Facile Synthesis and Insight of Atomically Dispersed Ni Catalyst on N-Doped Carbonized Lignin for Highly Efficient Electrochemical CO2 Reduction to CO.

For the electrochemical CO2 reduction reaction (CO2 RR), the single-metal atom catalysts (SACs) on N-doped carbon are considered promising alternatives to conventional catalysts owing to their unique electrocatalytic properties. However, environmentally friendly methods to prepare SACs are still required. Herein, Ni SAC was synthesized using lignin derived from biomass whose structural and chemical properties render it suitable as both a base carbon matrix and a metal chelating agent. The coordination environment of active Ni-Nx sites was readily manipulated by controlling thermal activation. The Ni SAC on lignin-derived N-doped carbon achieved an outstanding CO Faradaic efficiency of 98.2 % at -0.9 V vs. RHE, which is comparable to those of conventional SACs. Experimental results combined with DFT calculations demonstrate the optimal conditions for manufacturing Ni SAC which is highly selective for CO2 -to-CO conversion and the effect of the electronic structure of Ni atom on CO2 RR kinetics.

Engineering interfacial structures to accelerate hydrogen evolution efficiency of MoS2 over a wide pH range.

Developing low-cost electrocatalysts with outstanding electrochemical performance for water splitting over a wide pH range is urgently desired to meet the practical needs in different areas. Herein, a highly efficient hierarchical flower-like CoS2@MoS2 core-shell nanostructured electrocatalyst is fabricated by a two-step strategy, in which MoS2 nanosheets with a layered structure are grown on the CoS2 core supported on carbon paper (CP) and used as hydrogen evolution reaction (HER) electrocatalysts working in the whole pH range (0-14). Remarkably, benefiting from the interface-engineering in this 3D core-shell structure of the electrocatalyst, the optimum CoS2@MoS2/CP catalyst exhibits outstanding HER activity over a wide range of pH values and an overpotential of 69 mV in acidic solution, 145 mV in neutral solution and 82 mV in alkaline solution, respectively, to afford the standard current density of 10 mA cm-2. Furthermore, it demonstrates superior stability under different pH conditions for at least 48 h. Density functional theory (DFT) calculations are performed to gain further insight into the effect of CoS2@MoS2 interfaces, revealing that the strong interfacial interaction between CoS2 and MoS2 dramatically reduces the Gibbs free energy of hydrogen adsorption and the energy barrier for water dissociation, thus enhancing the electrochemical HER activity in the whole pH range (0-14).