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Developing non‐platinum group metal catalysts for the sluggish hydrogen oxidation reaction (HOR) is critical for alkaline fuel cells. To date, Ni‐based materials are the most promising candidates but still suffer from insufficient performance. Herein, we report an unconventional hcp/fcc Ni (u‐hcp/fcc Ni) heteronanocrystal with multiple epitaxial hcp/fcc heterointerfaces and coherent twin boundaries, generating rugged surfaces with plenty of asymmetric convex sites. Systematic analyses discover that such convex sites enable the adsorption of *H in unusual bridge positions with weakened binding energy, circumventing the over‐strong *H adsorption on traditional hollow positions, and simultaneously stabilizing interfacial *H2O. It thus synergistically optimizes the HOR thermodynamic process as well as reduces the kinetic barrier of the rate‐determining Volmer step. Consequently, the developed u‐hcp/fcc Ni exhibits the top‐rank alkaline HOR activity with a mass activity of 40.6 mA mgNi−1 (6.3 times higher than fcc Ni control) together with superior stability and high CO‐tolerance. These results provide a paradigm for designing high‐performance catalysts by shifting the adsorption state of intermediates through configuring surface sites. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) have been increasingly studied for electrocatalytic materials of the oxygen evolution reaction (OER) because of their tunable compositions, permanent porosity, multiple chemical functionalities, and well-dispersed metal centers. However, the electrocatalytic OER performance of conventional MOFs is limited due to their electrical conductivity. In this work, two-dimensional (2D) π–d-conjugated Co-based conductive MOFs (Co-HHTP) are first synthesized by a solvothermal method and used as the electrocatalysts for the OER. Density function theory calculations demonstrate that the obtained Co-HHTP has favorable electrical conductivity and a moderate d-band center, promoting the adsorption/desorption of the OER intermediates. As a result, the Co-HHTP shows an overpotential of 245 mV at a current density of 10 mA cm–2, a small Tafel slope of 70 mV dec–1, and great stability under alkaline conditions, exceeding Co-(OH)2, Co3O4, and most of the reported MOF-based electrocatalysts. In situ Raman spectroscopy reveals that the CoOOH transformed from Co-HHTP is the real active species during the OER process. This work provides a promising candidate for electrocatalytic water splitting with a high efficiency. [ABSTRACT FROM AUTHOR]

Photocatalytic nitrogen fixation using solar illumination under ambient conditions is a promising strategy for production of the indispensable chemical NH3. However, due to the catalyst's limitations in solar energy utilization, loss of hot electrons during transfer, and low nitrogen adsorption and activation capacity, the unsatisfactory solar‐to‐chemical conversion (SCC) efficiencies of most photocatalysts limit their practical applications. Herein, cerium oxide nanosheets with abundant strain‐VO defects were anchored on Au hollow nanomushroom through atomically sharp interfaces to construct a novel semiconductor/plasmonic metal hollow nanomushroom‐like heterostructure (denoted cerium oxide‐AD/Au). Plasmonic Au extended the absorption of light from the visible to the second near‐infrared region. The superior interface greatly enhanced the transfer efficiency of hot electrons. Abundant strain‐VO defects induced by interfacial compressive strain promoted adsorption and in situ activation of nitrogen, and such synergistic promotion of strain and VO defects was further confirmed by density functional theory calculations. The judicious structural and defect engineering co‐promoted the efficient nitrogen photofixation of the cerium oxide‐AD/Au heterostructures with a SCC efficiency of 0.1 % under simulated AM 1.5G solar illumination, which is comparable to the average solar‐to‐biomass conversion efficiency of natural photosynthesis by typical plants, thus exhibiting significant potential as a new candidate for artificial photosynthesis. [ABSTRACT FROM AUTHOR]