Cr Co-doping Research Articles

Self-supported FeCoNi(OHy)Ox oxy-hydroxide doped with Cr and Cu as robust low-loading catalyst for the alkaline oxygen evolution reaction

Self-supported FeCoNi(OHy)Ox oxy-hydroxides co-doped with Cr and Cu were obtained from a CrFeCoNiCu low ordered high entropy precursor synthesised by electrodeposition onto carbon cloth fibres (act-CrFeCoNiCu/CC). For comparison a dopant-free FeCoNi(OHy)Ox catalyst (act-FeCoNi/CC) was also synthesised following the same route. No heat treatment was performed to retain their low ordered structure. When assessed towards the oxygen evolution reaction (OER) in alkaline electrolyte, act-CrFeCoNiCu/CC and act-FeCoNi/CC catalyst reached a comparable current density of 10 mA cm−2 at ca. 1.6 VRHE (η10 of 380–390 mV). Nevertheless, Cr and Cu co-doping translated into improved stability. Evident degradation was observed during OER for act-FeCoNi/CC after 12 h operating at 100 mA cm−2, whereas no signs of degradation were detected for act-CrFeCoNiCu/CC under the same reaction conditions. The latter catalyst even delivered a constant potential for 160 h at 50 mA cm−2 aided to the stabilizing effect of Cr and Cu co-doping.

Highly catalytic performance for the selective C–H bond oxidation of p-chlorotoluene over Co, Cr co-doped OMS-2 catalyst

Using O2 as an oxidant, developing a non-noble metal catalyst for the selective catalytic C–H bond oxidation of p-chlorotoluene is desirable and challenging. In this work, a series of Co, Cr co-doped OMS-2 (Octahedral Molecular Sieve-2) catalysts were prepared by a conventional refluxing method. It was found that the incorporation of Co and Cr improved the catalytic activity for the selective oxidation of p-chlorotoluene to p-chlorobenzaldehyde. Among these catalysts, CoCr/OMS-2 (Co: Cr = 1: 1, mass ratio), the best catalyst, shows that the conversion and the selectivity of p-chlorobenzaldehyde is 94.8 % and 94.3 %, respectively. The enhanced catalytic activity was due to the larger specific surface area and even dispersion of active components. The characterization results also disclosed that the co-doping of Co and Cr increased the oxygen vacancy and enhanced the ability to activate the surface lattice oxygen. Additionally, density functional theory calculations demonstrated that co-doping of Co and Cr promoted the adsorption of p-chlorotoluene and O2, and decreased the energy barrier of rate-determining step (the conversion of p-chlorobenzyl alcohol to p-chlorobenzaldehyde). Besides, when H2O was added to the reaction system as the second solvent, the activation and dissociation of O2, and the formation of p-chlorobenzaldehyde were facilitated, in agreement with the experimental results. This work demonstrated the promotional effect of Co, Cr co-doped into OMS-2 catalyst and the role of H2O for the selective oxidation of p-chlorotoluene.

Influence of Cr and Mg co-doping on electrochemical performance of quaternary cathode materials for lithium-ion battery

Influence of Cr and Mg co-doping on electrochemical performance of quaternary cathode materials for lithium-ion battery

Vanadium substituted Fe, Cr co-doped high performance C/Na3V2(PO4)2F3 cathode for sodium-ion batteries

