O with excellent deuterium incorporation. Under visible‐light irradiation, evolution of a four‐coordinate Ni2+ species into a three‐coordinate Ni+ species was spectroscopically identified. In combination with theoretical calculations, the photo‐evolved Ni+ is posited as HO−Ni+−N2 with an uncoordinated, protonated pyridinic nitrogen, formed by coupled Ni2+ reduction and water dissociation. The paired Ni−N prompts hydrogen liberation from water, and it renders desorption of alkene preferred over further hydrogenation to alkane, ensuring excellent semihydrogenation selectivity.

Enrichment of Polarized Alkynes over Negatively Charged Pt for Efficient Electrocatalytic Semihydrogenation

“…We thus doubly checked the possibility of the effect of charge density on the step from C 8 H 8 * to C 8 H 9 * (Figure a) as the key step to promote selectivity. The optimized Pt//W 2 C-7.4 catalyst provided a high turnover frequency (TOF) value of 310 h –1 (Figure d), significantly surpassing the reported highest TOF values (49 h –1 ) of the benchmark catalysts in the literature, including electrocatalysts, ,,,− photocatalysts, − and thermal reaction systems − with high selectivity to alkenes using water as the green hydrogen source (Table S3). The remarkable electrocatalytic activity advantages, more than 6-fold, illustrate the excellent availability of the negatively charged Pt metals within the Pt//W 2 C dual-junction systems for real uses in electrochemical synthesis reactors.…”

Insights into the active nickel centers embedded in graphitic carbon nitride for the oxygen evolution reaction

“…This concentration value is much lower than that used in the DFT calculations (8 wt%, corresponding to one Ni atom per supercell including four monomers), but it agrees with the ones reported in the literature for similar materials. 28,57,66,67…”

Promotion of Photocatalytic Hydrogen Evolution under Visible Light with NiO/C Fabricated via a Super Facile and General Strategy

“…The presence of nickel within the porous hybrid structure is critical, as its higher work function compared to carbon allows it to act as an effective catalyst for the pHER. 56 (6) Electrons transferred from the carbon matrix to the nickel centers can further enhance the pHER efficiency by facilitating proton reduction. (7) It is important to note that the reaction is conducted in the presence of a sacrificial electron donor, such as LA.…”