The electrochemical CO₂ reduction reaction (CO₂RR) to formic acid (HCOOH) is constrained by slow kinetics and limited selectivity due to inefficient proton-coupled electron transfer (PCET). Herein, we synthesized Cu-doped BiO_2−x (CuBiO) nanosheets to facilitate proton transfer through reconstruction of the hydrogen-bond (HB) network, thereby accelerating the PCET process. The in-situ measurements reveal that part of the 4-coordinated hydrogen-bonded water (4-HB·H₂O) transforms into 2-coordinated hydrogen-bonded water (2-HB·H₂O) over CuBiO during CO₂RR. This reconstruction forms a linear proton transport pathway which efficiently promotes proton transport during PCET steps and concurrently inhibits the competing hydrogen evolution reaction. Density functional theory (DFT) calculations further elucidate that the Cu doping not only facilitates water dissociation into protons while inhibiting proton dimerization, but also enhances CO₂ activation and reduces the energy barrier for of *CO₂ → *OCHO. Ultimately, the CuBiO-6 displays highly efficient conversion of CO₂ to HCOOH with a Faradaic efficiency (FE) of 92.4% and maintains stable operation for over 22 h. These findings provide a novel strategy to accelerate the PCET through regulation of interfacial HB network towards efficient CO₂RR to HCOOH.

Electrocatalytic nitrite reduction reaction (NO₂⁻RR) to synthesize ammonia (NH₃) has been constrained by sluggish kinetics of water dissociation and the weak adsorption of nitrite. In this work, we develop an in-situ reconstruction strategy that transforms Ni-doped BiO_2−x (NiBiO_2−x) to Bi/NiBiO_2−x, which exhibits excellent activity and selectivity for NO₂⁻RR to synthesize NH₃. Diverse ex-situ and in-situ characterizations reveal potential-driven structural transformation from NiBiO_2−x to Bi/NiBiO_2−x, which features dual Ni²⁺-Bi⁰ active sites. The Ni²⁺ site is able to reduce the water dissociation barrier from 0.79 to 0.41 eV, while concurrently the Bi⁰ site can strengthen NO₂⁻ adsorption to promote *NO₂H intermediate formation. Consequently, the in-situ constructed Bi/NiBiO_2−x catalyst with Ni²⁺-Bi⁰ catalytic pairs enable an excellent NO₂⁻RR performance, achieving a NH₃ Faradaic efficiency (FE_NH3) of 94.5% at −0.6 V vs. RHE. The present study opens the new direction to in-situ construct high-performance electroreduction catalysts for small molecule synthesis.

Heterogeneous advanced oxidation processes (AOPs) based on non-radical reactive species are considered as a powerful technology for wastewater purification due to their long half-lives and high adaptation in a wide pH range. Herein, we fabricate surface Co defect-rich spinel ZnCo₂O₄ porous nanosheets, which can generate ≡Co^IV=O and ¹O₂ over a wide pH range of 3.81–10.96 by the formation of amphoteric ≡Zn(OH)₂ in peroxymonosulfate (PMS) activation process. Density functional theory (DFT) calculations show Co defect-rich ZnCo₂O₄ possesses much stronger adsorption ability and more electron transfer to PMS. Moreover, the adsorption mode changes from terminal oxygen Co–O–Co to Co–O, accelerating the polarization of adjacent oxygen, which is beneficial to the generation of ≡Co^IV=O and ¹O₂. Co defect-rich ZnCo₂O₄ porous nanosheets exhibit highly active PMS activation activity and stability in p-nitrophenol (PNP) degradation, whose toxicity of degradation intermediates is significant reduction. The Co defect-rich ZnCo₂O₄ nanosheet catalyst sponge/PMS system achieved stable and efficient removal of PNP with a removal efficiency higher than 93% over 10 h. This work highlights the development of functional catalyst and provides an atomic-level understanding into non-radical PMS activation process in wastewater treatment.

Two-dimensional (2D) semiconductor heterojunctions are considered as an effective strategy to achieve fast separation of photoinduced carriers. Herein, a novel CoWO₄/g-C₃N₄ (CWO/CN) p–n junction was synthesized using an electrostatic self-assembly method. The constructed 2D/2D p–n heterostructure had a rich hetero-interface, increased charge density, and fast separation efficiency of photoinduced carriers. The in-situ Kelvin probe force microscopy confirmed that the separation pathway of photoinduced carriers through the interface obeyed an II-scheme charge transfer mechanism. Experimental results and density functional theory calculations indicated the differences of work function between CWO and CN induced the generation of built-in electric field, ensuring an efficient separation and transfer process of photoinduced carriers. Under the optimized conditions, the CWO/CN heterojunction displayed enhanced photocatalytic H₂ generation activity under full spectrum and visible lights irradiation, respectively. Our study provides a novel approach to design 2D/2D hetero-structured photocatalysts based on p–n type semiconductor for photocatalytic H₂ generation.