In recent years, Na3V2(PO4)2F3 (NVPF) has been considered as one of the most promising candidates for cathodes in sodium ion batteries (SIBs). However, presence of vanadium makes the material costly. Besides, its electrochemical properties are hampered due to its low electronic conductivity. Herein, carbon coated Fe, Cr co-doped Na3V2(PO4)2F3 has been synthesized using rota-tumbler assisted sol–gel method. The effects of co-doping on structure, morphology and electrochemical performances are systematically studied. It is confirmed that co-doping of Fe and Cr can enhance the electrochemical performances of NVPF. Among all, Na3V1.9Fe0.095Cr0.005(PO4)2F3 shows a high initial capacity of 119.85 mAhg−1 at 0.1C and maintains a capacity retention of 88.58 % after 500 cycles at 1C. Increase in the size of the saddle point, planes of monocapped trigonal prisms and the hexagonal cavities help in decreasing the ion diffusion activation energy, thus improving the diffusivity of the doped material. The improved electrochemical performances can be attributed to the increase in the electronic conductivity of the material. Besides, vanadium reduction in the cathode aids in manufacturing cost reduction. Our work demonstrates that carbon coated Na3V1.9Fe0.095Cr0.005(PO4)2F3 can be considered as a potential cathode candidate for practical applications in SIBs.

Electronic and optical properties of Cr / Cl co-doped in single-layer MoS2: A first principles study

This study aims to investigate the co-doping effect of Cr and Cl in monolayer molybdenum disulfide (MoS2) crystals. Density functional theory (DFT) was used to study the electronic structure and optical properties of the doped material, employing the PBE-GGA calculation method for the exchange-correlation energy. Key factors such as density of states, band structure, dielectric function, photoconductivity, refractive index, and absorptivity were analyzed. The findings indicate that co-doping of Cr and Cl reduces the band gap and introduces impurity energy levels within the band gap, thereby improving the photocatalytic performance.

Studies on the Cooperative Influence of Cr and Mo on the Pitting Corrosion Resistance of Super Austenitic Stainless Steels

The effects of varying Cr and Mo concentrations on the pitting corrosion resistance of super austenitic stainless steels in Cl− solutions were investigated using a combination of immersion experiments, electrochemical measurements, X-ray photoelectron spectroscopy, and first-principles computational simulations. The surface characteristics, impedance, and defect concentration of the passive film were changed, and this eventually resulted in a decrease in the number of pitting pits. Due to a decrease in active sites within the passive film, a delayed beginning of pitting, and the combined effect of MoO42− inhibitors, it was discovered that an increasing Mo concentration slows the rate of pitting extension, resulting in reduced maximum pitting area and depth. Additionally, Mo increased the adsorption energy of nearby atoms, whereas Cr raised the adsorption energy of itself. Interestingly, compared with individual doping, co-doping of Cr and Mo increased work function and adsorption energy, indicating a synergistic impact in enhancing resistance to Cl− corrosion.

Effect of codoping of rare earth elements and Cr on multiferroic, optical and photocatalytic properties of BiFeO3

In the present work, first principle calculations have been performed to study the combined effect of A (Bi) and B (Fe) site doping on the structural, multiferroic, optical and photocatalytic properties of BiFeO3 (BFO). Rare earth elements (La, Ce, Gd, Nd, Er and Eu) are doped at the A-site while Cr is doped at the B-site in perovskite BFO. A variation in total magnetic moments and spontaneous polarization of the doped systems is observed that are governed by the introduction of the rare earth elements. A maximum polarization of 110μC/cm2 is obtained for (Gd,Cr) doped BFO and the maximum magnetization of 5.1μB/cell is obtained for (Nd,Cr) doped BFO. From the study of partial electronic density of states it has been observed that amongst all the dopants incorporated as rare earth elements, the (Er,Cr)BFO system exhibits the minimum bandgap of 1.94 eV and thus shifts the absorption edge deep into the visible region which has been confirmed through the optical spectra. The band-edge alignment of the pure and codoped systems has revealed that (Er,Cr)BFO exhibits the maximum potential to be a promising photocatalyst with improved efficiency as compared to pristine BFO.

