For steady electroconversion to value-added chemical products with high efficiency, electrocatalyst reconstruction during electrochemical reactions is a critical issue in catalyst design strategies. Here, we report a reconstruction-immunized catalyst system in which Cu nanoparticles are protected by a quasi-graphitic C shell. This C shell epitaxially grew on Cu with quasi-graphitic bonding via a gas–solid reaction governed by the CO (g) - CO₂ (g) - C (s) equilibrium. The quasi-graphitic C shell-coated Cu was stable during the CO₂ reduction reaction and provided a platform for rational material design. C₂₊ product selectivity could be additionally improved by doping p-block elements. These elements modulated the electronic structure of the Cu surface and its binding properties, which can affect the intermediate binding and CO dimerization barrier. B-modified Cu attained a 68.1% Faradaic efficiency for C₂H₄ at −0.55 V (vs RHE) and a C₂H₄ cathodic power conversion efficiency of 44.0%. In the case of N-modified Cu, an improved C₂₊ selectivity of 82.3% at a partial current density of 329.2 mA/cm² was acquired. Quasi-graphitic C shells, which enable surface stabilization and inner element doping, can realize stable CO₂-to-C₂H₄ conversion over 180 h and allow practical application of electrocatalysts for renewable energy conversion.

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The enhancement of the electrical conductivity by doping is important in hematite (α-Fe₂O₃) photoanodes for efficient solar water oxidation. However, in spite of many successful demonstrations using extrinsic dopants, such as Sn, Ti, and Si, the achieved photocurrent is still lower than the practical requirement. There is still lack of our understanding of how intrinsic oxygen defects can change the photocurrent and interact with the extrinsic dopants. In this study, we systematically investigate the interplay of oxygen vacancies and extrinsic Sn dopants in the context of photoanodic properties. As a result, we demonstrate that the controlled generation of oxygen vacancies can activate the photoactivity of pure hematite remarkably and further enhance the Sn doping effects synergistically. Furthermore, the correlated behavior of oxygen vacancies and Sn dopants is closely linked to the variation of electrical conductance and results in the optimum concentration region to show the high photocurrent and low onset voltage.