Electrolyte cations have been demonstrated to effectively enhance the rate and selectivity of the electrochemical CO 2 reduction reaction (CO 2 RR), yet their implementation in electrolyte-free membrane electrode assembly (MEA) electrolyzer presents significant challenges. Herein, an anchored cation strategy that immobilizes Cs + on carbon vacancies was designed and innovatively implemented in MEA electrolyzer, enabling highly efficient CO 2 electroreduction over commercial silver catalyst. Our approach achieves a CO partial current density of approximately 500 mA cm −2 in the MEA electrolyzer, three-fold enhancement compared to pure Ag. In situ Raman and theoretical analyses, combined with machine learning potentials, reveal anchored Cs induces an electric field that significantly promotes the adsorption of *CO 2 − intermediates through performing muti-point energy calculations on each structure. Furthermore, reduced adsorption of *OH intermediates effectively hampers competing hydrogen evolution reaction, as clarified by disk electrode experiments and density functional theory studies. Additionally, coupling our system with commercial polysilicon solar cells yields a notable solar-to-CO energy conversion efficiency of 8.3 %. This study opens a new avenue for developing effective cation-promoting strategy in MEA reactors for efficient CO 2 RR.

Methane chemistry is one of the “Holy Grails of catalysis”. It is highly desirable but challenge to transform methane into value-added chemicals, because of its high C-H bonding energy (435 kJ/mol), lack of π bonding or unpaired electrons. Currently, commercial methane conversion is usually carried out in harsh conditions with enormous energy input. Photocatalytic partial oxidation of methane to liquid oxygenates (PPOMO) is a future-oriented technology towards realizing high efficiency and high selectivity under mild conditions. The selection of oxidant is crucial to the PPOMO performance. Hence, attentions are paid to the research progress of PPOMO with various oxidants (O2, H2O, H2O2 and other oxidants). Moreover, the activation of the selected oxidants is also highly emphasized. Meanwhile, we summarized the methane activation mechanisms focusing on the C-H bond that was broken mainly by •OH radical, O− specie or photogenerated hole (h+). Finally, the challenges and prospects in this subject are briefly discussed.

Cocatalyst plays a critical role in photocatalytic overall water splitting (POWS). However, the typical metal cocatalysts aimed at promoting hydrogen evolution are also highly active for H2-O2 recombination. Here we report a new strategic approach of coating single-layer graphene selectively on metal cocatalyst by chemical vapor deposition to effectively suppress the backward reaction for efficient POWS. Pt@C/SrTiO3 demonstrates steady POWS activity in contrast to the rapid activity decline by 65% in 5 h of Pt/SrTiO3, and no obvious H2 and O2 consumption is observed over Pt@C/SrTiO3 during dark reaction. Experimental and theoretical calculation results indicate that the graphene prevents O2 from contacting Pt and the O2 dissociation as the rate-determining step of backward reaction is retarded. Moreover, this method demonstrates good universality and similar suppressing effect is also achieved over Rh, Pd@C. These findings may open a new pathway for developing effective cocatalysts with suppressed backward reaction for efficient POWS.

Exploring efficient electrocatalysts with fundamental understanding of the reaction mechanism is imperative in CO 2 electroreduction. However, the impact of sluggish water dissociation as proton source and the surface species in reaction are still unclear. Herein, we report a strategy of promoting protonation in CO 2 electroreduction by implementing oxygen vacancy engineering on Bi 2 O 2 CO 3 over which high Faradaic efficiency of formate (above 90%) and large partial current density (162 mA cm −2 ) are achieved. Systematic study reveals that the production rate of formate is mainly hampered by water dissociation, while the introduction of oxygen vacancy accelerates water dissociation kinetics by strengthening hydroxyl adsorption and reduces the energetic span of CO 2 electroreduction. Moreover, CO 3 * involved in formate formation as the key surface species is clearly identified by electron spin resonance measurements and designed in situ Raman spectroscopy study combined with isotopic labelling. Coupled with photovoltaic device, the solar to formate energy conversion efficiency reaches as high as 13.3%.

Cocatalysts are of great significance for photocatalytic overall water splitting (POWS). Ni-based cocatalysts are attractive candidates for replacing representative noble metals such as Pt, but they suffer from poor stability and low efficiency. Herein, Ni nanoparticles encapsulated in a nitrogen-doped ultrathin graphene (NC) layer are demonstrated to be an active, stable, and low-cost cocatalyst for POWS. It was determined that the H-2 evolution rate over Ni@NC/SrTiO3 (STO) is about 3.2 times that of Ni/STO and is even superior to that of a typical Pt cocatalyst. Experiments and XPS studies showed that the unfavorable oxidation of Ni during the reaction is effectively suppressed through the selective coating of N-doped graphene. In addition to the improvement in the charge carrier dynamics, a kinetic study revealed that the apparent activation energy of POWS is reduced by 44% after the introduction of N. With the help of a machine learning potential, an in-depth theoretical study was carried out, and active sites with appropriate H* adsorption were statistically clarified by performing single-point energy calculations for approximately 700 sites on each model structure. The theoretical calculations demonstrated that the distribution of active sites with high spin densities is remarkably promoted due to the modification of the electronic structure of graphene by N doping. This work demonstrates the great potential of using highly stable and active Ni-based photocatalysts for POWS.

Carbon nanofibers enriched in ring-defects significantly promote electrochemical water oxidation to hydrogen peroxide.

Zr-Al co-doped SrTiO3 with reduced Ti3+ concentration demonstrates more than 2 times enhancement compared with Al-doped SrTiO3 in photocatalytic overall water splitting. Systematic studies reveal that the co-doping of Zr4+ can reduce the substitution of Ti4+ by Al3+ and effectively suppress the formation of charge carrier recombination centers (Ti3+).