First-principles prediction of enhanced photocatalytic activity in La-X (X = Sc, V, Cr, Mn, Fe, Co, Ni, or Cu) Co-doped SrTiO3

The influence of La-X (X = Sc, V, Cr, Mn, Fe, Co, Ni, or Cu) co-doping on the electronic structure and photocatalytic activity of SrTiO3 system was investigated using the open-source software package Quantum Espresso (QE) based on density functional theory. Defect formation energy calculations showed an energy advantage for co-doped systems under Ti-poor and O-rich conditions. The La-V, La-Cr, La-Mn, La-Fe, and La-Ni co-doped systems showed magnetic properties with corresponding total magnetization of 0.08 µB, 2.97 µB, 3.30 µB, 1.00 µB and 1.00 µB, respectively. The La-X (X = V, Cr, Mn, Fe, Ni, or Cu) co-doped system exhibits photoabsorption activity in the visible region as compared to the pure SrTiO3. The La-X (X = Cr, Fe, Ni, or Cu) co-doped SrTiO3 exhibits a long carrier lifetime, especially the La-Fe co-doped system with a high effective mass ratio of holes to electrons of 5.79. However, the redox potential of the water decomposition reaction of the La-Cu co-doped system is too large, making it unsuitable for water splitting. In summary, the La-X (X = Cr, Fe, or Ni) co-doped systems exhibited intermediate states in the band structure and density of states, which better meet the specific requirements for photocatalysis compared to systems without intermediate states, showing superior photocatalytic potential. The band edge alignment of the three co-doped systems with water redox potentials demonstrated good matching. These findings suggest that La-X (X = Cr, Fe, or Ni) co-doped SrTiO3 is a promising candidate material for solar-driven water splitting.

A study of the effect of the Cu and Cr co-doping on structural, magnetic and dielectric properties of barium hexaferrites synthesized in presence of mentha leaves extract

In the reported research work, we investigated the structural, thermal, magnetic, surface morphology, Raman spectroscopic and dielectric properties of Cu-Cr co-substituted M-type barium hexaferrites for lossless low-frequency applications. By using the green synthesis approach with mentha leaves extract, we synthesized a series of M-type BaCuxCrxFe12‐2xO19 (0.0 ≤x≤0.5) hexaferrite with varying Cu-Cr content. A simple heat treatment method was used to prepare hexaferrite samples. The samples were heated to 1100 °C and thoroughly characterized for their structural, thermal, magnetic, Raman spectroscopic and low frequency dielectric study. The results of XRD finding revealed the formation of M-phase along with secondary phase of BaFe2O4. The Raman spectroscopic analysis shows the successful replacement of Cu and Cr ions in place of Fe ions, and the substituted samples hold the hexagonal shape as visible from FESEM images. All samples show a hard magnetic nature with multi-domain structures, and x = 0.2 composition has a maximum Ms of 68.99 Am2/kg and lowest Hc of 0.1 T. Cole-Cole graphs show shifting of peaks position with Cu-Cr substitutions and increasing frequency, which gives the insight of the role of grain and grain boundaries. These findings open up exciting possibilities for using these hexaferrites in loss-less, and low-frequency applications.

Microscopic mechanism of the effect of Nb and Cr co-doping on the strength and ductility of Ti2AlC/Ti3Al coherent interface

We employ first-principles calculations to study the adhesion work, interface energy, and electronic structure of Ti2AlC/Ti3Al interfaces. A novel interface mismatch model is proposed, and the interface mismatch degrees of Ti2AlC/Ti3Al interfaces are discussed and analyzed. The results show that the TiAl2-C coherent interface structure exhibits the highest adhesion work and the lowest interface energy, indicating that it has the greatest interfacial bonding strength and stability. The bonding properties of the Cr/Nb co-doped interface are evaluated through tensile strain calculations. The doping of Cr at the interface and Nb at the second layer near the interface significantly enhances the tensile strength and fracture toughness of the interface. This is due to the formation of strong covalent bonds between Cr, Ti, and C at the interface, as well as the presence of strong interactions between Cr and Nb at the fracture area. These findings are of significant importance for improving the performance of TiAl alloys and for the design and development of high-performance TiAl matrix composites materials.

