Modification of the Coordination Environment of Active Sites on MoC for High‐Efficiency CH₄ Production

Abstract

for improving the properties of catalysts and controlling catalysis. However, this modulation is of atomic-level precision and thus extremely difficult.Herein, we have successfully modified the coordination environment of active sites on the surfaces of MoC nanoparticles by anchoring pyridinic N atoms of porous graphene on Mo atoms adjacent to hollow sites, passivating the hollow sites and activating top sites of Mo atoms. MoC and its related materials have been widely used to catalyze various reactions, [3][4][5][6][7][8] of which the electrocatalytic hydrogen evolution reaction (HER) and the electrocatalytic reduction of CO 2 (CO 2 ECR) are both green processes to produce fuels for energy production use. The MoC family has exhibited excellent abilities to catalyze the HER, [6][7][8] which are significant breakthroughs showing the potential of the MoC-related materials for electrocatalysts and energy researches. However, for CH 4 , one of CO 2 ECR products, which has also attracted great attention for its compatibility with existing infrastructure and potential substitution for fossil fuels, the difficult removal of adsorbed OH (denoted as *OH) from the active sites of the MoC family causes their reported Faradaic efficiency (FE) to be no larger than 0.1%. [8] That is much Modulating the coordination environment of active sites on catalyst surfaces is crucial to developing effective catalysts and controlling catalysis. However, this may be a highly challenging procedure. Guided by the first-principles calculations, the modification of the coordination environment of active sites on MoC nanoparticle surfaces is experimentally accomplished by anchoring pyridinic N atom rings of holey graphene on Mo atoms. The rings produce electrostatic forces that enable the tuning of the Mo sites′ affinity to reaction intermediates, which passivates Mo hollow sites, activates Mo top sites, and reduces the overadsorption of OH on the Mo active sites, as predicted by calculations. The atomic-level modification is well confirmed by atomicresolution imaging, high-resolution electron tomography, synchrotron soft X-ray spectroscopy, and operando electrochemical infrared spectroscopy. Consequently, the Faradaic efficiency for CO 2 reduction to CH 4 is enhanced from 16% to 89%, a record high efficiency so far, in aqueous electrolytes. It also exhibits a negligible activity loss over 50 h.

Controllable States and Porosity of Cu‐Carbon for CO2 Electroreduction to Hydrocarbons

“…Both the Cu 2 O‐pC and Cu 2 O/CuO‐pC achieved a high maximum partial current density of −438.33 mA cm –2 (CH 4 ) and −577.66 mA cm –2 (C 2 H 4 ) at −1.58 V respectively. Such high partial current density of CH 4 and C 2 H 4 exceeded most of the CH 4 and C 2 H 4 producing catalysts according to our investigations (Figure 4e,f, Tables S1 and S2, Supporting Information) [ 3,7,9,15,21,24,28–31 ] and could close to the needs of commercial CO 2 RR catalysts. What's more, it could be seen from Figure 4c that the selectivity of CH 4 and C 2 H 4 was a competitive relation for Cu 2 O‐pC and Cu 2 O/CuO‐pC.…”

“…For all the samples, at very low potential, CO and H 2 were the main products, with the increase of the applied potential, the FE of CH 4 and C 2 H 4 were increased, which was in line with the result of previous research that CH 4 and C 2 H 4 were achieved at a high overpotential. [3] However, with the voltage increasing further, H 2 will inhibit the formation of CH Tables S1 and S2, Supporting Information) [3,7,9,15,21,24,[28][29][30][31] and could close to the needs of commercial CO 2 RR catalysts. What's more, it could be seen from Figure 4c that the selectivity of CH 4 and C 2 H 4 was a competitive relation for Cu 2 O-pC and Cu 2 O/ CuO-pC.…”

Oxygen Vacancy-Rich Amorphous Copper Oxide Enables Highly Selective Electroreduction of Carbon Dioxide to Ethylene

“…Furthermore, volumetric CO2 adsorption measurements were performed and verified that m-CuOx absorbs more CO2 than that of c-Cu2O (Fig. 2c), suggesting the increased CO2 adsorption capacity of m-CuOx 28,39 .…”

Dual-Doping Promotes the Carbon Dioxide Electroreduction Activity of MoS2 Nanosheet Array

“…Note that the FE CO remains above 69% in a wide potential range from −0.7 to −1.1 V vs RHE, suggesting the exclusive selectivity for CO production over N,P-MoS 2 NSA. As summarized in Figure 4c and Table S1, the optimal FE CO achieved by N,P-MoS 2 NSA demonstrated superior performance in comparison with those of previously reported MoS 2 -based catalysts, for example, Ndoped MoS 2 /N-doped carbon nanodots 20 (90.2% at −0.9 V vs RHE) and hydrophobic exfoliated MoS 2 12 (81.2% at −0.9 V vs RHE), and also a performance comparable to that of the stateof-the-art noble-metal-based catalysts [such as Ag nanosheets 35 (95% at −0.7 V vs RHE), nanoporous Au 36 (99% at −0.5 V vs RHE), and Pd−Au nanowires 37 (94.3% at −0.6 V vs RHE)]. In addition, the CO partial current density (j CO ) was depicted in Figure S4.…”