Yiyang Lin

Abstract Developing high-performance electrocatalysts toward hydrogen evolution reaction is important for clean and sustainable hydrogen energy, yet still challenging. Herein, we report a single-atom strategy to construct excellent metal-organic frameworks (MOFs) hydrogen evolution reaction electrocatalyst (NiRu 0.13 -BDC) by introducing atomically dispersed Ru. Significantly, the obtained NiRu 0.13 -BDC exhibits outstanding hydrogen evolution activity in all pH, especially with a low overpotential of 36 mV at a current density of 10 mA cm −2 in 1 M phosphate buffered saline solution, which is comparable to commercial Pt/C. X-ray absorption fine structures and the density functional theory calculations reveal that introducing Ru single-atom can modulate electronic structure of metal center in the MOF, leading to the optimization of binding strength for H 2 O and H*, and the enhancement of HER performance. This work establishes single-atom strategy as an efficient approach to modulate electronic structure of MOFs for catalyst design.

Abstract Iron phthalocyanine (FePc) is a promising non-precious catalyst for the oxygen reduction reaction (ORR). Unfortunately, FePc with plane-symmetric FeN 4 site usually exhibits an unsatisfactory ORR activity due to its poor O 2 adsorption and activation. Here, we report an axial Fe–O coordination induced electronic localization strategy to improve its O 2 adsorption, activation and thus the ORR performance. Theoretical calculations indicate that the Fe–O coordination evokes the electronic localization among the axial direction of O–FeN 4 sites to enhance O 2 adsorption and activation. To realize this speculation, FePc is coordinated with an oxidized carbon. Synchrotron X-ray absorption and Mössbauer spectra validate Fe–O coordination between FePc and carbon. The obtained catalyst exhibits fast kinetics for O 2 adsorption and activation with an ultralow Tafel slope of 27.5 mV dec −1 and a remarkable half-wave potential of 0.90 V. This work offers a new strategy to regulate catalytic sites for better performance.

Abstract Single-atom Fe-N-C catalysts has attracted widespread attentions in the oxygen reduction reaction (ORR). However, the origin of ORR activity on Fe-N-C catalysts is still unclear, which hinder the further improvement of Fe-N-C catalysts. Herein, we provide a model to understand the ORR activity of Fe-N 4 site from the spatial structure and energy level of the frontier orbitals by density functional theory calculations. Taking the regulation of divacancy defects on Fe-N 4 site ORR activity as examples, we demonstrate that the hybridization between Fe 3 dz 2 , 3 dyz (3 dxz ) and O 2 π* orbitals is the origin of Fe-N 4 ORR activity. We found that the Fe–O bond length, the d-band center gap of spin states, the magnetic moment of Fe site and *O 2 as descriptors can accurately predict the ORR activity of Fe-N 4 site. Furthermore, these descriptors and ORR activity of Fe-N 4 site are mainly distributed in two regions with obvious difference, which greatly relate to the height of Fe 3 d projected orbital in the Z direction. This work provides a new insight into the ORR activity of single-atom M-N-C catalysts.

Abstract Electrochemical production of hydrogen peroxide (H 2 O 2 ) through two‐electron (2 e − ) oxygen reduction reaction (ORR) is an on‐site and clean route. Oxygen‐doped carbon materials with high ORR activity and H 2 O 2 selectivity have been considered as the promising catalysts, however, there is still a lack of direct experimental evidence to identify true active sites at the complex carbon surface. Herein, we propose a chemical titration strategy to decipher the oxygen‐doped carbon nanosheet (OCNS 900 ) catalyst for 2 e − ORR. The OCNS 900 exhibits outstanding 2 e − ORR performances with onset potential of 0.825 V (vs. RHE), mass activity of 14.5 A g −1 at 0.75 V (vs. RHE) and H 2 O 2 production rate of 770 mmol g −1 h −1 in flow cell, surpassing most reported carbon catalysts. Through selective chemical titration of C=O, C−OH, and COOH groups, we found that C=O species contributed to the most electrocatalytic activity and were the most active sites for 2 e − ORR, which were corroborated by theoretical calculations.

Abstract Designing and synthesizing efficient molecular catalysts may unlock the great challenge of controlling the CO 2 reduction reaction (CO 2 RR) with molecular precision. Nickel phthalocyanine (NiPc) appears as a promising candidate for this task due to its adjustable Ni active‐site. However, the pristine NiPc suffers from poor activity and stability for CO 2 RR owing to the poor CO 2 adsorption and activation at the bare Ni site. Here, a ligand‐tuned strategy is developed to enhance the catalytic performance and unveil the ligand effect of NiPc on CO 2 RR. Theoretical calculations and experimental results indicate that NiPc with electron‐donating substituents (hydroxyl or amino) can induce electronic localization at the Ni site which greatly enhances the CO 2 adsorption and activation. Employing the optimal catalyst—an amino‐substituted NiPc—to convert CO 2 into CO in a flow cell can achieve an ultrahigh activity and selectivity of 99.8% at current densities up to −400 mA cm −2 . This work offers a novel strategy to regulate the electronic structure of active sites by ligand design and discloses the ligand‐directed catalysis of the tailored NiPc for highly efficient CO 2 RR.