Suppression of ferromagnetism due to N co-doping in Cr(II)-doped ZnS nanowires and their optical properties: Insights from density-functional calculations

Spin-related optical properties will be the main basis for future information technology, but they require microscopic ferromagnetic and anti-ferromagnetic couplings between the d-states of the transition metal ions or magnetic interaction between excitons and magnetic ions, all of which remain unclear in these diluted magnetic semiconductors.In this work, we studied the influence of Cr doping and co-doping of Cr with N on the electronic, optical, and magnetic properties of ZnS nanowires using spin-polarized density functional theory. According to our findings, Cr(II) doping induces a half-metallic state with a magnetic moment of 4 μB per Cr(II) ion. The ferromagnetic behaviors and high Curie temperature in undoped Cr(II)-doped ZnS nanowires were suppressed due to the hole-carriers introduced by N co-doping. The band-coupling model was used to explain ferromagnetic (FM) stability in Cr(II)-doped nanowires with and without N co-doping. The optical properties of undoped ZnS nanowire, doped, and co-doped wires have been computed, and it is found that the bandgap (3.49 eV) exhibits a red shift upon Cr(II) doping, with the energy bandgap falling from 3.49 to 3.20 eV, and the bandgap being further decreased to 3.05 eV upon N co-doping. Compared with pure ZnS nanowires, mono- and co-doped nanowires have a higher electron-hole pair formation rate and better optical properties. The d-state to d-state transitions of the Cr(II) ion in the wire occur in the mid-infrared and near-infrared red regions and are shifted to the high energy side by N co-doping. Furthermore, we correlated the optical band gap of ZnS nanowire and the d-d transition peak of Cr ions under different modes of magnetic coupling, and we found that the optical band gap and d-state to d-state transition peaks of Cr(II) ions shift to lower and higher energies in FM and AFM configurations, respectively. Such a shift in bandgap and d-d transition peaks of Cr(II) ions in the FM and AFM states of the far configuration was not observed.

Investigation of the effect of Cr co-doping on the refractive index, spectroscopic parameters and lasing of Nd:GdVO4 crystals

Cr co-doped (0.5, 1.0, 1.2 and 1.5 at.%) Nd (0.5 at.%):GdVO4 single crystals, used as laser gain medium, were grown by the optical floating zone technique to investigate the effect of Cr on the refractive index and spectroscopic properties. The ordinary (no) and extra-ordinary (ne) refractive index of 0.5 at.% Cr co-doped Nd:GdVO4 crystals was found to be lower than the 1.0 at.% Cr co-doped crystals, and thereafter it becomes almost constant up to 1.5 at.% of Cr co-doping. Further, the thermo-optic coefficient (dn/dT) of Cr co-doped Nd:GdVO4 crystals is positive with values ∼10−5/°C and the value is higher for ne compared to no for all the Cr doping concentrations. Further, the measured fluorescence lifetime of Nd ion decreases from 98 to 85 μs with the increase in Cr concentration. The Judd-Ofelt (JO) analysis revealed that the JO parameters for all the samples are Ω2 ∼9.6–10.6 × 10−20 cm2, Ω4 ∼6.5–7.0 × 10−20 cm2 and Ω6 ∼6.5–7.0 × 10−20 cm2. The radiative lifetime (∼100 μs) and emission cross section (∼3.2–4.1 × 10−19 cm2) are not affected significantly by the Cr co-doping. The investigation suggests that the inclusion of Cr ion in the crystal lattice does not deteriorate the overall spectroscopic properties of the Nd ions, thus Cr may act as an excellent activator for Q-switching in the Nd:GdVO4 laser gain medium. Further, the self Q-switching in the Cr co-doped Nd:GdVO4 laser element was demonstrated. A stable pulsed laser output at 1066 nm with power ∼105 mW, pulse width ∼477 ns and repetition rate ∼550 kHz was obtained in the 1.0 at.% Cr co-doped crystal.

Co-doping: An effective strategy for developing stable and high-speed Sb2Te-based phase-change memory

Balancing operation speed and thermal stability is a big challenge in phase change memory (PCM). In this work, a carbon (C) and chromium (Cr) co-doped Sb2Te strategy has been proposed for achieving high operation speed and high stability in PCM applications. In general, doping with the appropriate Cr element is beneficial to improve thermal stability, but it will sacrifice its operation speed. C-doping can enhance thermal stability and retain its fast phase transition properties due to the carbon elements tend to form agglomerates in the host that ameliorate disorder of the amorphous phase without loss of the phase transition rate. Intriguingly, the as-prepared C1.19Cr0.23Sb2Te material exhibits good data retention (T10-year @ 155.0 °C) and low-volume change rate (1.8%), as well as fast switching speed (4 ns) and good endurance (>1 × 105 cycles). This research indicates that C and Cr co-doping is an effective method to achieve excellent stability of phase-change materials without sacrificing the phase-transition rate of Sb2Te materials.

Preparation of long cycle lifespan spinel LiMn2O4 cathode material by a dual-modified strategy

Spinel LiMn2O4 has been identified as a cathode material with extensive application potential for Li-ion batteries. However, during cycling, the Jahn−Teller effect and Mn dissolution have a substantial impact on its specific capacity and cycle span. Herein, combining Fe and Cr elements co-doping with single crystal truncated octahedron morphology is proposed to solve these problems. The Fe−Cr co-doping markedly restrains the Jahn−Teller effect, and promotes the development of crystal and selective growth of crystal surfaces in spinel LiMn2O4. The high exposure (111) surfaces of the truncated octahedron reduce the dissolution of Mn, and a tiny proportion of (110) and (100) surfaces increase the diffusion channels of Li+. HAADF-STEM characterization indicates that the Fe and Cr elements largely replace the Mn atoms at the octahedral 16d site. Because of these advantages, the optimal LiFe0.05Cr0.08Mn1.95-xO4 (LFCMO-8) delivers excellent electrochemical performance with 119.6 mAh·g−1 discharge capacity and 78.1% capacity retention after 500 cycles at 1 C. At comparatively higher current densities of 20 C and 30 C, the superior capacity retention ratios of 79.8% and 87.3% are still achieved after 2000 cycles. Even at 40 C, the LFCMO-8 sample can still reach 98.8% capacity retention rate after 2000 cycles. After 1000 cycles at 5 C, the LFCMO-8 sample still maintained a capacity retention of 45.4% at high temperature (55 °C). ICP-OES test combined with a V-shaped tube device indicates that the Mn dissolution of LCFMO-8 only accounted for 11.8% of LiFe0.05Mn1.95O4 (LFMO). This study serves as a meaningful reference for the preparation of high-performance LiMn2O4 cathode materials.

Improvement in Corrosion Resistance and Interfacial Contact Resistance Properties of 316L Stainless Steel by Coating with Cr, Ti Co-Doped Amorphous Carbon Films in the Environment of the PEMFCs.

In order to obtain films with high corrosion resistance and excellent interfacial contact resistance (ICR) on 316L stainless steel used for bipolar plates in proton-exchange membrane fuel cells (PEMFCs), Cr, Ti co-doped amorphous carbon films were prepared on 316L stainless steel. The preparation method for the coating was magnetron sputtering. The doping amount of the Ti element was controlled by a Cr target and a Ti target current. The change in the structure and properties of the coating after the change from Cr single-element doping to Cr and Ti co-doping was studied. The change rule of the structure and properties of the coating from Cr single-element doping to Cr and Ti co-doping was studied. An increase in the Ti content led to a decreased grain boundary, a flatter surface, and a higher sp2-hybridized carbon content. TiC and CrC nanocrystals were formed in the amorphous carbon structure together. The amorphous carbon films doped with Cr and Ti simultaneously achieved a low ICR and high corrosion resistance compared with single-Cr-doped amorphous carbon. The enhanced corrosion resistance was attributed to the decreasing grain boundary, the formation of the TiC crystal structure, and the smaller grain size. The best performance was obtained at a Ti target current of 2A. Compared with bare 316L stainless steel, the corrosion resistance of Cr, Ti co-doped amorphous carbon (Icorr = 5.7 × 10-8 A/cm2, Ti-2 sample) was greatly improved. Because Ti doping increased the content of sp2-hybridized carbon in the coating, the contact resistance of the coating decreased. Moreover, the interfacial contact resistance was 3.1 mΩ·cm2 in the Ti-2 sample, much lower than that of bare 316L stainless steel. After the potentiostatic polarization test, the coating still had excellent conductivity.

Effect of Cr and La co-doping on the photocatalytic hydrogen production performance of Sr1-xLaxTi1-xCrxO3 nanofibers

The Sr1-xLaxTi1-xCrxO3 (x = 0–0.05) nanofibers were synthesized by electrospinning based on Pechini sol-gel method. The prepared Sr1-xLaxTi1-xCrxO3 nanofibers were analyzed by XRD, Raman, UV–vis spectra, XPS, SEM, TEM, transient photocurrent, electrochemical impedance and photocatalytic hydrogen evolution tests. The results showed that CrLa co-doped can expand the light absorption region of SrTiO3 from the ultraviolet region to the visible light, and significantly narrowed its band gap. Under visible light irradiation, Sr1-xLaxTi1-xCrxO3 nanofibers exhibited the best hydrogen evolution activity at x = 0.03, and the hydrogen evolution rate reached 106.2 μmol∙g−1∙h−1. This may be the result of the combined effect of the intermediate band gap and the band gap variation due to Cr doping.

Cr/S co-doped carbon nanofibers via electrospinning for high-performance Li/Na ion batteries

Carbon nanofibers (CNFs) have high specific surface area and great electrochemical stability as the anode materials for alkali metal batteries. However, they also have many defects such as low specific capacity and excessive voltage hysteresis, which hinder their wide application. In this work, Cr/S co-doped CNFs (Cr/S@CNFs) are successfully synthesized via electrospinning technique combined with high temperature treatment. As the anode for lithium ion batteries (LIBs), the Cr/S@CNFs electrode exhibits excellent cycle stability (291.7 mAh g−1 at 2 A g−1 after 900 cycles) and high rate performance (221.3 mAh g−1 at 10 A g−1). Moreover, the electrode also obtains the discharge capacity of 266.2 mAh g−1 after 100 cycles at 0.1 A g−1, showing good ion storage capacity for sodium ion batteries (SIBs). Such outstanding electrochemical performances attribute to the co-doping of Cr and S elements, presenting a reliable and efficient approach for the synthesis of high-performance anode materials.

Microstructure, mechanical and high-temperature tribological properties of MoS2-Cr-Ag composite films

In the present work, MoS2-Cr-Ag composite films with various Ag content were synthesized by magnetron sputtering. The microstructure, mechanical and high-temperature tribological properties of as-prepared films were systematically investigated. The results indicated that MoS2-Cr-Ag composite films showed the preferred orientation of (002) crystal plane, which makes it have a dense structure. The maximum micro-hardness of MoS2-Cr-Ag composite films reached up to 309 HV, which was more than 4 times that of pure MoS2. The tribological properties of MoS2-Cr-Ag composite films at room temperature were evaluated. It was found that MoS2-Cr-Ag composite films presented significantly superior tribological properties than MoS2-Cr film at room temperature, which could be ascribed to the addition of Ag inhibits the oxidation of MoS2 and promotes the formation of a dense transfer layer on the surface of friction pair during the friction process. Furthermore, the tribological properties of MoS2-Cr-Ag composite films at 350 °C in air were also evaluated. It was also found that MoS2-Cr-Ag composite films presented superior tribological properties than MoS2-Cr film, which could be ascribed to the formation of Ag2Mo4O13 during the friction process at elevated temperature. In particular, MoS2-Cr-Ag composite film with 9.22 at. % Ag presented superior tribological properties at room temperature and at 350 °C high temperature. These results indicated that the appropriate amount of Cr and Ag co-doping can significantly improve the tribological properties of MoS2-based films at room temperature and 350 °C in air. It provided a design methodology to ameliorate the tribological properties of MoS2 film.

Homogenous Cr and C Doped 3D Self-Supporting NiO Cellular Nanospheres for Hydrogen Evolution Reaction.

Hydrogen evolution reaction (HER) is one promising technique to obtain high-purity hydrogen, therefore, exploiting inexpensive and high-efficiency HER electrocatalysts is a matter of cardinal significance under the background of achieving carbon neutrality. In this paper, a hydrothermal method was used to prepare the Cr-NiC2O4/NF (Ni foam) precursor. Then, the NiO-Cr-C/NF self-supporting HER catalyst was obtained by heating the precursor at 400 °C. The catalyst presents a 3D cellular nanospheres structure which was composed of 2D nanosheets. Microstructure characterization shows that Cr and C elements were successfully doped into NiO. The results of electrochemical measurements and density functional theory (DFT) calculations show that under the synergy of Cr and C, the conductivity of NiO was improved, and the Gibbs free energy of H* (∆GH*) value is optimized. As a result, in 1.0 M KOH solution the NiO-Cr-C/NF-3 (Ni:Cr = 7:3) HER catalyst exhibits an overpotential of 69 mV and a Tafel slope of 45 mV/dec when the current density is 10 mA·cm−2. Besides, after 20 h of chronopotentiometry, the catalytic activity is basically unchanged. It is demonstrated that C and Cr co-doping on the lattice of NiO prepared by a simple hydrothermal method and subsequent heat treatment to improve the catalytic activity and stability of the non-precious metal HER catalysts in an alkaline medium is facile and efficient.

Simple Low Temperature Technique to Synthesize Sillenite Bismuth Ferrite with Promising Photocatalytic Performance

Sillenite-type members of the bismuth ferrite family have demonstrated outstanding potential as novel photocatalysts in environmental remediation such as organic pollutant degradation. This investigation has developed a low temperature one-step hydrothermal technique to fabricate sillenite bismuth ferrite Bi25FeO40 (S-BFO) via co-substitution of 10% Gd and 10% Cr in Bi and Fe sites of BiFeO3, respectively, by tuning hydrothermal reaction temperatures. Rietveld refined X-ray diffraction patterns of the as-synthesized powder materials revealed the formation of S-BFO at a reaction temperature of 120–160 °C. A further increase in the reaction temperature destroyed the desired sillenite structure. With the increase in the reaction temperature from 120 to 160 °C, the morphology of S-BFO gradually changed from irregular shape to spherical powder nanomaterials. The high-resolution TEM imaging demonstrated the polycrystalline nature of the S-BFO(160) nanopowders synthesized at 160 °C. The as-synthesized samples exhibited considerably high absorbance in the visible region of the solar spectrum, with the lowest band gap of 1.76 eV for the sample S-BFO(160). Interestingly, S-BFO(160) exhibited the highest photocatalytic performance under solar irradiation, toward the degradation of rhodamine B and methylene blue dyes owing to homogeneous phase distribution, regular powder-like morphology, lowest band gap, and quenching of electron–hole pair recombination. The photodegradation of a colorless organic pollutant (ciprofloxacin) was also examined to ensure that the degradation is photocatalytic and not dye-sensitized. In summary, Gd and Cr co-doping have proven to be a compelling energy-saving and low-cost approach for the formulation of sillenite-phase bismuth ferrite with promising photocatalytic activity.